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2021052038 Liu Minghao (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Zheng, Hao; Niu Fujun; Fang Jianhong; Lin Zhanju; Luo Jing and Yin Guoan. Cooling performance enhancement of a new expressway embankment in the Tibetan Plateau permafrost zone: Cold Regions Science and Technology, 190, Article 103345, illus. incl. 2 tables, sketch map, October 2021. Based on Publisher-supplied data.
The crushed-rock interlayer (CRI), as typical cooling technique used in the Qinghai-Tibet Railway, cannot be directly applied in expressways traversing permafrost areas because of the intense heat-absorption asphalt pavement. Sufficient cooling of permafrost foundation to meet the demand of engineering stability is an important issue. In this study, a CRI embankment combined with vertical ventilation ducts (VVDs) was designed to strengthen the convective cooling of wide expressways. To assess the performance of the combination design, a field experiment was conducted in the Tibet Plateau by building a full-scale expressway section. A numerical model was then developed and validated to analyze the heat transfer process and to predict its long-term thermal regimes considering climate warming. Results show that the new structure can produce an obviously increased convection cooling on permafrost foundation by enhancing the winter cold-energy utilization. The VVDs at the centerline play an effective role in dissipating heat accumulation in embankment center and can eliminate thermal asymmetry caused by plateau's prevalent wind direction. The combination of CRI and VVDs is effective to control ground temperature to improve expressway embankment stability. This new design could be considered for application in expressways built on permafrost stratum.
DOI: 10.1016/j.coldregions.2021.103345
2021052043 Alexeev, Sergey V. (Russian Academy of Sciences, Siberian Branch, Institute of the Earth's Crust, Laboratory of hydrogeology, Irkutsk, Russian Federation); Alexeeva, Ludmila P.; Vasil'chuk, Yurij K.; Svetlakov, Artem A. and Kulagina, Natalia V. Permafrost of the Oka Plateau (eastern Sayan Ridge): Permafrost and Periglacial Processes, 32(3), p. 368-391, illus. incl. 7 tables, September 2021.
This article presents the results of the first comprehensive study of permafrost and frost mounds in the Sentsa River valley on the Oka Plateau (Eastern Sayan Ridge). The lacustrine-alluvial deposits are represented by clayey silts and silts with visible ice contents up to 90%. Ground ice mainly comprises bicarbonate calcium or bicarbonate magnesium, enriched in ammonium, aluminium, silicon, phosphorus, iron and zinc. Rare earth element content varies from 0.010 to 0.500 mg/L. The distribution of d18O and d2H in the ground ice to a depth of 20 m reflects repeated changes during the freezing of the deposit. The mean annual temperature of frozen rocks is -1.0°C. From 2016, mean annual ground temperatures have been observed to be gradually increasing at a depth of 1.0 m, which correlates with a stable, positive trend of the mean annual air temperatures on the Oka Plateau over the past 60 years. The species and quantitative composition of the palynospectra of the permafrost provides the evidence of repeated changes in the habitat area of forests, as well as changes in the sedimentation regime in the Holocene. According to 14C dating of the soil horizons in the upper parts of the frost mounds, after the emptying of the paleo-lake, organic material intensely accumulated in the drained areas (from 0.5 to 0.2 ka) and ice-mineral frost mounds began to form. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2103
2021052045 Campbell, Seth William (University of Maine, School of Earth and Climate Sciences, Orono, ME); Briggs, Martin; Roy, Samuel G.; Douglas, Thomas A. and Saari, Stephanie. Ground-penetrating radar, electromagnetic induction, terrain, and vegetation observations coupled with machine learning to map permafrost distribution at Twelvemile Lake, Alaska: Permafrost and Periglacial Processes, 32(3), p. 407-426, illus. incl. sketch maps, 90 ref., September 2021.
We collected ground-penetrating radar (GPR) and frequency-domain electromagnetic induction (FDEM) profiles in 2011 and 2012 to identify the extent of permafrost relative to surface biomass and solar insolation around Twelvemile Lake near Fort Yukon, Alaska. We compared a Landsat-derived biomass estimate and modeled solar insolation from a digital elevation model to the geophysical measurements. We show correspondence between vegetation type and biomass relative to permafrost extent and seasonal freeze-thaw. Thicker permafrost (>&eq;25 m) was covered by greater biomass, and seasonal thaw depths in these regions were minimal (1 m). Shallow (1-3 m depth) and thin (20-50 cm) newly forming permafrost or frozen layers from the previous winter occurred below northward oriented slopes with thin biomass cover. South-facing slopes exhibited permafrost when there was enough biomass to shield incoming solar energy. We developed an artificial neural network to predict permafrost extent across the broader region by mapping GPR-observed instances of permafrost to FDEM, biomass, and terrain observations with 90.2% accuracy. We identified a strong linear correlation (r = -0.77) between permafrost probability and seasonal thaw depth, indicating that our models may also be used to explore thaw patterns and variability in active layer thickness. This study highlights the combined influence of biomass and terrain on the presence of permafrost and the value of evaluating such parameters via remote sensing to predict permafrost spatial or temporal variability. Incorporating diverse geophysical datasets with in-situ validation into machine learning models demonstrates a useful approach to upscale estimated permafrost extent across large Arctic expanses. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2100
2021051980 Duvillard, P. A. (STYX 4D, Le Bourget du lac, France); Ravanel, L.; Schoeneich, P.; Deline, P.; Marcer, M. and Magnin, F. Qualitative risk assessment and strategies for infrastructure on permafrost in the French Alps: Cold Regions Science and Technology, 189, Article 103311, illus., September 2021. Based on Publisher-supplied data.
In the current context of climate change, high Alpine rock slopes and surface deposits are affected by a series of geomorphological processes whose evolution is partly conditioned by permafrost warming and thawing. This degradation directly impacts infrastructure in high mountain areas (e.g., huts or ropeway transport systems). In this study, we aim to assess the level of risk of destabilization for infrastructure built on permafrost in the French Alps and to discuss the adaptation and mitigation strategies developed by stakeholders. The analysis combines an inventory of the high mountain infrastructure with several data layers - including two recently developed regional maps of permafrost - analysed within a Geographic Information System. We update a destabilization risk index previously developed to identify and rank infrastructure at risk with a hazard characterisation and a vulnerability diagnosis, based on newly available data. The most at-risk infrastructure according to this new risk index are compared with the strategies implemented by the stakeholders to adapt the foundation, reinforce the ground, reduce heat transfer in depth, or monitor the evolution of the ground. Most of the strategies used on the most at-risk cases are reactive to repair the infrastructure after a destabilization.
DOI: 10.1016/j.coldregions.2021.103311
2021052049 Emmert, Adrian (University of Würzburg, Institute of Geography and Geology, Wurzburg, Germany) and Kneisel, Christof. Internal structure and palsa development at Orravatnsrustir palsa site (central Iceland), investigated by means of integrated resistivity and ground-penetrating radar methods: Permafrost and Periglacial Processes, 32(3), p. 503-519, illus. incl. 6 tables, sketch map, 72 ref., September 2021.
The natural cyclical development of palsas makes it difficult to use visible signs of decay as reference points for environmental change. Thus, to determine the actual development stage of a palsa, investigations of the internal structure are crucial. Our study presents 2-D and 3-D electrical resistivity imaging (ERI) and 2-D ground-penetrating radar (GPR) results, measurements of surface and subsurface temperatures, and of the soil matric potential from Orravatnsrústir Palsa Site in Central Iceland. By a joint interpretation of the results, we deduce the internal structure (i.e., thickness of thaw zone and permafrost, ice/water content) of five palsas of different size and shape. The results differentiate between initial and mature development stages and show that palsas of different development stages can exist in close proximity. While internal characteristics indicate undisturbed development of four palsas, one palsa shows indications of environmental change. Our study shows the value of the multimethod geophysical approach and introduces measurements of the soil matric potential as a promising method to assess the current state of the subsurface. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2106
2021052046 Gagnon, Samuel (Université Laval, Centre d'Études Nordiques, Quebec City, QC, Canada) and Allard, Michel. Modeled (1990-2100) variations in active-layer thickness and ice-wedge activity near Salluit, Nunavik (Canada): Permafrost and Periglacial Processes, 32(3), p. 447-467, illus. incl. 6 tables, sketch map, 73 ref., September 2021.
Simulations with a one-dimensional heat transfer model (TONE) were performed to reproduce the near surface ground temperature regime in the four main types of soil profiles found in Narsajuaq River Valley (Nunavik, Canada) for the period 1990-2100. The permafrost thermal regime was simulated using climate data from a reanalysis (1948-2002), climate stations (1989-1991, 2002-2019) and simulations based on climate warming scenarios RCP4.5 and RCP8.5 (2019-2100). The model was calibrated based on extensive field measurements made between 1989 and 2019. The results were used to estimate when soil thermal contraction cracking will eventually stop and to forecast the melting of ice wedges due to active-layer thickening. For the period 1990-2019, all soil profiles experienced cracking every year until 2006, when cracking became intermittent during a warm period before completely stopping in 2009-2010, after which cracking resumed during colder years. Ice-wedge tops melted from 1992 to 2010 as the active layer thickened, indicating that top-down ice-wedge degradation can occur simultaneously with cracking and growth in width. Our predictions show that ice wedges in the valley will completely stop cracking between 2024 and 2096, first in sandy soils and later in soils with thicker organic horizons. The timing will also depend on greenhouse gas concentration trajectories. All ice wedges in the study area will probably experience some degradation of their main body before the end of the century, causing their roots to become relict ice by the end of the 21st century. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2109
2021052041 Guo Lei (Chinese Academy of Sciences, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); You Yanhui; Yu Qihao; Shi Zhaoyun; Li Hongbi and Wang Xinbin. Field investigation on the influence of periglacial processes on pile foundations on the Qinghai-Tibet Plateau: Permafrost and Periglacial Processes, 32(3), p. 335-348, illus. incl. sketch map, 52 ref., September 2021.
Periglacial processes can threaten the operation of engineering infrastructure. Based on field observations, the influence of four types of periglacial processes on tower foundations along the Qinghai-Tibet Engineering Corridor were investigated. These periglacial processes change the local thermal and hydraulic processes in soils around the pile foundations, thereby threatening their stability. Frost heaving-related periglacial phenomena and fast mass wasting are major threats for the operation of pile foundations. The long-term stability of pile foundations is also threatened by thermokarst-related periglacial processes and slow mass wasting under the evolving climate change scenario on the Qinghai-Tibet Plateau. Frost weathering has a slight impact on the stability of concrete pile heads, and the long-term effects of this cannot be ignored. In addition to the impacts of periglacial processes, piles are also affected by engineering problems in areas with shallow artesian ground water, where the use of thermosyphons is associated with frost jacking of the foundations. Further studies are needed on the thermal and hydraulic regimes in soils under the influence of artesian ground water and thermokarst lakes/ponds. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2092
2021051983 Kong, Xiangbing (Laval University, Department of Civil and Water Engineering, Quebec City, QC, Canada); Doré, Guy; Calmels, Fabrice and Lemieux, Chantal. Field and numerical studies on the thermal performance of air convection embankments to protect side slopes in permafrost environments: Cold Regions Science and Technology, 189, Article 103325, illus. incl. 4 tables, sketch map, September 2021. Based on Publisher-supplied data; includes appendix.
Shoulder air convection embankments (ACEs) are sufficient to counter the effect of ground staying relatively warm due to the insulation of snow accumulation on side slopes of northern transportation infrastructure. However, little information is available for the design procedure. This paper aims to propose new design guidelines and an engineering design chart to quantify the heat extraction capacity of shoulder ACEs. The tested shoulder ACE, constructed on the Alaska Highway at Beaver Creek, Yukon, in 2008, provided valuable data for the assessment of field performance and model development. Thermistor strings were installed under the centerline and under the side slope. Measurements indicated that the cooling of ground soils was significant mainly under the side slope during the monitoring years from 2009 to 2013. The data collected were also used to calibrate a coupled conduction-convection model to reproduce the thermal conditions and the changing temperature trend in the subgrade. An engineering design chart was developed based on the calibrated model, and was successfully validated using the thermal data from the Puvirnituq airstrip in Northern Quebec, Canada.
DOI: 10.1016/j.coldregions.2021.103325
2021052050 Legay, Alexandre (Université Savoie Mont Blanc, EDYTEM Lab, Le Bourget du Lac, France); Magnin, Florence and Ravanel, Ludovic. Rock temperature prior to failure; analysis of 209 rockfall events in the Mont Blanc Massif (Western European Alps): Permafrost and Periglacial Processes, 32(3), p. 520-536, illus. incl. 2 tables, sketch map, 65 ref., September 2021.
Periglacial rock walls are affected by an increase in rockfall activity attributed to permafrost degradation. While recent laboratory tests have asserted the role of permafrost in bedrock stability, linking experimental findings to field applications is hindered by the difficulty in assessing bedrock temperature at observed rockfall locations and time. In this study, we simulated bedrock temperature for 209 rockfalls inventoried in the Mont Blanc massif between 2007 and 2015 and 209,000 random events artificially created at observed rockfall locations. Real and random events are then compared in a statistical analysis to determine their significance. Permafrost conditions (or very close to 0°C) were consistently found for all events with failure depth > 6 m, and for some events affecting depths from 4 to 6 m. Shallower events were probably not related to permafrost processes. Surface temperatures were significantly high up to at least 2 months prior to failure, with the highest peaks in significance 1.5-2 months and 1-5 days before rockfalls. Similarly, temperatures at scar depths were significantly high, but steadily decreasing, 1 day to 3 weeks before failure. The study confirms that warm permafrost areas (> -2°C) are particularly prone to rockfalls, and that failures are a direct response to extraordinary high bedrock temperature in both frozen and unfrozen conditions. The results are promising for the development of a rockfall susceptibility index, but uncertainty analysis encourages the use of a greater rockfall sample and a different sample of random events. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2110
2021052047 Liu, Weibo (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Fortier, Richard; Molson, John and Lemieux, Jean-Michel. A conceptual model for talik dynamics and icing formation in a river floodplain in the continuous permafrost zone at Salluit, Nunavik (Quebec), Canada: Permafrost and Periglacial Processes, 32(3), p. 468-483, illus. incl. sketch maps, 50 ref., September 2021.
Icing occurs each winter along the floodplain of the Kuuguluk River in the continuous permafrost zone at Salluit in Nunavik (Quebec), Canada. The source of successive water overflows which thicken and enlarge this ice cover over time is suprapermafrost groundwater discharging from a talik below the riverbed. Electrical resistivity tomography was used to delineate the talik, while water level and temperature dataloggers were used to assess the thermo-hydraulic conditions of the riverbed. The mean annual riverbed temperature was 1.8°C in 2016 while the mean annual air temperature was -6.0°C. Hydraulic heads below the ice cover as high as 2.8 m and events of abrupt decreases in hydraulic head due to suprapermafrost groundwater overflow through cracks in the ice cover were monitored. An analytical solution based on beam mechanics theory was used to assess the water pressure-induced stresses which are sufficient to fracture the ice cover. A detailed conceptual model of the talik and icing dynamics is proposed to explain the cryo-hydrogeological processes taking place in this complex groundwater-river system. The groundwater pressure buildup in the talik during the winter is due to constricted flow of suprapermafrost groundwater in the talik. These results have implications for understanding the dynamics of river taliks and their use as potential water supplies in northern communities. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2111
2021052040 Liu Guangyue (Chinese Academy of Sciences, Cryosphere Research Station on Qinghai-Xizang Plateau, Lanzhou, China); Xie Changwei; Zhao Lin; Xiao Yao; Wu Tonghua; Wang Wu and Liu Wenhui. Permafrost warming near the northern limit of permafrost on the Qinghai-Tibetan Plateau during the period from 2005 to 2017; a case study in the Xidatan area: Permafrost and Periglacial Processes, 32(3), p. 323-334, illus. incl. 2 tables, sketch map, 38 ref., September 2021.
Permafrost that exists near the boundary of the permafrost zone is generally more sensitive to climate change. By analyzing ground temperatures observed from two 30-m-deep boreholes, a case study was conducted to present some characteristics of recent permafrost warming in the Xidatan area, near the northern limit of the permafrost zone on the Qinghai-Tibetan Plateau. The rate of permafrost degradation from top to bottom in the area was far less than that from bottom to top. Local conditions produced spatial differences in permafrost characteristics, and thus the site covered by alpine meadow had a thinner active layer and lower rate of change than the site with desert steppe. With permafrost warming, the depths of zero annual amplitude at the two sites showed significant decreasing trends, suggesting that the warming could change the proportion of unfrozen water and ice in permafrost, and then lead to a decrease in the mean thermal diffusivity of formation. Mean annual permafrost temperatures at depth of zero annual amplitude of the two boreholes were respectively -0.4°C and -0.7°C, indicating that high-temperature permafrost is widely distributed in the study area. The lower temperature permafrost had a higher warming rate and a higher upward shift rate of the permafrost base. The pattern of permafrost degradation near the limit of permafrost was characterized by nonuniform speed and staged development. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2089
2021052048 Sullivan, Taylor D. (University of Wyoming, Department of Geology and Geophysics, Laramie, WY); Parsekian, Andrew D.; Sharp, Janelle; Hanke, Philip J.; Thalasso, Frederic; Shapley, Mark; Engram, Melanie and Anthony, Katey Walter. Influence of permafrost thaw on an extreme geologic methane seep: Permafrost and Periglacial Processes, 32(3), p. 484-502, illus. incl. 3 tables, sketch map, 104 ref., September 2021.
The occurrence and magnitude of natural fossil methane (CH4) emissions in the Arctic are poorly known. Emission of geologic CH4, a potent greenhouse gas, originating beneath permafrost is of particular interest due to the potential for positive feedback to climate warming, whereby accelerated permafrost thaw releases permafrost-trapped CH4 in a future warmer climate. The development of through-going taliks in Arctic lakes overlying hydrocarbon reservoirs is one mechanism of releasing geologically sourced, subpermafrost CH4. Here we use novel gas flux measurements, geophysical observations of the subsurface, shallow sediment coring, high-resolution bathymetry measurements, and lake water chemistry measurements to produce a synoptic survey of the gas vent system in Esieh Lake, a northwest Alaska lake with exceedingly large geologic CH4 seep emissions. We find that microbially produced fossil CH4 is being vented though a narrow thaw conduit below Esieh Lake through pockmarks on the lake bottom. This is one of the highest flux geologic CH4 seep fields known in the terrestrial environment and potentially the highest flux single methane seep. The poleward retreat of continuous permafrost may have implications for more subcap CH4 release with increased permafrost thaw. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2114
2021052044 Swanson, David K. (National Park Service, Fairbanks, AK). Permafrost thaw-related slope failures in Alaska's Arctic national parks, c. 1980-2019: Permafrost and Periglacial Processes, 32(3), p. 392-406, illus. incl. 4 tables, sketch map, 53 ref., September 2021.
Active-layer detachments (ALD) and retrogressive thaw slumps (RTS) are landslides that occur as a result of thaw in permafrost regions. I mapped the extent of bare soil exposed in these thaw-related slope failures in four study areas with continuous permafrost in Alaska's Arctic National Parks, on mosaics of aerial photographs from 1977-1985 (sampling episode 1), satellite images from 2006-2009 (sampling episode 2), and satellite images from 2018-2019 (sampling episode 3). In all four study areas the count of ALD and RTS, and the area of bare soil they exposed, was greater during the first or second sampling episode than the third sampling episode, in spite of record high mean annual temperatures in 2014-2019. One study area had frozen debris lobes (FDL) in addition to ALD and RTS. In that study area the bare ground exposed by destabilization and rapid movement of FDL was greatest in the third sampling episode, probably as a result of deep thaw and talik formation. The destabilization of FDL in episode 3 was probably a long-term consequence of warming and permafrost loss, while the observed pulses of ALD and RTS in episodes 1 and 2 were closely tied to short-term deep thaw events in areas where the underlying permafrost remained stable. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.2098
2021051987 Tai Bowen (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Qingbai; Yue Zurun and Xu Hongbin. Ground temperature and deformation characteristics of anti-freeze-thaw embankments in permafrost and seasonal frozen ground regions of China: Cold Regions Science and Technology, 189, Article 103331, illus. incl. 1 table, sketch maps, September 2021. Based on Publisher-supplied data.
Embankment engineering in cold regions are at risk of seasonal freeze-thaw damage which seriously threatens the safe operation of vehicles. To ensure the long-term stability of embankment engineering in these areas, novel anti-freeze-thaw measures with differential filling materials should be taken. This study first analyzes the thermal-deformation characteristics and effects of two typical railway embankments with differential anti-freeze-thaw filling materials in permafrost and seasonal frozen ground regions based on ground temperature and deformation monitoring data. Then, on the basis of these results and previous research, the similarities and differences between the thermal-deformation characteristics of different embankments in permafrost and seasonal frozen ground regions are studied. Finally, the study summarizes fundamental principles for anti-freeze-thaw embankment measures in accordance with frozen ground type. Results demonstrate that: 1) the thaw settlement of permafrost embankments demonstrates persistence and is non-uniform, while the frost heave of embankments in seasonal frozen ground regions demonstrates cold shrinkage and heave delay; 2) understanding the development of the temperature and thickness of the seasonal thawing/freezing layer in time and space is key for preventing freeze-thaw damage in frozen ground regions; 3) the long-term stability of embankments in permafrost regions can be maintained by controlling the quantity of cold entrance and diffusion. For embankments in seasonal frozen ground regions, frost heave may be controlled by changing the property, water content, and temperature of filling materials. These findings will be helpful for better understanding the thermal-mechanical characteristics of embankments in different frozen ground regions, and for providing important technical guidance to ensure the operational efficiency of engineering projects.
DOI: 10.1016/j.coldregions.2021.103331
2021051981 Zueter, Ahmad F. (McGill University, Department of Mining and Materials Engineering, Montreal, QC, Canada); Newman, Greg and Sasmito, Agus P. Numerical study on the cooling characteristics of hybrid thermosyphons; case study of the Giant Mine, Canada: Cold Regions Science and Technology, 189, Article 103313, illus. incl. 4 tables, September 2021. Based on Publisher-supplied data.
Hybrid thermosyphons have been installed in several permafrost protection applications due to their ability to operate continuously irrespective of seasonal temperature variations. In winter seasons, the thermosyphon operates passively by transferring energy between the ground and cold ambient air; while in warmer/summer seasons, an active refrigeration plant is used as a substitute for colder climate to extract the heat and freeze the ground. This study presents a novel conjugate mathematical model of hybrid thermosyphons based on thermal resistance networks, coupled with transient two-phase artificial ground freezing heat flow based on the enthalpy method. The model is validated against laboratory experimental data from literature and field test data from the Giant Mine in Yellowknife, Canada. Various design and operating parameters are investigated with the aim to maximizing ground heat extraction while minimizing energy consumption. The results indicate that active refrigeration substantially accelerates the formation of the desired frozen ground volume. After a certain time, passive cooling mode can be continuously adopted to reduce the energy consumption of refrigeration plants while maintaining the desired frozen ground thickness. Finally, the model can be used to assist engineers and practitioners to optimize the design of hybrid thermosyphon for permafrost protection or other ground freezing applications.
DOI: 10.1016/j.coldregions.2021.103313
2021049240 Albaric, Julie (University of Bourgogne Franche-Comté, Chrono-environnement, Besancon, France); Kuhn, Daniela; Ohrnberger, Matthias; Langet, Nadege; Harris, Dave; Polom, Ulrich; Lecomte, Isabelle and Hillers, Gregor. Seismic monitoring of permafrost in Svalbard, arctic Norway: Seismological Research Letters, Pre-Issue Publication, illus. incl. sketch map, 63 ref., July 7, 2021.
We analyze data from passive and active seismic experiments conducted in the Adventdalen valley of Svalbard in the Norwegian Arctic. Our objective is to characterize the ambient wavefield of the region and to investigate permafrost dynamics through estimates of seismic velocity variations. We are motivated by a need for early geophysical detection of potentially hazardous changes to permafrost stability. We draw upon several data sources to constrain various aspects of seismic wave propagation in Adventdalen. We use f-k analysis of five years of continuous data from the Spitsbergen seismic array (SPITS) to demonstrate that ambient seismic noise on Svalbard consists of continuously present body waves and intermittent surface waves appearing at regular intervals. A change in wavefield direction accompanies the sudden onset of surface waves when the average temperature rises above the freezing point, suggesting a cryogenic origin. This hypothesis is supported further by our analysis of records from a temporary broadband network, which indicates that the background wavefield is dominated by icequakes. Synthetic Green's functions calculated from a 3D velocity model match well with empirical Green's functions constructed from the recorded ambient seismic noise. We use a shallow shear-wave velocity model, obtained from active seismic measurements, to estimate the maximum depth of Rayleigh wave sensitivity to changes in shear velocity to be in the 50-100 m range. We extract seasonal variations in seismic velocities from ambient noise cross-correlation functions computed over three years of SPITS data. We attribute relative velocity variations to changes in the ice content of the shallow (2-4 m depth) permafrost, which is sensitive to seasonal temperature changes. A linear decreasing trend in seismic velocity is observed over the years, most likely due to permafrost warming.
DOI: 10.1785/0220200470
2021051994 Liu, Chang (University of Arkansas, Department of Geosciences, Fayetteville, AR); Feng, Song and Huang Wei. An improved method for calculating the freezing/thawing index using monthly and annual temperature data: International Journal of Climatology, 41(9), p. 4548-4561, illus. incl. 1 table, 34 ref., July 2021.
Changes in soil thermal regimes in cold climates have widespread impacts on hydrology, ecology, and the carbon cycle. The annual freezing and thawing index, which is generally calculated using daily temperature, has been widely used to estimate the freezing depth, active layer thickness, and the distribution of permafrost. However, continuous and reliable daily temperature data are scarce in cold climates, while monthly and annual temperature data are more readily available. If daily temperature data are unavailable, these indices can be estimated based on monthly or annual temperature data. In this study, we developed a resampling method for estimating the annual freezing and thawing index and compared the results with those produced by the existing methods. Daily temperature data with a 0.5° resolution over the Northern Hemisphere during 1901-2012 were used to calculate the freezing/thawing index, and then the monthly and annual temperature were calculated and three different approaches were used to estimate the daily temperature and the freezing/thawing index. When the monthly data were used, the resampling method produced the smallest relative error (RE) and mean bias error (MBE), and the largest correlation in estimating the two indices, compared to the two other methods. Although the annual temperature data usually underestimate the freezing/thawing index, the RE is still <5% over most of the high-latitude regions. The results suggest that if the daily temperature can be reliably estimated using the resampling method, the thermal regimes of permafrost can be reliably estimated using modelled monthly temperature and/or reconstructed past monthly/annual temperature. These estimations can also be used to validate modelled paleo-permafrost and its variations. Additionally, our results indicate that after the 1970s the annual freezing index (DDF) increased substantially, while the frost index (FI) decreased substantially. Abstract Copyright (2021), Royal Meteorological Society.
DOI: 10.1002/joc.7085
2021052070 Maji, Vikram (University of Sussex, Permafrost Laboratory, Department of Geography, Brighton, United Kingdom) and Murton, Julian B. Experimental observations and statistical modeling of crack propagation dynamics in limestone by acoustic emission analysis during freezing and thawing: Journal of Geophysical Research: Earth Surface, 126(7), Article e2021JF006127, illus. incl. 5 tables, 30 ref., July 2021.
The timing and location of microcracking events, their propagation and coalescence to form macrocracks, and their development by tension, shearing or mixed modes are little known but essential to understanding the fracture of intact rock by freezing and thawing. The aims of the present study are to investigate the mechanisms and transition of microcracking and macrocracking during repeated freeze-thaw, and to develop a statistical model of crack propagation that assesses the distance and angular relationship of neighboring cracking events arranged in their temporal order of occurrence. Eight acoustic emission (AE) sensors mounted on a 300 mm cubic block of chalk captured the three-dimensional locations of microcracking events in their temporal order of occurrence during 16 seasonal freeze-thaw cycles simulating an active layer above permafrost. AE events occurred mostly during thawing periods (45%) and freeze-to-thaw transitions (37%) rather than during freezing periods (9%) and thaw-to-freeze transitions (8%), suggesting that most AE (microcrack) events were driven by the process of ice segregation rather than volumetric expansion. The outcomes of a novel statistical model of crack propagation based on two boundary conditions-inside-out and outside-in modes of cracking-were assessed based on Bayes' theorem by testing the hypothesis that the inside-out mode of cracking was favored by tensional activity, whereas the outside-in mode was supported by shearing events. In both situations, the hypothesis accounted for 54%-73% confidence level. The microcrack propagation model can distinguish reasonably between cracks formed by volumetric expansion and ice segregation. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2021JF006127
2021052057 Rogers, Jennifer A. (Florida State University, Department of Earth, Ocean, and Atmospheric Science, Tallahassee, FL); Galy, Valier; Kellerman, Anne M.; Chanton, Jeffrey P.; Zimov, Nikita and Spencer, Robert G. M. Limited presence of permafrost dissolved organic matter in the Kolyma River, Siberia revealed by ramped oxidation: Journal of Geophysical Research: Biogeosciences, 126(7), Article e2020JG005977, illus. incl. 3 tables, 74 ref., July 2021.
Increasing Arctic temperatures are thawing permafrost soils and liberating ancient organic matter, but the fate of this material remains unclear. Thawing of permafrost releases dissolved organic matter (DOM) into fluvial networks. Unfortunately, tracking this material in Arctic rivers such as the Kolyma River in Siberia has proven challenging due to its high biodegradability. Here, we evaluate late summer abruptly thawed yedoma permafrost dissolved organic carbon (DOC) inputs from Duvannyi Yar. We implemented ultrahigh-resolution mass spectrometry alongside ramped pyrolysis oxidation (RPO) and isotopic analyses. These approaches offer insight into DOM chemical composition and DOC radiocarbon values of thermochemical components for a permafrost thaw stream, the Kolyma River, and their biodegraded counterparts (n=4). The highly aliphatic molecular formula found in undegraded permafrost DOM contrasted with the comparatively aliphatic-poor formula of Kolyma River DOM, represented by an 8.9% and 2.6% relative abundance, respectively, suggesting minimal inputs of undegraded permafrost DOM in the river. RPO radiocarbon fractions of Kolyma River DOC exhibited no "hidden" aged component indicative of permafrost influence. Thermostability analyses suggested that there was limited biodegraded permafrost DOC in the Kolyma River, in part determined by the formation of high-activation energy (thermally stable) biodegradation components in permafrost DOM that were lacking in the Kolyma River. A mixing model based on thermostability and radiocarbon allowed us to estimate a maximum input of between 0.8% and 7.7% of this Pleistocene-aged permafrost to the Kolyma River DOC. Ultimately, our findings highlight that export of modern terrestrial DOC currently overwhelms any permafrost DOC inputs in the Kolyma River. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2020JG005977
2021050729 James, S. R. (U. S. Geological Survey, Geology, Geophysics, and Geochemistry Science Center, Denver, CO); Minsley, B. J.; McFarland, J. W.; Euskirchen, E. S.; Edgar, C. W. and Waldrop, M. P. The biophysical role of water and ice within permafrost nearing collapse; insights from novel geophysical observations: Journal of Geophysical Research: Earth Surface, 126(6), Article e2021JF006104, illus. incl. geol. sketch map, 95 ref., June 2021.
The impact of permafrost thaw on hydrologic, thermal, and biotic processes remains uncertain, in part due to limitations in subsurface measurement capabilities. To better understand subsurface processes in thermokarst environments, we collocated geophysical and biogeochemical instruments along a thaw gradient between forested permafrost and collapse-scar bogs at the Alaska Peatland Experiment site near Fairbanks, Alaska. Ambient seismic noise monitoring provided continuous high-temporal resolution measurements of water and ice saturation changes. Maps of seismic velocity change identified areas of large summertime velocity reductions nearest the youngest bog, indicating potential thaw and expansion at the bog margin. These results corresponded well with complementary borehole nuclear magnetic resonance measurements of unfrozen water content with depth, which showed permafrost soils nearest the bog edges contained the largest amount of unfrozen water along the study transect, up to 25% by volume. In situ measurements of methane within permafrost soils revealed high concentrations at these bog-edge locations, up to 30% soil gas. Supra-permafrost talik zones were observed at the bog margins, indicating talik formation and perennial liquid water may drive lateral bog expansion and enhanced permafrost carbon losses preceding thaw. Comparison of seismic monitoring with wintertime surface carbon dioxide fluxes revealed differential responses depending on time and proximity to the bogs, capturing the controlling influence of subsurface water and ice on microbial activity and surficial emissions. This study demonstrates a multidisciplinary approach for gaining new understanding of how subsurface physical properties influence greenhouse gas production, emissions, and thermokarst development. Abstract Copyright (2021), . American Geophysical Union. All Rights Reserved. This article has been contributed to by US Government employees and their work is in the public domain in the USA.
DOI: 10.1029/2021JF006104
2021050531 Lamontagne, Maurice (Geological Survey of Canada, Ottawa, ON, Canada) and Bent, Allison L. Earthquakes in the Eastern Canadian Arctic; past occurrences, present hazard, and future risk: Seismological Research Letters, Pre-Issue Publication, p. 53, illus. incl. 2 tables, sketch maps, 45 ref., May 5, 2021.
The Canadian Arctic encompasses several active seismic areas where a small number of significant earthquakes have been recorded since the early twentieth century. Our study area is defined as the eastern Canadian Arctic, an immense territory that covers 30% of the Canadian land mass. It includes the territory of Nunavut and the region of Nunavik in northern Quebec. Ten earthquakes had a moment magnitude (M) between 5.5 and 7.4, but only five can be considered significant because of their impact. Most were felt in communities at distances of a few hundreds of kilometers, but none exceeded modified Mercalli intensity (MMI) V. This article contains descriptions of the impact of these five earthquakes and of smaller ones that were felt in nearby communities. These macroseismic effects suggest stronger attenuation of MMIs than what is generally assumed for eastern North America. According to the current seismic zoning, very few communities face a significant earthquake hazard. Seismic risk has to consider that most high Arctic buildings are built on piles sitting on permafrost. It is believed that the newer engineered constructions would resist fairly well to seismic shaking, as opposed to buildings with older at grade foundations with little lateral resistance. The fast warming of the Arctic may lead to some thickening of the active layer of the permafrost, which may increase the potential for slope instabilities during earthquake shaking. The change would not be significant enough to alter the potential for local ground-motion amplification.
DOI: 10.1785/0220210014
2021050688 Wagner, Thomas (University of Graz, Institute of Earth Sciences, Graz, Austria); Kainz, Simon; Krainer, Karl and Winkler, Gerfried. Storage-discharge characteristics of an active rock glacier catchment in the Innere Olgrube, Austrian Alps: Hydrological Processes, 35(5), Article e14210, illus. incl. 2 tables, geol. sketch map, 66 ref., May 2021.
The active rock glacier "Innere Olgrube" and its catchment area (Otztal Alps, Austria) are assessed using various hydro(geo)logical tools to provide a thorough catchment characterization and to quantify temporal variations in recharge and discharge components. During the period from June 2014 to July 2018, an average contribution derived from snowmelt, ice melt and rainfall of 35.8%, 27.6% and 36.6%, respectively, is modelled for the catchment using a rainfall-runoff model. Discharge components of the rock glacier springs are distinguished using isotopic data as well as other natural and artificial tracer data, when considering the potential sources rainfall, snowmelt, ice melt and longer stored groundwater. Seasonal as well as diurnal variations in runoff are quantified and the importance of shallow groundwater within this rock glacier-influenced catchment is emphasized. Water derived from ice melt is suggested to be provided mainly by melting of two small cirque glaciers within the catchment and subordinately by melting of permafrost ice of the rock glacier. The active rock glacier is characterized by a layered internal structure with an unfrozen base layer responsible for groundwater storage and retarded runoff, a main permafrost body contributing little to the discharge (at the moment) by permafrost thaw and an active layer responsible for fast lateral flow on top of the permafrost body. Snowmelt contributes at least 1/3rd of the annual recharge. During droughts, meltwater derived from two cirque glaciers provides runoff with diurnal runoff variations; however, this discharge pattern will change as these cirque glaciers will ultimately disappear in the future. The storage-discharge characteristics of the investigated active rock glacier catchment are an example of a shallow groundwater aquifer in alpine catchments that ought to be considered when analysing (future) river runoff characteristics in alpine catchments as these provide retarded runoff during periods with little or no recharge. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1002/hyp.14210
2021048935 Zhang Guofei (Nanjing Normal University, Key Laboratory of Ministry of Education on Virtual Geographic Environment, Nanjing, China); Nan Zhuotong; Zhao Lin; Liang Yijia and Cheng Guodong. Qinghai-Tibet Plateau wetting reduces permafrost thermal responses to climate warming: Earth and Planetary Science Letters, 562, Article 116858, illus. incl. 2 tables, sketch maps, 50 ref., May 15, 2021.
Permafrost, as one of the cryospheric indicators, is extremely sensitive to climatic changes. The Qinghai-Tibet Plateau has experienced remarkable warming and wetting since the mid-1990s. Its recent wetting alters thermal and hydrological properties in permafrost regions and inevitably affects permafrost thermal dynamics. While previous studies mostly focused on the effects of warming on permafrost, little attention has been paid to the effects of concomitant wetting. Here, a land surface model adapted for permafrost simulation is employed to quantitatively investigate the impacts of climate warming and wetting on permafrost thermal regimes by setting up a group of hypothetical numerical scenarios on the basis of historical meteorological records. The results reveal that climate wetting reduces permafrost thermal responses to warming and this effect is especially evident in the arid and semi-arid zones. It was estimated that one-degree warming induces an average increase of 0.46 m in active layer thickness (ATL) and 0.53 °C in temperature at the top of permafrost (TTOP), and a 100 mm wetting in summer precipitation leads to a mean decrease of 0.35 m in ALT and 0.36 °C in TTOP. Furthermore, we found through the simulations that increased summer precipitation imposes dual effects on permafrost in semi-arid high altitudes.
DOI: 10.1016/j.epsl.2021.116858
2021051761 Hanacek, Martin (Masaryk University, Department of Geography, Polar-Geo-Lab, Brno, Czech Republic); Nyvlt, Daniel and Jennings, Stephen J. A. Thermal basal regime of the Elsterian ice sheet marginal zone in a hilly mountain foreland, Rychleby Mountains, eastern Sudetes: Boreas, 50(2), p. 582-605, illus. incl. geol. sketch map, strat. col., 130 ref., April 2021.
The Scandinavian Ice Sheet reached the Sudetes and Carpathian Mountains during the Elsterian glaciation. A long ice-sheet piedmont marginal zone affected by the rugged mountain foreland topography and associated slopes originated. This study focuses on the hilly Rychleby Mts. foreland (Eastern Sudetes, Czechia), which was a part of the piedmont marginal foreland zone of the ice sheet. The basal regime was reconstructed through an investigation of the sedimentology, structural features, and the nature of ice-sheet erosion of preglacial landscapes evident at two sites located ~3-5 km inside the maximum ice-sheet extent. These sites show a preglacial relief buried by sub- to supraglacial sediments. The sites were located under an ice cover of max. 200 m. Evidence of cold-based conditions (including palaeotors with delicate structures on the bedrock, almost absent striations on clasts, originally frozen unlithified sedimentary rafts) exists at both sites. Permafrost composed of coarse-grained sediments was subject to brittle deformation at the base of the ice sheet, whereas permafrost composed of fine-grained sediments underwent ductile deformation. The margin of the Scandinavian Ice Sheet in the Rychleby Mts. foreland was cold-based, therefore glacial erosion was not sufficient to significantly remodel the palaeotors into roches moutonnees. During ice-sheet decay, the preglacial landscape was partially buried by melt-out tills and meltwater sediments. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1111/bor.12505
2021051757 Zhu Chenyi (Peking University, School of Urban and Environmental Sciences, Laboratory for Earth Surface Processes, Beijing, China); Wang Hongya; Li Shuai; Luo Yao; Xue Tianyi; Song Yaqiong; Qiu An'an and Liu Hongyan. Mineral magnetism variables as potential indicators of permafrost aggradation and degradation at the southern edge of the permafrost zone, northeast China: Boreas, 50(2), p. 497-518, illus. incl. 4 tables, geol. sketch map, 65 ref., April 2021.
The northern Greater Khingan Range is located in northernmost Northeast China on the southern edge of the permafrost zone of the Northern Hemisphere. Isolated, sporadic and continuous permafrost belts are distributed from the southeast to the northwest in this area. Sixteen surface soil samples were collected from the three permafrost belts, and a 30-cm-deep soil profile was sampled from the continuous permafrost belt. A 70-cm-long sediment core was recovered from a small lake in the continuous permafrost belt. Measurements of mineral magnetism and analysis of total organic carbon (TOC) and total nitrogen (TN) were performed on the soil samples, while mineral magnetism measurements, pollen analysis and accelerator mass spectrometry (AMS) 14C dating were made on the lake sediment samples. The purpose was to explore whether the mineral magnetism of the soils and sediments in combination with TOC, C/N and pollen data would be indicative of recent and past permafrost alterations. Stable single domain (SSD) ferrimagnets were rarer in relative and/or absolute terms in the surficial isolated-sporadic permafrost and the upper horizons of the soil profile, suggesting stronger gleization and thawing. The variations in TOC and C/N support these inferences. Temporal changes in mineral magnetism of the sediment core indicate varying pedogenesis and gleization and permafrost aggradations and degradations in the catchment and shifts of the permafrost belts over the past ~1000 years. The reconstructed permafrost alterations attributable to local climate changes suggested by the pollen data can be related to northern hemispheric and regional climate changes in the past ~1000 years and are helpful for predicting migrations of the permafrost belts in the future. Abstract Copyright (2021), John Wiley & Sons, Ltd.
DOI: 10.1111/bor.12496
2021050188 Chuvilin, Evgeny (Skolkovo Institute of Science and Technology, Skolkovo Innovation Centre, Moscow, Russian Federation); Bukhanov, Boris; Grebenkin, Sergey; Tumskoy, Vladimir; Shakhova, Natalia; Dudarev, Oleg; Semiletov, Igor and Spasennykh, Mikhail. Thermal properties of sediments in the East Siberian Arctic Seas; a case study in the Buor-Khaya Bay: Marine and Petroleum Geology, 123, Article 104672, illus. incl. 4 tables, sketch map, 73 ref., January 2021.
The temperature and thermal properties of shelf sediments from the East Siberian, Laptev, and Kara Seas were determined from field investigations. The sediments were in an unfrozen cryotic state (ice-free) and showed negative temperatures, ranging from -1.0 to -1.4°C. These temperatures imply the presence of widespread subsea permafrost from the shelf to the continental slope of the East Siberian Arctic Seas, reaching ~1000-1500 km off the coast. The thermal conductivity and heat capacity of sediments (up to a depth of 0.5 m) from the Eastern Arctic Seas averaged 0.95 W/(m·K) and 3010 kJ/(m3·K), respectively. We also conducted temperature and thermal conductivity measurements of the upper sediment horizons of the permafrost in the Laptev Sea shelf (drilling depth of 57 m). The analysis of sediment cores ensured the determination of thermal conductivity with depth. We also analyzed the influence of moisture content, density, particle size distribution, salinity, and thermal state on sediment thermal conductivity. The thermal conductivity of unfrozen cryotic (ice-free) sediments was predominantly dependent on the contents of silt and clay. In general, unfrozen cryotic sandy sediments had a thermal conductivity range 1.7-2.0 W/(m·K), a moisture content of ~20%, and a density of 2.0-2.2 g/sm3. Frozen (ice-containing) sediments showed higher thermal conductivities of 2.5-3.0 W/(m·K), with a density of 1.9-2.0 g/cm3 and a moisture content exceeding 25-30%. The high thermal conductivity of sand was associated with low salinity (0.1-0.2%), high ice content, and moderate unfrozen water content.
DOI: 10.1016/j.marpetgeo.2020.104672
2021050234 Rodriguez-López, Juan Pedro (United Arab Emirates University, Department of Geology, Abu Dhabi, United Arab Emirates); van Vliet-Lanoë, Brigitte; López-Martínez, Jerónimo and Martín-García, Rebeca. Scouring by rafted ice and cryogenic patterned ground preserved in a Palaeoproterozoic equatorial proglacial lagoon succession, eastern India, Nuna Supercontinent: Marine and Petroleum Geology, 123, Article 104766, illus. incl. sketch map, sects., geol. sketch maps, 3 tables, strat. col., 162 ref., January 2021.
The Chaibasa Formation contains the oldest known record of ploughmarks formed by rafted ice preserved on Earth. The Palaeoproterozoic (Orosirian-Rhyacian, 1.86-2.1 Ga) Chaibasa Formation in the Dhalbhumgarh area, eastern India, represents sedimentation in an ice-contact proglacial lagoon affected by iceberg (bits and growlers) calving and lake-ice rafting. Ice scouring, both on muddy and sandy substrates, as well as ice "rosettes" developed as consequence of the ploughing action of floating icebergs that were moved by wind, meltwater floods and tidal currents on soft sediments. Muddy flats surrounding the proglacial lagoon underwent seasonal deep freezing conditions developing cryogenic patterned ground containing reticulate ice, ice veins and sand wedges, suggesting the occurrence of proglacial permafrost areas coeval with Proterozoic glaciers. The central part of the proglacial lagoon was characterized by deposition of glacial varves punctuated by pebble and cobble size angular dropstones accumulated in the basin as ice-rafted debris from floating ice. Evidences provided in this paper reinforced the idea that 1.86-2.1 Ga ago glacial conditions prevailed after the supposed ending of the Huronian glaciation. This paper provides detailed examples that can be used to recognize possible floating/drifted ice scours in other Precambrian successions, as these elements have largely passed undetected, being probably widely reported in the literature as generic soft-sediment deformation structures. Similar soft-sediment deformations from Precambrian clastic depositional systems should be re-evaluated as there is a significant possibility that most of the Precambrian iceberg-related structures had escape notice, as originally suggested Eyles et al. in 1997.
DOI: 10.1016/j.marpetgeo.2020.104766
2021048622 Fewster, Richard E. (University of Leeds, School of Geography, Leeds, United Kingdom); Morris, Paul J.; Swindles, Graeme T.; Gregoire, Lauren J.; Ivanovic, Ruza F.; Valdes, Paul J. and Mullan, Donal. Drivers of Holocene palsa distribution in North America: Quaternary Science Reviews, 240, Article 106337, illus. incl. 3 tables, sketch maps, 122 ref., July 15, 2020.
Palsas and peat plateaus are climatically sensitive landforms in permafrost peatlands. Climate envelope models have previously related palsa/peat plateau distributions in Europe to modern climate, but similar bioclimatic modelling has not been attempted for North America. Recent climate change has rendered many palsas/peat plateaus in this region, and their valuable carbon stores, vulnerable. We fitted a binary logistic regression model to predict palsa/peat plateau presence for North America by relating the distribution of 352 extant landforms to gridded modern climate data. Our model accurately classified 85.3% of grid cells that contain observed palsas/peat plateaus and 77.1% of grid cells without observed palsas/peat plateaus. The model indicates that modern North American palsas/peat plateaus are supported by cold, dry climates with large seasonal temperature ranges and mild growing seasons. We used palaeoclimate simulations from a general circulation model to simulate Holocene distributions of palsas/peat plateaus at 500-year intervals. We constrained these outputs with timings of peat initiation, deglaciation, and postglacial drainage across the continent. Our palaeoclimate simulations indicate that this climate envelope remained stationary in western North America throughout the Holocene, but further east it migrated northwards during 11.5-6.0 ka BP. However, palsa extents in eastern North America were restricted from following this moving climate envelope by late deglaciation, drainage and peat initiation. We validated our Holocene simulations against available palaeoecological records and whilst they agree that permafrost peatlands aggraded earliest in western North America, our simulations contest previous suggestions that late permafrost aggradation in central Canada was climatically-driven.
DOI: 10.1016/j.quascirev.2020.106337
2021051173 Winkler, Stefan (Julius-Maximilians-University Würzburg, Department of Geography and Geology, Wurzburg, Germany); Matthews, John A.; Haselberger, Stefan; Hill, Jennifer L.; Mourne, Richard W.; Owen, Geraint and Wilson, Peter. Schmidt-hammer exposure-age dating (SHD) of sorted stripes on Juvflye, Jotunheimen (central South Norway); morphodynamic and palaeoclimatic implications: Geomorphology, 353, Article 107014, March 15, 2020. Based on Publisher-supplied data.
Measurements with an electronic Schmidt-hammer (RockSchmidt) were conducted on 23 sites of sorted stripes (periglacial patterned ground) on Juvflye, Jotunheimen (central South Norway). All were located above the current lower limit of alpine permafrost. Performing Schmidt-hammer exposure-age dating (SHD) based on application of a new local age-calibration equation for RRock-values yielded SHD-ages between 7975±370 and 6660±355 years ago, which are closely comparable to results obtained previously from sorted circles at the same location. The age estimates are interpreted as 'composite' ages indicative of upfreezing of boulders, lateral sorting, and subsequent stabilisation. Formation of patterned ground essentially ceased with the onset of the regional Holocene Thermal Maximum (HTM). Neither sorted stripe sites at higher altitude, continuously underlain by permafrost during the entire Holocene, nor those at lower altitudes affected by re-aggradation of permafrost in the late Holocene show signs of significant recent morphodynamic activity. Likely explanations for early- to mid-Holocene stabilisation include (1) substantial changes of soil moisture conditions and related thermodynamics within the active layer affecting frost action, (2) loss of fine-grained substrate matrix from the coarse stripes and hence reduced frost susceptibility, and (3) exhaustion of supply of boulders from the fines-dominated areas. Whereas the sorted stripe data set as a whole did not reproduce the altitudinal gradient characteristic of sorted circles on Juvflye, the strength of the relationship between sorted stripe mean RRock-values and altitude increased with declining slope gradient. Although interpretation of SHD-ages for patterned ground remains challenging, this successful application of the electronic Schmidt-hammer, with its increased efficiency and technical improvements over the mechanical Schmidt-hammer, offers considerable potential for future SHD-studies in both morphodynamic and palaeoclimatic contexts.
DOI: 10.1016/j.geomorph.2019.107014
2021051125 Walter, Fabian (Eidgenössische Technische Hochschule Zurich, Laboratory of Hydraulics, Hydrology and Glaciology, Zurich, Switzerland); Amann, Florian; Kos, Andrew; Kenner, Robert; Phillips, Marcia; de Preux, Antoine; Huss, Matthias; Tognacca, Christian; Clinton, John; Diehl, Tobias and Bonanomi, Yves. Direct observations of a three million cubic meter rock-slope collapse with almost immediate initiation of ensuing debris flows: Geomorphology, 351, Article 106933, illus. incl. geol. sketch maps, 42 ref., February 15, 2020.
Catastrophic collapse of large rock slopes ranks as one of the most hazardous natural phenomena in mountain landscapes. The cascade of events, from rock-slope failure, to rock avalanche and the near-immediate release of debris flows has not previously been described from direct observations. We report on the 2017, 3.0 ´ 106 m3 failure on Pizzo Cengalo in Switzerland, which led to human casualties and significant damage to infrastructure. Based on remote sensing and field investigations, we find a change in critical slope stability prior to failure for which permafrost may have played a destabilizing role. The resulting rock avalanche traveled for 3.2 km and removed over one million m3 of glacier ice and debris deposits from a previous rock avalanche in 2011. Whereas this entrainment did not lead to an unusually large runout distance, it favored debris flow activity from the 2017 rock avalanche deposits: the first debris flow occurred with a delay of 30 s followed by ten debris flows within 9.5 h and two additional events two days later, notably in the absence of rainfall. We hypothesize that entrainment and impact loading of saturated sediments explain the initial mobility of the 2017 rock avalanche deposits leading to a near-immediate initiation of debris flows. This explains why an earlier rock avalanche at the same site in 2011 was not directly followed by debris flows and underlines the importance of considering sediment saturation in a rock avalanche's runout path for Alpine hazard assessments.
DOI: 10.1016/j.geomorph.2019.106933
2021051092 Bashkuyev, Yu. B. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Institut Fizicheskogo Materialovedeniya, Ulan-Ude, Russian Federation); Dembelov, M. G. and Khaptanov, V. B. Elektricheskiye svoystva merzlykh porod na poberezh'ye moray Laptevykh po dannym radiovolnovykh izmereniy [Electrical properties of the permafrost on Laptev Sea coast; data from radio-wave measurements]: Kriosfera Zemli = Earth Cryosphere, 23(2), p. 88-96 (English sum.), illus. incl. 2 tables, sketch map, 24 ref., April 2019.
The electrical properties of permafrost in the Arctic coast near the Tiksi Bay have been studied by VLF to MF radio-frequency impedance sounding combined with VHF-UHF georadar surveys. The subsurface in the area shows heterogeneous geoelectrical patterns with variations according to lithology and particle size distribution. More heterogeneity is due to the presence of ice wedges and lenses of saline groundwater (cryopegs), as well as to flow of supra- and intra-permafrost waters. Joint interpretation of radio-frequency impedance and GPR data provide constraints on the shallow subsurface structure in the Arctic coast in the vicinity of Tiksi and on particular electrical properties of cryopegs. The properties of permafrost revealed by surveys at low and medium RF bands are included in the geoelectrical database for layered permafrost.
2021051088 Berdnikov, N. M. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Tyumenskiy Nauchnyy Tsentr, Institut Kriosfery Zemli, Tyumen, Russian Federation); Gravis, A. G.; Drozdov, D. S.; Ponomareva, O. E.; Moskalenko, N. G. and Bochkarev, Yu. N. L'distost' mnogoletnemerzlykh porod, slagayushchikh bugry pucheniya v basseyne reki Nadym [Ice content in permafrost heaving mounds in the Nadym River basin]: Kriosfera Zemli = Earth Cryosphere, 23(2), p. 29-37 (English sum.), illus., 23 ref., April 2019.
The "clastic type" ice-cored frost mounds are widespread in the northern taiga of West Siberia. Besides, morphologically different forms of permafrost-related hummocky terrain are developed, differentiating from the "classic" frost mounds by size and flat tops. Using core samples from the ten-meter deep boreholes, the authors have analyzed the total thickness of segregated ice and the contribution of ice inclusions to the total soil ice content, to determine the origin of such flat-topped frost mounds. Good correlation has been revealed between surface elevations and volumetric ice content of sediments composing the mounds, whose iceness is found to be higher than in the depression between them. These facts indicate the local nature of ice segregation and therefore suggest that the investigated landforms were formed by the frost heave processes, rather than being remnant permafrost landforms.
2021051090 Chuvilin, E. M. (Skolkovskiy Institut Nauki i Tekhnologiy, Skolkovo, Russian Federation); Davletshina, D. A. and Lupachik, M. V. Gidratoobrazovaniye v merzlykh i ottaivayushchikh metanonasyshchennykh porodakh [Gas hydrate formation in frozen and thawing methane-saturated sediments]: Kriosfera Zemli = Earth Cryosphere, 23(2), p. 50-61 (English sum.), illus. incl. 3 tables, 64 ref., April 2019.
The formation of pore gas hydrates in frozen and thawing sand and silt sampled in permafrost areas has been studied in experiments using a special system. As demonstrated by the experimental results, gas hydrates form rapidly in gas-saturated sediments at constant negative temperatures from 0 to -8°C. The accumulation kinetics of pore gas hydrates in permafrost has multiple controls: temperature, initial ice saturation, and salinity of soils, as well as type of hydrate-forming gas. The process can resume after its decay due to melting of residual pore ice not yet converted to hydrate.
2021051091 Kaverin, D. A. (Rossiyskaya Akademiya Nauk, Komi Nauchnyy Tsentr, Institut Biologii, Syktyvkar, Russian Federation); Pastukhov, A. V.; Novakovskiy, A. B.; Biazi, K.; Marushchak, M. and Elsakov, V. V. Vliyaniye landshaftnykh i klimaticheskikh faktorov na glubinu sezonnogo protaivaniya v pochvakh bugristykh torfyanikov (na primere ploshchadki CALM R52) [Influence of landscapes and climate on active layer depth in peatlands; CALM R52 Site as example]: Kriosfera Zemli = Earth Cryosphere, 23(2), p. 62-71 (English sum.), illus. incl. 3 tables, sketch map, 28 ref., April 2019.
The data obtained during the five-year (2013-2017) active layer monitoring in soils of permafrost peat plateau at the Circumpolar Active Layer Monitoring site R52 (Seida) in the European Northeast of Russia (the Usa River basin) are presented. Analysis of the impact of landscape and climatic factors allowed one to estimate the spatial-temporal differentiation of the active layer thickness. The spatial heterogeneity of seasonal thaw depth is governed by the topography of the peatland site dominated by drained peat mounds covered with shrubby moss vegetation and bare peat circles, with fens occupying a small area only. Relative elevation and surface soil moisture are found to be major factors affecting the active layer thickness within peat mounds covered with shrubby moss vegetation. In the bare peat circles, snow depth and microtopography exert a primary control on thaw depth. The active layer thickness dynamics during the research period was characterized by a positive trend. The airfrost number is interpreted as the most effective climatic parameter for estimation of inter-annual dynamics of the active layer depth in peat soils.
2021051089 Tarbeyeva, A. M. (Moskovskiy Gosudarstvennyy Universitet, Moscow, Russian Federation); Lebedeva, L. S.; Yefremov, V. S.; Krylenko, N. V.; Surkov, V. V.; Shamov, V. V. and Lutsenko, T. N. Usloviya i protsessy formirovaniya chetkovidnogo rusla maloy reki kriolitozony (na primere r Shestakovka, tsentral'naya Yakutiya) [Processes and conditions of bead-shaped channel formation in small rivers of the permafrost zone; Shestakovka River in central Yakutia as an example]: Kriosfera Zemli = Earth Cryosphere, 23(2), p. 38-49 (English sum.), illus. incl. sect., sketch map, 29 ref., April 2019.
Observations on the thermal regime of soils, formation and destruction of river ice were carried out, the hydrological characteristics were obtained and the geological structure of a small river in central Yakutia was investigated in order to identify the processes forming the beaded shape of the river channel. This type of a channel is widespread in permafrost regions, characterized by alternation of the channel extension, "beads", and narrow runs, predetermining the specific thermal, water and ice regime of the river, which leads to alternation of the periods of mixing and stratification of the water, to the presence of pressured unfrozen water in winter, and the appearance of ice mounds and local underwater taliks. Despite the presence of thawed sediments under the channel, thermokarst does not play a significant role in the modern formation of the beads due to the low ice content in the underlying sediments. The maximum water discharges flow above the ice cover, so the expansion and deepening of the pools by the water flow is possible only when anomalously high flow events occur after thawing of ice in the channel. Significant mechanisms of modern deepening and widening of the beads can consist in repeated extrusion and subsequent removal of suspended matter and bottom sediments under cryostatic pressure during freezing of the channel, as well as stresses that occur on the ice-ground contact during freezing, leading to destruction of the banks.
2021048254 Velikin, S. A. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Institut Merzlotovedeniya, Vilyuyskaya Nauchno-Issledovatel'skaya Merzlotnaya Stantsiya, Chernyshevskiy Settlement, Russian Federation). Ispol'zovaniye tekhnologiy 3D-obrabotki dannykh elektrotomografii v zadachakh monitoringa sostoyaniya osnovaniy gidrotekhnicheskikh sooruzheniy v kriolitozone [Application of 3D electric tomography for monitoring of dam foundations in the permafrost zone]: Geofizika (Moscow), 2019(1), p. 25-32 (English sum.), illus., 15 ref., 2019.
Self-potential (SP) anomalies of diffusion-adsorption (DA) origin frequently considered as filtration anomalies that are the case of false discovery. In nature DA anomalies are widespread while filtration anomalies are more in the rear. To distinguish these anomalies the author considers correlation of SP potential and apparent resistivity values along the same profile. In case of DA anomalies there is a linear correlation between SP potential and logarithm of apparent resistivity.
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2021050582 Althuizen, Inge (NORCE Norwegian Research Centre, Bergen, Norway); Christiansen, Casper; Dörsch, Peter; Kjaer, Sigrid; Michelsen, Anders; Risk, David; Westermann, Sebastian and Lee, Hanna. Abrupt thaw enhances annual global warming potential of an actively degrading permafrost peatland [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12231, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Global scale warming has led to permafrost thaw, which may release large amounts of carbon to the atmosphere as CO2 and CH4, potentially accelerating global warming (i.e. a positive feedback). However, uncertainty in the mechanisms controlling carbon mineralization is compounded by concurrent changes in soil hydrology associated with permafrost thaw. Thawing permafrost can lead to surface water accumulation in some areas and seasonal or permanent soil drying in areas where permafrost thaw opens up new channels of water to penetrate into the groundwater system. The complexity of the hydrologic response to permafrost thaw increases the challenge in generating reliable estimates of the permafrost carbon climate feedback. Furthermore, limited observational data exist to i) quantify the effects of permafrost thaw on net tundra carbon budgets, particularly on an annual basis, and ii) as well as constrain the underlying processes governing carbon release under aerobic and anaerobic conditions. Here, we investigated how changes in local hydrology affects CO2 and CH4 release from permafrost soils by establishing a field gradient study in northern Norway (69°N), where recent abrupt degradation of permafrost created thaw ponds in palsa-mire ecosystems. The site exhibits a natural gradient of permafrost thaw, which also corresponds to a strong hydrological gradient (i.e. dry palsas with intact permafrost, seasonally inundated thaw slumps, and thaw ponds). Since 2017, we have used a range of manual and automated techniques to measure changes in vegetation, soil and water microclimate, biogeochemistry, and soil CO2 and CH4 concentrations and efflux across the permafrost thaw gradient. Our preliminary results show that abrupt permafrost thaw and landscape subsidence -- both intermediate slumping and thaw pond formation -- increase net annual carbon loss from this type of subarctic wetland. Permafrost thaw approximately doubles CO2 emissions from thaw slumps compared to vegetated or soil palsas. Furthermore, CH4 release greatly increased across the permafrost thaw gradient. While vegetated palsas were small sinks of atmospheric CH4 during the growing season, permafrost thaw slumping and pond formation led to a dramatic increase in CH4 efflux compared to bare palsas. In contrast, bare soil palsas on were the most important source of N2O. Soil profile CO2 and CH4 concentrations in thawed permafrost plots were overall highly enriched relative to palsa profiles, reflecting soil conditions with inundated pore space and low oxygen availability along the permafrost thaw gradient. We therefore conclude that abrupt thaw will increase annual carbon loss in subarctic palsa wetlands. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-12231
2021050647 Aref, Mohammad M. (Universität Potsdam, Institute of Geosciences, Potsdam, Germany); Bookhagen, Bodo and Strecker, Manfred R. Evolution of large bedrock landslides in the south-central Andes of NW Argentina [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14234, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Deep-seated, slow moving bedrock landslides are significant natural disasters with severe socio-economic repercussions. During the past decades, an acceleration of these hazards has been reported globally due to changes in seasonal freeze-thaw cycles, permafrost thawing, infrastructure development and other anthropogenic sources, changes of precipitation and groundwater levels, and variation in seismic activity. Interferometric Synthetic Aperture Radar(InSAR) is a powerful tool to map landslides movement from space and the Sentinel 1 C-band radar mission provides a high temporal resolution data source to investigate seasonal and intra-annual changes of landslide behaviour. To construct a 2D/3D displacement field, we decompose a combination of different look angles and InSAR ascending and descending tracks of different sensors including Sentinel and ALOS 1 PALSAR data. The ionospheric delay for InSAR observations is estimated with a split range-spectrum technique because significant ionospheric total electron content variation is common in our study area in the Central Andes. Both statistical phase-based and weather model estimation approaches are implemented to minimize the effect of tropospheric signal on InSAR observations. Our observations identify several areas with rapid translational slide movements exceeding 5-10 cm/y. Multi-annual and inter-annual behaviour of deformation is extracted through time series analysis and a hierarchical clustering approach is used to identify geographic areas with similar characteristics and rates. We show the wide-spread spatial distribution of unstable hill slopes in the Eastern Cordillera of the south-central Andes, especially at high elevations where field observations are difficult. We identify driving forces to be a combination of pre-existing geologic structures and climatic parameters.
DOI: 10.5194/egusphere-egu21-14234
2021050627 Bearzot, Francesca (Universita Milano Bicocca, Department of Earth and Environmental Sciences, Milan, Italy); Garzonio, Roberto; Di Mauro, Biagio; Hauck, Christian; Delaloye, Reynald; Di Cella, Umberto Morra; Cremonese, Edoardo; Pogliotti, Paolo; Crosta, Giovanni Battista; Colombo, Roberto; Frattini, Paolo and Rossini, Micol. Monitoring the dynamics of an alpine rock glacier with repeated UAV and GNSS data [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14788, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Time series of rock glaciers (RG) movements in the European Alps indicate an acceleration in permafrost creep in recent decades in relation to an increase in ground temperatures and water content. In this work, we analyse the geomorphological changes of an active RG located in the Western European Alps, in Valtournenche Valley (AO, Italy). Five photogrammetric surveys were realized on the RG between 2015 to 2019, using a senseFly eBee RTK and a DJI Phantom 4 UAVs. During UAV acquisitions, 21 ground control points were placed all over the study area and their coordinates were measured in GNSS RTK mode, for georeferencing each photogrammetric model. The monitoring activity also includes GNSS campaigns, carried out annually since 2012, which provides high accurate surface displacement measurements but limited to 54 points. In addition, in July 2015 two Electrical Resistivity Tomography profiles were performed, with the Wenner-Schlumberger configuration, to identify the internal structure and potential ground ice content inside the main body of the RG. The Structure-from-Motion technique was used to generate orthophotos and digital surface models with a resolution of 5 cm/px. Successively, we estimated the three-dimensional change of the surface displacements (surface lowering and accumulation processes) of the RG comparing pairs of point clouds, using the Multiscale Model to Model Cloud Comparison (M3C2 plug-in). A first evaluation of the horizontal surface velocity was computed identifying corresponding features manually on the orthophotos through time and a second assessment was performed based on repeated GNSS campaigns. Surface velocity obtained by orthophotos manual identifications is validated against repeated GNSS measurements. The analysis shows a good correlation at all magnitudes with a R2 equal to 0.988 and RMSE of 26 cm. The RG shows a clear distinction in creep dynamics between a faster western part (values up to 1.8 m/y) and a slower eastern part, with values below 0.1 m/y in the most upstream part. Considering the period 2012-2020, maximum peak of surface velocity is reached in 2015, followed by a velocity decrease until 2017-2018 when the smallest movements are recorded. However, the following two years (2018-2019 and 2019-2020) are marked by a gradual increase in surface horizontal velocity. The absence of significant of any significant movement in the upstream part is related to the lack of permafrost consecutive to the development and advance of a local glacier during the Little Ice Age. The slower eastern part is almost gently inclined and corresponds to a currently degrading part of the RG, with an ice melt-induced subsidence of up to 5 cm/year. The faster area is also the steepest, where the driving stress is also the largest. The presence of the frozen ground at depth, probably its structure and thermal state, but also the topographical settings are the main factors explaining the current RG flow pattern. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-14788
2021050641 Bedington, Michael (Plymouth Marine Laboratory, Plymouth, United Kingdom); Torres, Ricardo; Polimene, Luca; Wallhead, Phillip; Juhls, Bennett; Palmtag, Juri; Strauss, Jens and Mann, Paul J. Impacts of riverine terrestrial organic matter on the lower trophic levels of an Arctic shelf ecosystem [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12897, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The Arctic ocean receives 11% of the entire global river discharge via several great Arctic rivers that drain vast catchments underlain with carbon-rich permafrost. Arctic marginal shelf seas are therefore heavily influenced by terrestrial dissolved organic matter (tDOM) supply, influencing coastal biogeochemical processes and food-webs, as well as physio-chemical properties (e.g. stratification or nutrient concentrations). Whilst carbon and associated macronutrients supplied by tDOM may enhance the nutrient and carbon substrates for lower trophic levels (phytoplankton/zooplankton), promoting increased local and regional productivity, it can also have opposing effects through a series of indirect processes (e.g. increased light absorption limiting light penetration through the water column). Understanding the relative importance and timing of these processes, and how they vary spatially, is necessary to identify how land-ocean interfaces currently operate. Future climate scenarios indicate increased quantities of riverine tDOM delivered to the near-shore, with increased freshwater runoff and greater terrestrial permafrost thaw and erosion. This is likely to be exacerbated by the disappearance of seasonal sea ice cover and increased coastal erosion rates. We can therefore expect changes in planktonic phenology and productivity, with concomitant changes in bacterial and higher trophic level success. Understanding how these factors interact and may change under future climate scenarios is therefore critical to predict the future impact on shelf sea Arctic ecosystems and the ecosystem services they provide. In the Changing Arctic Carbon cycle in the cOastal Ocean Near-shore (CACOON) project (UK-Germany collaboration) we are using coupled hydrodynamic-biogeochemical models in the extensive shallow shelf of the Laptev sea to explore the relationship between these factors. The ecosystem model ERSEM has been adapted to explicitly include a tDOM component. This coupled model system allows us to investigate both the role of present day tDOM in an Arctic coastal ecosystem and to project the potential impacts of increased tDOM input in future.
DOI: 10.5194/egusphere-egu21-12897
2021050628 Bertone, Aldo (University of Bologna, Department of Biological, Geological and Environmental Sciences, Bologna, Italy); Barboux, Chloé; Brardinoni, Francesco; Delaloye, Reynald; Mair, Volkmar; Pellegrinon, Gabriel; Monier, Tania and Strozzi, Tazio. A complementary kinematic approach to inventory rock glaciers applied to case studies of the Swiss and Italian Alps [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14661, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Rock glaciers are the best visual expression of creeping mountain permafrost. Their dynamics, which largely depend on climatic forcing, provide information about the mountain permafrost and may locally pose risk to infrastructures. The International Permafrost Association (IPA) Action Group on Rock glacier inventories and kinematics, launched in 2018, fosters the activities of a research network focused on the definition of standardized guidelines for inventorying rock glaciers, including information on rock-glacier displacement rate. The ESA Permafrost_CCI project further sustains this initiative, and proposes a standardized method to implement kinematics-based rock glacier inventories. The proposed method exploits interferometric data from spaceborne Synthetic Aperture Radar (InSAR) to derive the kinematic information of existing or newly-compiled rock glacier inventories. In particular, areas identified as slope movements within rock glacier polygons are delineated on interferograms as "moving areas", and are assigned a velocity class. Subsequently, a specific kinematic class is assigned to each rock glacier unit according to the velocity class and extension of the relevant moving areas. This method is applied on two regions: the Western part of the Swiss Alps and the South-Western part of the South Tyrol (Italian Alps). Both are located at the same latitude, with rock glaciers in the Swiss part lying at slightly higher altitudes, and experiencing higher mean annual precipitation. Rock glacier polygons were drawn from existing inventories, the kinematic information was extracted exploiting InSAR data acquired between 2018 and 2019 from the Sentinel-1 constellation. In the Swiss and Italian parts, we inventoried 660 and 783 moving areas (1443 in total). Collectively, it was possible to assign a kinematic attribute to 913 rock glaciers, providing a more objective and quantitative activity classification (compared to the qualitative active, inactive, and relict categories). In the Swiss part, 14% of the rock glaciers are moving in the magnitude order of a meter/year or faster, 43% in the magnitude order of one to several dm/yr, 36% from one to several cm/yr, the others are with unreliable movements (7%). In the Italian part, these percentages are 1% (meter/year or faster), 42% (one to several dm/yr), 39% (one to several cm/yr) and 18% (no reliable), respectively. Preliminary analyses on the Italian part are conducted on 467 additional rock glaciers recognized as geomorphologically relict: 68% are not moving or not moving fast enough to be detected, 9% have sectors moving up to several cm/yr, and the remaining 23% of relict rock glaciers have no reliable information on movement. Preliminary results show how this approach allows to provide complementary kinematic information to the geomorphological approach, improving the knowledge on the activity status in a given time and in a given region. Since several studies have reported trends towards displacement acceleration, applying this approach over long periods will allow assessing the response of a wide selection of landforms to (warmer) climatic forcing. Furthermore, this approach is a very useful tool to help select representative rock glaciers of a region, on which to apply more accurate monitoring approaches.
DOI: 10.5194/egusphere-egu21-14661
2021050661 Blöcher, Johanna (Czech University of Life Sciences, Faculty of Environmental Sciences, Prague, Czech Republic); Mayer, Petr and Kuraz, Michal. Simple numerical strategies to model freezing in variably-saturated soil with the standard finite element method [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-873, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
An accurate representation of freezing and thawing in soil covers many applications including simulation of land surface processes, hydrology, and degrading permafrost. Freezing and thawing tightly couple water and heat flow, where temperature and temperature gradients influence the water flow and phase changes, and water content and flow influence the heat transport. In most porous media, the interface between liquid and frozen water is not sharp and a slushy zone is present. A common observation of freezing soil is water accumulation towards the freezing front due to Cryosuction. A mathematical model can be derived using the Clausius-Clapeyron equation, which allows the derivation of a soil freezing curve relating temperature to pressure head. This is based on the assumption that soil freezing is similar to soil drying. Many models still lack features such as Cryosuction. We believe that this may be due to numerical issues that model developers face with their current solver and discretization setup. Implementing freezing soil accurately is not straight-forward. Using the Clausius-Clapeyron creates a discontinuity in the freezing rate and latent heat at the freezing point and little attention has been paid to the adequate description of their numerical treatment and computational challenges. Discretizing this discontinuous system with standard finite element methods (standard Galerkin type) can cause spurious oscillations because the standard finite element method uses continuous base/shape functions that are incapable of handling discontinuity of any kind within an element. Similarly, standard finite difference methods are also not capable of handling discontinuities. In this contribution, we present the application of regularization of the discontinuous term, which allows the use of the standard finite element method. We implemented the model in the open-source code base DRUtES (www.drutes.org). We verify this approach on synthetic and various real freezing soil column experiments conducted by Jame (1977) and Mizoguchi (1990).
DOI: 10.5194/egusphere-egu21-873
2021050615 Bolch, Tobias (University of Saint Andrews, School of Geography and Sustainable Development, St. Andrews, United Kingdom); King, Owen; Ferguson, James; Mölg, Nico; Vieli, Andreas and Pellicciotti, Francesca. Evolution and hydrological importance of debris-covered glaciers and ice-debris landforms [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14966, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Debris-covered glaciers and ice-debris landforms such as rock glaciers are common in many mountain areas of Earth, are important for the debris transport system and contain a significant amount of ice. The presence, amount and characteristics of debris can strongly alter ice melt and the evolution of glaciers and ice-debris landforms. However, debris cover and debris content exhibits strong spatial variations. To understand the evolution and physiognomies of ice-debris complexes it is important to consider both debris supply and transport as well as deposition, which are impacted by climatic conditions, topography and lithology. A holistic approach to the investigation of these coupled complex systems seems thus crucial. In this talk we present findings from our work based on in-situ investigations (e.g. geophysical methods), multitemporal high resolution remotely sensed imagery (including historical aerial images, Corona KH 4 images and recent data) and modelling (including surface ablation, englacial debris transport and ice flow) conducted on selected debris-covered glaciers and ice debris landforms worldwide. Results show that a significant amount of ice is buried beneath debris cover in glacier forefields, ice cored moraines and rock glaciers under permafrost conditions. The response of rock glaciers to climate change is heterogenous with overall increasing velocities and on average only slight surface elevation changes. Slight increases in surface elevation occur their termini while debris-covered glaciers show on average a clear signal of surface lowering and decreasing velocities. The heterogeneity of debris cover can to a large extend be explained by the different debris sources and the characteristics of the headwalls while englacial and supraglacial streams favour the evolution of rough surface topography on debris-covered glaciers with the presence of ice cliffs. The findings will be illustrated with specific examples from the Swiss Alps, the Himalaya and the Tien Shan.
DOI: 10.5194/egusphere-egu21-14966
2021050613 Brauchle, Joerg (Deutsches Zentrum für Luft- und Raumfahrt, Institut für Optische Sensorsysteme, Berlin, Germany); Bucher, Tilman; Hein, Daniel; Berger, Ralf; Gessner, Matthias and Stebner, Karsten. Capabilities and applications of MACS aerial camera systems for environmental research [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16302, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
High resolution remote sensing under harsh environmental condition on special carriers requires instruments which are more flexible und more ruggedized than devices off the shelf. Particularly addressing environmental research in polar and high alpine regions, a family of cameras developed by the DLR is presented. The MACS systems are specifically made for the use on airborne platforms. Due to scalability, small sensors like single sensors on rugged fixed-wing UAVs can be realized. The configuration can be extended to RGB/NIR/TIR oblique viewing rigs with up to 5 coordinated cameras on manned aircraft. By processing such images, photogrammetric products like change detection, classification, elevation models and mapping mosaics are derived for regional areas. Further applications are the evaluation of algorithms in the field of AI for spaceborne imagery or the investigation of acquiring a particular combination of spectral bands. These systems are able to deal with extreme illumination conditions and flight envelopes. Based on recent projects, the presentation shows examples and experiences, such as acquisition of the world's highest glacier in Nepal, thermal infrared permafrost mapping of Ny Alesund/Svalbard and sea ice measurements with a ground resolution of 3cm in the Fram Strait. Ideas for future sensors are indicated such as an UAV-based system with instant image transmission and a lightweight, high resolution sensor for stratospheric platforms.
DOI: 10.5194/egusphere-egu21-16302
2021050645 Bruckner, Thomas (University of Erlangen-Nuremberg, Institute of Geography, Erlangen, Germany); Farias-Barahona, David; Fürst, Johannes; Mergili, Martin; Sepulveda, Sergio; Pena, Humberto; Casassa, Gino and Braun, Matthias. Reconstruction constraints on the Estero Parraguirre ice-rock avalanche in 1987, Central Andes of Chile; new insights from remote sensing and numerical modeling [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13019, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
On 29th of November of 1987, a large ice-rock avalanche occurred in a permafrost area of the central Andes of Chile. This event has been considered one of the most destructive events in that area in the last decades. The ice-rock avalanche initiated at an elevation of 4350 m, above the Estero Parraguirre. Due to the large amounts of ice and snow and the high potential energy, this avalanche developed into a debris flow propagating down the valley, reaching a travel distance of approx. 57 km after 2 hours. On the way, many people lost their lives, and two hydroelectric power plants were destroyed. The avalanche was likely triggered by warm temperature anomalies and snow build-up at high elevation linked to the concurrent and strong El Nino event in 1987. In this study, we use old topographic maps and aerial photographs, acquired just a few days after the event, and satellite imagery to constrain the trigger volume and to accurately compute the general mass displacement. A physically-based multi-phase mass flow model is employed to retrace the dynamics and characteristics of this debris-flow event. Previous studies suggested a trigger volume of about 6 x 106 m3. After entrainment along the flow path, the debris flow reached a total volume of 15 x 106 m3. First results of our study suggest that the trigger volume was significantly larger than previously thought. The next step is to shed light on possible entrainment scenarios, which will be constrained by and assessed against the observed elevation changes/mass displacement. The reconstruction of this event is crucial to better assess future events and thus to develop successful mitigation strategies.
DOI: 10.5194/egusphere-egu21-13019
2021050656 Cao, Mengli (Alfred-Wegener-Institut, Geoscience Department, Bremen, Germany); Hefter, Jens; Tiedemann, Ralf; Lembke-Jene, Lester and Mollenhauer, Gesine. Deglacial records of terrigenous organic matter accumulation off the Yukon and Amur Rivers using lignin phenols and long-chain n-alkanes as biomarkers [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-10875, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Anthropogenic climate change has profound impacts on Arctic temperatures, with consequences for Arctic ecosystems and landscapes, and the stability of organic-rich permafrost deposits. When mobilized, these permafrost deposits might release vast amounts of greenhouse gases. We use periods of past rapid warming in the high latitudes as analogues to study the ecological changes and effects on permafrost stability under climate change. We used marine sediment cores from the Bering and Okhotsk Sea continental margins, off the mouths of the Yukon and Amur rivers, to study two types of terrigenous biomarkers, which trace different terrestrial organic carbon (OC) components and transport pathways, and cover the early deglaciation to the early Holocene. The Yukon basin remains within the permafrost-affected region today, whereas the Amur basin changed from being subject to complete permafrost cover during the last glacial to permafrost-free conditions today. Vascular plant-derived lignin phenols were analyzed and compared to published n-alkane content data. The carbon- and sediment-normalized contents of the vanillyl phenols (V), syringyl phenols (S), and cinnamyl phenols (C) phenols (?8 and ?8) reflect the content of lignin dominantly transported by river runoff. The C/V and S/V ratios serve to distinguish between woody and non-woody tissues of angiosperms and gymnosperms. The acid to aldehyde ratios of V and S phenols ((Ad/Al)V and (Ad/Al)S) indicate the degree of lignin degradation. In addition, the ratio of 3,5-dihydroxybenzoic acid to V (3,5Bd/V) likely reflects the wetland extent, while lignin reflects primarily transportation into the marine sediment via surface runoff. In contrast, the n-alkane contents represent primarily terrigenous organic matter eroded from deeper deposits and a second marker for wetland extent via the Paq index. Lignin and n-alkane mass accumulation rates (MAR) can thus be used to reconstruct the mobilization of different carbon pools and the relative timing of the processes leading to their export to the ocean. The MAR of biomarkers and the wetland indicators 3,5 Bd/V and Paq start to increase in the Bering Sea sediment during the early deglaciation (19-14.6 ka BP), while no obvious change in lignin MAR in the Okhotsk Sea occurred during this time. We observe distinct peaks of mass accumulation rates, wetland indices and indicators for degradation of lignin (Ad/Al) in both sediment cores during the warm Bolling-Allerod (12.9-14.6 ka BP) and Pre-Boreal (9-11.5 ka BP) intervals, and during the Younger Dryas cold spell (11.5-12.9 ka BP). In contrast, in the Okhotsk Sea, the ratios of S/V and C/V did not change before the Preboreal. Our biomarker data suggest that the permafrost in the Yukon basin may have started to be remobilized by inland warming leading to wetland development in the early deglaciation, while the onset of permafrost degradation in the Amur basin occurred during the Preboreal.
DOI: 10.5194/egusphere-egu21-10875
2021050633 Cheng, Yifan (National Center for Atmospheric Research, Boulder, CO); Newman, Andrew; Swenson, Sean; Lawrence, David; Craig, Anthony and Hamman, Joseph. A novel application of an Adaptive Surrogate-based Modeling Optimization (ASMO) for the Community Territory System Model (CTSM) in Alaska [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3776, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Climate-induced changes in snow cover, river flow, and freshwater ecosystems will greatly affect the indigenous groups in the Alaska and Yukon River Basin. To support policy-making on climate adaptation and mitigation for these underrepresented groups, an ongoing interdisciplinary effort is being made to combine Indigenous Knowledge with western science (URL: https://www.colorado.edu/research/arctic-rivers/). A foundational component of this project is a high fidelity representation of the aforementioned land surface processes. To this end, we aim to obtain a set of reliable high-resolution parameters for the Community Territory System Model (CTSM) for the continental scale domain of Alaska and the entire Yukon River Basin, which will be used in climate change simulations. CTSM is a complex, physically based state-of-the-science land surface model that includes complex vegetation and canopy representation, a multi-layer snow model, as well as hydrology and frozen soil physics necessary for the representation of streamflow and permafrost. Two modifications to the default CTSM configuration were made. First, we used CTSM that is implemented with hillslope hydrology to better capture the fine-scale hydrologic spatial heterogeneity in complex terrain. Second, we updated the input soil textures and organic carbon in CTSM using the high-resolution SoilGrid dataset. In this study, we performed a multi-objective optimization on snow and streamflow metrics using an adaptive surrogate-based modeling optimization (ASMO). ASMO permits optimization of complex land-surface models over large domains through the use of surrogate models to minimize the computational cost of running the full model for every parameter combination. We ran CTSM at a spatial resolution of 1/24th degree and a temporal resolution of one hour using the ERA5 reanalysis data as the meteorological forcings. The ERA5 reanalysis data were bias-corrected to account for the orographic effects. We will discuss the ASMO-CTSM coupling workflow, performance characteristics of the optimization (e.g., computational cost, iterations), and comparisons of the default configuration and optimized model performance. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-3776
2021050646 Cicoira, Alessandro (Swiss Federal Institute of Technology, Snow and Avalanche Simulation Laboratory, Lausanne, Switzerland); Blatny, Lars; Li, Xingyue; Troilo, Fabrizio; Kenner, Robert and Gaume, Johan. A material point method for alpine mass movements [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5258, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Gravitational mass movements pose a threat to the population of numerous mountainous regions around the globe. Climate change affects these processes and their related hazards by influencing their triggering, flow and deposition mechanisms, overall increasing the number of natural catastrophes. Numerical modelling is an essential tool for the analysis and the management of such hazards: it allows the quantitative description of the runout and pressure of rapid mass movements and may contribute to better understand the effects of climate change on their size, frequency, and dynamics. Several depth-averaged models are already operational and commonly applied by practitioners and scientists. Yet, a unified model able to simulate multi-phase cascading events, including their initiation, propagation, entrainment and finally impact on structures is still missing. Hence, more detailed models are required to advance our understanding of the physics behind gravitational mass movements and ultimately to contribute improving hazard assessment and risk management. Here, we present some preliminary results of the development of a hybrid Eulerian-Lagrangian Material Point Method (MPM) with finite strain elasto-plasticity to simulate in a unified manner: i) permafrost instabilities and failure initiation; ii) rock and ice avalanche dynamics; iii) solid-fluid interaction and phase transition from rock avalanches to debris-flows. In order to simulate the mechanical behaviour of rock and ice, we propose a Drucker-Prager softening constitutive law accounting for cohesion, internal and residual friction. We calibrate this constitutive law on the basis of state of the art laboratory experiments. The model is applied to synthetic slope geometries to evaluate their stability and investigate subsequent rock fragmentation processes. At a larger scale, dynamics simulations are compared against observations of full-scale process chains. In particular, we implement the two real-scale cases of the rock-avalanche from the Piz Cengalo (CH) and ice- and snow-avalanche from the Grandes Jorasses (IT). The 3D implementation of the model allows to accurately reproduce the initial conditions of an event and complex phenomena such as reported ballistic trajectories non adherent to the ground. Secondary releases due to the mass flow (such as snow or glacier-ice entertainment) and phase changes can be simulated realistically. We test the potential of the model in a broad range of settings and highlight the major gaps to be filled in the near future.
DOI: 10.5194/egusphere-egu21-5258
2021050602 Corbea-Pérez, Alejandro (Universidad de Oviedo, Department of Mining Exploitation and Prospecting, Oviedo, Spain); Vieira, Goncalo; Recondo, Carmen; Baptista, Joana; Calleja, Javier F. and Lee, Hyoungseok. Evaluating the potential of MODIS-LST for monitoring ground surface temperatures in the maritime Antarctic (Barton Peninsula, King George Island, Antarctic) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-10415, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Land surface temperature is an important factor for permafrost modelling as well as for understanding the dynamics of Antarctic terrestrial ecosystems (Bockheim et al. 2008). In the South Shetland Islands the distribution of permafrost is complex (Vieira et al. 2010) and the use of remote sensing data is essential since the installation and maintenance of an extensive network of ground-based stations are impossible. Therefore, it is important to evaluate the applicability of satellites and sensors by comparing data with in-situ observations. In this work, we present the results from the analysis of land surface temperatures from Barton Peninsula, an ice-free area in King George Island (South Shetlands). We have studied the period from March 1, 2019 to January 31, 2020 using data from the Moderate Resolution Imaging Spectroradiometer (MODIS) Land Surface Temperature (LST) and in-situ data from 6 ground temperature loggers. MOD11A1 and MYD11A1 products, from TERRA and AQUA satellites, respectively, were used, following the application of MODIS quality filters. Given the scarce number of high-quality data as defined by MODIS, all average LST with error=2K were included. Dates with surface temperature below -20°C, which are rare in the study area, and dates when the difference between MODIS and in-situ data exceeded 10°C were also examined. In both cases, those days on which MOD09GA/MYD09GA products showed cloud cover were eliminated. Eight in-situ ground temperature measurements per day were available, from which the one nearest to the time of satellite overpass was selected for comparison with MODIS-LST. The results obtained show a better correlation with daytime data than with nighttime data. Specifically, the best results are obtained with daytime data from AQUA (R2 between 0.55 and 0.81). With daytime data, correlation between MODIS-LST and in-situ data was verified with relative humidity (RH) values provided by King Sejong weather station, located in the study area. When RH is lower, the correlation between LST and in-situ data improves: we obtained correlation coefficients between 0.6-0.7 for TERRA data and 0.8-0.9 for AQUA data with RH values lower than 80%. The results suggest that MODIS can be used for temperature estimation in the ice-free areas of the Maritime Antarctic. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-10415
2021050617 Cusicanqui, Diego (Université Grenoble Alpes, Institut de Géosciences de l'Environnement, Grenoble, France); Rabatel, Antoine; Bodin, Xavier; Vincent, Christian; Thibert, Emmanuel; Duvillard, Pierre Allain and Revil, André Using historical aerial imagery to assess multidecadal kinematics and elevation changes; application to mountain permafrost in the French Alps [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16371, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Glacial and periglacial environments are highly sensitive to climate change, even more in mountain areas where warming is faster and, as a consequence, perennial features of the cryosphere like glaciers and permafrost have been fast evolving in the last decades. In the European Alps, glaciers retreat and permafrost thawing have led to the destabilization of mountain slopes, threatening human infrastructures and inhabitants. The observation of such changes at decadal scales is often limited to sparse in situ observations. Here, we present three study cases of mountain permafrost sites based on a multidisciplinary approach over almost seven decades. The goal is to investigate and quantify morphodynamic changes and understand the causes of these evolutions. We used stereo-photogrammetry techniques to generate orthophotos and (DEMs) from historical aerial images (available, in France since 1940s). From this, we produced diachronic comparison of DEMs to quantify vertical surface changes, as well as feature tracking techniques of multi-temporal digital orthophotos for estimating horizontal displacement rates. Locally, high-resolution datasets (i.e. LiDAR surveys, UAV acquisitions and Pléiades stereo imagery) were also exploited to improve the quality of photogrammetric products. In addition, we combine these results with geophysics (ERT and GPR) to estimate the ice content, geomorphological surveys to describe the complex environments and the relationship with climatic forcing. The first study case is the Laurichard rock glacier, where we were able to quantify changes of emergence velocities, fluxes, and volume. Together with an acceleration of surface velocity, important surface lowering have been found over the period 1952-2019, with a striking spatiotemporal reversal of volume balance. The second study site is the Tignes glacial and periglacial complex, where the changes of thermokarstic lakes surface were quantified. The results suggest that drainage probably affects the presence and the evolution of the largest thermorkarst. Here too, a significant ice loss was found on the central channel concomitant to an increase in surface velocities. The third study site is the Chauvet glacial and periglacial complex where several historical outburst floods are recorded during the 20th century, likely related to the permafrost degradation, the presence of thermokarstic lakes, and an intra-glacial channel. The lateral convergence of ice flow, due to the terrain subsidence caused by the intense melting, may cause the closure of the channel with a subsequent refill of the thermokarstic depression and finally a new catastrophic event. Our results highlight the important value of historical aerial photography for having a longer perspective on the evolution of the high mountain cryosphere, thanks to accurate quantification of pluri-annual changes of volume and surface velocity. For instance, we could evidence : (1) a speed-up of the horizontal displacements since the 1990s in comparison with the previous decades; (2) an important surface lowering related to various melting processes (ice-core, thermokarst) for the three study sites; (3) relationships between the observed evolution and the contemporaneous climate warming, with a long-term evolution controlled by the warming of the ground and short-term changes that may relate to snow or precipitation or to the activity of the glacial-periglacial landforms.
DOI: 10.5194/egusphere-egu21-16371
2021050598 de Bruin, Jelte (Universiteit Wageningen, Environmental Sciences Group, Wageningen, Netherlands); Bense, Victor and van der Ploeg, Martine. Determining permafrost active layer thermal properties of the Qinghai-Tibet Plateau using field observations and numerical modelling [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9377, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Permafrost has become thermally instable as a result of surface warming, which has an uncertain impact on future hydrogeological conditions and the associated mobilisation of carbon and release into the atmosphere. Numerical modelling can provide insights into future permafrost spatial and temporal dynamics. However, crucial observational data of permafrost active-layer thermal properties; thermal conductivity and heat capacity are sparse, resulting in a large uncertainty in forecasts of the future development of the active layer. Therefore, our study aims to develop a methodology to numerically determine the permafrost thermal and soil properties from observations of temperature time-series in the subsurface, in order to reduce the current model uncertainty. We used an ensemble of 786 numerical 1D permafrost models fitted against observed active layer temperature data from the Qinghai-Tibetan Plateau (QTP)1 to find the optimal values for the soil thermal conductivity, heat capacity and porosity. Optimal parameter values are determined by finding the minimum RMSE, KGE and using the Russell error measure. We find optimized values for bulk volumetric heat capacity 1.3-1.85 106J/m3°C , bulk thermal conductivity 0.9-1.1 W/m°C and porosity between 0.25-0.35 (-), which are in agreement with typical ranges reported in literature for similar settings on the QTP. In a further sensitivity study, the 3 optimal parameter combinations were used to model the active layer thickness over a 100-year period with a gradual hypothetical air temperature increase of 5°C. The results indicate a substantial difference in rate of thawing and increase in depth of the active layer for these models, with a maximum time-lag of roughly 15 years in before the models reach the same active layer thawing depth. The study shows how numerical models can be applied to determine active layer thermal properties without the need for field samples, opening up new possibility for in-situ permafrost temperature observation.
DOI: 10.5194/egusphere-egu21-9377
2021050584 de Vrese, Philipp (Max Planck Institute for Meteorology, Land in the Earth System, Hamburg, Germany) and Brovkin, Victor. Legacy effects of climate overshoot scenarios in permafrost-affected regions [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13099, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Difficulties to quickly reduce carbon emissions to levels compatible with the long-term goal of the Paris Agreement increase the likelihood of scenarios that temporarily overshoot the respective climate targets. We used simulations with JSBACH, the land surface component of the Max-Planck-Institute for Meteorology's Earth system model MPI-ESM1.2 to investigate the long-term response of the terrestrial Arctic to climate stabilization at such a climate target. In particular, we seek to answer the question whether the state of permafrost-affected soils and the Arctic carbon cycle could converge to different equilibria depending on the climate trajectory that precedes climate stabilization at 1.5°C above pre-industrial levels. To this end, we compare simulations that are forced with the same non-transient atmospheric conditions -- corresponding to the 1.5°C-target -- but started from different initial conditions. One simulation was initialized with the conditions before and one simulation with the conditions after a temperature overshoot which follows SSP5-8.5 until the year 2100 subsequent to which the atmospheric conditions are reversed to the 1.5°C-target. Our results reveal that feedbacks between water-, energy- and carbon cycles allow for path-dependent steady-states in permafrost-affected regions. These depend on the soil organic matter content at the point of climate stabilization, which is significantly affected by the soil carbon loss resulting from overshooting the climate target. Here, the simulated steady-states do not only differ with respect to the amount of carbon stored in the frozen fraction of the soil, but also with respect to soil temperatures, the soil water content and even net primary productivity and soil respiration.
DOI: 10.5194/egusphere-egu21-13099
2021050611 Delage, Emmanuel (Université Clermont Auvergne, Laboratoire Magmas et Volcans, Clermont, France); van Wyk de Vries, Benjamin; Philippe, Meven; Conway, Susan J.; Morino, Costanza; Llerena, Nelida Manrique; Contreras, Rigoberto Aguilar; Soncco, Yhon; Saemundsson, Thorsteinn and Helgason, Jon Kristinn. Visualising and experiencing geological flows in virtual reality [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8801, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Resilience to natural hazards depends on a person's ability to envision an event and its consequences. While real life experience is precious, a real event experience is rare, and sometimes fatal. So, virtual reality provides a way to getting that experience more frequently and without the inconvenience of demise. Virtual reality can also enhance an event to make it more visible, as often things happen in bad weather, at night or in other inconvenient moments. The 3DTeLC software (an output from an ERASMUS+ project, URL: http://3dtelc.lmv.uca.fr/) can handle high-resolution 3D topographic models and the user can study natural hazard phenomena with geological tools in virtual reality. Topography acquired from drone or plane acquisitions, can be made more accessible to researchers, public and stakeholders. In the virtual environment a person can interact with the scene from the first person, drone or plane point of view and can do geological interpretation at different visualization scales. Immersive and interactive visualization is an efficient communication tool (e.g. Tibaldi et al 2019 - Bulletin of Volcanology DOI: URL: https://dx.doi.org/10.1007/s00445-020-01376-6). We have taken the 3DTeLC workflow and integrated a 2.5D flow simulation programme (VOLCFLOW-C). The dynamic outputs from VOLCFLOW-C are superimposed into a single visualization using a new tool developed from scratch, which we call VRVOLC. This coupled visualization adds dynamic and realistic understanding of events like lahars, lava flows, landslides and pyroclastic flows. We present two examples of this, one developed on the Digital Terrain Model of Chachani Volcano, Arequipa Peru, to assist with flood and lahar visualisation (in conjunction with INGEMMET, UNESCO IGCP project 692 Geoheritage for Resilience and Cap 20-25 Clermont Risk). And another with an Icelandic debris slide that occurred in late 2014 possibly related to permafrost degradation (in conjunction with the ANR PERMOLARDS project). We thank out 3DTeCL colleagues, without which this would not be possible, and acknowledge financial support for the PERMOLARDS project from French National Research Agency (ANR-19-CE01-0010), and this is part of UNESCO IGCP 692 Geoheritage for Resilience
DOI: 10.5194/egusphere-egu21-8801
2021050625 Dennis, Donovan P. (German Research Centre for Geosciences, Potsdam, Germany); Scherler, Dirk; Niedermann, Samuel; Hippe, Kristina; Wittmann, Hella; Ravanel, Ludovic; Tremblay, Marissa; Guralnik, Benny and Lupker, Maarten. Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc Massif using in situ cosmogenic 3He-10Be-14C [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15023, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed "frost-cracking window." Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background "steady-state" erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides 3He-10Be-14C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity. From cosmogenic 10Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak's surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr-1 and 1.0 mm yr-1, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic 3He-derived paleotemperatures. The corresponding cosmogenic 14C/10Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed "buzzsaws" operating on glacial-interglacial timescales. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-15023
2021050654 dos Santos, Fernando Acacio Monteiro (Universidade de Lisboa, Lisbon, Portugal); Farzamian, Mohammad; Esteves, Miguel; Vieira, Goncalo and Hauck, Christian. Development of low cost autonomous electrical resistivity monitoring systems for continuous active-layer monitoring in harsh environment [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12883, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The last overview of the thermal state in the Western Antarctic Peninsula shows that permafrost is close to 0oC in the region. This fact reinforces the importance to study the evolution of permafrost and active layer in the region. However, monitoring of the active layer and permafrost dynamics in Antarctica is generally conducted using only 1-dimensional borehole and meteorological data, which restricts the analysis to point information that often lack representatives at the field scale. In addition, being an invasive technique, the drilling of boreholes disturbs the subsurface and is not feasible to conduct over large areas, especially in environmentally sensitive ecosystems such as the Antarctic. In this context, we developed automated electrical resistivity tomography (A-ERT) systems using a 4POINTLIGHT_10W (Lippmann) instrument with a solar panel-driven battery and multi-electrode configuration for autonomous and non-invasive monitoring of active layer and permafrost in Antarctica. The A-ERT measurements are sensitive to the electrical conductivity of materials, allowing to distinguish between frozen and unfrozen soil and thus to monitor the active layer dynamics including freezing, thawing, water infiltration and refreezing processes in a spatial context. We deployed the system in two monitoring sites at Deception and Livingstone Islands (South Shetland Islands, Maritime Antarctica) for quasi-continuous measurements at 6h interval from early 2019 and 2020 respectively. Detailed investigation of the A-ERT data and obtained models reveals that the A-ERT system can detect the seasonal active-layer freezing and thawing events with very high resolution. In addition, the brief surficial refreezing and thawing of the active layer during summer and winter respectively were well resolved by A-ERT data, highlighting the significance of the continuous A-ERT monitoring setup which enables detecting fast changes in the active layer during short-lived extreme meteorological event. This suggests that the A-ERT measurements can provide valuable subsurface information to improve the spatio-temporal understanding of active layer and permafrost dynamics with very high resolution and minimal environmental disturbance in Antarctica. The set-up is very flexible and can be used with different configurations to investigate different depth ranges for site-specific detailed investigation.
DOI: 10.5194/egusphere-egu21-12883
2021050642 Ewald, Andreas (Universität Salzburg, Department of Geography and Geology, Salzburg, Austria); Otto, Jan-Christoph; von Hagke, Christoph and Lang, Andreas. Combining surface characteristics and rock-mechanical properties to identify unstable glacier headwalls on a regional scale [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15947, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Global warming triggered retreat of alpine glaciers exposes large surface areas in the proglacial zone but also a significant headwall area above. The thermal and mechanical changes in the headwalls foster destabilisation and trigger rockfalls. Patterns of headwall destabilisation are complex due to variable rock strength and external atmospheric forcing and results are usually site-specific and do not allow regional scale stability assessments. In order to understand sensitivity of alpine rock walls to instability following glacier retreat on a regional scale, we classify glacier headwalls based on a combination of surface and rock-mechanical characteristics. This includes (i) a semi-automatic detection of glacier headwalls using object-based image analysis, (ii) a morphometric analysis of headwalls, (iii) a regionalisation of rock-mechanical properties of the bedrock, and (iv) an analysis of other site conditions like potential permafrost occurrence and glacier retreat. We apply this workflow in the Hohe Tauern Range, Austria, to identify headwalls in recently deglaciated cirques and valleys with the highest potential for increased slope instability and rock fall processes. For the central Hohe Tauern Range high-resolution digital datasets of topography, geology, glacier extent, and permafrost distribution are available. eCognition was used for semi-automatic headwall detection. Segmentation is derived from DEM derivatives like slope, aspect and a TPI-based landform classification. Headwall segments are classified based on slope and elevation thresholds that have been identified and validated using manual headwall mapping. Foliation information extracted from regional geological maps was compared to local geological surveys in order to specify type of foliation. Bedrock structure was interpolated based on a non-continuous azimuth distribution approach (NADIA). By combining topographic and geological data we derived a geotechnical classification scheme from cataclinal to anaclinal slopes with various dip-slope relations. Preliminary results indicate that semi-automated headwall detection largely reproduces local observations. However, we observed an overestimation of 61% of total headwall area compared to the manually mapped headwalls. The rate of undetected areas is considered to be negligible. Overestimation mainly arises from inclusion of high-altitude profile straight slopes, matching the classification requirements without obvious glacial imprints such as schrundlines. Landform classification revealed a dominance of cataclinal slopes in the entire landscape. At steeper terrain, including glacier headwalls, anaclinal slopes prevail. Unstable situations such as overdip slopes are rare and predominantly found in the lower sections of glacier headwalls marked by schrundlines. Steep permafrost rock walls were found to be almost exclusively anaclinal, which might be considered as site-specific. Our approach offers a new methodology to detect deglaciating headwalls and characterise their sensitivity to instability at a regional scale. Our classification can be used for up-scaling local headwall dynamics for a better anticipation of the destabilisation pattern of steep alpine slopes following glacier retreat.
DOI: 10.5194/egusphere-egu21-15947
2021050606 Freitas, Pedro (Universidade de Lisboa, Centre of Geographical Studies, Lisbon, Portugal); Vieira, Goncalo; Mora, Carla; Canario, Joao; Folhas, Diogo and Vincent, Warwick F. Ultra-high resolution assessment of potential impacts of vegetation shadows on satellite-derived spectral signals from small thermokarst lakes in the boreal forest-tundra transition zone (subarctic Canada) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15405, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Warming of the circumpolar north is accelerating permafrost thaw, with implications for landscapes, hydrology, ecosystems and the global carbon cycle. In subarctic Canada, abrupt permafrost thaw is creating widespread thermokarst lakes. Little attention has been given to small waterbodies with area less than 10,000 m2, yet these are biogeochemically more active than larger lakes. Additionally, the landscapes where they develop show intense shrubification and terrestrialization processes, with increases in area and height of shrub and tree communities. Tall vegetation that is colonizing waterbody margins can cast shadows that impact productivity, thermal regime and the water spectral signal, which in satellite data generates pixels with mixed signatures between sunlit and shaded surfaces. We undertook UAV surveys using optical and multispectral sensors at long-term monitoring sites of the Center for Northern Studies (CEN) in subarctic Canada, from the sporadic (SAS/KWAK) to the discontinuous (BGR) permafrost zones in the boreal forest-tundra transition zone. This ultra-high spatial resolution data enabled spectral characterization and 3D reconstruction of the study areas. Ultra-high resolution digital surface models were produced to model shadowing at satellite overpass time (WorldView, PlanetScope and Sentinel-2). We then analyzed the impacts of surrounding vegetation and cast shadows on lake surface spectral reflectance derived from satellite imagery. Ultra-high resolution UAV data allows generating accurate shadow models and can be used to improve the assessment of errors and accuracy of satellite data analysis. Particularly, we identify different spectral signal impacts of cast shadows according to lake color, which highlight the need for special attention of this issue onto lakes with more turbidity.
DOI: 10.5194/egusphere-egu21-15405
2021050644 Fullin, Nicola (University of Ferrara, Dipartimento di Fisica e Scienze della Terra, Ferrara, Italy); Ghirotti, Monica; Donati, Davide and Stead, Doug. Characterising the kinematics of the Joffre Peak landslides using a combined numerical modeling-remote sensing approach [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-154, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Geological structure and kinematics are often the most important factors controlling the stability of high rock slopes; their characterization can provide insights that are instrumental in understanding the behaviour of a slope in addition to its evolution with time. In this research, we used a combined remote sensing-numerical modelling approach to characterize the Joffre Peak landslides (British Columbia, Canada), two rock avalanche events that occurred on May, 13th and 16th 2019. The May 13th event involved a volume of 2-3million m3, and resulted in a runout distance of 6 km. The May 16th event involved a volume of 2-3 million m3, and a runout distance of 4 km. The failure was likely promoted by permafrost degradation and reduction in shear strength along geological structures (in our simulation checked in dry condition). Using a wide range of techniques, including Structure-from-Motion photogrammetry, virtual outcrop discontinuity mapping, GIS analysis, and 3D distinct element numerical modelling, we investigated the important role that structural geology and slope kinematics played prior to and during the Joffre landslide events. In particular, we demonstrate that i) a very persistent, sub-vertical geological structures formed the lateral and rear release surfaces of the rock mass volume that failed as two discrete landslide events. The landslide blocks were separated by one such sub-vertical structure, which remains visible in the fresh landslide scar; ii) the first block, failed on May 13th 2019, involving planar sliding failure mechanism, possibly promoted by progressive failure and propagation of discontinuities along the basal surface. The detachment of this block enhanced the kinematic freedom of the second landslide block, which, on May 16th, failed as wedge/toppling mechanism; iii) the first landslide block acted as a key block; its displacement and failure provided the kinematic freedom for the occurrence of the second landslide. In this paper we show that combining remote sensing mapping and 3D numerical modelling allows for the identification of the structural geological features controlling the stability and evolution of high rock slopes in alpine environments. We also show that constraining and validating the numerical modelling results using historical data is of paramount importance to ensure that the correct failure mechanism of the landslides is simulated.
DOI: 10.5194/egusphere-egu21-154
2021050649 Gadal, Sébastien (Aix-Marseille Université, Aix-Marseille, France); Zakharov, Moisei; Kamicaityte, Jurate; Savvinova, Antonina and Danilov, Yuri. Environmental vulnerability modeling in the extensively urbanized Arctic center integrating remote sensing, landscape mapping, and local knowledge [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16268, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Arctic extensively urbanized centers are subject to the impact of many negative environmental phenomena progressing in terms of global climate change and regional development in Yakutia in the context of poor and missing databases. For this reason, the modeling of the risk exposures is based on combining the remote sensing, and local knowledge of inhabitants. According to the occurrences of the natural hazards, the territorial management and the decision-making system require the identification and assessment of natural risks to which the rural populations localized in the towns and villages are exposed, for example, in the urban center of Khamagatta located at 70km to the North from Yakutsk near the Lena River. The main environmental vulnerability exposures are seasonal: springtime floods between May and June, the forest fires from June to August, the cyclic permafrost degradation, and river erosion impacts. The current vulnerability impacts, damages to the lands and the settlements, and the populations risk exposures are analyzed from the maps of vulnerabilities created from remote sensing satellite Sentinel 2A/B series, with the local knowledge of the inhabitants of Khamagatta who lived and perceived all events. All the data generated, maps, models of vulnerability exposures, and local knowledge are integrated, combined, and merged into the geographic information system (GIS). The GIS modeling combines the risk of natural hazards and the damages, and the risk knowledge and perceptions of the inhabitants. Land uses, Landscape classification, and the land cover is made by Object-Based Image Analysis (OBIA) using an optical time series of Sentinel 2 images (2015-2020) including the population knowledge for the recognition of the environmental vulnerabilities. The methodological approach included the participation of local people in workshops through discussion and participatory mapping, questionnaires, and interviews in two stages. The first stage included the development of the knowledge database for a comprehensive understanding of the life of the local population, including the forms of adaptation to the negative natural phenomena. The collected information is delocalized and integrated into the GIS. The second stage consisted of validation and discussion, including stakeholders (municipality and rescue services) to increase the reliability and legitimacy of the research results. Perceptions of the inhabitants of Khamagatta are correlated with the maps of risk exposures generated by remote sensing to increase the accuracy of the environmental process modeling and landscape classification. The combination of the environmental change dynamics, the impacts on the towns and villages with the human perception and experience constitutes the main base supporting the prevention mapping of the natural hazards. This data could be very useful in planning the development of Arctic towns and villages and proposing evolution scenarios and urban planning models and strategies for increasing their resilience and adaptation to climate change consequences.
DOI: 10.5194/egusphere-egu21-16268
2021050583 Georgievski, Goran (Max Planck Institute for Meteorlogy, Bremerhaven, Germany); de Vrese, Philipp; Hagemann, Stefan and Brovkin, Victor. High-northern-latitudes permafrost extend in MPI-ESM simulations of SSP126 and SSP585 [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12828, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The representation of permafrost related processes in Earth System Models (ESM) remains a challenge. A recent collaboration between two related projects (Kohlenstoff im Permafrost (Carbon in Permafrost) - KoPf, and Study Of the Development of Extreme Events over Permafrost areas - SODEEP) yielded a new vertical structure of the soil column in JSBACH, the land component of the Max Planck Institute (MPI) for Meteorology ESM (MPI-ESM). This feature resulted in a better representation of the vertical soil moisture dynamics and the energy transfer due to soil freezing and thawing, which is particularly relevant for the high northern latitudes. Although, air temperatures are simulated reasonably well with the MPI-ESM, care must be taken not to introduce a bias when implementing new processes in the model or changing existing parametrizations. Here we investigate the permafrost extent in two Shared Socioeconomic Pathways (SSP) simulations (SSP126 and SSP585) with the MPI-ESM using prescribed ocean surface boundary conditions. Our results show a consistency between terrestrial and atmospheric dynamics, when comparing the permafrost extent determined on basis of simulated active layer thickness (soil variable) and Day Degree Thaw Index (DDTI; atmospheric variable). The latter is calculated as the annual sum of positive average daily 2m air temperatures and its square root can be used as an indicator of annual maximum thaw depth. The SSP126 simulation shows that both DDTI and thaw depth stabilize within the range of the present-day interannual variability, while SSP585 indicates a substantial deepening of the active layer - resulting in a complete disappearance of near-surface permafrost in large parts of the high northern latitudes - and DDTI in SSP585 simulation increases in excess of 2000°C. These values at present characterize northern mid-latitudes i.e. landscapes not underlined by permafrost. A preliminary analysis indicates that the decline of the permafrost extent in SSP585 occurs mostly during the second half of 21st century. Furthermore, the SSP585 simulation also shows an increase in the number of extreme events relevant for permafrost degradation. The investigated extreme climate patterns (as defined in the frame of the SODEEP project) include abrupt warming (defined as occurrence of annual mean temperature above 5-year running mean) and increase in seasonal precipitation anomalies, as well as changes in specific snow characteristics.
DOI: 10.5194/egusphere-egu21-12828
2021050634 Han, Li (Ruprecht-Karls-Universität Heidelberg, Department of Geography, Heidelberg, Germany) and Menzel, Lucas. Terrestrial hydroclimatic variability in basins of southern Siberia driven by different states of permafrost degradation [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-4682, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Changes in the cryosphere caused by global warming are expected to alter the hydrologic system, with inevitable consequences for freshwater availability to humans and ecosystems. Quantitative understandings of the historical hydrologic changes in response to permafrost degradation is essential for projecting future changes with respect to the continuing and possibly intensifying warming. Here we investigate past hydro-climatic changes over three southern Siberian basins with diverse permafrost properties: in the Selenga catchment, all three permafrost types occur, i.e., discontinuous, sporadic and isolated permafrost; the Lena Basin (at gauge Tabaga) is mostly underlain by discontinuous permafrost, while the Aldan is dominated by continuous permafrost. Based on the reconstruction of terrestrial water storage changes (TWS) from the GRACE satellite mission and hydro-climatic time series over the period 1984-2013, our results show very different change patterns in the TWS among these three basins. There is an unprecedented reduction of TWS (-9.8 km3) in the Selenga basin, but remarkable increases (14.4 km3 and 13.1 km3) in the Lena-Tabaga and Aldan basins, respectively. The diverse changes in TWS, runoff and precipitation over each basin suggest different hydrologic response mechanisms to permafrost degradation under a warming climate. The Selenga, dominated by lateral degradation (i.e., decreasing permafrost extent), suffers severe water loss via deep infiltration of water that was previously stored close to the surface, which induces a drier surface and subsurface drainage system. In contrast, in the Aldan basin, determined by vertical degradation, thicker active layers develop which sustain a water-rich surface and subsurface environment. In the Lena-Tabaga basin finally, which is characterized by both lateral and vertical degradations, the further development of lateral degradation has led to a stronger increase in groundwater storage in comparison to surface runoff during the increased precipitation states, suggesting a potentially groundwater-dominated hydrologic system in this basin. Our findings are of great importance for the regional water management in permafrost-affected regions under ongoing warming.
DOI: 10.5194/egusphere-egu21-4682
2021050595 Hauck, Christian (Université de Fribourg, Department of Geosciences, Fribourg, Switzerland). Electrical resistivity contrast between active layer and frozen ground; why is it similar for different sites over many order of magnitudes? [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15414, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Geophysical techniques are widely used to detect and characterise permafrost. Among them, electrical methods such as Electrical Resistivity Tomography (ERT) or Vertical Electrical Soundings (VES), which measure the electrical resistivity of the ground, have a very long and successful tradition in all kind of permafrost applications in polar, mountain and subsea terrain. Similarly, electromagnetic methods, which measure the inverse of resistivity, the electrical conductivity, are more and more used for permafrost applications. The reason for the good applicability lies in the fact that the electrical resistivity of most materials increases sharply at the freezing point. The nature of this increase is due to several processes such as the reduction of the electrically conducting liquid water content during phase change and the reduced mobility of the ions in the liquid phase. How much the resistivity increases upon freezing depends therefore on the specific physical properties of the material (e.g. porosity, pore water resistivity), which can be completely different for the different permafrost environments and lithospheric materials. On the other hand, when plotting the resistivity of the active layer against the resistivity of the frozen layer for a multitude of data sets, most permafrost occurrences follow a similar quantitative relationship, although their lithopsheric and geomorphological characteristics are very different. In this contribution we will analyse the reasons for this relationship using theoretical considerations and verify it with a newly compiled resistivity data set of more than 100 permafrost occurrences. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-15414
2021050607 Heim, Birgit (Alfred-Wegener-Institut Helmholtz-Zentrum fuer Polar und Meeresforschung, Polar Terrestrial Environmental Systems, Potsdam, Germany); Shevtsova, Iuliia; Kruse, Stefan; Herzschuh, Ulrike; Buchwal, Agata; Rachlewicz, Grzegorz and Bartsch, Annett. Landscape-level remote sensing for upscaling of land cover, above ground biomass and above ground carbon fluxes in the Lena River delta (northern Yakutia, Russia) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13497, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Vegetation biomass is a globally important climate-relevant terrestrial carbon pool. Landsat, Sentinel-2 and Sentinel-1 satellite missions provide a landscape-level opportunity to upscale tundra vegetation communities and biomass in high latitude terrestrial environments. We assessed the applicability of landscape-level remote sensing for the low Arctic Lena Delta region in Northern Yakutia, Siberia, Russia. The Lena Delta is the largest delta in the Arctic and is located North of the treeline and the 10°C July isotherm at 72° Northern Latitude in the Laptev Sea region. We evaluated circum-Arctic harmonized ESA GlobPermafrost land cover and vegetation height remote sensing products covering subarctic to Arctic land cover types for the central Lena Delta. The products are freely available and published in the PANGAEA data repository under URL: https://doi.org/10.1594/PANGAEA.897916, and URL: https://doi.org/10.1594/PANGAEA.897045. Vegetation and biomass field data (30 m´30 m plot size) and shrub samples for dendrology were collected during a Russian-German expedition in summer 2018 in the central Lena Delta. We also produced a regionally optimized land cover classification for the central Lena Delta based on the in-situ vegetation data and a summer 2018 Sentinel-2 acquisition that we optimized on the biomass and wetness regimes. We also produced biomass maps derived from Sentinel-2 at a pixel size of 20 m investigating several techniques. The final biomass product for the central Lena Delta shows realistic spatial patterns of biomass distribution, and also showing smaller scale patterns. However, patches of high shrubs in the tundra landscape could not spatially be resolved by all of the landscape-level land cover and biomass remote sensing products. Biomass is providing the magnitude of the carbon flux, whereas stand age is irreplaceable to provide the cycle rate. We found that high disturbance regimes such as floodplains, valleys, and other areas of thermo-erosion are linked to high and rapid above ground carbon fluxes compared to low disturbance on Yedoma upland tundra and Holocene terraces with decades slower and in magnitude smaller above ground carbon fluxes. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-13497
2021050591 Hesse, Jan Christopher (Technische Universität Darmstadt, Department of Geothermal Science and Technology, Darmstadt, Germany); Kupfernagel, Jan-Henrik; Schedel, Markus; Welsch, Bastian; Nuller, Lutz and Sass, Ingo. Experimental investigation of freeze-thaw processes in soils and grouting materials [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15247, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Freezing and thawing in the subsurface is often related to complex technical handling of possible influences on the engineered structures (e.g. permafrost or geothermal heat pumps). Freeze-thaw processes in the vicinity of borehole heat exchangers can significantly impair the system. However, for groundwater protection and thermal efficiency, the hydraulic and thermal integrity of such systems must be permanently ensured for the complete operation time. Detailed knowledge on freeze-thaw processes in porous media, such as soils or geotechnical grouts, and the driven parameters, is still pending. Freezing in porous media does not occur as a sudden transition from pure liquid water to the ice phase, but rather within a freezing interval strongly depending on various boundary conditions such as soil type or pore water chemistry. As the content of frozen and unfrozen water has a strong impact on material properties, it is essential to have suitable information about the different factors influencing freezing processes as well as the thermo-hydraulic-mechanical (THM) effects on porous media due to phase change. Thus, a THM laboratory experiment was developed and built to gain more knowledge on freeze-thaw processes and their effects on soil and grouting materials. The experiment consists of a modified triaxial test, enabling for controlled temperature and hydraulic flow conditions, that is combined with an ultrasonic measurement device to determine the unfrozen water content. In this contribution, results of the THM experiment are presented, whereas the following parameters were investigated: The freezing interval using P-wave velocity, freezing pressure as well as axial and radial volume expansion due to ice formation as well as the influence of hydraulic flow on the ice formation. First, benchmark experiments were conducted on well-characterized solid rock samples to avoid any influence of a variable sample pore structure during the experiments. Further experiments focused on the investigation of soil samples of different texture classes. For upscaling to real scale applications, the experimental findings will be implemented in numerical models.
DOI: 10.5194/egusphere-egu21-15247
2021050599 Immerzeel, Walter (Universiteit Utrecht, Utrecht, Netherlands); Martin, Léo; Brun, Fanny; Westermann, Sebastian; Fiddes, Joel; Kraaijenbrink, Philip and Mathys, Tamara. Modeling recent permafrost thaw and associated hydrological changes in an endorheic Tibetan watershed [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12135, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Permafrost has a crucial influence on sub-surface water flow and thus on the hydrology of catchments. Its thawing drives the release of frozen water and a transition from surface-water-dominated systems to groundwater-dominated systems. In the context of global warming, these hydrological modifications are of critical importance for extensive headwater regions such as the Qinghai-Tibet Plateau (QTP) and the Himalayas. Permafrost covers a significant proportion of these regions (40% of the QTP), which are major water towers of the world. Therefore, improving our understanding and ability to quantify these changes are a key scientific challenge. Many watersheds of the QTP have seen their hydrologic budget modified over the last decades as evidenced by strong lake level variations observed in endorheic basins. Yet, the possible contribution of permafrost thaw to these variations has not been assessed. The Paiku basin (central Himalayas, southern TP) finds itself in a similar situation. The Paiku lake at the lowest point of this endorheic basin has exhibited important level decreases since the 70's and thus offers the possibility to test the potential role of permafrost thaw on these hydrologic changes. We present permafrost simulations at the scale of the basin over the last four decades that reproduce its degradation as result of regional climatic change. We use the Cryogrid model to simulate the surface energy balance, snow pack dynamics and the ground thermal regime while accounting for the phase changes and the soil water budget. Because the surface radiative, sensitive and latent heat fluxes in alpine environments are strongly dependent on the physiography the model is forced with distributed downscaled forcing data produced with the TOPOSCALE model to account for this spatial variability. Simulated surface conditions are evaluated against meteorological data acquired within the basin and remotely sensed surface temperatures. The simulations show that, contrary to large scale estimates of permafrost occurrence probability, an important part of the basin is underlaid by permafrost. During the simulated period, permafrost distribution and active layer exhibit limited variations (active layer deepening neighboring 10 cm) yet deeper ground temperatures (7-8 m) show a warming close to 0.8 degree (0.2 degree per decade). These first results tend to indicate a limited contribution of permafrost to the catchment hydrology over the last decades, a trend that could be significantly modified in the future if the simulated warming rates persist and lead to increased permafrost thawing
DOI: 10.5194/egusphere-egu21-12135
2021050624 Kellerer-Pirklbauer, Andreas (Universität Graz, Institute of Geography and Regional Science, Graz, Austria) and Lieb, Gerhard Karl. Ground thermal contrasts and variability at an alpine pyramidal peak in central Austria (Innerer Knorrkogel, Venediger Mountains) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12588, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Ground temperatures in alpine environments are severely influenced by slope orientation (aspect), slope inclination, local topoclimatic conditions, and thermal properties of the rock material. Small differences in one of these factors may substantially impact the ground thermal regime, weathering by freeze-thaw action or the occurrence of permafrost. To improve the understanding of differences, variations, and ranges of ground temperatures at single mountain summits, we studied the ground thermal conditions at a triangle-shaped (plan view), moderately steep pyramidal peak over a two-year period (2018-2020). We installed 18 monitoring sites with 23 sensors near the summit of Innerer Knorrkogel (2882 m a.s.l.), in summer 2018 with one- and multi-channel datalogger (Geoprecision). All three mountain ridges (east-, northwest-, and southwest-facing) and flanks (northeast-, west-, and south-facing) were instrumented with one-channel dataloggers at two different elevations (2840 and 2860 m a.s.l.) at each ridge/flank to monitor ground surface temperatures. Three bedrock temperature monitoring sites with shallow boreholes (40 cm) equipped with three sensors per site at each of the three mountain flanks (2870 m a.s.l.) were established. Additionally, two ground surface temperature monitoring sites were installed at the summit. Results show remarkable differences in mean annual ground temperatures (MAGT) between the 23 different sensors and the two years despite the small spatial extent (0.023 km2) and elevation differences (46 m). Intersite variability at the entire mountain pyramid was 3.74°C in 2018/19 (mean MAGT: -0.40°C; minimum: -1.78°C; maximum: 1.96°C;) and 3.27°C in 2019/20 (mean MAGT: 0.08°C; minimum: -1.54°C; maximum: 1.73°C;). Minimum was in both years at the northeast-facing flank, maximum at the south-facing flank. In all but three sites, the second monitoring year was warmer than the first one (mean +0.48°C) related to atmospheric differences and site-specific snow conditions. The comparison of the MAGT-values of the two years (MAGT-2018/19 minus MAGT-2019/20) revealed large thermal inhomogeneities in the mountain summit ranging from +0.65° (2018/19 warmer than 2019/20) to -1.76°C (2018/19 colder than 2019/20) at identical sensors. Temperature ranges at the three different aspects but at equal elevations were 1.7-2.2°C at ridges and 1.8-3.7°C at flanks for single years. The higher temperature range for flank-sites is related to seasonal snow cover effects combined with higher radiation at sun-exposed sites. Although the ground temperature was substantially higher in the second year, the snow cover difference between the two years was variable. Some sites experienced longer snow cover periods in the second year 2019/20 (up to +85 days) whereas at other sites the opposite was observed (up to -85 days). Other frost weathering-related indicators (diurnal freeze-thaw cycles, frost-cracking window) show also large intersite and interannual differences. Our study shows that the thermal regime at a triangle-shaped moderately steep pyramidal peak is very heterogeneous between different aspects and landforms (ridge/flank/summit) and between two monitoring years confirming earlier monitoring and modelling results. Due to high intersite and interannual variabilities, temperature-related processes such as frost-weathering can vary largely between neighbouring sites. Our study highlights the need for systematic and long-term ground temperature monitoring in alpine terrain to improve the understanding of small- to medium-scale temperature variabilities. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-12588
2021050655 Klahold, Johanna (Rheinisch-Westfälische Technische Hochschule Aachen, Institute for Applied Geophysics and Geothermal Energy, Aachen, Germany); Hauck, Christian and Wagner, Florian. Ice or rock matrix? Improved quantitative imaging of alpine permafrost evolution through time-lapse petrophysical joint inversion [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-4509, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Quantitative estimation of pore fractions filled with liquid water, ice and air is one of the prerequisites in many permafrost studies and forms the basis for a process-based understanding of permafrost and the hazard potential of its degradation in the context of global warming. The volumetric ice content is however difficult to retrieve, since standard borehole temperature monitoring is unable to provide any ice content estimation. Geophysical methods offer opportunities to image distributions of permafrost constituents in a non-invasive manner. A petrophysical joint inversion was recently developed to determine volumetric water, ice, air and rock contents from seismic refraction and electrical resistivity data. This approach benefits from the complementary sensitivities of seismic and electrical data to the phase change between ice and liquid water. A remaining weak point was the unresolved petrophysical ambiguity between ice and rock matrix. Within this study, the petrophysical joint inversion approach is extended along the time axis and respective temporal constraints are introduced. If the porosity (and other time-invariant properties like pore water resistivity or Archie exponents) can be assumed invariant over the considered time period, water, ice and air contents can be estimated together with a temporally constant (but spatially variable) porosity distribution. It is hypothesized that including multiple time steps in the inverse problem increases the ratio of data and parameters and leads to a more accurate distinction between ice and rock content. Based on a synthetic example and a field data set from an Alpine permafrost site (Schilthorn, Swiss Alps) it is demonstrated that the developed time-lapse petrophysical joint inversion provides physically plausible solutions, in particular improved estimates for the volumetric fractions of ice and rock. The field application is evaluated with independent validation data including thaw depths derived from borehole temperature measurements and shows generally good agreement. As opposed to the conventional petrophysical joint inversion, its time-lapse extension succeeds in providing reasonable estimates of permafrost degradation at the Schilthorn monitoring site without a priori constraints on the porosity model.
DOI: 10.5194/egusphere-egu21-4509
2021050651 Klein, Konstantin (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, Potsdam, Germany); Lantuit, Hugues; Heim, Birgit; Doxaran, David; Nitze, Ingmar and Juhls, Bennet. High resolution turbidity modelling in Arctic nearshore environments [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-10073, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The Arctic is directly impacted by climate change. The increase in air temperature drives the thawing of permafrost and an increase in coastal erosion and river discharge. This leads to a greater input of sediment and organic matter into coastal waters, which substantially impacts the ecosystems, the subsistence economy of the local population, and the climate because of the transformation of organic matter into greenhouse gases. Yet, the patterns of sediment dispersal in Arctic nearshore zones and their role in the Carbon cycle are not well known due to difficult accessibility and challenging weather conditions. In this study we present the first multi-sensor turbidtiy- reflectance relationship that was specifically calibrated for Arctic nearshore environments. Field data was collected during summer seasons 2018 and 2019 in the inner shelf waters of the Canadian Beaufort Sea close to Herschel Island Qikiqtaruk. The turbidity-reflectance relationship was calibrated to mid to high spatial resolution sensors which are used in ocean color remote sensing, including Landsat 8, Sentinel 2, and Sentinel 3, using the relative spectral response functions. The results for Landsat 8 and Sentinel 2 are very promising and showcase the possibility to resolve sediment accumulations, sediment pathways and filaments at higher detail than before. Both sensors are able to resolve high turbidity close to the coast with values comparable to our field measurements. Sentinel 3, on the other hand, is too coarse to resolve these features but provides great applicability due to its high temporal resolution. The transferability of these relationships to nearshore environments outside the Canadian Beaufort Sea has to be tested in the future with the potential to map the sediment dispersal in nearshore environments at a circum- Arctic scale.
DOI: 10.5194/egusphere-egu21-10073
2021050630 Lehmann, Benjamin (University Savoie Mont Blanc, Le Bourget-du-Lac, France); Anderson, Robert S.; Bodin, Xavier; Valla, Pierre G. and Carcaillet, Julien. Reconstruction of the dynamics and origin of rock glaciers in an alpine environment [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2627, 6 ref., 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Rock glaciers are one of the most frequent cryospheric landform in mid-latitude mountain ranges. They influence the evolution of alpine environments on short (years to decades) and long (centuries to millennia) time scales. As a visible expression of mountain permafrost as well as an important water reserve in the form of ground ice, rock glaciers are seen as increasingly important in the evolution of geomorphology and hydrology of mountain systems in the context of climate change and deglaciation. On longer time scales, rock glaciers transport boulders produced by the erosion of the headwall upstream and downstream and therefore participate in shaping mountain slopes. Despite their importance, the dynamics and origin of rock glaciers are poorly understood. In this study, we propose to address two questions: 1) How does the dynamics of rock glaciers change over time? 2) What is the origin of rock glaciers and what is their influence on the evolution of alpine environments? These two questions require an evaluation of the surface velocity field of rock glaciers by relating short and long time scales. To solve this problem, we combine complementary methods including remote sensing, geochronology with a mechanical model of rock glacier dynamics. We apply this approach to the rock glacier complex of the Vallon de la Route in the Massif du Combeynot (French alps). In order to reconstruct the displacement field of the rock glacier on modern time scales, we used remote sensing methods (i.e., image correlation and InSAR). Over longer periods (103 to 104 years), we used cosmogenic terrestrial nuclides (TCN) dating. By applying this methodology to boulder surfaces at different positions along the central flow line of the rock glacier, from the headwall to its terminus, we will be able to convert the exposure ages into surface displacement. The use of dynamic modelling of rock glaciers [6] will allow us to relate the surface kinematics to short to long time scales. It will then be possible to discuss the age, origin of rock glaciers and how topo-climatic and geomorphological processes control their evolution in Alpine environment.
DOI: 10.5194/egusphere-egu21-2627
2021050620 Li, Dongfeng (National University of Singapore, Department of Geography, Singapore, Singapore); Lu, Xixi and Zhang, Ting. Fluvial sediment fluxes response to modern climate change and human activities in the Tibetan Plateau and its margins [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-130, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Sediment flux in cold environments is a crucial proxy to link glacial, periglacial, and fluvial systems and highly relevant to hydropower operation, water quality, and the riverine carbon cycle. However, the long-term impacts of climate change and multiple human activities on sediment flux changes in cold environments remain insufficiently investigated due to the lack of monitoring and the complexity of the sediment cascade. Here we examine the multi-decadal changes in the in-situ observed fluvial sediment fluxes from two types of basins, namely, pristine basins and disturbed basins, in the Tibetan Plateau and its margins. The results show that the fluvial sediment fluxes in the pristine Tuotuohe headwater have substantially increased over the past three decades (i.e., a net increase of 135% from 1985-1997 to 1998-2017) due to the warming and wetting climate. We also quantify the relative impacts of air temperature and precipitation on the increases in the sediment fluxes with a novel attribution approach and finds that climate warming and intensified glacier-snow-permafrost melting is the primary cause of the increased sediment fluxes in the pristine cold environment (Tuotuohe headwater), with precipitation increase and its associated pluvial processes being the secondary driver. By contrast, the sediment fluxes in the downstream disturbed Jinsha River (southeastern margin of the Tibetan Plateau) exhibit a net increase of 42% from 1966-1984 to 1985-2010 mainly due to human activities such as deforestation and mineral extraction (contribution of 82%) and secondly because of climate change (contribution of 18%). Then the sediment fluxes dropped by 76% during the period of 2011-2015 because of the operations of six cascade reservoirs since 2010. In an expected warming and wetting climate for the region, we predict that the sediment fluxes in the pristine headwaters of the Tibetan Plateau will continue to increase throughout the 21st century, but the rising sediment fluxes from the Tibetan Plateau would be mostly trapped in its marginal reservoirs. Overall, this work has provided the sedimentary evidence of modern climate change through robust observational sediment flux data over multiple decades. It demonstrates that sediment fluxes in pristine cold environments are more sensitive to air temperature and thermal-driven geomorphic processes than to precipitation and pluvial-driven processes. It also provides a guide to assess the relative impacts of human activities and climate change on fluvial sediment flux changes and has significant implications for water resources stakeholders to better design and manage the hydropower dams in a changing climate. Such findings may also have implications for other cold environments such as the Arctic, Antarctic, and other high mountainous basins.
DOI: 10.5194/egusphere-egu21-130
2021050637 Li, Zhen (GFZ German Research Centre for Geosciences, Potsdam, Germany); Kempka, Thomas; Spangenberg, Erik and Schicks, Judith. Quantification of methane hydrate formation in the Large-scale Reservoir Laboratory Simulator (LARS) by numerical simulations [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-1312, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Natural gas hydrates are considered as one of the most promising alternatives to conventional fossil energy sources, and are thus subject to world-wide research activities for decades. Hydrate formation from methane dissolved in brine is a geogenic process, resulting in the accumulation of gas hydrates in sedimentary formations below the seabed or overlain by permafrost. The LArge scale Reservoir Simulator (LARS) has been developed (Schicks et al., 2011, 2013; Spangenberg et al., 2015) to investigate the formation and dissociation of gas hydrates under simulated in-situ conditions of hydrate deposits. Experimental measurements of the temperatures and bulk saturation of methane hydrates by electrical resistivity tomography have been used to determine the key parameters, describing and characterising methane hydrate formation dynamics in LARS. In the present study, a framework of equations of state to simulate equilibrium methane hydrate formation in LARS has been developed and coupled with the TRANsport Simulation Environment (Kempka, 2020) to study the dynamics of methane hydrate formation and quantify changes in the porous medium properties in LARS. We present our model implementation, its validation against TOUGH-HYDRATE (Gamwo & Liu, 2010) and the findings of the model comparison against the hydrate formation experiments undertaken by Priegnitz et al. (2015). The latter demonstrates that our numerical model implementation is capable of reproducing the main processes of hydrate formation in LARS, and thus may be applied for experiment design as well as to investigate the process of hydrate formation at specific geological settings. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-1312
2021050608 Limbrock, Jonas K. (Universtiy of Bonn, Institute of Geosciences, Bonn, Germany); Weigand, Maximilian and Kemna, Andreas. Textural and mineralogical controls on temperature dependent SIP behavior during freezing and thawing [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14273, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Geoelectrical methods are increasingly being used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties are sensitive to the phase change of liquid to frozen water. Here, electrical resistivity tomography (ERT) is most commonly applied, using resistivity as a proxy for various quantities, such as temperature or ice content. However, it is still challenging to distinguish between air and ice in the pore space of the rock based on resistivity alone due to their similarly low electrical conductivity. Meanwhile, geoelectrical methods that utilize electrical polarization effects to characterize permafrost are also being explored. For example, the usage of the spectral induced polarization (SIP) method, in which the complex, frequency-dependent impedance is measured, can reduce ambiguities in the subsurface conduction properties, considering the SIP signature of ice. These measurements seem to be suitable for the quantification of ice content (and thus the differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites. However, to improve the interpretation of SIP measurements, it is necessary to understand in more detail the electrical conduction and polarization properties as a function of temperature, ice content, texture, and mineralogy under frozen and partially frozen conditions. In the study presented here, electrical impedance was measured continuously using SIP in the frequency range of 10 mHz to 45 kHz on various water-saturated solid rock and loose sediment samples during controlled freeze-thaw cycles (+20°C to -40°C). These measurements were performed on rock samples from different alpine permafrost sites with different mineralogical compositions and textures. For all samples, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperature. Also, hysteresis between freezing and thawing behavior is observed for all measurements. During freezing, a jump within the temperature-dependent resistance is observed, suggesting a lowering of the freezing point to a critical temperature where an abrupt transition from liquid water to ice occurs. During thawing, on the other hand, there is a continuous decrease in the measured resistance, suggesting a continuous thawing of the sample. The spectra of impedance phase, which is a measure for the polarization, exhibit the same qualitative, well-known temperature-dependent relaxation behaviour of ice at higher frequencies (1 kHz-45 kHz), with variations in shape and strength for different rock texture and mineralogy. At lower frequencies (1 Hz-1 kHz), a polarization with a weak frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, which likewise depends on the texture as well as on the mineralogy of the respective sample. This polarization response partially vanishes during freezing. Overall, the investigated SIP spectra do not only show a dependence on texture and mineralogy, but mainly a dependence on the presence of ice in the sample as well as temperature. This indicates the possibility of a thermal characterization, as well as a determination of the ice content, of permafrost rocks using SIP.
DOI: 10.5194/egusphere-egu21-14273
2021050616 Lindner, Fabian (LMU Munich, Munich, Germany) and Wassermann, Joachim. Single-station seismic monitoring of permafrost on Mt. Zugspitze (Germany) over the past 15 years [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9420, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Permafrost thawing affects mountain slope stability and can trigger hazardous rock falls. As rising temperatures promote permafrost thawing, spatio-temporal monitoring of long-term and seasonal variations in the perennially frozen rock is therefore crucial in regions with high hazard potential. With various infrastructure in the summit area and population in the close vicinity, Mt. Zugspitze in the German/Austrian Alps is such a site and permafrost has been monitored with temperature logging in boreholes and lapse-time electrical resistivity tomography. Yet, these methods are expensive and laborious, and are limited in their spatial and/or temporal resolution. Here, we analyze continuous seismic data from a single station deployed at an altitude of 2700 m a.s.l. in a research station, which is separated by roughly 250 m from the permafrost affected ridge of Mt. Zugspitze. Data are available since 2006 (with some gaps) and reveal high-frequency (>1 Hz) anthropogenic noise likely generated by the cable car stations at the summit. We calculate single-station cross-correlations between the different sensor components and investigate temporal coda wave changes by applying the recently introduced wavelet-based cross-spectrum method. This approach provides time series of the travel time relative to the reference stack as a function of frequency and lag time in the correlation functions. In the frequency and lag range of 1-10 Hz and 0.5-5 s respectively, we find various parts in the coda that show clear annual variations and an increasing trend in travel time over the past 15 years of consideration. Converting the travel time variations to seismic velocity variations (assuming homogeneous velocity changes affecting the whole mountain) results in seasonal velocity changes of up to a few percent and on the order of 0.1% decrease per year. Yet, estimated velocity variations do not scale linearly with lag time, which indicates that the medium changes are localized rather than uniform and that the absolute numbers need to be taken with caution. The annual velocity variations are anti-correlated with the temperature record from the summit but delayed by roughly one month. The phasing of the annual seismic velocity change (relative to the temperature record) is in agreement with a previous study employing lapse-time electrical resistivity tomography. Furthermore, the decreasing trend in seismic velocity happens concurrently with an increasing trend in temperature. The results therefore suggest that the velocity changes are related to seasonal thaw and refreeze and permafrost degradation and thus highlight the potential of seismology for permafrost monitoring. By adding additional receivers and/or a fiber-optic cable for distributed acoustic sensing, hence increasing the spatial resolution, the presented method holds promise for lapse-time imaging of permafrost bodies with high spatio-temporal resolution from passive measurements.
DOI: 10.5194/egusphere-egu21-9420
2021050592 Lysdahl, Asgeir Kydland (Norwegian Geotechnical Institute, Oslo, Norway); Bazin, Sara; Harstad, Andreas Olaus and Frauenfelder, Regula. Active layer and bedrock mapping in permafrost with electrical resistivity tomography and induced polarization; a case study from Svalbard [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14497, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Design and construction of infrastructure in frozen permafrost soils demands for detailed investigation of the ground characteristics prior to the construction process. Variations in ground temperature affect the physical properties of permafrost, such as amount of unfrozen water content and ice content. In addition, aggradation and degradation of permafrost induce changes of its physical properties. Ground-based Electrical Resistivity Tomography (ERT) and Induced Polarization (IP) surveying can be used to characterize near-surface ground conditions to a few tens of meters depth, especially when calibrated by boreholes. Measured electrical resistivity is temperature-dependent, which makes ERT a suitable tool in permafrost investigations. The temperature dependence is most pronounced for temperatures below freezing point. Electrical resistivity rises exponentially during freezing, when unfrozen water content within a substrate decreases. The electrical resistivity is, thus, very sensitive to phase changes between water and ice and we usually observe a lack of resistivity contrast at lithological interfaces. Direct translation from resistivity to lithology is, therefore, seldomly possible in permafrost. While ERT is successful for mapping the active layer, further interpretation of resistivity profiles is thus impeded by the lack of resistivity contrast within the permafrost. Indeed, the lithological structures are hidden by the strong resistivity of the frozen layer. By adding complementary information, IP measurements can help separate effects due to freezing and lithology. The IP effect can be measured in the time-domain, simultaneously with the ERT measurements, and with the same equipment. The IP effect occurs after abruptly interrupting the current flow between the current electrodes. The voltage across the potential electrodes does not drop to zero instantaneously, but decays exponentially. The decay time can be used to estimate the chargeability of the ground. Here, we present three examples where combined ERT- and IP-surveying was used to detect the interface between sediments and bedrock within permafrost soils, and to investigate potential environmental hazards related to run-off paths from existing and planned landfills. Study sites were an active landfill near the town of Longyearbyen, and two potentially new landfills near Longyearbyen and Barentsburg, respectively (the latter one for surplus masses resulting from coal mining). As permafrost traditionally had been seen as a natural flow barrier for such landfills, understanding its degradation owing to climate change was considered key in the planning of future sites. Eight profiles were carried out in September 2018, when expected active layer thicknesses were at their maxima. Two-dimensional inversion was performed with the commercial software RES2DINV for the resistivity data and Ahrusinv for the chargeability data. The results of our case studies show the benefit of simultaneous ERT- and IP-measurements, to both map active layer depths and determine sediment depths in permafrost areas. They also gave valuable insights in understanding potential environmental hazards related to run-off from the landfill, as a consequence of water entering the landfill in the summer period. ERT/IP surveys are flexible and relatively easy to deploy. The technique is non-destructiv and is, therefore, also suitable for maintenance studies in vulnerable arctic Tundra environments.
DOI: 10.5194/egusphere-egu21-14497
2021050652 Magee, Craig (University of Leeds, Leeds, United Kingdom); Jackson, Christopher A. L.; Kling, Corbin L. and Byrne, Paul K. Imaging the subsurface structure of pit craters [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5067, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Pit craters are enigmatic sub-circular depressions observed on rocky and icy planetary bodies across the Solar System. These craters do not primarily form during catastrophic impact or the forcible eruption of subsurface materials, but likely due to collapse of subsurface cavities following fluid (e.g., magma) movement and/or extensional tectonics. Pit craters thus provide important surficial records of otherwise inaccessible subsurface processes. However, unlocking these pit crater archives is difficult because we do not know how their surface expression relates to their subsurface structure or driving mechanisms. As such, there is a variety of hypotheses concerning pit crater formation, which variously relate cavity collapse to: (i) opening of dilatational jogs during faulting; (ii) tensile fracturing; (iii) karst development; (iv) permafrost melting; (v) lava tube evacuation; (vi) volatile release from dyke tip process zones; (vii) pressure waning behind a propagating dike tip; (viii) migration of magma away from a reservoir; and/or (ix) hydrothermal fluid movement inducing host rock porosity collapse. Validating whether these proposed mechanisms can drive pit crater formation and, if so, identifying how the physical characteristics of pits can be used to infer their driving mechanisms, is critical to probing subsurface processes on Earth and other planetary bodies. Here we use seismic reflection data from the North Carnarvon Basin offshore NW Australia, which provides ultra-sound like images of Earth's subsurface, to characterize the subsurface structure of natural pit craters. We extracted geometrical data for 61 pits, and find that they are broadly cylindrical, with some displaying an inverted conical (trumpet-like) morphology at their tops. Fifty-six pit craters, which are sub-circular and have widths of ~150-740 m, extend down ~500 m to and are aligned in chains above the upper tips of dikes; crater depths are ~12-225 m. These dike-related pit craters occur within long, linear graben interpreted to be bound by dyke-induced normal faults. Five pit craters, which are ~140-740 m wide and ~32-107 m deep, formed independent of dykes and are associated only with tectonic normal faults. Our preliminary data reveal a moderate, positive correlation between crater width and depth but there is no distinction between the depth and width trends of pit craters associated with dikes and those with tectonic normal faults. To test whether our quantitative data can be used to inform interpretation of pit craters observed on other planetary bodies, we compare their morphology to those imaged in Noctis Labyrinthus on Mars; there are >200 pit craters here, most of which occur in chains, with widths ranging from 369-11743 m and depths from 1-1858 m. Overall, we show reflection seismology is a powerful tool for studying the three-dimensional geometry of pit craters, with which we can test pit crater formation mechanisms. We anticipate future seismic-based studies will improve our understanding of how the surface expressions of pit craters (either in subaerial or submarine settings) can be used to reconstruct subsurface structures and processes on other planetary bodies, where such subsurface information is not currently available.
DOI: 10.5194/egusphere-egu21-5067
2021050593 Maierhofer, Theresa (Technical University of Vienna, Department of Geodesy and Geoinformation, Vienna, Austria); Limbrock, Jonas K.; Katona, Timea; Drigo, Elisabetta; Hilbich, Christin; Di Cella, Umberto Morra; Kemna, Andreas; Hauck, Christian and Flores-Orozco, Adrian. Seasonal and annual dynamics of frozen ground at a mountain permafrost site in the Italian Alps detected by spectral induced polarization [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14598, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Warming of permafrost regions with an associated increase in subsurface temperatures has been reported worldwide. Thus, long-term monitoring of the thermal state of permafrost and the associated ground ice contents has become an essential task also for the European Alps. Geophysical methods have proven to be well-suited to support and interconnect spatially sparse borehole data and investigate the distribution and temporal evolution of permafrost. In particular, electrical resistivity tomography (ERT) is a widely applied technique for permafrost characterization, commonly associated with a significant increase in the electrical resistivity upon freezing. However, air is also characterized by high electrical resistivity values complicating the interpretation of ERT results. Recent studies have revealed that the spectral induced polarization (SIP) response of frozen rocks is affected by the temperature-dependent polarization behaviour of ice at higher frequencies. Thus, the SIP or complex resistivity method offers potential for an improved characterization of permafrost sites. We here present SIP imaging results conducted over a broad range of frequencies (0.1-225 Hz) at an operational long-term permafrost monitoring site covering a period of one and a half years. The selected study area Cervinia Cime Bianche (Italian Alps) is situated at an elevation of ~3100 m and provides comprehensive geophysical, borehole temperature and water content data for validation. Shielded cables and an adequate measuring protocol were deployed to minimize the electromagnetic coupling in the SIP data. Data were collected as normal and reciprocal pairs for the quantification of data error, and we developed an analysis scheme for data quality that considers changes in time and in the frequency to remove spatial and temporal outliers and erroneous measurements. To understand the temperature dependence of the polarization response, we compare our field results with SIP laboratory measurements on water-saturated rock samples, collected in close proximity to the monitoring profile, in a frequency range of 10 mHz to 45 kHz during controlled freeze-thaw cycles (+20°C to -40°C). Our field results show clear seasonal changes in the complex resistivity images. Resistivity magnitude shows an increase in winter and decrease in summer throughout the image plane, with most prominent changes at shallow depths, where also resistivity phase shows distinctly increased (absolute) values in winter for frequencies above 10 Hz. This region coincides with the active layer as monitored by borehole temperature logging, suggesting that especially the polarization response is indicative of the seasonal freezing and thawing of the ground. This interpretation is confirmed by the laboratory measurements on the rock samples from the site, which upon freezing and thawing exhibit an absolute phase increase with decreasing temperature at higher frequencies (above 10 Hz for temperatures down to -10°C), with the general spectral behaviour being consistent with the known polarization properties of ice. We conclude that with appropriate measurement and processing procedures, the characteristic dependence of the SIP response of frozen rocks on temperature, and thus ice content, can be utilized in field surveys for an improved assessment of thermal state and ice content at permafrost sites.
DOI: 10.5194/egusphere-egu21-14598
2021050621 Marr, Philipp (Universität Wien, Department of Geography and Regional Research, Vienna, Austria); Winkler, Stefan; Dahl, Svein Olaf and Löffler, Jörg. Palaeoclimatic and morphodynamic implications of Holocene boulder-dominated periglacial and paraglacial landforms in Rondane, south Norway [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12172, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Periglacial, paraglacial and related boulder-dominated landforms constitute a valuable, but often unexplored source of palaeoclimatic and morphodynamic information. The timing of landform formation and stabilization can be linked to past cold climatic conditions which offers the possibility to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, paraglacial alluvial fan, rock-slope failure) in Rondane, eastern South Norway for the first time. On the basis of an old and young control point a local calibration curve was established from which surface exposure ages of each landform were calculated. The investigation of formation, stabilization and age of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its connectivity to landform evolution. The obtained SHD age estimates range from 11.15±1.22 to 3.99±1.52 ka which shows their general inactive and relict character. Most surface exposure ages of the sorted stripes cluster between 9.62±1.36 and 9.01±1.21 ka and appear to have stabilized towards the end of the 'Erdalen Event' or in the following warm period prior to 'Finse Event'. The blockfield age with 8.40±1.16 ka indicates landform stabilization during 'Finse Event', around the onset of the Holocene Thermal Maximum (~8.0-5.0 ka). The paraglacial alluvial fan with its four subsites shows age ranges from 8.51±1.63 to 3.99±1.52 ka. The old exposure age points to fan aggradation follow regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Surface exposure age of the rock-slope failure with 7.39±0.74 ka falls into a transitional climate period towards the Holocene Thermal Maximum (~8.0-5.0 ka). This indicates that climate-driven factors such as decreasing permafrost depth and/or increasing hydrological pressure negatively influence slope stability. Our obtained first surface exposure ages from boulder-dominated landforms in Rondane give important insights to better understand the palaeoclimatic variability in the Holocene. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-12172
2021050622 Maslakov, Alexey (Moskovskiy Pedagogicheskiy Gosudarstvennyy Universitet im. M.V. Lomonosova, Geographical Department, Moscow, Russian Federation); Komova, Nina; Egorov, Evgeny; Mikhaylyukova, Polina; Grishchenko, Mikhail and Zotova, Larisa. Permafrost vulnerability to contemporary climate changes in eastern Chukotka coastal plains (NE Russia) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2196, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Recent permafrost degradation is detected in many cold regions of the world. This process is due to surface lowering caused by ice-rich sediments thaw and massive ice beds melt. Eastern Chukotka coastal plains polygon is one of the key sites for studying climate change's impact on permafrost conditions and human activity. This region is the habitat of indigenous people, concentrated in the coastal villages. The study site is approximately 400 km2 in area and characterized by a variety of landscape, geomorphological, and permafrost conditions. Using remote sensing data, field observations, and shallow drilling results, we ranked and delineated the areas on their susceptibility to thermokarst, thermal erosion, and solifluction activation due to the further air temperature increasing and potential human disturbances. Spatial analysis on current thaw settlement rates combined with drilling data allowed us to map the areas with a high concentration of surficial massive ice beds. These studies provide a better understanding of permafrost conditions in Eastern Chukotka and its response to human impact and climate change. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-2196
2021050597 Medina, Katy (National Institute for Research on Glaciers and Mountain Ecosystems, Huaraz, Peru); Loarte, Edwin; Badillo-Rivera, Edwin; León, Hairo; Bodin, Xavier and Huggel, Christian. Analysis of the spatial distribution and characteristics of the rock glaciers in the Ampato, Vilcanota and La Viuda Cordilleras southern and central Peru [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8466, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Rock glaciers (RG) are visual evidence of mountain permafrost, and are one of the most important geomorphological features in the Peruvian Andes. The main objective of this research was to determine the spatial distribution of RG, their degree of activity, as well as their morphological and climatic characteristics in Cordilleras Vilcanota (Southeast), Ampato (Southwest) and La Viuda (Center). For this study, we used high-resolution images from Google Earth-Pro, SASPlanet and a DEM ALOS PALSAR (12.5 m) to identify and digitize the RG based on their geomorphological attributes, and we derived the potential incoming solar radiation (PISR), based on the DEM. The WorldClim dataset (1970-2000) was used to determine the mean annual air temperature (MAAT) and the precipitation in the analyzed zones. The Cordillera Ampato, with 139 RGs, presents the lowest minimum altitude of the RGs inventory (4537 m a. s. l.), the lowest MAAT (-0.4°C), lower slope (18°) and concentrates the highest PISR (1083 kWh/m2). The Cordillera Vilcanota concentrates a lower number of RGs (54), a higher minimum altitude of RGs (4733 m a.s.l.) and a relatively higher MAAT (1.9°C). Comparing both southern Cordilleras with respect to Cordillera central (La Viuda), it has the lowest amount of RG (8), a higher minimum altitude of RG (4747 m a.s.l.), higher slope (23°), higher MAAT (2.2°C) and lower persistence of snow cover. With regard to the RG activity, it was found that the quantity of active RG compared to inactive RG is in a proportion of 1.6 in Cordillera Ampato and 0.2 in Cordilleras Vilcanota and La Viuda. Finally, the spatial distribution analysis shows that the greatest amount of RGs is located in the southern zone, decreasing towards the northern regions of Peru while the opposite occurs with the average MAAT of the RG, that is, the MAAT decreases as the RG moves to southern regions of Peru. On the other hand, the SW zone (dry climate) concentrates the largest amount of RG compared to the SE zone (wet climate). In addition, the topoclimatic parameters condition the formation of RG in the Cordilleras of study. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-8466
2021050590 Miesner, Frederieke (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Overduin, Pier Paul and Stevens, Christopher. Seasonal variations in bottom water temperatures and their influence on subaquatic permafrost thermal regimes [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14883, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The thermal regime in sediment below the ocean or lakes is mostly governed by the sea or lake bed temperature and by the geothermal heat flow. This thermal regime will determine whether permafrost beneath water bodies is preserved or how rapidly it thaws. Thermal modelling uses mean annual bottom water temperatures to calculate permafrost presence or absence, while predictions of shallow sediment thermal regimes must be forced with time series of changing bottom water temperatures that also account for freezeback of the water column to the bottom, forming bottom-fast ice. However, continuous, annual measurements of bottom water temperatures in Arctic lakes and coastal marine settings are hard to obtain and therefore scarce. Waves and sea ice movement make deployment and recovery of instruments difficult. We provide a parameterization of the bottom water temperature function that relies on easier to obtain variables, such as the mean, minimum and maximum air temperature and the water depth, by comparing measured and modelled shallow sediment thermal regimes from the Arctic. We use a parameterization based on a simple cosine for the water temperature with mean temperature, amplitude and time shift and add the minimum water temperature to obtain a 4 parameter function. For shallow regions with bottom-fast ice, additionally the duration of the ice-growth and -melting period as well as the minimum air temperature are needed. We test our parameterizations with a globally unique data set of 4 years of ground temperature data collected from the seabed to a depth of 10 m from the near shore zone of the Mackenzie Delta. At the instrumented sites, permafrost is present beneath mostly freshwater bottom-fast and floating ice. Forward modeling of sediment temperatures is performed using the 1D heat transfer model CryoGrid with depth dependent thermal properties. We neglect advective processes and long-term temperature trends in the bottom water temperatures. Rough parameterization of the annual variation of water bottom temperatures reproduce measured water temperatures with a RMSE of 20-40%. The resulting modeled sediment temperature field based on 10 years of repeated parameterized bottom water temperatures matches the modeled sediment temperature field based on measured water temperatures in terms of permafrost characteristics, including the depth of the active layer defined by the 0°C isotherm over the year. However, both modelled temperature fields yield significantly higher sediment temperatures than the measured sediment temperature field. This may be the result of choice of sediment thermal properties in the thermal model or shifts in the duration of bottom-fast ice contact or on-ice snow Since modelled temperature fields from both repeated measured and parameterized bottom water temperatures show the same deviation, it suggests that the bottom water temperatures were warmer during the measurement period than the average over the previous 10 years.
DOI: 10.5194/egusphere-egu21-14883
2021050626 Minotti, Federica (Free University of Bozen-Bolzano, Faculty of Science and Technology, Bozen-Bolzano, Italy); Kofler, Christian; Gems, Bernhard; Mair, Volkmar and Comiti, Francesco. Rock glacier sediment, kinematics and geomorphometry; a study case from the Eastern Italian Alps [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9653, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Rock glaciers are important geomorphological structures of high mountain environments and fundamental indicators for permafrost. They consist of unconsolidated rock debris--generally derived from talus or till--held together by ice, moving slowly downslope due to the gravitation in combination with uncountable freeze-thaw-cycles in the active layer. The downslope movement of rock glaciers leads to lobate structures with depressed areas as well as ridges where the sediments tend to accumulate, creating a typical surface morphology defined as "ridges and furrows". This study focuses on the analysis of one rock glacier system located in the Pfitsch/Vizze valley (South Tyrol), in the Eastern Italian Alps. The debris in this area comprises exclusively the granitic Central Gneiss of the Tauern window. Rock glacier sediment derives from talus, consisting essentially of more or less foliated to planar angular material, which was essentially formed by frost weathering. The size and shape of sediments present at the surface of the rock glacier system were analyzed in correlation with displacement and geomorphometry, with the hypothesis that sediments shape and size at different sites across the rock glacier might relate to its past and present dynamics. The displacement analyses were carried out to quantify rock glaciers movements during the last 20 years, and the geomorphometrical characteristics were investigated to identify specific geometrical attributes that may be linked to internal ice changes. Clasts analysis showed how rock glacier sediments are very heterogeneous, with dimensions being mainly determined by transport distance, and sphericity and roundness by lithology. A role of sediments characteristics on displacement rate did not turn out evident. Convexities and concavities observed on the study site are apparently created respectively by the accumulation of sediments and the collapse of the structure due to the internal ice melting. Indeed, the recent, marked increase in air temperature observed in the last decades in the Alps has likely caused an accelerated ice melting in the less protected--in terms of solar radiation--rock glaciers, as is the case for our study area. Sediments here are no longer bound by ice and have become rather unstable. Therefore, the monitoring of rock glaciers is fundamental to anticipate future changes in the type and magnitude of natural hazards originating at high elevations, as thicker layers of sediments are becoming increasingly unstable.
DOI: 10.5194/egusphere-egu21-9653
2021050660 Monteux, Sylvain; Keuper, Frida; Wild, Birgit; Beer, Christian; Blume-Werry, Gesche; Fontaine, Sebastien; Gavazov, Konstantin; Gentsch, Norman; Guggenberger, Georg; Hallin, Sara; Hugelius, Gustav; Jalava, Mika; Juhanson, Jaanis; Koven, Charles; Krab, Eveline J.; Kuhry, Peter; Kummu, Matti; Revaillot, Sandrine; Richter, Andreas; Shahzad, Tanvir; Vergruggen, Erik; Walz, Josefine; Weedon, James T. and Dorrepal, Ellen. Microbial functional limitations and rhizosphere priming effect in permafrost [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16305, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Considering the potential positive feedback between climate warming and the release of greenhouse gases following the increased decomposition of the organic matter stored in permafrost soils as they thaw is an important challenge for the upcoming climate change assessments. While our understanding of physico-chemical constraints on thawing permafrost SOM decomposition has vastly improved since IPCC's fifth assessment report, biotic interactions can still be the source of large uncertainties. Here we discuss the effects of two biotic interactions in the context of thawing permafrost: rhizosphere priming effect and microbial functional limitations. Rhizosphere priming effects are still-unclear mechanisms that result in increased SOM decomposition rates in the vicinity of plant roots. We consider these effects through the PrimeSCale modeling framework, discussing its predictions and its limitations, in particular which observations and data should be acquired to further improve it. Microbial functional limitations were recently evidenced in permafrost microbial communities and consist in missing or impaired functions, likely due to strong environmental filtering over millennial time-scales. We present what this mechanism can imply in terms of permafrost soil functioning and briefly discuss what could be the next steps before its inclusions in modeling efforts. co-authors: Frida Keuper, Birgit Wild, Christian Beer, Gesche Blume-Werry, Sebastien Fontaine, Konstantin Gavazov, Norman Gentsch, Georg Guggenberger, Sara Hallin, Gustaf Hugelius, Mika Jalava, Jaanis Juhanson, Charles Koven, Eveline J. Krab, Peter Kuhry, Matti Kummu, Sandrine Revaillot, Andreas Richter, Tanvir Shahzad, Erik Verbruggen, Josefine Walz, James T. Weedon, Ellen Dorrepaal [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-16305
2021050605 Mora, Carla (Universidade de Lisboa, Lisbon, Portugal); Vieira, Goncalo; Pina, Pedro; Whalen, Dustin and Bartsch, Annett. Evaluation of PAZ satellite imagery for the assessment of intra-seasonal dynamics of permafrost coasts (Beaufort Sea, Canada) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15632, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Arctic permafrost coasts represent about 34% of the Earth's coastline, with long sections affected by high erosion rates, increasingly threatening coastal communities. Year-round reduction in Arctic sea ice is forecasted and by the end of the 21st century, models indicate a decrease in sea ice area from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the ice-free season leads to a longer exposure to wave action. Monitoring the Arctic coasts is limited by remoteness, climate harshness and difficulty of access for direct surveying, but also, when using satellite remote sensing, by frequent high cloudiness conditions and by illumination. In order to overcome these limitations, three sites at the Beaufort Sea Coast (Clarence lagoon, Hopper Island and Qikiqtaruk/Herschel Island) have been selected for monitoring using very high-resolution microwave X-band spotlight PAZ imagery from Hisdesat. Bluff top, thaw-slump headwalls and water lines were digitised from images acquired during the ice-free seasons of 2019 and 2020 at sub-monthly time-steps. The effects of coastal exposure on delineation accuracy in relation to satellite overpass geometry have been assessed and coastal changes have been quantified and compared to meteorological and tide-gauge data. The results show that PAZ imagery allow for monitoring and quantifying coastal changes at sub-monthly intervals and following the evolution of coastal features, such as small mud-flow fans and retrogressive thaw slumps. This shows that high resolution microwave imagery has a strong potential for significantly advancing coastal monitoring in remote Arctic areas. This research is part of project Nunataryuk funded under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 773421) and of Hisdesat project Coastal Monitoring for Permafrost Research in the Beaufort Sea Coast (Canada).
DOI: 10.5194/egusphere-egu21-15632
2021050586 Morse, Peter (Geological Survey of Canada, Ottawa, ON, Canada); Sladen, Wendy; Kokelj, Steve; Parker, Ryan; Smith, Sharon and Rudy, Ashley. Spatial variability in periglacial terrain conditions, northwestern Canada [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13344, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Throughout much of northern Canada there is an inadequate knowledge of permafrost and periglacial terrain conditions, which impedes development of climate-resilient northern infrastructure, identification of potential geohazards, decision making regarding resource development, and inferring past and future landscape evolution. Using a land systems approach to better understand formation of landscapes and thaw-sensitive terrains of northern Yukon and northwestern Northwest Territories, we aim to describe the permafrost-related landform-sediment assemblages that exist in the region. Permafrost is continuous in the region, but variations in geology, landscape history, climate, relief, ecology, and other natural processes have produced a diverse range of permafrost conditions and landforms. Using the 875 km-long Dempster and Inuvik-to-Tuktoyaktuk highway corridors (DH-ITH) as a regional transect, and high-resolution satellite imagery, a robust methodology was implemented to identify and digitize (at 1:5000 scale) 8793 landforms (589 km2) within a 10 km-wide corridor (8530 km2) and classify them according to main formational process (hydrological, periglacial, and mass movement). Surficial geology data were extracted from available data sets. Landform densities in all feature classes vary substantially along the transect according to physiographic region and surficial geology. The northern 39% of the corridor is characterized by generally rolling or planar relief, numerous waterbodies (19%), and the remaining land area by mostly morainal (67%), glaciofluvial (12%), lacustrine (7%), and alluvial (7%) deposits. By count, it contains 53% of mapped features and the majority of periglacial (67%) and hydrological (70%) features. In particular, the Tuktoyaktuk Coastlands, Peel Plain, and Mackenzie Delta, contain the greatest density of mapped landforms within the corridor, which cover nearly 23%, 15%, and 15% of the land area of these physiographic regions, respectively. These extents reflect the amount of ground ice and level of permafrost-thaw sensitivity of these regions. In contrast, the physiographic regions of the southern 61% of the study area are characterized by high relative relief, few waterbodies (0.2%), and the land area mainly by colluvial (63%), alluvial (18%), and morainal (14%) deposits. Most mass movement features occur here (85% by count), and are concentrated in the Ogilvie Mountains (n 1027; 108 km2). This feature inventory provides the basis for developing spatial models of landscape-thaw susceptibility, which can inform risk assessment and improve decision making regarding public safety and environmental management. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-13344
2021050631 Nesterova, Nataliia (Melnikov Permafrost Institute, North-Eastern Permafrost Station, Magadan, Russian Federation); Makarieva, Olga; Zemlyanskova, Anastasia and Ostashov, Andrey. Climate change impact on water exchange processes in the cryolithozone of the north-east of Russia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-204, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Climate warming cause the transformation of hydrological cycle in cold regions of the Northern Hemisphere. The aim of this research is to study the climate change impact on water exchange processes in the cryolithozone of the North-East of Russia. The study presents the results of the analysis of changes in the characteristics of the climate (air temperature, precipitation), water discharge, soil temperature at the 80 cm depth and river-ice cover for a period of 50 years (1966-2018) and historical and modern data of aufeis area. Climate. The annual air temperature in the region increased by 2.3°C on average. The analysis of annual precipitation showed multidirectional changes. However, most of the stations are characterized by a significant negative trend of precipitation in the winter and a positive annual trend of mixed and liquid precipitation with an increase in their share in the autumn months. Permafrost. The average annual soil temperature at the 80 cm depth increased by 1.7° at 7 of the 11 stations in the studied area. The maximum change reached 4.8° in June at the Verkhoyansk station. Streamflow. Significant increase of streamflow in the autumn-winter period (from August to December) at most of the rivers have been established. Even though permafrost warming is leading to deepening of active layer, we hypothesized that the main reason of base flow increase is the transition of precipitation from solid to liquid and corresponding increase of streamflow in September, continuing in the following months. There is a significant shift in the dates of spring freshet floods in May. But it does not lead to a decrease of runoff in June. This may indicate an increase of contribution to streamflow of such sources as thawing permafrost, glaciers and aufeis. The river-ice cover. There are significant changes in the characteristics of the river ice cover and the time of the river ice formation. On average, at 19 analyzed river gauges the decrease of river ice cover maximum depth was 41 cm (28%) and the period of formation of river ice with a thickness of 60 cm (necessary for using winter roads for passenger cars) has shifted to later period by 7-40 days. The aufeis. Aufeis is an important part of groundwater and surface flow interaction in the studied area. The analysis of the historical data and its comparison to modern distribution of aufeis in the region have shown significant changes. The total number (area) of aufeis was 4642 (7181 km2), according to the historical data (Cadastre of aufeis, 1958), and 6217 (3579 km2), according to Landsat data (2013-2019), which is 1.3 times higher by number, but 2 times less by total area. The study indicates that considerable transformations are going on in all parts of hydrological cycle. The analysis results are used as the base for planning new multidisciplinary research to assess and project the changes in the natural conditions and water cycle in the cryolithozone of the North-East of Russia.
DOI: 10.5194/egusphere-egu21-204
2021050603 Newman, Andrew (National Center for Atmospheric Research, Research Applications Lab, Boulder, CO); Cheng, Yifan; Musselman, Keith; Craig, Anthony; Swenson, Sean; Hamman, Joseph and Lawrence, David. High-resolution regional climate simulations of Arctic [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6085, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The Arctic has warmed during the recent observational record and is projected to keep warming through the end of the 21st century in nearly every future emissions scenario and global climate model. This will drive continued thawing of permafrost-rich soils, alter the partitioning of rain versus snow events, and greatly affectthe water cycle and land-surface processes across the Arctic. However, previous analyses of these impacts using dynamical models have relied on global climate model output or relatively coarse regional climate model simulations. In the coarse simulations, projections of changes to the water cycle and land-surface processes in areas of complex orography and high land-surface heterogeneity, which are characteristic of many regions in the Arctic, may thus be limited. Here, we discuss recent work examining high-resolution regional climate simulations over Alaska and NW Canada. Completed and upcoming simulations have been and will be run at a 4 km grid spacing, which is sufficient to resolve orography across this region's mountain ranges. The initial simulation results are very encouraging and show the regional climate model yields a realistic representation of the seasonal and spatial evolution of precipitation, temperature, and snowpack compared to previous studies across Alaska and other Arctic regions. A paired future climate simulation uses the Pseudo-Global Warming (PGW) approach, where the end of century ensemble mean monthly climate perturbations (CMIP5 RCP8.5) are used to incorporate the thermodynamic effects of future warming into the present-day climate as represented by ERA-Interim reanalysis data. Changes in major components of the hydroclimate (e.g. precipitation, temperature, snowfall, snowpack) are projected to sometimes be significant in this future scenario. For example, the seasonal snow cover in some regions is projected to mostly disappear. However, there are also projected increases in snowpack in historically very cold areas (e.g. high elevations) that are able to stay cold enough in the future to support snowfall and snowpack. Finally, we will present a new effort to couple an advanced land-surface model, the Community Terrestrial Systems Model (CTSM), within the Regional Arctic Systems Model (RASM) in an effort to better represent complex land-surface and subsurface (e.g. permafrost, streamflow availability timing and temperatures) processes for climate change impact studies. CTSM is a complex physically based land-surface model that is able to represent multiple snow layers, a complex canopy, and multiple soil layers including organic matter and frozen soils, which enables us to explicitly represent spatial variability in the regional hydroclimate and land states (e.g. permafrost) at relatively high spatial resolutions relative to other simulations (4 km land and atmosphere grids). Successful coupling of CTSM within RASM has been completed and we will discuss some preliminary land-atmosphere coupled test results.
DOI: 10.5194/egusphere-egu21-6085
2021050600 Offer, Maike (Technische Universität München, Chair of Landslide Research, Munich, Germany); Scandroglio, Riccardo; Draebing, Daniel and Krautblatter, Michael. 4D-quantification of alpine permafrost degradation in a bedrock ridge using multiple inversion schemes and deformation measurements [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13419, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Warming of permafrost in steep rock walls decreases their mechanical stability and could triggers rockfalls and rockslides. However, the direct link between climate change and permafrost degradation is seldom quantified with precise monitoring techniques and long-term time series. Where boreholes are not possible, laboratory-calibrated Electrical Resistivity Tomography (ERT) is presumably the most accurate quantitative permafrost monitoring technique providing a sensitive record for frozen vs. unfrozen bedrock. Recently, 4D inversions allow also quantification of frozen bedrock extension and of its changes with time (Scandroglio et al., in review). In this study we (i) evaluate the influence of the inversion parameters on the volumes and (ii) connect the volumetric changes with measured mechanical consequences. The ERT time-serie was recorded between 2006 and 2019 in steep bedrock at the permafrost affected Steintalli Ridge (3100 m asl). Accurately positioned 205 drilled-in steel electrodes in 5 parallel lines across the rock ridge have been repeatedly measured with similar hardware and are compared to laboratory temperature-resistivity (T-r) calibration of water-saturated samples from the field. Inversions were conducted using the open-source software BERT for the first time with the aim of estimating permafrost volumetric changes over a decade. (i) Here we present a sensitivity analysis of the outcomes by testing various plausible inversion set-ups. Results are computed with different input data filters, data error model, regularization parameter (l), model roughness reweighting and time-lapse constraints. The model with the largest permafrost degradation was obtained without any time-lapse constraints, whereas constraining each model with the prior measurement results in the smallest degradation. Important changes are also connected to the data error estimation, while other setting seems to have less influence on the frozen volume. All inversions confirmed a drastic permafrost degradation in the last 13 years with an average reduction of 3.900±600 m3 (60±10% of the starting volume), well in agreement with the measured air temperatures increase. (ii) Average bedrock thawing rate of ~300 m3/a is expected to significantly influence the stability of the ridge. Resistivity changes are especially evident on the south-west exposed side and in the core of the ridge and are here connected to deformations measured with tape extensometer, in order to precisely estimate the mechanical consequences of bedrock warming. In summary, the strong degradation of permafrost in the last decade it's here confirmed since inversion settings only have minor influence on volume quantification. Internal thermal dynamics need correlation with measured external deformation for a correct interpretation of stability consequences. These results are a fundamental benchmark for evaluating mountain permafrost degradation in relation to climate change and demonstrate the key role of temperature-calibrated 4D ERT.
DOI: 10.5194/egusphere-egu21-13419
2021050601 Otto, Jan-Christoph (Universität Salzburg, Department of Geography and Geology, Salzburg, Austria); Fleischer, Fabian; Junker, Robert and Hölbling, Daniel. Debris-cover on glaciers in the Austrian Alps; regional patterns, changes and significance [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2036, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Debris cover on glaciers is an important component of glacial systems as it influences climate-glacier dynamics and thus the lifespan of glaciers. Increasing air temperatures, permafrost thaw, as well as rock faces freshly exposed by glacier downwasting results in increased rockfall activity and debris input into the glacier system. In the ablation zone, negative mass balances result in an enhanced melt-out of englacial debris to the glacier system. Glacier debris cover thus represents a signal of climate warming in mountain areas. To assess the temporal development of debris on glaciers of the Eastern Alps, Austria, we mapped debris cover on 255 of the more than 800 glaciers using Landsat data at three time steps between 1996 and 2015. We applied a ratio-based threshold classification technique using existing glacier outlines. The debris cover evolution was subsequently compared to glacier changes. Glacier and glacier catchment characteristics have been analysed using GIS techniques and statistics in order to investigate potential reasons for debris cover change. Across the Austrian Alps debris cover increased by more than 10% between 1996 and 2015 while glaciers retreated significantly in response to climate warming. Debris cover distribution shows regional variability with some mountain ranges being characterised by mean debris cover on glaciers of up to 75%. We also observed a general rise of mean elevation of debris cover on glaciers in Austria. Debris cover distribution and dynamics are highly variable due to topographic, lithological and structural settings that determine the amount of debris delivered to and stored in the glacier system. Lower relative debris cover is observed on glaciers with higher mean and maximum elevation. Additionally, glaciers with increased mean slope, as well as catchments with large areas of steep slopes and a high elevation range of these slopes tend to show higher debris cover. Both parameters indicate that the influence of the steep rockwalls in the glacier catchment is a first order control on debris cover at regional scale. We can also show that catchments with a high percentage of potential permafrost distribution contain glaciers with a higher relative debris cover. Despite strong variation in debris cover, all glaciers investigated melted at increasing rates. We conclude that the retarding effects of debris cover on the mass balance and melt rate of Austrian glaciers is strongly subdued compared to other mountain areas. The study indicates that if this trend continues many glaciers in Austria may become fully debris covered in the future. However, since debris cover seems to have little impact on melt rates in the study area it will therefore not lead to a prolonged existence of debris-covered ice compared to clean ice glaciers.
DOI: 10.5194/egusphere-egu21-2036
2021050638 Pavoni, Mirko (Universita di Padova, Department of Geoscience, Padua, Italy) and Boaga, Jacopo. Frozen soils characterization by the use of ERT and EMI methods; cases in the Dolomites (Italy) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2146, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Nowadays, tourism and sport activities make the Alps high mountain environment widely populated. As example, the Dolomites (UNCESCO site, North-East Italy) host millions of tourists every year. Consequently, many infrastructures (e.g. roads, cable cars and hotels) have been built in these areas, and are subject to instabilities hazards as landslide, avalanches or frozen soils problems. Mountain permafrost is in fact one of the many aspects to be considered for the natural hazards and risk management in high mountains environment. Due to the atmospheric warming trend, mountain permafrost is thawing and its degradation is influencing the triggering and the evolvement of natural hazards processes such as rockfalls, landslides, debris flows and floods. We have nearly 5000 rock glaciers in the alps, as highlighted in the inventory of the PermaNET project (2011), therefore the study and monitoring of these periglacial forms has both a scientific and economic importance. Geophysical surveys have been historically applied in this kind of environment, in particular the Electrical Resistivity Tomography (ERT) for the characterization of the active layer thickness (ALT). The technique exploits the high electrical resistivity contrast between frozen and non-frozen debris, and, over the last years, has allowed the researchers to achieve very relevant results. However, performing these measurements is expensive both in terms of time and equipment, particularly considering that the rock glaciers are often very difficult to reach. Thus, usually we are not able to perform many investigation lines and, as the results are 2D resistivity sections, it is very difficult to obtain enough information to completely characterize a heterogeneous environment such as a rock glacier. For this reason, we tried to apply the EMI method (in the frequency domain) for the characterization of the ALT. EMI method, in fact, theoretically allows us to define the distribution of electrical resistivity in the first subsoil in a very quick way, simply by transporting the device over the interested area. Compared to ERT, it is potentially able to characterize much larger areas of a rock glacier, albeit with a lower resolution and penetration. On the other hand, because the high resistivities of the frozen ground, EMI do not guarantee an optimal working and rigorous acquisition protocol must be adopted. We tested ERT and EMI measurements along the same investigation lines, in two different sites of the Dolomites area (the Murfreit and Biz Boe rock glaciers). Finally, we discussed the advantages and disadvantages of both the techniques. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-2146
2021050623 Popescu, Razvan (University of Bucharest, Faculty of Geography, Bucharest, Romania); Vespremeanu-Stroe, Alfred; Vasile, Mirela; Andrian, Ilie; Calisevici, Sabina and Niculita, Bogdan. New findings regarding the ground air circulation by chimney effect in low-altitude permafrost susceptible porous screes (Detunata Goala, Romanian Carpathians) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7878, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Seasonally differentiated ground air circulation in low altitude porous talus slopes from temperate regions known as chimney circulation creates the conditions for permafrost development in their lower parts well below the regional permafrost altitudinal limit. So far it was shown that the cold air adsorption and warm air exfiltration areas during winter correspond to the lower and upper areas respectively of talus slopes and that they are quite stable and regular in extent and shape. New aerial survey in early winter at Detunata Goala scree with a complex talus slope-rock glacier morphology performed immediately in the days following light snow falls allowed the precise detection of warm air areas positions, shape and temporal changes within hours and days. Several triangular-shaped stripes were found to occur continuously from lower to upper parts of talus slopes and morphometric analysis on a high resolution UAV-derived DEM revealed that they correspond to the central longitudinal axis of debris cones composing the talus slopes. Thermal monitoring of air between the blocks was also performed at the location of these stripes where a thermal gradient was found to occur: the atmospheric/ground air temperature contrast increases upwards and towards the axis of talus cones reaching a maximum of >10°C (+5.3°C in the ground versus -5°C outside). In the rock glacier lobe area, the warm air evacuation is different and presents a linear configuration. This work discusses the relation between the morphometry of the deposit and warm air evacuation areas and their short term thermal regime. Also, it discusses new geophysical investigations results (electrical resistivity tomography and seismic refraction tomography) performed at the end of the warm season of 2020 in the coldest area of the scree. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-7878
2021050658 Prokushkin, Anatoly (Russian Academy of Sciences, Sukachev Institute of Forest, Krasniayrsk, Russian Federation); Novenko, Elena; Kupryanov, Dmitry and Serikov, Sergey. Peat isotopic composition of a deep deposit of palsa mire for the reconstruction of environmental changes in permafrost domain of northern Siberia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5395, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Palsa peatlands are a significant carbon pool in Northern hemisphere which is subjected to change due to accelerated permafrost thaw and peat decomposition with progressing global warming. On the other hand, peat deposits of palsas serve as an important conduit of information about variability of environment conditions in the past millennia and respective vegetation changes. In our study we applied the multi-proxy record to distinguish variation in hydrothermal regimes of palsa peatland in Northern Siberia and to trace the likely diagenetic alteration of accumulated peat. The study site is located 10 km North-East of Igarka settlement (67°31'N, 86°38'E) within the area underlain discontinuous permafrost. The peat core was obtained in the central intact part of elevated (ca. >3.5 m above surrounding hollows) dry hummock. The active layer, thawed seasonally layer, at the coring site was about 0.6 m. The entire depth of peat deposit was 8.6 m, but interrupted with several relatively thin (0.1-0.2 m) ice-rich lenses. Thawed and frozen peat samples of 0.5-5.0 cm thickness (mean = 2.8 cm) were collected at 2.5-12.0 cm step (mean=5.4 cm) depending on the amount of peat material. Collected samples (n=160) after drying at 60oC for 48 h were subjected to the analysis for C and N content, stable isotopic composition of C and N. These measurements will further accompany radiocarbon dating, loss on ignition, plant macrofossil and macro charcoal analyses. The analyzed 8.6 m deep peat core demonstrated the large variation of C (17.3-54.7%) and N (0.37-3.26%) contents as well as C:N ratios (14-134). The isotopic depth profile was in the range from -24.51 to -34.31 ppm for d13C and from -1.77 to 6.96 ppm for d15N. The highest enrichment in 15N (2.69±1.60 ppm d15N) was found in seasonally thawed layer (≤&eq;0.6 m). A layer close to the bottom (6.9-8.3 m) contained peat the most depleted by 13C (<-30 ppm d13C). Meanwhile, along the peat profile depth we detected significant fluctuations in these parameters suggesting the different periods with specific environmental conditions. Further combined with radiocarbon dating and plant macrofossil analyses we will attempt to capture the changes occurred during the past epochs in an input matter (vegetation changes and/or its productivity), decomposition rates as well as hydrothermal regimes and permafrost processes like aggradation (e.g. hummock uplift and cryoturbation) and degradation (e.g. hummock collapse, shifts from minerotrophic to ombrotrohic conditions and vice versa).
DOI: 10.5194/egusphere-egu21-5395
2021050653 Rasmussen, Christian (Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany); Overduin, Paul; Boike, Julia; Ryberg, Trond and Haberland, Christian. Passive seismic investigations of subaquatic permafrost [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12118, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Large quantities of organic carbon are known to be sequestered within subaquatic permafrost as gas hydrates. Therefore, knowledge of the extent and thaw rate is of critical importance to our understanding of global climate change. Investigations of sub-aquatic permafrost have focussed on its physical characteristics via drilling or probing, and through the limited application of geophysical methods. Active seismic methods have been most widely employed, especially for petroleum exploration, but recently passive methods have been used to investigate the seabed using ambient noise. The Horizontal-to-Vertical Spectral Ratio (HVSR) method has previously been shown to accurately determine permafrost thaw depth below the sea floor in marine and lacustrine environments, based on the collection of seismic data over a period of weeks. In this study, we test the use of short-term seabed HVSR seismic surveys and explore possibilities for optimizing the method in a wide variety of subaquatic environments. The method was successfully used in a thermokarst lake, a lagoon and river channels of the Lena Delta (Russia), as well as in marine shelf environments in the Laptev Sea (Russia) and Tuktoyaktuk Island (NW Canada). Study areas where validation data was available were preferred and selected when possible. A passive seismic measuring device, consisting of a watertight metal cannister containing three-component broad-band seismometers, was lowered down to the sea floor from a small boat and left to collect data for 3-4 minutes. The data was recorded at a sample rate of 100Hz. Post-processing and analysis were done with MATLAB. The three seismic signals were individually detrended, the offset was removed and the power spectral density was calculated. The smoothing function proposed by Konno and Ohmachi (1998) was applied to each signal with a smoothing coefficient of 40. Lastly the H/V (Horizontal / Vertical) amplitude was calculated. The H/V amplitude was plotted against signal frequencies from 0 to 50 Hz. The peak resonance frequency is believed to indicate the ice-bonded permafrost table (IBPT) thereby enabling us to determine thaw depth from the H/V plots, assuming a simple 2-layer model: thawed layer over frozen ground, characterized by low and high wave speeds, respectively. Results generally display a good correlation, on average within 0.6 meters, between the thaw depth determined from HVSR and from physical validation, although HVSR often generates a thaw depth deeper than indicated by validation data. This may be a result of complex permafrost systems where several "zones" of frozen and unfrozen ground, of varying thickness, is present below the water bodies. We conclude that the method has the potential to be an effective (fast) non-invasive tool for investigating the extent and, if repeated, the thaw rate of subaquatic permafrost. Further field testing is planned in order to continue the development and optimization of the method.
DOI: 10.5194/egusphere-egu21-12118
2021050588 Ross, Cameron (Royal Military College of Canada, Department of Civil Engineering, Kingston, ON, Canada); Beddoe, Ryley and Siemens, Greg. Equilibrium spin-up of cold and warm permafrost models [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13922, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Initialization (spin-up) of a numerical ground temperature model is a critical but often neglected step for solving heat transfer problems in permafrost. Improper initialization can lead to significant underlying model drift in subsequent transient simulations, distorting the effects on ground temperature from future climate change or applied infrastructure. In a typical spin-up simulation, a year or more of climate data are applied at the surface and cycled repeatedly until ground temperatures are declared to be at equilibrium with the imposed boundary conditions, and independent of the starting conditions. Spin-up equilibrium is often simply declared after a specified number of spin-up cycles. In few studies, equilibrium is visually confirmed by plotting ground temperatures vs spin-up cycles until temperatures stabilize; or is declared when a certain inter-cycle-temperature-change threshold is met simultaneously at all depths, such as DT≤&eq;0.01°C per cycle. In this study, we investigate the effectiveness of these methods for determining an equilibrium state in a variety of permafrost models, including shallow and deep (10-200 m), high and low saturation soils (S=100 and S=20), and cold and warm permafrost (MAGT=~-10°C and >-1°C). The efficacy of equilibrium criteria 0.01°C/cycle and 0.0001°C/cycle are compared. Both methods are shown to prematurely indicate equilibrium in multiple model scenarios. Results show that no single criterion can programmatically detect equilibrium in all tested models, and in some scenarios can result in up to 10°C temperature error or 80% less permafrost than at true equilibrium. A combination of equilibrium criteria and visual confirmation plots is recommended for evaluating and declaring equilibrium in a spin-up simulation. Long-duration spin-up is particularly important for deep (10+ m) ground models where thermal inertia of underlying permafrost slows the ground temperature response to surface forcing, often requiring hundreds or even thousands of spin-up cycles to establish equilibrium. Subsequent transient analyses also show that use of a properly initialized 100 m permafrost model can reduce the effect of climate change on mean annual ground temperature of cold permafrost by more than 1°C and 3°C under RCP2.6 and RCP8.5 climate projections, respectively, when compared to an identical 25 m model. These results have important implications for scientists, engineers and policy makers that rely on model projections of long-term permafrost conditions.
DOI: 10.5194/egusphere-egu21-13922
2021050648 Ruggiero, Livio (National Institute of Geophysics and Volcanology, Rome, Italy); Sciarra, Alessandra; Galli, Gianfranco; Mazzini, Adriano; Mazzoli, Claudio; Tartarello, Maria Chiara; Florindo, Fabio; Wilson, Gary; Bigi, Sabina; Sassi, Raffaele; Anderson, Jacob and Ciotoli, Giancarlo. First measurements of 222Rn and 220Rn activities in soil in Taylor Valley, Antarctica [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5100, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Warming global climate threatens the stability of the polar regions and may result in cascading broad impacts. Studies conducted on permafrost in the Arctic regions indicate that these areas may store almost twice the carbon currently present in the atmosphere. Therefore, permafrost thawing has the potential to magnify the warming effect by doubling the more direct anthropogenic impact from burning of fossil fuels, agriculture and changes in land use. Permafrost thawing may also intensify the Rn transport due to the increase of fluid saturation and permeability of the soil. A detailed study of 222Rn and 220Rn activity levels in polar soils constitutes a starting point to investigate gas migration processes as a function of the thawing permafrost. Although several studies have been carried out in the Arctic regions, there is little data available from the Southern Hemisphere. The Italian - New Zealand "SENECA" project aims to fill this gap and to provide the first evaluations of gas concentrations and emissions from permafrost and/or thawed shallow strata of the Taylor Valley, Antarctica. Taylor Valley is one of the few Antarctic regions that are not covered by ice and therefore is an ideal target for permafrost investigations. Results from our first field observations highlight very low values for 222Rn (mean 621 Bq m-3, max value 1,837 Bq m-3) and higher values for 220Rn (mean 11,270 Bq m-3, max value 27,589 Bq m-3), suggesting a shallow source. These measured activity values are essentially controlled by the radionuclide content in the soil, by the permeability and porosity of the soil, and by the water content. This dataset also represents an important benchmark for future measurements to track the melt progress of Antarctic permafrost.
DOI: 10.5194/egusphere-egu21-5100
2021050610 Rukhlov, Alexei S. (British Columbia Ministry of Energy, Mines and Low Carbon Innovation, Geological Survey, Victoria, BC, Canada); Ootes, Luke; Hickin, Adrian S. and Mashyanov, Nikolay R. Mercury vapour haloes in near-surface air above ore deposits and faults on Vancouver Island, British Columbia, Canada [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3473, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Volatile geogenic components, such as CO2, He, Rn, and Hg0, form haloes in soil gas and near-surface air directly above mineral deposits. This contrasts with lithochemical, hydrochemical, and biochemical dispersion haloes that can be laterally displaced or obscured by transported overburden. Mercury vapour surveys have been used in exploration, because Hg occurs in most types of enogenic ore deposit types and is highly mobile. Low background concentrations in the atmosphere (1.2 to 1.5 ng/m3) enable detecting even weak Hg emissions directly above buried ore deposits. In this study, we measured Hg vapour in air 1-50 cm above ground at 15 sites on Vancouver Island, British Columbia, Canada. To evaluate the effectiveness of the method across a range of settings, these sites include different types of known mineralized zones, barren rocks, and faults, both buried and exposed. The direct and continuous analysis via a portable RA-915M mercury analyzer reveals Hg vapour concentrations ranging from 0.5 to 54.4 ng/m3. The highest Hg concentration was observed above tailings at the Bentley Au occurrence, possibly due to the amalgamation technique used for fine gold extraction between late 1800s and early 1900s. Prominent Hg vapour haloes mark shear-hosted Cu-Ag-Au sulphides at Mount Skirt (13.4x background Hg), epithermal Au-Ag-Cu at Mount Washington (8.9x background Hg), and sediment-covered polymetallic volcanogenic massive sulphides at the Lara-Coronation occurrence (4.2 to 6.6x background Hg). Basalt-hosted Cu-Ag-Au sulphide zones at the Sunro past producer are marked by weak Hg vapour anomalies relative to local background. Faults, including the Leech River fault, which was active in the Quaternary, are also marked by weak Hg vapour anomalies. The study confirms that, although the Hg level is influenced by weather, the real-time Hg vapour measurement of near-surface air can instantly delineate mineralized zones and fault structures that are buried under overburden 10s of m thick. In contrast to soil gas sampling, this simple and rapid technique can be applied to mineral exploration and geological mapping under overburden above any type of surface, including outcrops, talus, bogs, water bodies, snow, and permafrost. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-3473
2021050594 Schroeder, Tanja (Technische Universität München, Chair of Landslide Research, Munich, Germany) and Krautblatter, Michael. A high-resolution multi-phase thermo-geophysical permafrost rock model to verify long-term ERT monitoring at the Zugspitze (German/Austrian Alps) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15231, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed. We developed a new, numerical, thermo-geophysical rock permafrost model (TGRPM) to assess spatial-temporal variations of the ground thermal regime in steep permafrost rock walls on the basis of 13-years of Electrical Resistivity Tomography (ERT) monitoring of permafrost at the Zugspitze. TGRPM is a simple to understand and workable numerical 2D MATLAB-model, which is adaptable to different topographic and sub-surface conditions, and further relies on a minimum of input-data to assess the surface energy balance and the ground thermal regime. It simulates the thermal response for permafrost rock walls, including their complex topography, to climate forcing over multiple years. It aims to assess seasonal and long-term permafrost development in steep alpine rock walls, as well as serving as a straightforward calculation routine, which is solely based on physical processes and does not require any fitting of certain parameters. At first, the model was tested against direct temperature measurements from the LfU-borehole at the Zugspitze summit to prove its accuracy. Then, it is run against a 13-year ERT data-set from the Zugspitze Kammstollen to validate the ERT measurements. Here, we show the first thermo-geophysical model referencing thermal evolution in a permafrost rock wall with temperature-calibrated ERT. The TGRPM successfully computes the thermal evolution within the Zugspitze mountain ridge from a 2D coupled energy balance and heat conduction scheme in complex topography. It furthermore validates the temperature-resistivity relationship by Krautblatter et al. (2010) for natural rock walls reaching a correlation of 85 to 95% between measured, ERT-derived and modelled temperatures.
DOI: 10.5194/egusphere-egu21-15231
2021050635 Sicaud, Eliot (University of Montreal, Department of Geography, Montreal, QC, Canada); Franssen, Jan; Dedieu, Jean-Pierre and Fortier, Daniel. Clustering analysis for the hydro-geomorphometric characterization of the George River watershed (Nunavik, Canada) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-206, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
For remote and vast northern watersheds, hydrological data are often sparse and incomplete. Fortunately, remote sensing approaches can provide considerable information about the structural properties of watersheds, which is useful for the indirect assessment of their hydrological characteristics and behavior. Our main objective is to produce a high-resolution territorial clustering based on key hydrologic landscape metrics for the entire 42000 km2 George River watershed (GRW), located in Nunavik, northern Quebec (Canada). This project is being conducted in partnership with the local Inuit communities of the GRW for the purpose of generating and sharing knowledge to anticipate the impact of climate and socio-environmental change in the GRW. Our clustering approach employs Unsupervised Geographic Object-Based Image Analysis (GeOBIA) applied to the entire GRW with the subwatersheds as our objects of analysis. The landscape metric datasets used to generate the input variables of our GeOBIA classification are raster layers with a 30 m´30 m pixel resolution. Topographic metrics are derived from a Digital Elevation Model (DEM) and include elevation, slopes, aspect, drainage density and watershed elongation. Land cover spectral metrics comprised in our analysis are the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Moisture Index (NDMI) (Gao, 1996) and the Normalized Difference Water Index (NDWI) (McFeeters, 1996), which are all computed from a Landsat-8 cloud-free surface reflectance mosaic dating from 2015. Rasterized maps of surface deposit distribution and permafrost distribution, both produced by the Ministere des Forets, de la Faune et des Parcs of Quebec (MFFP), respectively constitute the surface and subsurface metrics of our GeOBIA. The clustering algorithm used in this Unsupervised GeOBIA is the Fuzzy C-Means (FCM) algorithm. The FCM algorithm provides the objects a set of membership coefficients corresponding to each cluster. The greatest membership coefficient is then used to attribute the distinct subwatersheds to a cluster of watersheds with similar hydro-geomorphometric characteristics. The classification returns a Fuzzy Partition Coefficient (FPC), which describes how well-partitioned our dataset is. The FPC can vary greatly depending on the number of clusters we want to produce. Thus, we find the optimal number of clusters by maximizing the FPC. Preliminary clustering results, computed only with topographic and land cover metrics, have identified two distinct watershed classes/clusters. In general, "Type 1" subwatersheds are clustered over the southern and northwestern portion of the GRW and are characterized by low to moderate elevation, high vegetation cover, high moisture and high surface water cover. Whereas "Type 2" subwatersheds located over the northeastern portion of the GRW are characterized by high elevation, low vegetation cover, low moisture and low surface water cover. These results will be refined with the use of additional metrics and will provide the detailed understanding necessary to assess how the hydrological regime of the river and its tributaries will respond to climate change, and how landscape change and human activities (e.g., planned mining development) may impact the water quality of the George River and its tributaries. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-206
2021050614 Sobiech-Wolf, Jennifer (University of Münster, Institute for Landscape Ecology, Munster, Germany); Ullmann, Tobias and Dierking, Wolfgang. SMART; Space Monitoring of ARctic Tundra landscapes [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14864, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Satellite remote sensing as well as in-situ measurements are common tools to monitor the state of Arctic environments. However, remote sensing products often lack sufficient temporal and/or spatial resolution, and in-situ measurements can only describe the environmental conditions on a very limited spatial scale. Therefore, we conducted an air-borne campaign to connect the detailed in-situ data with poor spatial coverage to coarse satellite images. The SMART campaign is part of the ongoing project "Characterization of Polar Permafrost Landscapes by Means of Multi-Temporal and Multi-Scale Remote Sensing, and In-Situ Measurements", funded by the German Research Foundation (DFG). The focus of the project is to close the gap between in-situ measurements and space-borne images in polar permafrost landscapes. The airborne campaign SMART was conducted in late summer 2018 in north-west Canada, focussing on the Mackenzie-Delta region, which is underlain by permafrost and rarely inhabited. The land cover is either dominated by open Tundra landscapes or by boreal forests. The Polar-5 research-aircraft from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Germany, was equipped with a ground penetrating radar, a hyperspectral camara, a laserscanner, and an infrared temperature sensor amongst others. In parallel to the airborne acquisition, a team collected in-situ data on ground, including manual active layer depth measurements, geophysical surveying using 2D Electric Resistivity Tomography (ERT), GPR, and mapping of additional land cover properties. The database was completed by a variety of satellite data from different platforms, e.g. MODIS, Landsat, TerraSAR-X and Sentinel-1. As part of the project, we analysed the performance of MODIS Land surfaces temperature products compared to our air-borne infrared measurements and evaluated, how long the land surface temperatures of this Arctic environment can be considered as stable. It turned out that the MODIS data differ up to 2°C from the air-borne measurements. If this is due to the spatial difference of the measurements or a result of data processing of the MODIS LST products is part of ongoing analysis.
DOI: 10.5194/egusphere-egu21-14864
2021050640 Sun Yuqin (Peking University, College of Engineering, Beijing, China); Clauson, Kale; Zhou Min; Sun Ziyong; Zheng Chunmiao and Zheng Yan. Unraveling the groundwater transit time control of permafrost derived dissolved organic carbon processing in a hillslope headwater watershed of Qinghai-Tibetan Plateau [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-377, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Climate warming leads to massive thaws of the northern permafrost that has increased the release of soil organic carbon (SOC) to streams and rivers partly as dissolved organic carbon (DOC). The transport pathways of SOC releasing into porewater and entering into stream are undergoing profound hydrological changes triggered by permafrost thawing, yet the role that the groundwater plays in processing the permafrost derived DOC is ambiguous. Unravelling how subsurface flow affects permafrost sourced DOC processing is important especially in alpine watersheds of high-altitude permafrost region with extensive surface - groundwater interaction. Here, eight types of water were sampled from a small (25 km2), alpine (elevation 2960 to 4820 m a.s.l.) watershed named Hulugou watershed (HLGW) with variably degraded permafrost in the Qinghai-Tibetan Plateau (QTP) in July and September of 2012, 2013 and 2018. The three end-members (glacier-snow meltwater, precipitation, and frozen soil meltwater) analysis suggested contribution of frozen soil meltwater to all types of water with variable DOC levels (0.4 to 22.6 mg L-1, n=113), as constrained by d18O and electrical conductivity (EC). Spatial patterns of DOC quantity and quality between stream and subsurface waters (groundwater, spring, and seepage-II) point to differences in surface - groundwater exchanges in the upper-, mid- and lower stretch of the watershed. To evaluate the extent of DOC loss (DDOC), DDOC is calculated using an initial DOC (DOC0) estimated from mixing of three endmembers, minus the measured DOC concentration. The significant correlations between DDOC with proportion of protein-like fluorophores (r=-0.69, p<0.01) and relatively aromatic C levels (r=-0.62, p=0.02) indicate DDOC corresponding to the extent of microbial utilization of DOC in subsurface environment. Using previously established DOC biodegradation kinetics of 0.25 d-1 in headwaters of QTP, the mean transit time of groundwater is estimated to be 6 and 20 days based on changes in subsurface DDOC of 32% and 74% from the outlet of HLGW for July and September, respectively. The more rapid groundwater transit time corresponds to the higher concentration and more boilable DOC in July (3.5 mg L-1, protein-like: 98%) than in September (1.0 mg L-1, protein-like: 53±26%). Together with the mass balance of DOC input and export fluxes showing half loss of C in HLGW, our results indicate that rapid groundwater transit time is associated with permafrost derived DOC processing in alpine hillslope subject to warming.
DOI: 10.5194/egusphere-egu21-377
2021050650 Surovyatkina, Elena (Potsdam Institute for Climate Impact Research, Complex Systems, Potsdam, Germany). The impact of Arctic warming on the timing of Indian monsoon and ice season in the Sea of Okhotsk [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13582, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
In 2020, the Arctic Circle warming in Siberia was extraordinary. Strong anticyclones have been dominant over a large area in Northern Siberia through spring. It resulted in an all-time high-temperature record in the Arctic Circle - more than 6°C above the average (1981-2010). Thus, it accelerated the melting of snow, ice, permafrost and has gotten the wildfire in Siberia off to an unusually early and severe start. The Arctic warming has repercussions not only for Siberia but for the entire Eurasia and the Northern Hemisphere. Specifically, the Arctic conditions affect atmospheric circulation in the Pacific Ocean and the strength and direction of trade winds in the tropical zone. Here, I show that Arctic Circle warming has impacted the timing of monsoon and sea ice seasons. First, I found the observational evidence of Arctic warming causing colder than average temperatures over the east of Eurasia, Central Europe, and Central Asia. Notably, North Pakistan and Northern India saw temperatures distinctly below the long-term average (1981-2010): 4°C below from March to December. Second, I took this evidence into account while developing a new method for forecasting the sea-ice timing and the recent long-range forecasting method of monsoon season. Third, based on the forecast results for 2020, I found that utilizing only recent trends is an inadequate strategy for predictions. However, considering the current Arctic warming outcomes in specific regions overcomes this problem and results in successful forecasts for both sea-ice and monsoon seasons. The results imply that when North Pakistan's temperature is cooler than usual: (i) it slows down an advance of monsoon, (ii) it accelerates the cooling of the entire Indian subcontinent during withdrawal from northern Pakistan to the east coast of central India. Hence, North Pakistan's cooling in 2020 caused a protracted offensive and early end of the Indian summer monsoon, thus, shortening its duration. As a result, it led to the early onset of the seasonal wind reversal in the eastern Pacific Ocean in the middle of October and, therefore, to the surprisingly early onset of the winter monsoon in South Asia and India. The consequences of this change in monsoon timing strongly affected 70% of the Indian population directly related to farming. In the Sea of Okhotsk in 2020, the sea ice retreated early due to heatwaves in Siberia. In December, the onset date of ice season was around average, but ice grew faster than average, creating a hazard to navigation safety. Hence, the proposed forecasting methodology applied to India and the Sea of Okhotsk opens new possibilities to forecasting monsoon and sea ice seasons around the globe. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-13582
2021050659 Sycheva, Svetlana (Russian Academy of Sciences, Institute of Geography, Moscow, Russian Federation); Frechen, Manfred; Terhorst, Birgit; Sedov, Sergey and Khokhlova, Olga. Stratigraphy and chronology of late Pleistocene loess-paleosol sequence of the East European Plain and correlation with late Pleistocene archives of Europe [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-650, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
A detailed pedocryostratigraphic scheme of the Late Pleistocene periglacial region of the East European Plain has been developed on the basis of study of the paleorelief, sediments, paleosols, and cryogenic horizons. OSL and 14C-dating of paleosols and sediments in Aleksandrov quarry and in other sections made it possible to substantiate this scheme and correlate it with analogous ones for different regions of Europe. The loess-paleosol sequence in Aleksandrov quarry (51°05'N, 36°08'E) does not have an analogous with respect to the completeness in the whole East European Plain. In the filling of paleobalka the Ryshkovo paleosol of the Mikulino interglacial (MIS 5e) is observed. Over this paleosol, the Valdai soil-sediment series (MIS 5d-MIS 2) is located. It includes four interstadial soils, two of them of the Early Valdai (Kukuevo and Streletsk ones), and two, sometimes three, of the Middle Valdai (Aleksandrov, Hydrouzel and Bryansk ones). The OSL date, 127±8 ka BP, (beginning of MIS 5e) was obtained for a sample taken from the bottom of the Ryshkovo soil. The interglacial soil is overlain by the Seym layer formed mainly from destroyed and redeposited horizons of this soil. For the upper part of the Seym layer, OSL dates of 115±7 ka BP and 112±20 ka BP were obtained (MIS 5d). But the process of burial of Ryshkovo soil in the bottom of the paleobalka began at the end of the interglacial after a catastrophic forest fire. Large post-permafrost deformations - pseudomorphosis is confined to Selikhovodvor loess - MIS 4 (65±8 ka BP). Two soils occurring between Seym and Selikhovodvor loesses: Kukuevo and Streletsk - Early Valdai (MIS 5c and MIS 5a). For Mlodat loess which separates those two soils (MIS 5b), OSL dates of 91±1 and 89±7 ka BP were obtained. For paleosols of Middle Valdai (MIS 3), 14C-dates were obtained: Aleksandrov (53.742-2.124 ka cal BP) and Bryansk soils (37.618±0.668 ka cal BP). For Tuskar loess, which separates Alexandrov and Bryansk soils, OSL dates of 50±3 and 51±3 ka BP were obtained. The new stratigraphic scheme of Late Pleistocene agrees with the ideas of researchers from Eastern, Central, and Western Europe , which allows the following correlations. The identified paleosols correspond to the following intervals: Ryshkovo-Eemian interglacial (127-117 ka BP); Kukuevo to Amersfoort+Brorup-Saint-Germain 1 (105-95 ka BP); Streletsk-Odderade to Saint-Germain 2 (about 85-75 ka BP); Aleksandrov to Oerel (56-53 ka BP); Hydrouzel to Moershoofd - Poperinge (44-45 ka BP) and Hengelo (40-38 ka BP); and Bryansk (33-27 ka BP) to Stillfried B, Denekamp or Grand Bois interstadials. The reconstructed Late Pleistocene loess-paleosol sequence has the most similar structure with loess-paleosol sequences of Ukraine, with sequence Dolni Vestonice in Moravia (Czech Republik), Stillfried in Austria and Mainz-Weisenau in the Rhenish area (Germany), and other archives. This work was supported by RFBR, grant N19-29-05024 mk. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-650
2021050664 Szatmari, Roland (University of Debrecen, Department of Theoretical Physics, Debrecen, Hungary) and Kun, Ferenc. Anisotropic fragmentation of shrinking thin layers on a substrate [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12679, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Layers of dense pastes, colloids attached to a substrate often undergo sequential cracking due to shrinkage stresses caused by desiccation. From the spectacular crack patterns of dried out lake beds through the polygonal ground patterns of permafrost regions to the formation of columnar joints in cooling volcanic lava, shrinkage induced cracking is responsible for a large variety of complex crack structures in nature. Under laboratory conditions this phenomenon is usually investigated by desiccating thin layers of dense colloidal suspensions in a container, which typically leads to polygonal crack patterns with a high degree of isotropy. It is of great interest how to control the structure of shrinkage induced two-dimensional crack patterns also due to its high importance for technological applications. Recently, it has been demonstrated experimentally for dense calcium carbonate and magnesium carbonate hydroxide pastes that applying mechanical excitation by means of vibration or flow of the paste the emerging desiccation crack pattern remembers the direction of excitation, i.e. main cracks get aligned and their orientation can be tuned by the direction of mechanical excitation. In order to understand the mechanism of this memory effect, we investigate a fragmentation process of a brittle, cylindrical sample, where the driving force of the cracking coming from a continuous shrinkage, which sooner or later destroys the cohesive forces between the structure's building blocks. Our study is based on a two dimensional discrete element model, where the material is discretised via a special form of the Voronoi-tesselation, with the so-called randomised vector lattice which allows to fine-tune the initial disorder of the system. We assume that the initial mechanical vibration imprints plastic deformation into the paste, which is captured in the model by assuming that the local cohesive strength of the layer has a directional dependence: the layer is stronger along the direction of vibration. We demonstrate that - based on this simple assumption - the model well reproduces the qualitative features of the anisotropic crack patterns observed in experiments. Gradually increasing the degree of anisotropy the system exhibits a crossover from an isotropic cellular structure to an anisotropic one. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-12679
2021050643 Voit, Klaus (University of Natural Resources and Life Sciences, Institute of Applied Geology, Vienna, Austria); Fey, Christine; Rechberger, Christina; Mair, Volkmar and Zangerl, Christian. Geological investigation and movement analysis of the deep-seated compound rockslide Laatsch, south Tyrol [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5622, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
In Alpine areas, deep-seated rockslides are relatively common. They are mostly based on geological and tectonic conditions and triggered by permafrost degradation, snowmelt or heavy rainfall events. A striking example is situated near Laatsch, South Tyrol, at the valley entrance of the Münstertal at close range to the national road SS41 leading to the Swiss border. The activation of the movement occurred in the year 2000, showing a rapid expansion since the year 2012 causing a relocation of the road in 2014. The U-shaped valley of the Munstertal was formed by glaciers, the valley floor is filled with alluvial sediments. The Mountain ridge runs approx. 2,100 m above the Adriatic Sea, valley floor at approx. 1,000 m above Adriatic Sea. The slope gradient varies between 30 and 50°. The rockslide situated in this slope is approx. 400 m wide, approx. 700 m in height at its longest extension, with a slide surface ca. 50-100 m deep summing up to an instable rock volume of approximately 5 to 10 million m3 and monthly average movement rates of 0.1 to 0.55 m. Geological mapping and analysis were performed for the detailed identification of the cause of failure and occurring failure types such as sliding, falling, toppling and flow. The different gneiss bedrock types mainly consist of Quartz, Feldspar, Muscovite and Calcite, foliation is mainly caused by Muscovite layers. Muscovite-rich shearing planes could also be identified via thin section analysis. The foliation dips with a dip of ca. 10-20° mainly towards Northeast and therefore is orientated towards the slope. Two sets of very steep dipping joins are present deeply fragmenting the rock mass providing starting points or lines for the development of scarp surfaces. Deep weathering of the disintegrated gneiss bed rock could be observed at tectonically induced fracture surfaces. Weathering progresses along scarps and developed tension cracks further eroding and dissembling the rock mass. Movement analysis of different slabs were performed twice a year using multi-temporal terrestrial laser scanning (TLS) between 2017 and 2020. Along this sliding surface, rock material is transported as individual slabs showing mainly a translational movement behavior with minor internal deformation. These slabs are visually recognizable on site as well as during the analysis of movement rates of laserscanning series measurements. Main mass transport occurs from upper steep slope areas to areas of lower slope angle within and at the foot of the rockslide. General movement occurs via a basal slip surface with an average thickness of failure volume of approx. 50 to 100 Meters. Volume of displaced material during accompanied processes of rock fall and rock topple events amounts to 2,000-5,000 m3 depending on the size of the event. These types of rock movement mainly take place along outbreak recesses at the rockslide flanks, scarps and at the internal slab margins. These falls and topples can also be detected through several laserscanning measurement series.
DOI: 10.5194/egusphere-egu21-5622
2021050609 Wengler, Marc (Bundesgesellschaft für Endlagerung, Peine, Germany); Göbel, Astrid; Hoyer, Eva-Maria; Liebscher, Axel; Reiche, Sönke; Völkner, Eike and Rühaak, Wolfram. Significance of long-term climate evolution and associated impacts on the long-term safety of a high-level radioactive waste repository within the German siting process [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15771, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
According to the 'Act on the Organizational Restructuring in the Field of Radioactive Waste Disposal' the BGE was established in 2016. The amended 'Repository Site Selection Act' (StandAG) came into force in July 2017 and forms the base for the site selection by clearly defining the procedure. According to the StandAG the BGE implements the participative, science-based, transparent, self-questioning and learning procedure with the overarching aim to identify the site for a high-level radioactive waste (HLW) repository in a deep geological formation with best possible safety conditions for a period of one million years. The German site selection procedure consists of three phases, of which Phase 1 is divided into two steps. Starting with a blanc map of Germany, the BGE completed Step 1 in September 2020 and identified 90 individual sub-areas that provide favorable geological conditions for the safe disposal of HLW in the legally considered host rocks; rock salt, clay and crystalline rock. Based on the results of Step 1, the on-going Step 2 will narrow down these sub-areas to siting regions for surface exploration within Phase 2 (section 14 StandAG). Central to the siting process are representative (Phase 1), evolved (Phase 2) and comprehensive (Phase 3) preliminary safety assessments according to section 27 StandAG. The ordinances on 'Safety Requirements' and 'Preliminary Safety Assessments' for the disposal of high-level radioactive waste from October 2020 regulate the implementation of the preliminary safety assessments within the different phases of the siting process. Section 2 of the 'Safety Requirements' ordinance provides requirements to evaluate the long-term safety of the repository system; amongst others, it states that all potential effects that may affect the long-term safety of the repository system need to be systematically identified, described and evaluated as "expected" or "divergent" evolutions. Additionally, the ordinance on 'Preliminary Safety Assessments' states in section 7, amongst others, that the geoscientific long-term prediction is a tool to identify and to evaluate geogenic processes and to infer "expected" and "divergent" evolutions from those. Hence, considering the time period of one million years for the safe disposal of the HLW and the legal requirements, it is essential to include long-term climate evolution in the German site selection process to evaluate the impact of various climate-related scenarios on the safety of the whole repository system. To better understand and evaluate the influence of climate-related processes on the long-term safety of a HLW repository, climate-related research will be a part of the BGE research agenda. Potential research needs may address i) processes occurring on glacial-interglacial timescales (e.g. the inception of the next glaciation, formation and depth of permafrost, glacial troughs, subglacial channels, sea-level rise, orbital forcing) and their future evolutions, ii) effects on the host rocks and the barrier system(s) as well as iii) the uncertainties related to these effects but also to general climate models and predictions. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-15771
2021050639 Woo, Audrey (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada); McKenzie, Jeffrey and Carey, Sean. A three-dimensional groundwater flow simulation of Granger Basin, Yukon, Canada [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6675, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Groundwater flow and exfiltration (discharge) in Arctic and Subarctic mountain regimes is poorly understood yet plays an important role in areas underlain by continuous and discontinuous permafrost. Permafrost, ground with a perennial temperature below 0°C, acts as an impermeable barrier to groundwater flow and influences hydrogeologic connectivity and storage. The Arctic is warming at twice the global average rate, leading to rapid permafrost thaw with unclear consequences for groundwater systems. In this study, we develop a numerical groundwater model of the Granger Basin, Yukon, to further our understanding of the influence of permafrost and thaw on groundwater flow in basins impacted by climate change. Granger Basin is a 7.6 km2 headwater catchment located within the Wolf Creek Research Basin, Yukon, Canada. It is representative of a subarctic-continental mountain environment with already observable climate change impacts. To date, there has been limited hydrogeology monitoring or numerical modeling at this site. To investigate cryohydrogeologic processes within the basin, we integrate existing field data, including 30 years of hydrometeorological records and geophysical data into a three-dimensional numerical model with saturated-unsaturated groundwater flow. We use the SUTRA-ice numerical model that couples groundwater flow and energy transport with dynamic freeze-thaw processes. The model incorporates both time-dependent thermal and hydrological surface boundary conditions and is used parametrically to understand the generation of groundwater baseflow in this setting. We will present initial results that will evaluate the impact of different hydrogeologic properties on the generation of groundwater streamflow in Wolf Creek, how permafrost in transition affects the groundwater system, and provide the framework for future research directions.
DOI: 10.5194/egusphere-egu21-6675
2021050589 Yanagiya, Kazuki (Hokkaido University, Graduate School of Science, Sapporo, Japan); Furuya, Masato; Iwahana, Go and Danilov, Petr. Thaw subsidence and frost heave caused by 2018-20 forest fires around Batagay; validation with multiple InSAR data and field observation [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14093, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The Arctic has experienced numerous fires in last year, and from June to August 2020, satellite data showed record carbon dioxide emissions from forest fires. Peatland in the Arctic contains large amounts of organic carbon, and their release into the atmosphere can create positive feedbacks for further increase of air temperature. In addition, forest fires burn the surface vegetation layer that has been acting as a heat insulator, which will accelerate the thawing of permafrost on scales of years to decades. Although the thaw depth can recover together with the recovery of surface vegetation, the massive segregated ice is not recoverable once it melted. Our study area is around the Batagay, Sakha Republic, Eastern Siberia. In June 2020, Verkhoyansk, located about 55 km west of Batagay, recorded the highest daily maximum temperature of 38.0 degrees Celcius. The Sentinel-2 optical satellite images showed a number of forest fires in 2019-20. We detected the surface deformation signals at each fire site with the remote-sensing method called InSAR (Interferometric Synthetic Aperture Radar). Also, we conducted a field observation in September 2019 for validations: 1) installed a soil thermometer and soil moisture meter; 2) established a reference point for leveling and first survey; 3) measured the thawing depth with a frost probe. For seasonal ground deformations immediately after the fire, we mainly analyzed Sentinel-1 images. Sentinel-1 is the ESA's C-band SAR satellite, which has a short imaging interval of 12 days. As the short wavelength, vegetation changes lost coherence, and some pairs failed to detect ground deformation signals immediately after the fire. However, after the end of September, we detected displacements toward the satellite line-of-sight direction at all the fire sites. It indicates uplift signals due presumably to frost heave at the fire scar. For long-term deformations over one year, we used ALOS2 imaged derived by JAXA's L band SAR satellite. In the previous studies in Alaska, the ground deformation signal immediately after a fire could not be detected due to the coherence loss in the pairs derived from pre-fire and post-fire SAR images. Indeed, we could not detect deformation signals at the fire scars from the June pairs derived before and after the fire. However, the January pairs and March pairs, both of which were acquired before and after the fire, showed relatively high coherence even in the fire scar and indicated clear subsidence signals by as much as 15 cm. We interpret that, because the studied Verkhoyansk Basin is very dry and has little snow cover, the microwaves could penetrate the snow layer, which allowed us to detect deformation signals even in winter. Yanagiya and Furuya (2020) validated the consistency of the winter uplift signal for the 2014 fire site. We also analyzed the SM1 high spatial resolution mode (3 m) ALOS2 InSAR to investigate the specific ground deformation at each fire site. [Copyright Author(s) 2021. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
DOI: 10.5194/egusphere-egu21-14093
2021050587 Yokohata, Tokuta (National Institute for Environmental Studies, Tsukuba, Japan); Saito, Kazuyuki; Iwahana, Go; Ito, Akihiko and Tanaka, Katsumasa. Model improvement and projection of permafrost degradation and greenhouse gas emission [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13891, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
To date, the treatment of permafrost in earth system models has been simplified due to the prevailing uncertainties in the processes involving frozen ground. In this study, we improved the modeling of permafrost physical processes in a state-of-the-art earth system model (MIROC) by taking into account some of the relevant physical properties of soil such as changes in the thermophysical properties due to freezing (URL: https://doi.org/10.1186/s40645-020-00380-w). As a result, the improved version of the model was able to reproduce a more realistic permafrost distribution at the southern limit of the permafrost area by increasing the freezing of soil moisture in winter. The improved modeling of permafrost processes also had a significant effect on future projections. Using the conventional formulation, the predicted cumulative reduction of the permafrost area by year 2100 was approximately 60% (40-80% range of uncertainty from a multi-model ensemble) in the RCP8.5 scenario, while with the improved formulation, the reduction was approximately 35% (20-50%). Our results indicate that the improved treatment of permafrost processes in global climate models is important to ensuring more reliable future projections. In addition, the processes of greenhouse gas (GHG) emissions due to permafrost degradation are not considered in many earth-system models. Therefore, we developed a model to diagnose that processes by using the output of earth system models (URL: https://doi.org/10.1186/s40645-020-00366-8). The model called PDGEM (Permafrost Degradation and GHG Emission Model) describes the thawing of the Arctic permafrost including the Yedoma layer due to climate change and the GHG emissions. Our model simulations show that the total GHG emissions from permafrost degradation in the RCP8.5 scenario was estimated to be 31-63 PgC for CO2 and 1261-2821 TgCH4 for CH4 (68th percentile of the perturbed model simulations, corresponding to a global average surface air temperature change of 0.05-0.11°C), and 14-28 PgC for CO2 and 618-1341 TgCH4 for CH4 (0.03-0.07°C) in the RCP2.6 scenario. An advantage of PDGEM is that geographical distributions of GHG emissions can be estimated by combining a state-of-the-art land surface model featuring detailed physical processes with a GHG release model using a simple scheme, enabling us to consider a broad range of uncertainty regarding model parameters. In regions with large GHG emissions due to permafrost thawing, it may be possible to help reduce GHG emissions by taking measures such as restraining land development.
DOI: 10.5194/egusphere-egu21-13891
2021050632 Zemlianskova, Anastasiia (Saint Petersburg State, Department of Earth Sciences, Saint Petersburg, Russian Federation); Makarieva, Olga and Nesterova, Nataliia. Processes of runoff formation at the Putorana Plateau (central Siberia, Russia) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-208, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
The Putorana Plateau is located in the North-West of the Central Siberian Plateau in the Krasnoyarsk Territory in permafrost zone. Some mountain peaks reach a height of 1400-1700 m. The plateau is composed of stepped canyons formed by the outpouring of a huge mass of red-hot basalts. The Putorana Plateau is the territory that is still unexplored in hydrological terms. Climate change contributes to an increase in the thickness of seasonal thawing, therefore, the conditions of runoff formation change. The purpose of the work is to study the factors of runoff formation, including the research of geocryological conditions based on short-term expedition data of the State Hydrological Institute (St. Petersburg, Russia) collected in small catchments in 1988-1990. The object of study is the catchment of the stream Dupkun (an area of 2.75 sq. km), which is located in the basin of the Kureyka river basin, the right tributary of Yenisei River in the southwestern part of the Putorana Plateau. The maximum height of the catchment is 1228 m, and the hydrological gauge is located at an altitude of 923 m. The average slope of the catchment area is 12°. The landscape is a moss-grass mountain tundra, and perennial snowfields are also formed. The expedition studies in the period from July 19 to September 4, 1990 included the collection of hydrometeorological information, the determination of soil characteristics (moisture content, temperature, structure at different depths and landscapes), and the study of snow cover. The route studies were conducted to determine the characteristics of landscapes, vegetation and soils in the basins of the rivers Kureyka and Khantayka. The data of the expedition studies were processed, digitized and systematized. Based on the collected material, the water balance of the stream Dupkun was calculated. The presence of perennial snowfields has a significant impact on the formation of runoff. At the beginning of observations, the area of snowfields was 15%, the average snow height was 2.6 m, and the average density was 0.7 g/cm3. At the end of observations, snowfields occupied 8% of the catchment area. For 20 days, the snowmelt depth was 38 mm, the precipitation reached 140 mm, and the runoff was 167 mm. The runoff coefficient is 0.89. During the entire observation period, the runoff reached 355 mm. These observations are considerable value due to the lack of knowledge of the geocryological, landscape and hydrological conditions of the Putorana Plateau. Since there are practically no hydrological stations in this region that study the processes of flow formation, the collected data become even more unique. Extremely scarce data allowed to conduct the assessment and verification of the parameters of the hydrological model "Hydrograph". The developed set of the model parameters was used to simulate the river flow of tundra landscapes of the Putorana Plateau and assess its contribution to the formation of the water balance of the territory in the current climate.
DOI: 10.5194/egusphere-egu21-208
2021050636 Zhang Fan (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Beijing, China); Xiao Xiong and Wang Guanxing. Runoff generation processes in permafrost-influenced area of the Heihe River headwater [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-1660, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Permafrost degradation under global warming may change the hydrological regime of the headwater catchments in alpine area such as the Tibetan Plateau (TP). In this study, he runoff generation processes in permafrost-influenced area of the Heihe River Headwater were investigated with the following results: 1) The observed stable isotope values of various water types on average was roughly in the order of snowfall and snowmelt<bulk soil water (BSW)<rainfall , stream water, mobile soil water (MSW), and lateral subsurface flow. The depleted spring snowmelt and enriched summer rainfall formed tightly bound soil water and MSW, respectively. The dynamic mixing between tightly bound soil water and MSW resuted in BSW with more depleted and variable stable isotopic feature than MSW. 2) Along with the thawing of the frozen soil, surface runoff and shallowsubsurface flow (SSF) at 30?60 cm was the major flow pathway in the permafrost influenced alpine meadow hillslope during spring snowmelt and summer rainfall period, reapectively, with the frozen soil maintaining supra-permafrost water level. 3) Comparison between two neighouring catchments under similar precipitation conditions indicated that streamflow of the lower catchment with less permafrost proportion and earlier thawing time has larger SSF and higher based flow component, indicating the potential changes of hydrological regims subject to future warming.
DOI: 10.5194/egusphere-egu21-1660
2021050604 Zwieback, Simon (University of Alaska at Fairbanks, Geophysical Institute, Fairbanks, AK) and Meyer, Franz. Identifying ice-rich permafrost using remotely sensed late-season subsidence [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-985, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.
Despite the critical role of ground ice for permafrost ecosystems and terrain stability, we lack fine-scale ground ice maps across almost the entire Arctic. This is chiefly because ground ice cannot be observed directly from space. Here, we analyse late-season subsidence from Sentinel-1 InSAR satellite observations as a physically based indicator of vulnerable excess ground ice at the top of permafrost. The key idea is that the thaw front can penetrate materials that were previously perennially frozen at the end of a warm summer, triggering subsidence where the permafrost is ice rich. We assess the idea by comparing the InSAR observations to permafrost cores and an independently derived ground ice classification. We find that the late-season subsidence in an exceptionally warm summer was 4-8 cm (5th-95th percentile) in the ice-rich areas, while it was lower in ice-poor areas (-1 to -2 cm). The observed distributions for ice-rich and ice-poor terrain overlapped by only 2%, demonstrating high sensitivity and specificity for identifying top-of-permafrost excess ground ice. The strengths of late-season subsidence include the ease of automation and its applicability to areas that lack conspicuous manifestations of ground ice, as often occurs on hillslopes. The biggest limitation is that it is not sensitive to excess ground ice below the thaw front and thus the total ice content. A further challenge is the sub-resolution variability in ground ice, ice-wedge polygons being a striking example, which needs to be accounted for when interpreting and validating the results. We expect late-season subsidence to enhance the automated mapping of ice-rich permafrost terrain, complementing existing (predominantly non-automated) approaches based on largely indirect associations of ice content with vegetation and periglacial landforms. The suitability of satellite-observed late-season subsidence for mapping ice-rich permafrost can contribute to anticipating terrain instability in the Arctic and sustainably stewarding its ecosystems.
DOI: 10.5194/egusphere-egu21-985
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The USPA is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute (AGI), with support from the National Science Foundation (NSF), has migrated the previous Cold Regions Bibliography to a new platform. Included are the USPA supported PMAs dating back to 2011. The Bibliography is searchable at 
