Permafrost Monthly Alerts (PMAs)

USPA LogoThe 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


To view a list of the individual PMAs follow the button below.

View all PMAs


The PMA program is made possible by the following sponsors:

AFI Logo GWS Logo CS Logo




Entries in each category are listed in chronological order starting with the most recent citation. The July PMA contains 95 citations from the 2021 meeting of the European Geosciences Union general assembly.

Browse by Reference Type:

Serial | Conference


2021045217 Kirkwood, J. Adam. H. (Laurentian University, Department of Biology, Sudbury, ON, Canada); Roy-Léveillée, Pascale; Mykytczuk, Nadia; Packalen, Maara; McLaughlin, Jim; Laframboise, Amy and Basiliko, Nathan. Soil microbial community response to permafrost degradation in palsa fields of the Hudson Bay Lowlands; implications for greenhouse gas production in a warming climate: Global Biogeochemical Cycles, 35(6), Article e2021GB006954, illus. incl. 4 tables, sketch map, 79 ref., June 2021.

Permafrost thaw in northern peatlands alters the ground thermal conditions, moisture, and chemistry that control microbial activity responsible for the production of greenhouse gases (GHGs) like methane from decomposing organic matter. This paper examines interactions between microbial communities, peat chemistry, moisture content, and temperature in the context of degrading palsa fields in the vast (372,000 km2), carbon rich, and rapidly warming permafrost peatlands of the Hudson Bay Lowlands. The temperature sensitivities of microbial GHG production and consumption from palsa and fen peat were assessed, and microbial community structure was examined as a potential constraint on GHG production in relation to changes in peat chemistry associated with thermokarst encroachment and active layer deepening. High CH4 production was observed from thermokarst peat, under controlled moisture and temperature conditions, associated with increased pH. A shift in methanogen taxonomic and metabolic diversity favoring aceticlastic methanogenesis was associated with changes in peat chemistry and pH from palsa to thermokarst fen peat. In palsa peat, CH4 production rates were lowest but most sensitive to temperature variations, due to recalcitrant carbon compounds. CH4 production was highly sensitive to increased temperatures, yet was balanced by high temperature sensitivity of CH4 oxidation in oxic conditions, consistent with the low temperature sensitivity of fluxes observed in field studies from other permafrost peatlands. Building on the microbial controls in this study, future work should explore how permafrost degradation and increased hydrological connectivity to mineral substrates are changing in this globally significant permafrost peatland, and how this impacts net CH4 emissions. Abstract Copyright (2021), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GB006954

2021045995 Savi, Sara (University of Potsdam, Institute of Geosciences, Potsdam, Germany); Comiti, Francesco and Strecker, Manfred R. Pronounced increase in slope instability linked to global warming; a case study from the eastern European Alps: Earth Surface Processes and Landforms, 46(7), p. 1328-1347, illus. incl. 2 tables, geol. sketch maps, 106 ref., June 15, 2021.

In recent decades, slope instability in high-mountain regions has often been linked to increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small- to medium-sized mass movements in a high-elevation catchment of the Italian Alps (Sulden/Solda basin). We found that slope-failure events (mostly in the form of rockfalls) have increased since the 2000s, whereas the occurrence of debris flows has increased only since 2010. The current climate-warming trend registered in the study area apparently increases the elevation of rockfall-detachment areas by approximately 300 m, mostly controlled by the combined effects of frost-cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity-duration rainfall distribution. Potential debris-flow events in this environment may additionally be influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden/Solda basin (above ca. 2500 m above sea level [a.s.l.]), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 2000s, and that an increase in rockfalls and debris flows during spring and summer can be inferred. Our study thus confirms that "forward-looking" hazard mapping should be undertaken in these increasingly frequented, high-elevation areas of the Alps, as environmental change has elevated the overall hazard level in these regions. Abstract Copyright (2021), John Wiley & Sons, Ltd.

DOI: 10.1002/esp.5100

2021043926 Obu, Jaroslav (University of Oslo, Department of Geosciences, Oslo, Norway). How much of the Earth's surface is underlain by permafrost?: Journal of Geophysical Research: Earth Surface, 126(5), Article e2020JF006123, illus. incl. 1 table, 23 ref., May 2021.

More than 80% of studies reporting the area on Earth underlain by permafrost refer to the extent of the permafrost region, which accounts for around 21 million km2 (22% of the Northern Hemisphere's exposed land surface). Since each permafrost zone (continuous, discontinuous, sporadic, and isolated, which combined represent the permafrost region) is not entirely underlain by permafrost, the actual area underlain by permafrost (permafrost area) accounts for approximately 14 million km2 (15% of the exposed land surface area in the Northern Hemisphere). Such overstatements create a general impression that there is 6 million km2 more permafrost than currently estimated. I highlight the known differences between the terms permafrost region and permafrost area, along with explaining the possible reasons leading to these overstatements. Recent studies estimating permafrost area extent are summarized to provide a baseline for the geoscientific community and general public about the actual area underlain by permafrost for different parts of the globe. Abstract Copyright (2021). The Authors.

DOI: 10.1029/2021JF006123

2021047746 Zhang Saize (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Niu Fujun; Wang Jinchang and Dong Tianchun. Evaluation of damage probability of railway embankments in permafrost regions in Qinghai-Tibet Plateau: Engineering Geology, 284, Article 106027, illus. incl. 3 tables, sketch maps, 69 ref., April 2021.

The Qinghai-Tibet Railway (QTR) has been operating since 2006. It crosses continuous permafrost regions in the Qinghai-Tibet Plateau. Half of these regions are characterized by high ground temperature and ice content, and slight changes in the permafrost may cause embankment damage. In this study, the deformed embankment data of the QTR collected from 2010 to 2018 were analyzed. The analysis results showed that the total length of deformed embankments of the QTR in the permafrost regions was 22.97 km, and the damage rate since its completion in 2006 was approximately 5.4%. The results also indicated that the embankments stabilized over time. In 2010, the deformed embankments that were reinforced consisted of 26 sites and were 7.64-km long, whereas in 2018, only a 0.48-km long site was reinforced. In this study, a damage probability model of the embankments is developed. The damage probability of the embankments along the QTR in permafrost regions was classified into five grades: slight, low, moderate, high, and extremely-high damage probability levels. The total lengths of embankment sections with slight, low, moderate, high, and extremely-high levels of damage probability are 190.38, 161.42, 61.72, 13.51, and 2.99 km, respectively. It is suggested that damage-free embankment sections with high and extremely-high levels of damage probability should be monitored more closely during railway embankment maintenance. This study provides a reference for the application of the logistic regression model to establish the damage probability model of railway embankments in permafrost regions.

DOI: 10.1016/j.enggeo.2021.106027

2021044939 Ni Jie (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Tonghua; Zhu Xiaofan; Hu Guojie; Zou Defu; Wu Xiaodong; Li Ren; Xie Changwei; Qiao Yongping; Pang Qiangqiang; Hao Junming and Yang Cheng. Simulation of the present and future projection of permafrost on the Qinghai-Tibet Plateau with statistical and machine learning models: Journal of Geophysical Research: Atmospheres, 126(2), Article e2020JD033402, illus. incl. 4 tables, sketch maps, 113 ref., January 27, 2021.

The comprehensive understanding of the occurred changes of permafrost, including the changes of mean annual ground temperature (MAGT) and active layer thickness (ALT), on the Qinghai-Tibet Plateau (QTP) is critical to project permafrost changes due to climate change. Here, we use statistical and machine learning (ML) modeling approaches to simulate the present and future changes of MAGT and ALT in the permafrost regions of the QTP. The results show that the combination of statistical and ML method is reliable to simulate the MAGT and ALT, with the root-mean-square error of 0.53°C and 0.69 m for the MAGT and ALT, respectively. The results show that the present (2000-2015) permafrost area on the QTP is 1.04 ´ 106 km2 (0.80-1.28 ´ 106 km2), and the average MAGT and ALT are -1.35 ± 0.42°C and 2.3 ± 0.60 m, respectively. According to the classification system of permafrost stability, 37.3% of the QTP permafrost is suffering from the risk of disappearance. In the future (2061-2080), the near-surface permafrost area will shrink significantly under different Representative Concentration Pathway scenarios (RCPs). It is predicted that the permafrost area will be reduced to 42% of the present area under RCP8.5. Overall, the future changes of MAGT and ALT are pronounced and region-specific. As a result, the combined statistical method with ML requires less parameters and input variables for simulation permafrost thermal regimes and could present an efficient way to figure out the response of permafrost to climatic changes on the QTP. Abstract Copyright (2020), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020JD033402

2021044777 Liu Xin (Lanzhou University, Laboratory of Western China's Environmental Systems, Lanzhou, China); Wang Yibo; Yang Wenjing; Lv Mingxia and Zhao Haipeng. Effects of freezing-thawing cycle on the daily evapotranspiration of alpine meadow soil in Qinghai-Tibet Plateau: Environmental Earth Sciences, 79(24), Article 533, illus. incl. 3 tables, sketch map, 56 ref., December 2020.

The study of the diurnal response mechanism of the actual evapotranspiration (ETa) to the environment in the permafrost regions of the Qinghai-Tibet Plateau (QTP) using the LYS30 micro-evaporation instrument found that there are different feedbacks to the ETa under freezing and thawing cycles. The ETa process during the winter cooling period (WC) and the spring warming period (SW) is snow and ice sublimation and is mainly affected by the vapour pressure deficit (VPD). In the summer thawing period (ST), ETa can reach the maximum value when all meteorological elements reach a certain range of change at the same time, while ETa will decrease when the meteorological elements are not qualified. During the autumn freezing period (AF), the amount of condensate reached a maximum at 7:00, and due to the sudden change in meteorological elements at 9:00, the ETa increased rapidly at a rate higher than the condensation rate that occurred between 7:00 and 9:00. We also found that in different stages of freezing and thawing, the two physical processes of condensation and evaporation alternated in 1 day, with the process of evaporation occurring during the day and the condensation process occurring during the night. The diurnal response mechanism of the ETa to the environment in the permafrost regions of the QTP is expected to reveal the mechanism of soil hydrological processes and will provide a theoretical and scientific basis for water balance analysis and ecological environment protection in permafrost regions.

DOI: 10.1007/s12665-020-09290-y

2021043872 Monteux, Sylvain (Umea University, Department of Ecology and Environmental Sciences, Abisko, Sweden); Keuper, Frida; Fontaine, Sébastien; Gavazov, Konstantin; Hallin, Sara; Juhanson, Jaanis; Krab, Eveline J.; Revaillot, Sandrine; Verbruggen, Erik; Walz, Josefine; Weedon, James T. and Dorrepaal, Ellen. Carbon and nitrogen cycling in yedoma permafrost controlled by microbial functional limitations: Nature Geoscience, 13(12), p. 794-798, illus. incl. 1 table, 95 ref., December 2020.

DOI: 10.1038/s41561-020-00662-4

2021043780 Ren Shuai (Peking University, School of Urban Planning and Design, Shenzhen, China); Ding Jinzhi; Yan Zhengjie; Cao Yingfang; Li Juan; Wang Yonghui; Liu Dan; Zeng Hui and Wang Tao. Higher temperature sensitivity of soil C release to atmosphere from northern permafrost soils as indicated by a meta-analysis: Global Biogeochemical Cycles, 34(11), Article e2020GB006688, illus. incl. sketch maps, 74 ref., November 2020.

The loss of carbon from soils to the atmosphere resulting from climate change is projected to be large, but these projections exhibit significant uncertainty, largely due to insufficient knowledge of the patterns and controls of the temperature sensitivity of soil microbial respiration. Here we synthesized data from 52 soil incubation studies across the Northern Hemisphere to assess the spatial patterns of Q10 and its key drivers in different soil layers and geographic zones. The mean Q10 was 2.51±1.13 across the northern ecosystems, but it exhibited significant variability. After averaged by ecosystem types, the highest mean Q10 value was observed in the northern permafrost soils, where the Q10 values were nearly 18% higher than those in nonpermafrost regions. The temperature sensitivity was larger in subsoil than in topsoil layers, particularly in permafrost subsoils. Besides, the dominant factors that correlate with Q10 values are the carbon input, described by satellite-derived net primary productivity (NPP) in the topsoil and the soil C:N ratio in the subsoil. Based on the main factors affecting Q10, we provide a gridded Q10 data set for the midhigh-latitude areas, which further indicates that northern permafrost regions are more sensitive to climate warming than others. These results highlight the key role played by the permafrost in the temperature sensitivity of soil C release, and the necessity of including depth-specific soil C release processes in models, if we are to make better predictions of the soil C dynamics in future climate change scenarios. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GB006688

2021043779 Shu, Shijie (University of Illinois at Urbana-Champaign, Department of Atmospheric Sciences, Urbana, IL); Jain, Atul K.; Koven, Charles D. and Mishra, Umakant. Estimation of permafrost SOC stock and turnover time using a land surface model with vertical heterogeneity of permafrost soils: Global Biogeochemical Cycles, 34(11), Article e2020GB006585, illus. incl. 3 tables, sketch maps, 90 ref., November 2020.

We developed vertically resolved soil biogeochemistry (carbon and nitrogen) module and implemented it into a land surface model, ISAM. The model captures the vertical heterogeneity of the northern high latitudes permafrost soil organic carbon (SOC). We also implemented D14C to estimate SOC turnover time, a critical determinant of SOC stocks, sequestration potential, and the carbon cycle feedback under changing atmospheric CO2 concentration [CO2] and climate. ISAM accounted for the vertical movement of SOC caused by cryoturbation and its linkage to frost heaving process, oxygen availability, organo-mineral interaction, and depth-dependent environmental modifiers. After evaluating the model processes using the site and regional level heterotrophic respiration, SOC stocks, and soil D14C profiles, the vertically resolved soil biogeochemistry version of the model (ISAM-1D) estimated permafrost SOC turnover time of 1,443 years, which is about 3 times more than the estimation based on the without vertically resolved version of ISAM (ISAM-0D). ISAM-1D-simulated SOC stocks for permafrost regions was 319 Pg C in the top 1 m soil depth by the 2000s, about 80% higher than the estimates based on ISAM-0D. ISAM-1D SOC stock and turnover time were compared well with the observations. However, the longer SOC turnover time preserves less SOC stocks due to the lower carbon use efficiency (CUE) for SOC than ISAM-0D and thus respires more SOC than being transferred downward by cryoturbation. ISAM-1D simulated reduced SOC sequestration (3.7 Pg C) compared to ISAM-0D (4.8 Pg C) and published Earth system models (ESMs) over the 1860s-2000s, due to weaker [CO2]-carbon cycle and stronger climate-carbon cycle feedbacks, highlighting the importance of the vertically heterogeneous soil for understanding the permafrost SOC sinks. Abstract Copyright (2020). The Authors.

DOI: 10.1029/2020GB006585

2021047120 Peng Xiaoqing (Lanzhou University, Key Laboratory of Western China's Environmental Systems (Ministry of Education), College of Earth and Environmental Sciences, Lanzhou, China); Zhang Tingjun; Frauenfeld, Oliver W. and Du Ran. Permafrost response to land use and land cover change in the last millennium across the Northern Hemisphere: Land Degradation & Development, 31(14), p. 1823-1836, illus. incl. 2 tables, 83 ref., August 30, 2020.

Land use and land cover change (LULCC) can alter surface climate through biogeophysical feedbacks including the modification of energy, moisture, and momentum exchanges between the land and atmosphere. Permafrost, a component of the cryosphere, plays an important role in the climate system. However, the role of permafrost in LULCC in cold regions is still not clearly understood. Here, we employ a LULCC sensitivity experiment carried out by the community Earth system model last millennium ensemble project to investigate the effect of LULCC in permafrost regions across the Northern Hemisphere during 850-2005. LULCC is associated with statistically significant large-scale cooling in permafrost regions. The overall area-averaged annual surface air temperature decreased 0.37°C during 850-2005, and soil temperature decreased 0.39°C. Active layer thickness declined at a rate of -0.54 cm/100 year ± 0.023 cm, with a net decline of 6.24 ± 0.26 cm during 850-2005 in association with LULCC. Soil moisture also showed a decrease, most pronounced in summer and autumn. Seasonally, the greatest surface air temperature decreases occurred in autumn at a rate of -0.042°C/100 year, and 0.2 m winter soil temperature decreased 0.036°C/100 year, both with time lags. Comparisons of cooling associated with LULCC demonstrate that permafrost regions are more sensitive to LULCC than the rest of the Northern Hemisphere. Abstract Copyright (2020), John Wiley & Sons, Ltd.

DOI: 10.1002/ldr.3578

2021046379 Beya, Fabrice (Universite du Quebec en Abitibi-Temiscamingue, Research Institute on Mining and Environment (RIME), Rouyn-Noranda, QC, Canada); Mbonimpa, Mamert; Belem, Tikou; Li Li; Marceau, Ugo; Kalonji, Patrick; Benzaazoua, Mostafa and Ouellet, Serge. Mine backfilling in the permafrost; Part I, Numerical prediction of thermal curing conditions within the cemented paste backfill matrix: Minerals (Basel), 9(3), Article 165, illus. incl. 4 tables, 56 ref., 2019.

The mechanical behavior of cemented paste backfill (CPB) in permafrost regions may depend on the thermal curing conditions. However, few experimental data are available for calibrating and validating numerical models used to predict these conditions. To fill this gap, a three-dimensional (3D) laboratory heat transfer test was conducted on CPB placed in an instrumented barrel and cured under a constant temperature of -11 °C. Results were used to calibrate and validate a numerical model built with COMSOL Multiphysics. The model was then used to predict the evolution of the temperature field for CPB cured under the thermal boundary conditions for a backfilled mine stope in the permafrost (at -6 °C). Numerical results indicated that the CPB temperature gradually decreased with time such that the entire CPB mass was frozen about five years after stope backfilling. However, the permafrost equilibrium temperature of -6 °C was not reached throughout the entire CPB mass even after 20 years of curing. In addition, the evolution of the temperature field in the permafrost rock showed that the thickness of the thawed portion reached about 1 m within 120 days. Afterwards, the temperature continues to drop over time and the thawed portion of the permafrost refreezes after 365 days.

DOI: 10.3390/min9030165

2021046455 Galanin, A. A. (Rossiyskaya Akademiya Nauk, Institut Merzlotovedeniya im. P. I. Mel'nikova, Yakutsk, Russian Federation); Pavlova, M. R.; Papina, T. S.; Eyrikh, A. N. and Pavlova, N. A. Stabil'nye izotopy 18O i D v klyuchevykh komponentakh vodnogo stoka i kriolitozony tsentral'noy Yakutii (Vostochnaya Sibir') [Stable isotopes 18O and D in the permafrost and meteoric waters of central Yakutia (Eastern Siberia)]: Led i Sneg = Ice and Snow, 59(3), p. 333-354 (English sum.), illus. incl. 1 table, sketch map, 35 ref., 2019.

On the basis of about 430 analyses, the 18O and D compositions (%o) of atmospheric precipitation, ground ice, surface and inter-permafrost underground waters of cryogenic-aeolian landscapes of Central Yakutia (Eastern Siberia) are discussed. Precipitation compositions here demonstrate a large annual variation (from -6.12 to -45.0 % for d18O, and from -72.1 to -350.1 % for dD), and they are described by the Local Meteoric Water Line according to the equation dD = 7.81518O - 1.57). In winter and in the process of spring melting, the snow storage is subjected to a significant evaporative fractionation, that is expressed by the equation dD = 6.85518O - 31.9. The heaviest and deuterium-depleted compositions (d18O = -19.3 %, dD = -160.9, dexc = -6.7 %) are found in the last snow patches in early June. The lightest compositions similar to the present-day winter precipitation (snow) are characteristic of the polygonal wedge ices (PWI) of the Central Yakutia. The most lightweight (from -30 to -34 % for d18O, and from 240 to 275% for dD) were established to be typical for the ancient PWI, dated by the first half of the Late Pleistocene (MIS 3-4). Heavier compositions (d18O = -27.2±1.4, dD = -215.8±8.5, dexc = 1.7±3.1 %) with obvious features of evaporative fractionation correspond to younger PWI (MIS 2-1). The heaviest compositions (d18O = -12.2±0.7, dD = -99.2±4.7, dexc = -2.0±0.8 %) and high angular coefficients of approximating equations were determined in the investigated cave ices of sublimation origin, that implies the atmospheric origin of them. The current processes of evaporative fractionation are the most intensively reflected in the waters of aeolian lakes (d18O = -11.8±3.5, dD = -120.2±18.4, dexc = -25.8±10.5 %), and the compositions are described by the regression equation 5D = 5.52 d18O - 54.12 (R2 = 0.97). The phenomenal objects of the cryogenic-eolian landscapes of the Central Yakutia are high-debit underground sources. Among all other components of the water flows, composition of these sources is the most stable (d18O = -21.6±0.8, dD = -172.6±5.1, dexc = 0.23±3.0 %). The regression of compositions of the largest underground source Bulus is approximated by the equation 5D = 6.31 d18O - 36.7 (R2 = 0.78), that is indicative to significant evaporative fractionation and close relation with the aeolian lakes in the alimentation area.

DOI: 10.15356/2076-6734-2019-3-414

2021046373 Mbonimpa, Mamert (Research Institute on Mines and the Environment, Rouyn-Noranda, QC, Canada); Kwizera, Parrein and Belem, Tikou. Mine backfilling in the permafrost; Part II, Effect of declining curing temperature on the short-term unconfined compressive strength of cemented paste backfills: Minerals (Basel), 9(3), Article 172, illus. incl. 1 table, 39 ref., 2019.

When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days' curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications.

DOI: 10.3390/min9030172

Back to the Top



2021047965 Allain, Alienor (Université Paris-Sorbonne, Paris, France); Alexis, Marie Anne; Agnan, Yannick; Humbert, Guillaume; Parlanti, Edith; Sourzac, Mahaut; Guittet, Amélie; Anquetil, Christelle; Aubry, Emmanuel; Vaury, Véronique and Rouelle, Maryse. Chemical characterization of water extractable organic matter from plants; a better understanding of soil dissolved organic matter sources and path in permafrost thawing regions [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12002, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In present permafrost thawing context, dissolved organic matter (DOM) is a key component that controls organic and inorganic material transfer from soil to hydrographic systems. In terrestrial environments, vegetation is the main source of DOM, before degradation by microorganisms. DOM stoichiometry, aromaticity, composition or quantity control its fate, and referential data characterizing the initial DOM originating from plant biomass leaching are scarce. To better understand its dynamic, this study focuses on the characterization of water extractable organic matter ("WEOM": a proxy of DOM) of main plant species belonging to different plant functional types typical of the subarctic region (lichen, willow, birch, and Eriophorum). Dissolved organic carbon (C) and dissolved nitrogen (N) contents of WEOM samples were measured, as well as organic C and total N contents of ground plant leaf samples ("bulk" samples). C/N ratio of bulk samples and WEOM fractions were compared to evaluate the potential extractability of C and N. The composition of both WEOM and bulk samples were characterized through solid state 13C Nuclear Magnetic Resonance (NMR) and compared. Absorbance and 3D fluorescence measurements were also performed on WEOM samples to characterize their optical properties. WEOM is significantly more extractable in vascular plants compared to non-vascular ones. Moreover, N is more extractable than C in all lichen species and Eriophorum, whereas C is as extractable as N in Salix and Betula pubescens samples. Betula nana is the only species with C more extractable than N. The solid state 13C NMR spectra of bulk sample are very similar to the spectra of corresponding WEOM, except for Eriophorum. For this species, carbonyl C contributes to 5% of bulk sample spectrum, compared to 14% of the WEOM spectrum. Based on absorbance measurements, optical index were calculated: E2/E3 is significantly higher for non-vascular plants, whereas E2/E4, E3/E4 and slope ratio (SR) do not show significant difference between plant functional types. In 3D fluorescence spectra, the contribution of "Protein-like" peak is lower for vascular plants compared to lichens, and is maximum for Eriophorum. Our results highlighted the influence of plant species on the quantity and quality of produced DOM: WEOM production process is different between vegetation species due to the quality, especially hydrophobicity and extractability of bulk OM components. The high contribution of C-N bonds in WEOM of Eriophorum might be especially important for potential complexation between DOM and trace elements like cadmium (Nigam et al., 2000). Likewise, aromatic C observed only in vascular plant WEOM samples are known to bond have a good affinity with many elements like iron, vanadium and chromium (Gangloff et al., 2014). Under climate change, vegetation cover of the Arctic region is evolving with the moving of the treeline northward and a local increase of the proportion of shrubs (Berner et al., 2013). Accordingly, significant change of DOM composition are expected with potential influence on organic and inorganic material dynamics. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-12002

2021048029 Baral, Prashant (NIIT University, Computer Science and Engineering, India) and Allen, Simon. Using systematic review to analyse climate change impacts and adaptation associated with mountain permafrost [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9381, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Mountain permafrost in Asia incorporates permafrost in the mountains of the Hindu Kush Himalayan region, Central Asia, Russia, Mongolia, Qinghai Tibetan plateau and other mountain ranges in China. Changes in climate variables in recent decades have considerably influenced permafrost in these regions and produced vivid impacts. While climate change impacts on mountain permafrost in the alpine regions of Europe, US and Canada are relatively well documented, records about mountain permafrost in Asia are mostly available for the Qinghai Tibetan plateau region and a few other mountain ranges in China. Considerably little information is available for the Hindu Kush Himalayan region and other mountain ranges in Asia. This systematic review analyses climate change related impacts and adaptation in mountain permafrost regions of Asia and attempts to evaluate the status of knowledge based on peer-reviewed journal publications. Impacts on hydrology, geomorphology and ecology were examined and resulting socioeconomic effects were considered. Additionally, ongoing and potential adaptation practices were explored. Warming climate has been found responsible for a gradual shift of the lower limit of mountain permafrost in the region. Increased probabilities of mass wasting events due to reduced slope stability, changes in composition and quality of fresh water resources, irregularities in seasonal flows, changes in permafrost ecosystems and contemporaneous need for the protection of engineered constructions were identified as some of the key impacts. There is a high necessity for increased understanding of mountain permafrost and well-designed response actions to evaluate processes and interactions influencing changes in the natural environment and subsequent effects on sustainable living conditions. Therefore, suitable risk management practices need to be designed with a proper consideration of the anticipated future dynamics of climate, economy and society. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9381

2021048012 Bartolomé, Miguel (Museo Nacional de Ciencias Naturales, Spain); Moreno, Ana; Luetscher, Marc; Spötl, Christoph; Leunda, Maria; Cazenave, Gerard; Belmonte, Ánchel; Osácar, Cinta; Cheng Hai; Edwards, Richard Lawrence and Sancho, Carlos. Cryogenic cave carbonate formation during the industrial era in the central Pyrenees (Iberian Peninsula) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14487, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Cryogenic cave carbonates (CCC) are rare speleothems that form when water freezes inside cave ice bodies. CCC have been used as an proxy for permafrost degradation, permafrost thickness, or subsurface ice formation. The presence of these minerals is usually attributed to warm periods of permafrost degradation. We found coarse crystalline CCC types within transparent, massive congelation ice in two Pyrenean ice caves in the Monte Perido Massif: Devaux, located on the north face at 2828 m a.s.l., and Sarrios 6, located in the south face at 2780 m a.s.l. The external mean annual air temperature (MAAT) at Devaux is ~0°C, while at Sarrios 6 is ~2.5°C. In the Monte Perdido massif discontinuous permafrost is currently present between 2750 and 2900 m a.s.l. and is more frequent above 2900 m a.s.l. in northern faces. In Devaux, air and rock temperatures, as well as the presence of hoarfrost and the absence of drip sites indicate a frozen host rock. Moreover, a river flows along the main gallery, and during winters the water freezes at the spring causing backflooding in the cave. In contrast, Sarrios 6 has several drip sites, although the gallery where CCC were collected is hydrologically inactive. This gallery opened in recent years due to ice retreat. During spring, water is present in the gallery due to the overflow of ponds forming beneath drips. CCC commonly formed as sub-millimeter-size spherulites, rhombohedrons and rafts. 230Th ages of the same CCC morphotype indicate that their formation took place at 1953±7, 1959±14, 1957±14, 1958±15, 1974±16 CE in Devaux, while in Sarrios 6 they formed at 1964±5, 1992±2, 1996±1 CE. The cumulative probability density function indicates that the most probable formation occurred 1957-1965 and 1992-1997. The instrumental temperature record at 2860 m a.s.l. indicates positive MAAT in 1964 (0.2°C) and 1997 (0.8°C). CCC formation could thus correspond with those two anomalously warm years. The massive and transparent ice would indicate a sudden ingress of water and subsequent slow freezing inside both caves during those years. Probably, CCC formation took place at a seasonal scale during the annual cycle.

DOI: 10.5194/egusphere-egu21-14487

2021048008 Beltrami, Hugo (Saint Francis Xavier University, Climate & Atmospheric Sciences Institute, Antigonish, NS, Canada); Cuesta-Valero, Fracisco José; García-García, Almudena; Gruber, Stephan and Jaume-Santero, Fernando. Assessing Arctic ground surface temperatures from borehole temperatures and paleoclimatic model simulations [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9222, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The surface temperature response to changes in our planet's external forcing is larger at higher latitudes, a phenomenon known as polar amplification. The Arctic amplification has been particularly intense during the last century, with arctic-wide paleoclimatic reconstructions and state-of-the-art model simulations revealing a twofold arctic warming in comparison with the average global temperature increase. As a consequence, Arctic ground temperatures respond with rapid warming, but this response varies with snow cover and permafrost processes. Thus, changes in arctic ground temperatures are difficult to reconstruct from data, and to simulate in climate models. Here, we reconstruct the ground surface temperature histories of 120 borehole temperature profiles above 60°N for the last 400 years. Past surface temperature evolution from each profile was estimated using a Perturbed Parameter Inversion approach based on a singular value decomposition method. Long-term surface temperature climatologies (circa 1300 and 1700 CE) and quasi-steady state heat flow are also estimated from linear regression through the depth range 200 to 300 m of each borehole temperature profile. The retrieved temperatures are assessed against simulated ground surface temperatures from five Past Millennium and five Historical experiments from the Paleoclimate Modelling Intercomparison Project Phase III (PMIP3), and the fifth phase of the Coupled Model Intercomparison Project (CMIP5) archives, respectively. Preliminary results from borehole estimates and PMIP3/CMIP5 simulations reveal that changes in recent Arctic ground temperatures vary spatially and are related to each site's earlier thermal state of the surface. The magnitudes of ground warming from data and simulations differ with large discrepancies among models. As a consequence, a better understanding of freezing processes at and below the air-ground interface is necessary to interpret subsurface temperature records and global climate model simulations in the Arctic.

DOI: 10.5194/egusphere-egu21-9222

2021048031 Bernhard, Philipp (ETH Zürich, Department of Civil, Environmental, and Geomatic Engineering, Zurich, Switzerland); Zwieback, Simon and Hajnsek, Irena. Area and volume quantification of Arctic thaw slumps using time-series of digital elevation models generated from radar interferometry [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2280, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to terrain-altering thermokarst in a warming climate. Among the most rapid and dramatic changes are retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making their change visible by comparing digital elevation models over time. In this study we use digital elevation models generated from single-pass radar TanDEM-X observations to derive volume and area change rates for retrogressive thaw slumps. At least three observations in the timespan from 2011 to 2017 are available with a spatial resolution of about 12 meter and a height sensitivity of about 0.5-2 meter. Our study regions include regions in Northern Canada (Peel Plateau/Richardson Mountains, Mackenzie River Delta Uplands, Ellesmere Island), Alaska (Noatak Valley) and Siberia (Yamal, Gydan, Taymyr, Chukotka) covering an area of 220.000 km2 with a total number of 1853 thaw slumps. In this presentation we will focus on the area and volume change rate probability density functions of the mapped thaw slumps in these study areas. For landslides in temperate climate zones the area and volume change probability density function typically follow a distribution that can be characterized by three quantities: A rollover point defined as the peak in the distribution, a cutoff-point indicating the transition to a power law scaling for large landslides and the exponential beta coefficient of this power law. Here we will show that thaw slumps across the arctic follow indeed such a distribution and that the obtained values for the rollover, cutoff and beta coefficient can be used to distinguish between regions. Furthermore we will elaborate on possible reason why arctic thaw slumps can be described by such probability density functions as well as analyzing the differences between regions. This characterization can be useful to further improve our understanding of thaw slump initiation, the investigation of the drivers of their evolution as well as for modeling future thaw slump activity.

DOI: 10.5194/egusphere-egu21-2280

2021047973 Bristol, Emily (University of Texas at Austin, Marine Science Institute, Austin, TX); Connolly, Craig; Lorenson, Thomas; Richmond, Bruce; Ilgen, Anastasia; Choens, R. Charles; Bull, Diana; Kanevskiy, Mikhail; Iwahana, Go; Jones, Benjamin; Spencer, Robert and McClelland, James. Land-to-ocean fluxes and biolability of organic matter eroding along the Beaufort Sea coast near Drew Point, Alaska [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9260, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Coastal erosion rates are increasing along the Alaskan Beaufort Sea coast due to increases in wave action, the increasing length of the ice-free season, and warming permafrost. These eroding permafrost coastlines transport organic matter and inorganic nutrients to the Arctic Ocean, likely fueling biological production and CO2 emissions. To assess the impacts of Arctic coastal erosion on nearshore carbon and nitrogen cycling, we examined geochemical profiles from eroding coastal bluffs and estimated annual organic matter fluxes from 1955 to 2018 for a 9 km stretch of coastline near Drew Point, Alaska. Additionally, we conducted a laboratory incubation experiment to examine dissolved organic carbon (DOC) leaching and biolability from coastal soils/sediments added to seawater. Three permafrost cores (4.5-7.5 m long) revealed that two distinct horizons compose eroding bluffs near Drew Point: Holocene age, organic-rich (~12-45% total organic carbon; TOC) terrestrial soils and lacustrine sediments, and below, Late Pleistocene age marine sediments with lower organic matter content (~1% TOC), lower carbon to nitrogen ratios, and higher d13C-TOC values. Organic matter stock estimates from the cores, paired with remote sensing time-series data, show that erosional TOC fluxes from this study coastline averaged 1,369 kg C m-1 yr-1 during the 21st century, nearly double the average flux of the previous half century. Annual TOC flux from this 9 km coastline is now similar to the annual TOC flux from the Kuparuk River, the third largest river draining the North Slope of Alaska. Experimental work demonstrates that there are distinct differences in DOC leaching yields and the fraction of biodegradable DOC across soil/sediment horizons. When core samples were submerged in seawater for 24 hours, the Holocene age organic-rich permafrost leached the most DOC in seawater (~6.3 mg DOC g-1 TOC), compared to active layer soils and Late-Pleistocene marine-derived permafrost (~2.5 mg DOC g-1 TOC). Filtered leachates were then incubated aerobically in the dark for 26 and 90 days at 20°C to examine biodegradable DOC (i.e. the proportion of DOC lost due to microbial uptake or remineralization). Of this leached DOC, Late Pleistocene permafrost was the most biolabile over 90 days (31±7%), followed by DOC from active layer soils (24±5%) and Holocene-age permafrost (14%±3%). If we scale these results to a typical 4 m tall eroding bluff at Drew Point, we expect that ~341 g DOC m-2 will rapidly leach, of which ~25% is biodegradable. These results demonstrate that eroding permafrost bluffs are an increasingly important source of biolabile DOC, likely contributing to greenhouse gas emissions and marine production in the coastal environment. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9260

2021047967 Bröder, Lisa (Swiss Federal Institute of Technology, Department of Earth Sciences, Zurich, Switzerland); Hirst, Catherine; Opfergelt, Sophie; Lattaud, Julie; Haghipour, Negar; Eglinton, Timothy; Vonk, Jorien and Fouché, Julien. Mobilization of particulate organic matter and minerals in Zackenberg Valley, Greenland [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-11539, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Ongoing warming of the Northern high latitudes has intensified abrupt thaw processes throughout the permafrost zone. The resulting terrain disturbances are prone to release large amounts of particulate organic matter (OM) from deeper permafrost soils with thus far poorly constrained decay kinetics. Organo-mineral interactions may inhibit OM decomposition, thereby mediating the release of carbon to the atmosphere. Yet how these interactions evolve upon release and during transport along the fluvial continuum is still insufficiently understood. Here we investigate the mobilization of particulate OM from disturbed permafrost soils to the aquatic environment in the Zackenberg watershed in Northeastern Greenland. We collected soil samples in a thermo-erosion gully and a retrogressive thaw slump, as well as suspended solids and stream sediments along the glacio-nival Zackenberg River, including its tributaries, and a small headwater stream (Graenselv) affected by abrupt permafrost thaw. To evaluate the organic and mineral material transported, we compare mineral element and organic carbon (OC) concentrations, bulk carbon isotopes (13C and 14C), together with source-specific molecular biomarkers (plant-wax lipids and branched glycerol dialkyl glycerol tetraethers, brGDGTs) for the suspended load with their soil and sediment counterparts. Preliminary results show large contrasts in OC concentrations as well as D14C between the glacio-nival river and the headwater stream, as well as between the different thaw features. The retrogressive thaw slump mobilizes relatively OC-poor material with very low D14C signatures suggesting a petrogenic contribution, while soil samples from the thermo-erosion gully had higher OC concentrations and D14C values. For Graenselv, D14C values of the particulate OC were lower close to the eroding stream bank, whereas the Zackenberg main stem displayed fairly constant D14C values, with some of the Zackenberg tributaries delivering relatively organic-rich particles low in D14C. Molecular biomarker analyses will provide additional information on specific OM sources, while X-ray Diffraction (XRD) and X-ray Fluorescence (XRF) analyses on the soils, sediments and suspended mineral load will give more detailed insights into the composition of the mineral matrices. By combining these analytical methods, we aim to improve our understanding of the interactions between minerals and OM and thereby help to constrain the fate of mobilized OM upon permafrost thaw. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-11539

2021047975 Bruhn, Anders Dalhoff (Technical University of Denmark, Section for Oceans and Arctic, Lyngby, Denmark); Stedmon, Colin A.; Comte, Jérôme; Matsuoka, Atsushi; Speetjens, Neik Jesse; Tanski, George; Vonk, Jorien E. and Sjostedt, Johanna. Permafrost-derived dissolved organic matter character controls microbial community composition in Arctic coastal waters [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13069, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Climate warming is accelerating erosion rates along permafrost-dominated Arctic coasts. To study the impact of erosion on marine microbial community composition and growth in the Arctic coastal zone, dissolved organic matter (DOM) from three representative glacial landscapes (fluvial, lacustrine and moraine) along the Yukon coastal plain, are provided as substrate to marine bacteria using a chemostat setup. Our results indicate that chemostat cultures with a flushing rate of approximately a day provide comparable DOM bioavailability estimates to those from bottle experiments lasting weeks to months. DOM composition (inferred from UV-Visible spectroscopy) and biodegradability (inferred from DOC concentration, bacterial production and respiration) significantly differed between the three glacial deposit types. DOM from fluvial and moraine deposit types shows more terrestrial characteristics with lower aromaticity (SR: 0.63 (±0.02), SUVA254: 1.65 (±0.06) respectively SR: 0.68 (±0.00), SUVA254: 1.17 (±0.06)) compared to the lacustrine deposit type (SR: 0.71 (±0.02), SUVA254: 2.15 (±0.05)). The difference in composition of DOM corresponds with the development of three distinct microbial communities, with a dominance of Alphaproteobacteria for fluvial and lacustrine deposit types (relative abundance 0.67 and 0.87 respectively) and a dominance of Gammaproteobacteria for moraine deposit type (relative abundance 0.88). Bacterial growth efficiency (BGE) is 66% for moraine-derived DOM, while 13% and 28% for fluvial-derived and lacustrine-derived DOM respectively. The three microbial communities therefore differ in their net effect on DOM utilization. The higher BGE value for moraine-derived DOM was found to be due to a larger proportion of labile colourless DOM. The results from this study, therefore indicate a substrate control of marine microbial community composition and activities, suggesting that the effect of permafrost thaw and erosion in the Arctic coastal zone will depend on subtle differences in DOM related to glacial deposit types. These differences further determines the speed and extent of DOM mineralization and thereby carbon channelling into biomass in the microbial food web. We therefore conclude that marine microbes strongly respond to the input of terrestrial DOM released during coastal erosion of Arctic glacial landscapes. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13069

2021047993 Byun, Eunji (University of Waterloo, Department of Earth and Environmental Sciences, Waterloo, ON, Canada); Rezanezhad, Fereidoun; Fairbairn, Linden; Basiliko, Nathan; Price, Jonathan; Quinton, William; Roy-Léveillée, Pascale; Webster, Kara and Van Cappellen, Philippe. Temperature and moisture controls on non-growing season CO2 emissions in laboratory incubations with soils from northern peatlands [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6281, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Canada has extensive peat deposits in northern high latitude wetlands and permafrost ecosystems. Peat accumulation represents a natural long-term carbon sink attributed to the cumulative excess of growing season net ecosystem production over non-growing season net mineralization. However, near-surface peat deposits are vulnerable to climate change and permafrost landscape transition. One specific concern is a potential rapid increase in the non-growing season carbon loss through enhanced organic matter mineralization under a warming climate. Our experimental study explores the response of peat CO2 exchanges to (1) temperature, using the conventional Q10 parameter, and (2) moisture content. The observed responses are expected to reflect, at least in part, differential soil microbial adaptations to varying wetland conditions, across two northern ecoclimatic zones. Laboratory incubations were carried out with shallow peat samples from different depths collected at seven Canadian wetland sites and adjusted to five moisture levels. For each subsample (varying by site, depth and moisture content), CO2 fluxes were measured at 12 sequential temperature settings from -10 to 35°C. For each subsample, the data were fitted to an exponential equation to derive a Q10 value. In general, boreal peat samples were more temperature sensitive than temperate peat. The optimum moisture level for CO2 release was determined for all the subsamples and related to variations in wetland vegetation and landform types. As a general trend, increasing water saturation reduced the CO2 release rate from a given subsample. We further tested a flexible curve-fitting equation, as recently proposed on a theoretical basis, to recompile the data by ecoclimatic peat type and to account for the non-growing season dynamics. These findings will contribute to Canada's national carbon budget model by guiding the development and calibration of the peatland module. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-6281

2021048030 Cao Bin (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, China); Gruber, Stephan; Zheng Donghai and Li Xin. Underestimated snow density in ERA5-Land as a cause for warm bias of soil temperature over permafrost regions [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-1645, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

ERA5 is the latest generation atmospheric reanalysis produced by the European Centre for Medium-Range Weather Forecasts (ECMWF). ERA5-Land (ERA5L) is derived by running the land component of ERA5, Tiled ECMWF Scheme for Surface Exchanges over Land with a revised land surface hydrology (HTESSEL), at an increased resolution of 0.1°. This study evaluates ERA5L soil temperature in permafrost regions based on observations and published permafrost products. We find that ERA5L overestimates soil temperature in northern Canada and Alaska but underestimates it in mid-low latitudes, leading to a near-zero overall bias (-0.08°C). The warm bias of ERA5L soil is more pronounced in winter than in other seasons. As calculated from its soil temperature, ERA5L overestimates active-layer thickness and underestimates near-surface (<1.89 m) permafrost area. This is thought to be due in part to the shallow soil column and coarse vertical discretization of the land surface model and to warmer simulated soil. The soil temperature bias in permafrost regions correlates well with the bias in air temperature and with snow height. A review of the ERA5L snow parameterization in the code and a simulation example comparison with permafrost-specific processes rich model (GEOtop) both point to an error in snow metamorphism of HTESSEL leading to a low bias in ERA5L snow density as a possible cause for the warm bias in soil temperature. The apparent disagreement of station-based and areal evaluation techniques highlights challenges in our ability to test permafrost simulation models. While global reanalyses are important drivers for permafrost simulation, we conclude that ERA5L soil data are not well suited for informing permafrost research and decision making directly. To address this, future soil temperature products in reanalyses will require permafrost-specific alterations to their land surface models. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-1645

2021048034 Chen, Yueli (Ludwig-Maximilians University Munich, Department of Geography, Munich, Germany); Wang Lingxiao; Bernier, Monique and Ludwig, Ralf. Retrieving freeze/thaw-cycles using Sentinel 1 data in eastern Nunavik (Québec, Canada) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6241, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In the terrestrial cryosphere, freeze/thaw (FT) state transitions play an important and measurable role for climatic, hydrological, ecological, and biogeochemical processes in permafrost landscapes. Satellite active and passive microwave remote sensing has shown its principal capacity to provide effective monitoring of landscape FT dynamics. Sentinel-1 continues to deliver high-resolution microwave remote sensing than ever before and has therefore a large potential of usage for monitoring. In light of this, the capability and responses of its radar backscatter to landscape FT processes in different surface soil depths should be examined to provide a thorough grounding for a robust application of the F/T retrieval algorithm. This study presents a seasonal threshold approach, which examines the time series progression of remote sensing measurements relative to signatures acquired during seasonal reference frozen and thawed states. It is developed to estimate the FT-state from the Sentinel 1 database and applied and evaluated for the region of Eastern Nunavik (Quebec, Canada). In this course, the FT state transitions derived from Sentinel 1 data are compared to temporally overlapping situ measurements of soil moisture from different depths within the top 20cm soil. This work allows to explore differences in the sensitivity of the Sentinel 1 at different surface soil depths in higher detail; this information is used to examine the penetration performance of the Sentinel 1 under different conditions of permafrost and permafrost-dominated landscapes. This work is dedicated to providing more accurate data to capture the spatio-temporal heterogeneity of freeze/thaw transitions. As Sentinel-1 continues to deliver high-quality information, the provided threshold algorithm delivers an extended time series to analyze FT-states and improve our understanding of related processes in permafrost landscapes.

DOI: 10.5194/egusphere-egu21-6241

2021047963 Chernykh, Denis (Russian Academy of Sciences, Pacific Oceanological Institute, Vladivostok, Russian Federation); Kosmach, Denis; Konstantinov, Anton; Salomatin, Aleksander; Yusupov, Vladimir; Shakhova, Natalia; Gustafsson, Orjan; Gershelis, Elena; Dudarev, Oleg and Semiletov, Igor. First experimental estimation of the methane ebullition fraction in water column from the bottom to the surface; application for the east Siberian Arctic shelf [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-4013, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The key area of the Arctic ocean for atmospheric venting of CH4 is the East Siberian Arctic Shelf (ESAS). The ESAS covers >2 million square kilometers (equal to the areas of Germany, France, Great Britain, Italy, and Japan combined). This vast yet shallow region has recently been shown to be a significant modern source of atmospheric CH4, contributing annually no less than terrestrial Arctic ecosystems; but unlike terrestrial ecosystems, the ESAS emits CH4 year-round due to its partial openness during the winter when terrestrial ecosystems are dormant. Emissions are determined by and dependent on the current thermal state of the subsea permafrost and environmental factors controlling permafrost dynamics. Releases could potentially increase by 3-5 orders of magnitude, considering the sheer amount of CH4 preserved within the shallow ESAS seabed deposits and the documented thawing rates of subsea permafrost reported recently. The purpose of this work is to determine the methane ebullition fraction in water column: from the bottom to the surface, which is a key to evaluate quantitively methane release from the ESAS bottom through the water column into the atmosphere. A series of 351 experiments was carried out at to determine the quantity of methane (and other greenhouse gases) delivered by bubbles of various sizes through a water column into the atmosphere. It has been shown for depth up to 22 m (about 30% of the ESAS) that pure methane bubbles, depending on their diameter and water salinity, transported to the surface from 60.9% to 85.3% of gaseous methane. This work was supported in part by grants from Russian Scientific Foundation (No. 18-77-10004 to DCh, DK, AK, No. 19-77-00067 to EG), the Ministry of Science and Higher Education of the Russian Federation (grant ID: 075-15-2020-978 to IS). The work was carried out as a part of Federal[W1] assignment No. AAAA-A17-117030110031-6 to AS. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-4013

2021048009 Churakova Sidorova, Olga (Siberian Federal University, Institute of Ecology and Geography, Krasnoyarsk, Russian Federation); Fonti, Marina; Siegwolf, Rolf; Trushkina, Tatyana; Vaganov, Eugene and Saurer, Matthias. Response of Siberian trees to climatic changes over the past 1500 years [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8995, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

We use an interdisciplinary approach combining stable isotopes in tree rings, pollen data, ice cores from temperature-limited environment in the Siberian north and developed a comprehensive description of the climatic changes over the past 1500 years. We found that the Climatic Optimum Period was warmer and drier compared to the Medieval one, but rather similar to the recent period. Our results indicate that the Medieval Warm period in the Taimyr Peninsula started earlier and was wetter compared to the northeastern part of Siberia (northeastern Yakutia). Summer precipitation reconstruction obtained from carbon isotopes in tree-ring cellulose from Taimyr Peninsula significantly correlated with the pollen data of the Lama Lake (Andreev et al. 2004) and oxygen isotopes of the ice core from Severnaya Zemlya (Opel et al. 2013) recording wetter climate conditions during the Medieval Warm period compared to the northeastern part of Siberia. Common large-scale climate variability was confirmed by significant relationship between oxygen isotope data in tree-ring cellulose from the Taimyr Peninsula and northeastern Yakutia, and oxygen isotope ice core data from Severnaya Zemlja during the Medieval Warm period and the recent one. Finally, we showed that the recent warming on the Taimyr Peninsula is not unprecedented in the Siberian north. Similar climate conditions were recorded by stable isotopes in tree rings, pollen, and ice core data 6000 years ago. On the northeastern part of Siberia newly developed a 1500-year summer vapor pressure deficit (VPD) reconstruction showed, that VPD increased recently, but does not yet exceed the maximum values reconstructed during the Medieval Warm period. The most humid conditions in the northeastern part of Siberia were recorded in the Early Medieval period and during the Little Ice Age. However, the increasing VPD under elevated air temperature in the last decades affects the hydrological regime of these sensitive ecosystems by greater evapotranspiration rates. Further VPD increase will significantly affect Siberian forests most likely leading to drought even under additional access of thawed permafrost water. This work was supported by the FP7-PEOPLE-IIF-2008 - Marie Curie Action: "International Incoming Fellowships" 235122 and "Reintegration Fellowships" 909122 "Climatic and environmental changes in the Eurasian Subarctic inferred from tree-ring and stable isotope chronologies for the past and recent periods" and the Government of Krasnoyarsk Kray and Russian Foundation for Basic Research and Krasnoyarsk Foundation 20-44-240001 "Adaptation of conifer forests on the north of the Krasnoyarsk region (Taimyr Peninsula) to climatic changes after extreme events over the past 1500 years" awarded to Olga V. Churakova (Sidorova).

DOI: 10.5194/egusphere-egu21-8995

2021048007 Cuesta-Valero, Francisco José (Saint Francis Xavier University, Climate & Atmospheric Sciences Institute, Antigonish, NS, Canada); García-García, Almudena; Beltrami, Hugo; González-Rouco, J. Fidel and García-Bustamante, Elena. Long-term global ground heat flux and continental heat storage from geothermal data [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-589, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Energy exchanges among climate subsystems are of critical importance to determine the climate sensitivity of the Earth's system to changes in external forcing, to quantify the magnitude and evolution of the Earth's energy imbalance, and to make projections of future climate. Additionally, climate phenomena sensitive to land heat storage, such as permafrost stability and sea level rise, are important due to their impacts on society and ecosystems. Thus, ascertaining the magnitude and change of the Earth's energy partition within climate subsystems has become urgent in recent years. Here, we provide new global estimates of changes in ground surface temperature, ground surface heat flux and continental heat storage derived from geothermal data using an expanded database and new techniques developed in the last two decades. This new dataset contains 253 recent borehole profiles that were not included in previous estimates of global continental heat storage. In addition, our analysis considers additional sources of uncertainty that were not included in previous borehole studies. Results reveal markedly higher changes in ground heat flux and heat storage within the continental subsurface during the second half of the 20th century than previously reported, with a land mean temperature increase of 1 K and continental heat gains of around 12 ZJ relative to preindustrial times. Half of the heat gained by the continental subsurface since 1960 have occurred in the last twenty years. These results may be important for estimates of climate sensitivity based on energy budget constrains, as well as for the evaluation of global transient climate simulations in terms of the Earth's heat inventory and energy-dependent subsurface processes. Our estimate of land heat storage is included in the new assessment of the components of the Earth's heat inventory recently released (von Schuckmann et al. 2020), together with the oceans, the atmosphere and the cryosphere. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-589

2021048033 Descarrega, Didac Pascual (Lund University, Physical Geography and Ecosystem Science, Lund, Sweden) and Johansson, Margareta. Contrasting thermal responses of permafrost to winter warming events under different snow regimes in the subarctic [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5788, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Winter warming events (WWE) in the Swedish subarctic are abrupt and short-lasting (hours-to-days) events of positive air temperature that occur during wintertime, sometimes accompanied by rainfall (rain on snow; ROS). These events cause changes in snow properties, which affect the below-ground thermal regime that, in turn, controls a suite of ecosystem processes ranging from microbial activity to permafrost and vegetation dynamics. For instance, winter melting can cause ground warming due to the shortening of the snow cover season, or ground cooling as the reduced snow depth and the formation of refrozen layers of high thermal conductivity at the base of the snowpack facilitate the release of soil heat. Apart from these interacting processes, the overall impacts of WWE on ground temperatures may also depend on the timing of the events and the preceding snowpack characteristics. The frequency and intensity of these events in the Arctic, including the Swedish subarctic, has increased remarkably during the recent decades, and is expected to increase even further during the 21st Century. In addition, snow depth (not necessarily snow duration) is projected to increase in many parts of the Arctic, including the Swedish subarctic. In 2005, a manipulation experiment was set up on a lowland permafrost mire in the Swedish subarctic, to simulate projected future increases in winter precipitation. In this study, we analyse this 15-year record of ground temperature, active layer thickness, and meteorological variables, to evaluate the short- (days to weeks) and long-term (up to 1 year) impacts of WWE on the thermal dynamics of lowland permafrost, and provide new insights into the influence of the timing of WWE and the underlying snowpack conditions on the thermal response of permafrost. On the short-term, the thermal responses to WWE are faster and stronger in areas with a shallow snowpack (5-10 cm), although these responses are more persistent in areas with a thicker snowpack (>25 cm), especially after ROS events. On the long term, permafrost in areas with a thicker snowpack exhibit a more durable warming response to WWE that results in thicker active layers at the end of the season. On the contrary, we do not observe a correlation between WWE and end of season active layer thickness in areas with a shallow snowpack.

DOI: 10.5194/egusphere-egu21-5788

2021048016 Dietze, Elisabeth (Alfred-Wegener-Institute, Helmholtz-Centre for Polar and Marine Research, Potsdam, Germany); Mangelsdorf, Kai; Weise, Jasmin; Matthes, Heidrun; Lisovski, Simeon and Herzschuh, Ulrike. The potential and limitations of long-term fire regime reconstructions in eastern Siberia based on sedimentary charcoal and low-temperature fire markers [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8974, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Forest fires are an important factor in the global carbon cycle and high latitude ecosystems. Eastern Siberian tundra, summergreen larch-dominated boreal forest on permafrost and evergreen boreal forest have characteristic fire regimes with varying fire intensities. Yet, it is unknown which role fire plays in long-term climate-vegetation-permafrost feedbacks and how high-latitude fire regimes and ecosystems will change in a warmer world. To learn from fire regime shifts during previous interglacials, prior to human presence, we use lake-sedimentary charcoal as proxy for high-intensity forest fires and monosaccharide anhydrides (i.e. levoglucosan, mannosan, galactosan: MA) as molecular proxies for low-temperature biomass burning, typical for surface fires in modern larch forest. However, MA pathways from source to sink and their stability in sediments are very poorly constrained. Recently, Dietze et al. (2020) found MA in up to 420 kyr old sediment of Lake El'gygytgyn (ICDP Site 5011-1), NE Siberia, suggesting that they are suitable proxies for fires in summergreen boreal forests. Surprisingly, the ratios of the MA isomers were exceptionally low compared to published emission ratios from modern combustions. To understand what MA from Arctic lake sediments tell us, we have analyzed the MA and charcoal composition in modern lake surface sediments of Lake El'gygytgyn and three East Siberian lakes and we compare them to late glacial-to-interglacial El'gygytgyn records. The three Siberian lakes were chosen to represent spatial analogues to the El'gygytgyn conditions during MIS 5e and 11c. We discuss first results of the modern sediments in context of recent MODIS- and Landsat-based fire extents and biome-specific land cover data, a wind field modelling using climate data over eastern Siberia, and lake-catchment configurations from TDX-DEM analysis to assess potential fire proxy source areas and regional-to-local transport processes. Thereby, we provide insights into the meaning of sedimentary fire proxies, crucial for a sound reconstruction of long-term fire regime histories.

DOI: 10.5194/egusphere-egu21-8974

2021048037 Dominé, Florent (Université Laval, Takuvik Joint International Laboratory, Quebec City, QC, Canada); Fourteau, Kevin and Picard, Ghislain. Shrubs covered by snow in the High Arctic cool down permafrost in winter by thermal bridging through frozen branches [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7222, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Warming-induced shrub expansion on Arctic tundra is generally thought to warm up permafrost, as shrubs trap blowing snow and increase the thermal insulation effect of snow, limiting permafrost winter cooling. We have monitored the thermal regime of permafrost on Bylot Island, 73°N in the Canadian high Arctic at nearby herb tundra and shrub tundra sites. Once adjusted for differences in air temperature, we find that shrubs actually cool permafrost by 0.6°C over November-March 2019, despite a snowpack twice as insulating in shrubs. By simulating the rate of propagation of thermal perturbations and using finite element calculations, we show that heat conduction through frozen shrub branches have a winter cooling effect of 1.5°C which compensates the warming effect induced by the more insulating snow in shrubs. In spring shrub branches under snow absorb solar radiation and accelerate permafrost warming. Over the whole snow season, simulations indicate that heat and radiation transfer through shrub branches result in a 0.3°C cooling effect. This is contrary to many previous studies, which concluded to a warming effect, sometimes based on environmental manipulations that may perturb the natural environment. The impact of shrubs on the permafrost thermal regime may need to be re-evaluated.

DOI: 10.5194/egusphere-egu21-7222

2021048011 Donner, Anika (Universität Innsbruck, Institute of Geology, Innsbruck, Austria); Spötl, Christoph; Töchterle, Paul; Hajdas, Irka and Moseley, Gina E. First investigations of fine-grained cryogenic cave carbonates from a High Arctic permafrost karst system in Greenland [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14642, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In recent years, cryogenic cave carbonates (CCC) have become the focus of studies tracking past climate change in periglacial environments. Two types of these speleothems occur, fine-grained CCC (CCCfine), which form due to the rapid freezing of a thin water film on ice, and coarse-grained CCC whose origin is related to the slow freezing of water pockets inside cave ice. Here, we report for the first time the occurrence of CCCfine from a cave in northeast Greenland, presently situated in continuous permafrost. Eqik Qaarusussuaq (Cove Cave), located at 80.2°N, is a 103 m long, gently-dipping phreatic passage that was discovered during the 2019 Greenland Caves Project Expedition ( CCCfine were found in a dry chamber 65 m behind the entrance. The cave air temperature at the CCC site of -14.7°C contrasts with outside air temperatures of up to +18.0°C in July 2019. This, together with current dry conditions at the sampling site, indicates that water infiltration, necessary for CCC formation, is not possible under present-day climate conditions. This is further supported by a lack of ice found within the cave. Stable isotope analyses of CCC show d18O values ranging from -21.9 to -16.0 ppm and d13C values between 8.4 and 11.7 ppm VPDB. While the d13C values are consistent with published data of CCCfine from caves at lower latitudes, the d18O values are significantly lower and plot in the field of CCCcoarse (cf. Zak et al., 2018). This shift reflects the much lower d18O values of meteoric precipitation in northeast Greenland compared to lower latitude sites. Exploratory radiocarbon dating suggests that CCCfine formed in this High Arctic cave as recent as during the end of the Little Ice Age.

DOI: 10.5194/egusphere-egu21-14642

2021047995 Fewster, Richard (University of Leeds, School of Geography, Leeds, United Kingdom); Morris, Paul; Ivanovic, Ruza; Swindles, Graeme; Peregon, Anna and Smith, Chris. Simulating future distributions of northern permafrost peatlands [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7450, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Northern permafrost peatlands represent one of Earth's largest terrestrial carbon stores and are highly sensitive to climate change. Whilst frozen, peatland carbon fluxes are restricted by cold temperatures, but once permafrost thaws and saturated surficial conditions develop, emissions of carbon dioxide (CO2) and methane (CH4) substantially increase. This positive feedback mechanism threatens to accelerate future climate change globally. Whilst future permafrost distributions in mineral soils have been modelled extensively, the insulating properties of organic soils mean that peatland permafrost responses are highly uncertain. Peatland permafrost is commonly evidenced by frost mounds, termed palsas/peat plateaus, or by polygonal patterning in more northerly regions. Although the distribution of palsas in northern Fennoscandia is well-studied, the extent of palsas/peat plateaus and polygon mires elsewhere remains poorly constrained, which currently restricts predictions of their future persistence under climate change. Here, we present the first pan-Arctic analyses of the modern climate envelopes and future distributions of permafrost peatland landforms in North America, Fennoscandia, and Western Siberia. We relate a novel hemispheric-scale catalogue of palsas/peat plateaus and polygon mires (>2,100 individual sites) to modern climate data using one-vs-all (OVA) binary logistic regression. We predict future distributions of permafrost peatland landforms across the northern hemisphere under four Shared Socioeconomic Pathway (SSP) scenarios, using future climate projections from an ensemble of 12 general circulation models included in the Coupled Model Intercomparison Project 6 (CMIP6). We then combine our simulations with recent soil organic carbon maps to estimate how northern peatland carbon stocks may be affected by future permafrost redistribution. These novel analyses will improve our understanding of future peatland trajectories across the northern hemisphere and assist predictions of climate feedbacks resulting from peatland permafrost thaw. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-7450

2021047991 Fiencke, Claudia (Universität Hamburg, Institute of Soil Science, Hamburg, Germany); Sanders, Tina; Zell, Nadine; Pfeiffer, Eva-Maria and Beer, Christian. Nitrogen loss in river and erosion banks in form of reactive dissolved nitrogen and nitrous oxide via microbial nitrification in permafrost-affected soils in the Lena Delta in the Siberian Arctic [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14915, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Permafrost affected soils store a huge amount of organic matter including carbon and nitrogen. But especially permafrost is expected to degrade significantly through deepening and erosion processes with important consequences for freshwater systems. Although Arctic ecosystems are strongly limited by bioavailable nitrogen (N), the loss of vegetation by thermokarst and lack of vegetation on riverbanks probably establish conditions for imbalance in the nitrogen cycle, therefore higher N-availability for microbial transformations and in consequence loss of reactive nitrogen. Here we present data from expeditions in 2008 and 2019, where we found indeed relatively high concentrations of dissolved inorganic nitrogen, mainly as ammonium (up to approx. 10 mg N g dw-1) in the active layer of dry no vegetated carbon poor mineral soils of the riverbank and cliff (recently eroded by the Lena river). In the stratified permafrost-affected soils of the riverbank nitrate accumulated during the summer period, especially in more organic silty layers (4% SOM) to extremely high concentrations (up to approx. 90 mg N-nitrate g dw-1). Decreasing ammonium and increasing nitrate concentrations during the vegetation period hint to the aerobic nitrification process, which is the main source of nitrate in terrestrial ecosystem. Together with high nitrate concentrations in the field, these soil layers showed high potential nitrification rates in aerobic incubation experiments (max. 14.4 mg N g dw-1 d-1, 21,6 g N m-3 d-1, 5°C) combined with high varying but significant N2O production rates (max. 150 mg N-N2O m-3 d-1, 5°C). Since nitrification rates positively respond to temperature (max. Q10 of 4) and ammonium availability, climate change may cause an increasing release of gaseous N-loss (N2O) or leaching of nitrate and dissolved organic nitrogen (DON) to aquatic ecosystems with further consequences. Hot spots of high N-availability in no vegetated river and erosion banks likely influence the microbial induced C cycle as C-mineralization but also atmospheric methane oxidation, which might be the interest of future studies. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-14915

2021047999 Flamand, Aude (Universite du Quebec a Rimouski, ISMER, Rimouski, QC, Canada); Chaillou, Gwénaëlle; Kipp, Lauren and Whalen, Dustin. Characterization of an optical signature of the DOM of the coastal permafrost in the Mackenzie Delta, by PARAFAC analysis [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16506, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Global warming increases the thawing rate of the permafrost in high northern latitudes. The Arctic soil organic carbon accounts for over 50% of global soil carbon which is roughly twice the amount present in the atmosphere. An increasing amount of the newly mobilized old organic carbon, and its associated compounds, originating from permafrost thaw, is expected to be delivered to the Arctic Ocean by rivers and groundwater discharges all along the Arctic coastline. Absorbance and fluorescence spectroscopy can be used to identify a specific optical signature of permafrost-derived solutes with the objective of studying their transport and transformation to coastal waters. Emission-excitation spectra (EEMs) from three sampling sites along the coastal area of the delta were assessed and parallel factor analysis (PARAFAC) was used to identify three different components characterizing the origin and the nature of the organic carbon present in various types of samples (massive ice, groundwater, seawater and water samples on top/bottom of slumps). This study suggests that the carbon originating from the thawing of the permafrost could indeed be traced along the coastal area of the Delta. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-16506

2021048010 Fonti, Marina (Siberian Federal University, Institute of Ecology and Geography, Laboratory of Ecosystems Biogeochemistry, Krasnoyarsk, Russian Federation); Churakova Sidorova, Olga and Tychkov, Ivan. Intra-annual climatic signal in tree rings of Larix sp. based on the Vaganov-Shashkin model output [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9278, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Air temperature increase and change in precipitation regime have a significant impact on northern forests leading to the ambiguous consequences due to the complex interaction between the ecosystem plant components and permafrost. One of the major interests in such circumstances is to understand how tree growth of the main forest species of the Siberian North will change under altering climatic conditions. In this work, we applied the process-based Vaganov-Shashkin model (VS - model) of tree growth in order to estimate the daily impact of climatic conditions on tree-ring width of larch trees in northeastern Yakutia (Larix cajanderi Mayr.) and eastern Taimyr (Larix gmelinii Rupr. (Rupr.) for the period 1956-2003, and to determine the extent to which the interaction of climatic factors (temperature and precipitation) is reflected in the tree-ring anatomical structure. Despite the location of the study sites in the harsh conditions of the north, and temperature as the main limiting factor, it was possible to identify a period during the growing season when tree growth was limited by lack of soil moisture. The application of the VS-model for the studied regions allowed establishing in which period of the growing season the water stress is most often manifest itself, and how phenological phases (beginning, cessation, and duration of larch growth) vary among the years. The research was funded by RFBR, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, project number 20-44-240001 and by the Russian Ministry of Science and Higher Education (projects FSRZ-2020-0010).

DOI: 10.5194/egusphere-egu21-9278

2021047971 Fouche, Julien (Universite de Montpellier, Laboratoire d'Etude des Interactions entre Sol-Agrosystème-Hydrosystème, Montpellier, France); Shakil, Sarah; Hirst, Catherine; Bröder, Lisa; Agnan, Yannick; Sjoberg, Ylva and Bouchard, Frédéric. The SPLASH Action Group; towards standardized sampling strategies along the soil-to-hydrosystems continuum in permafrost landscapes [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-11184, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The Action Group called 'Standardized methods across Permafrost Landscapes: from Arctic Soils to Hydrosystems' (SPLASH), funded by the International Permafrost Association, is a community-driven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils, sediments, surface water bodies and coastal environments across permafrost landscapes. This unified approach will allow data to be shared and compared, thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds. This is an international and transdisciplinary effort aiming to provide a fieldwork "tool box" of the most relevant sampling schemes and sample conservation procedures for mineral and organic permafrost pools. With climate change, permafrost soils are undergoing drastic transformations. Both localized abrupt thaw (thermokarst) and gradual ecosystem shifts (e.g., active layer thickening, vegetation changes) drive changes in hydrology and biogeochemical cycles (carbon, nutrients, and contaminants). Mineral and organic components interact along the "lateral continuum" (i.e., from soils to aquatic systems) changing their composition and reactivity across the different interfaces. The circumpolar Arctic region is characterized by high spatial heterogeneity (e.g., geology, topography, vegetation, and ground-ice content) and large inter-annual and seasonal variations in local climate and biophysical processes. Common sampling strategies, applied in different seasons and locations, could help to tackle the spatial and temporal complexity inextricably linked to biogeochemical processes. This unified approach developed in permafrost landscapes will allow us to overcome the following challenges: (1) identifying interfaces where detectable changes in mineral and organic components occur; (2) allowing spatial comparison of these detectable changes; and (3) capturing temporal (inter-/intra-annual) variations at these interfaces. In order to build on the great effort to better assess the permafrost feedback to climate change, there is an urgent need for a set of community-based protocols to capture changes the dynamics of organics and minerals during their lateral transport. Here, we present the first results from an online survey recently conducted among researchers from different disciplines. The survey inputs provide valuable information about the common approaches currently applied along the "soil-to-hydrosystems" continuum and the specific challenges associated with permafrost studies. These results about the 'WHAT, WHERE, WHEN, and HOW' of field sampling (e.g., sample collection, filtration, conservation...) allow for identifying the most relevant sampling strategies and also the current knowledge gaps. Finally, we present examples of the protocols available to investigate organic and mineral components from soils to marine environments, on which a synoptic sampling strategy can be built. All forthcoming contributions from our community are still welcome, helping the SPLASH team to fill up the most adapted tool box to Arctic permafrost landscapes.

DOI: 10.5194/egusphere-egu21-11184

2021048026 Frimberger, Theresa (Technichal University of Munich, Landslide Research Group, Munich, Germany); Andrade, Daniel and Krautblatter, Michael. Towards a better understanding of the role of glacier retreat and permafrost degradation in triggering secondary lahars [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13502, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

As everywhere in the Andes, tropical glaciers have been rapidly retreating since several decades. The glaciers of Cotopaxi volcano, Ecuador, have been reduced in area by about 50% since 1976 (Caceres, 2017). The Cotopaxi is mostly famous for its capacity to produce massive lahars during volcanic eruptions, but comparably smaller, secondary lahars generated in post-eruptive periods by heavy rainfall occur more frequently on the volcano's flanks. However, since a few years, secondary lahars that originate in proglacial areas without any clear trigger mechanism are recorded at Cotopaxi. This raises the question of whether there exists a process-based link between the occurrence of secondary lahars and the retreat of cold-based glaciers with accompanied permafrost degradation in the former subglacial frozen pyroclastic material over the following years and decades. Here, we present the data obtained from laboratory-calibrated Electrical Resistivity Tomography (ERT) and Seismic Refraction Tomography (SRT) conducted near the glacier margin between 5000 and 5300 m asl, which provide a better understanding of frozen/unfrozen conditions and the structure of the subsurface. In addition, data loggers have been recording surface air temperatures close to the glacier since May 2018. Our measurements show that permafrost cannot develop under current thermal conditions, but high electrical resistivities at depths of 10-20 m correspond to calibrated rock temperatures below 0°C. The detected frozen lenses may act as detachment planes of periglacial secondary lahars in pyroclastic material recently exposed by glacier retreat.

DOI: 10.5194/egusphere-egu21-13502

2021048042 Gadylyaev, Damir (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Nitzbon, Jan; Schlüter, Steffen; Köhne, John Maximilian; Grosse, Guido and Boike, Julia. Applying computed tomography (CT) scanning for segmentation of permafrost constituents in drill cores [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-11395, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Computed X-ray Tomography is a non-destructive technique that allows three-dimensional imaging of soil samples' internal structures, determined by variations in their density and atomic composition. This study's objective was to develop an image processing workflow for the quantitative analysis of ice cores using high-resolution CT in order to determine the volume fraction and vertical distribution of ice, mineral, gas, and organic matter in permafrost cores. We analyzed a 155 cm permafrost core taken from a Yedoma permafrost upland on Kurungnakh Island in the Lena River Delta (northeast Siberia). The obtained results were evaluated and compared with the results of detailed, but sample-destructive laboratory analysis. The frozen permafrost core was subjected to a computerized X-ray imaging procedure with a resolution of 50 micrometers. As a result, we obtained 31000 images. Noise in the raw images is removed with a non-local means denoising filter. We chose multilevel thresholding method for the image segmentation step. Threshold values were determined based on the histograms of the images. We measured the volumetric ice content (VIC) using Java-based image processing software (ImageJ). In addition, the vertical profiles were analyzed in 1-2cm intervals. We received bulk densities and VIC by freeze-drying and standard laboratory analysis. From the top of the core and until roughly 86 cm, it mainly consists of ice and organic, with an average of 67% and 30% results, respectively. The rest of the volume is divided almost equally between air and mineral parts. Below 86 cm, it consists almost entirely of pure ice. The ice content constitutes around 97% of the composition, and air rises to roughly 3%, while mineral and organic are almost equal to zero. The difference between VIC derived through CT scan and laboratory-derived VIC lies within the range of -37% to 25%. However, the vast majority of values lie within the range of -10% to 10%. This image processing technique to quantify VIC provides a non-destructive analog to traditional laboratory analysis that could help increasing the vertical resolution for quantifying mineral, ice, gas, and organic components in permafrost cores as well as enhance the volumetric estimate.

DOI: 10.5194/egusphere-egu21-11395

2021047989 Galbraith, John (Virginia Polytechnic Institute and State University, Blacksburg, VA); Krasilnikov, Pavel and Rumpel, Cornelia. Boreal vegetation and soil carbon dynamics in response to a changing climate and soil variables [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13331, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Many soils in the Boreal forest regions of the Arctic store very large amounts of carbon in the active layer above permafrost, and store significant amounts of carbon within the permafrost. Soils that are well drained, high in rock fragments, shallow to rock or rubble, or covered with ice are exceptions. No other region on Earth stores more carbon on average than the Arctic regions, especially in wetlands. However, changes in vegetation and soil are expected under warming climates. Research questions have arisen about future changes in vegetation and net carbon flux as soil and air temperatures climb, as precipitation amount and type changes, and as the growing season lengthens. A review of recent literature will be conducted to look at effects of vegetation change and annual carbon dynamics in Boreal forest and wetland soils under warming climates. Environmental variables such as soil temperature, hydrology, microbial and higher plant growth, digestibility of young and old carbon, fire, location zone, extent and type of permafrost thaw slow vs sudden collapse), and N and P nutrient balances will affect carbon stocks in addition to changing climate. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13331

2021048036 Galera, Leonardo de Aro (Universität Hamburg, Institut für Bodenkunde, Hamburg, Germany); Knoblauch, Christian; Eckhardt, Tim; Beer, Christian and Pfeiffer, Eva-Maria. CH4 and CO2 fluxes at sites with different hydrological patterns in the polygonal tundra of Samoylov Island, northeastern Siberia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-137, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In the last two decades, there were registered record high permafrost temperatures promoting permafrost thawing and leading to additional CO2 and CH4 emissions. It is crucial to assess the amount of C that is mineralized to CH4, due to its higher global warming potential (GWP) compared to CO2. The role of CH4 in the total C emissions is mainly governed by the hydrological patterns of ecosystems. CH4 oxidation is another critical process and is largely controlled by vegetation. The soil CO2:CH4 production ratio shows the contribution of CH4 to the C emission budget of a determined area. Few studies evaluated in situ CO2:CH4 production ratios. Our objective was to assess CH4 emissions and the heterotrophic CO2:CH4 production ratios in the Siberian tundra during the growing season. To accomplish these goals, we measured CH4 and CO2 fluxes using the chamber technique in the polygonal tundra of Samoylov Island in the Lena River Delta, Northeastern Siberia. The plant-mediated CH4 transport and the heterotrophic respiration (Rh) were determined by comparing plots with and without vegetation through a trenching experiment. To account for the differences between wet and dry tundra, one representative polygon was selected, measurements were made at its water-saturated center and at its drained rim. We also estimated the C budget of the polygonal tundra of Samoylov Island during the measurement period. This is the first study measuring and calculating in situ CO2:CH4 ratios from the Rh of the soil. The CH4 emissions at the polygon center were much higher than the rim and showed evident seasonality. The polygon center median CH4 flux of 26 mg.m-2.d-1 decreased by 80% when the vegetation was removed, indicating the relevance of plant-mediated CH4 transport in these emissions. This was not detected at the polygon rim that had much lower emissions (1.8 mg.m-2.d-1). The heterotrophic CO2:CH4 ratios varied from 1 to 100 at the polygon center, and from 100 to 1000 at the polygon rim, showing the greater importance of CH4 production to the heterotrophic C release at the polygon center. The polygonal tundra on Samoylov Island was a C sink during the measurement period. The wet tundra had a CO2-C sequestration rate (-23 kg CO2-C.ha-1.d-1) more than 3 times higher than the dry tundra (-7 kg CO2-C.ha-1.d-1). Overall, the CH4 emissions represent a decrease of just 5% in the total CO2-e offset of the tundra in Samoylov during the growing season. The CH4 emissions measured in this study were low. However, it is important to point out that only the growing season is considered, and the off-season and winter C emissions might be significant. Our results stress the high microscale variability of emissions of CO2 and CH4, specially related to hydrology, topography, and vegetation.

DOI: 10.5194/egusphere-egu21-137

2021048032 Gay, Bradley (George Mason University, Department of Geography and Geoinformation Science, Fairfax, VA); Armstrong, Amanda; Osmanoglu, Batuhan; Montesano, Paul; Ranson, Kenneth and Epstein, Howard. Examination of current and future permafrost dynamics across the North American taiga-tundra ecotone [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3066, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In the Arctic, the spatial distribution of boreal forest cover and soil profile transition characterizing the taiga-tundra ecological transition zone (TTE) is experiencing an alarming transformation. The SIBBORK-TTE model provides a unique opportunity to predict the spatiotemporal distribution patterns of vegetation heterogeneity, forest structure change, arctic-boreal forest interactions, and ecosystem transitions with high resolution scaling across broad domains. Within the TTE, evolving climatological and biogeochemical dynamics facilitate moisture signaling and nutrient cycle disruption, i.e. permafrost thaw and nutrient decomposition, thereby catalyzing land cover change and ecosystem instability. To demonstrate these trends, in situ ground measurements for active layer depth were collected to cross-validate below-ground-enhanced modeled simulations from 1980-2017. Shifting trends in permafrost variability (i.e. active layer depth) and seasonality were derived from model results and compared statistically to the in situ data. The SIBBORK-TTE model was then run to project future below-ground conditions utilizing CMIP6 scenarios. Upon visualization and curve-integrated analysis of the simulated freeze-thaw dynamics, the calculated performance metric associated with annual active layer depth rate of change yielded 76.19%. Future climatic conditions indicate an increase in active layer depth and shifting seasonality across the TTE. With this novel approach, spatiotemporal variation of active layer depth provides an opportunity for identifying climate and topographic drivers and forecasting permafrost variability and earth system feedback mechanisms.

DOI: 10.5194/egusphere-egu21-3066

2021047951 Gelfan, Alexander (Russian Academy of Sciences, Water Problems Institute, Moscow, Russian Federation) and Kalugin, Andrey. Permafrost in the Caspian Sea basin in the late glacier era as a possible trigger of the sea transgression; checking the hypothesis using a hydrological model [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3812, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Paleogeographic data give grounds to assert that at the end of the Valdai Ice Age, transgressions of the Caspian Sea took place, and the sea level during these periods exceeded the current one by tens of meters. The physical mechanisms, climatic or others, that could have caused such an extreme sea level rise have not yet been established. At the same time, in the modern Volga basin, traces of very large ancient river channels are widespread, which could have been formed by ancient rivers with the water flow 2-3 times larger than the modern rivers. Thus, the hypotheses of the extreme rise in the Caspian Sea level can be reduced to considering possible sources of the increase in the flow of the ancient rivers. However, the question of possible sources of such a significant river flow remains open. At the end of the Paleocene - beginning of the Holocene, precipitation over the Caspian Sea catchment was not higher than now, the contribution of melted glacial waters in the Late Glacial Era was also insignificant. Hypotheses about significant changes in the catchment area of the Caspian Sea during those times are not confirmed by paleogeographic data either. In our work, we test the hypothesis that the river inflow into the ancient Caspian Sea could significantly exceed the current inflow due to the spread of post-glacial permafrost over the sea catchment area, which contributed to a decrease in runoff losses due to infiltration into frozen soils. The physical validity of the above hypothesis was tested using numerical experiments with a hydrological model of the Volga River basin, developed on the basis of the ECOMAG modeling platform. Assuming that the climatic conditions in the modern Volga basin area during the Late Glacial Era were close to the current conditions, numerical experiments were carried out to simulate deep freezing of soil throughout the entire territory of the modern Volga basin area. It is shown that under permafrost conditions, the Volga River runoff increases by 15-20% and does not provide a twofold rise in water inflow into the sea, estimated from paleogeographic data. At the same time, the experiments have shown that such extreme inflow of water into the Caspian Sea could be formed under the conditions of deep freezing of soils and in the absence of seasonal thawing of the frozen catchment area, i.e. at a colder climate than the modern one. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3812

2021048028 Giardino, Marco (Universita di Torino, Department of Earth Sciences, Turin, Italy); Montani, Antonio; Tamburini, Andrea; Calvetti, Francesco; Martelli, Davide; Salvalai, Graziano; Tognetto, Federico and Perotti, Luigi. Climate change and cryosphere in high mountains; updates from the Capanna Margherita Hut study case (Punta Gnifetti, Monte Rosa Massif, Pennine Alps) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15577, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Mountain glaciers and permafrost are among the most evident geomorphological tracers of climate change. In the last decades, they showed a growing and faster response also at very high elevations, leading to increased instability of the Alpine landscape. In the meanwhile, they became of great interest also for their possible interactions with human activities and infrastuctures. On the highest massif of the Alps, as for example the Monte Rosa, this interaction is mainly represent by the one with mountaineering activities. The top of Gnifetti Peak (4554 m a.s.l.), with the Capanna Margherita hut (the highest in Europe), is under investigation to better understand the effects of global warming on hut stability and mountaineering routes safety. Thanks to the cooperation between the Italian Alpine Club (CAI), University of Turin (UniTo), Politecnico di Milano (PoliMi) and IMAGEO srl, a first assessment of geological and glacial settings of hut surroundings have been performed on 2019. Data collection continued on 2020, by means of comparative analyses designated to: a) identify the relevant geomechanical features for rock mass stability; b) verify permafrost related instabilities; c) reconstruct the ice-covered morphology of the Punta Gnifetti peak; d) calculate rock-building interactions. Here below the related results: 1) A 3D model of the area has been obtained by integrating helicopter-borne photogrammetry with terrestrial laser scanner surveys. 2) Glacier thickness at the Colle Gnifetti has been established thanks to GPR survey. 3) From the comparison of a large number of historical pictures a first multi-temporal stability analysis highlighted sector of greater instability. Results of this work are freely available on the website 4) The geomechanical features of the rock mass below and around the hut have been retrieved from the analysis of the dense point cloud provided by terrestrial laser scanner integrated with direct field investigations. 5) Constructive drawing of the hut have been obtained from the terrestrial laser scanner point cloud integrated with manual measurements taken inside the structure. 6) 3D numerical modelling are going to be applied in order to simulate the interactions between the hut and the foundation rock on the base of the above data. The ongoing activities are addressed to a detailed study of more vulnerable sectors of the Punta Gnifetti to better understand morphodynamics and possible interactions with mountaineering activities. This will be performed through a two-way investigation. On one hand, a link with alpine guides and mountain hut keepers has been established, in order to have "sentries" ready to report instabilities and detect new hazards and risks. On the other hand, a monitoring network will be installed around Capanna Margherita in order to collect data on weather, glacier and permafrost conditions.

DOI: 10.5194/egusphere-egu21-15577

2021048000 Gonçalves-Araujo, Rafael (Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark); Granskog, Mats; Osburn, Christopher and Stedmon, Colin. A pan-Arctic algorithm for DOC concentrations from CDOM spectra [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12720, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The surface layer of the Arctic Ocean carries a higher dissolved organic carbon (DOC) content than other ocean basins. Climate change impacts the Arctic aquatic DOC-pool by e.g., introducing DOC trapped in permafrost soils as they thaw and by increasing the terrestrial runoff and primary production. Sampling for DOC in the Arctic is rather challenging given its remoteness and difficult access to the region and that it is not possible yet to determine DOC concentrations from instruments deployed in the field. Compared to DOC, colored dissolved organic matter (CDOM) absorption spectroscopy is an easy-to-measure, relatively quick and cost-effective approach which is often closely related to DOC concentrations in water samples. In regions in close proximity to rivers, linear relationships between CDOM absorption at 350nm (a350) and DOC often can be found and, thus, have improved prediction of DOC using two end-members. However, in regions with two or more end-members of comparable DOC concentrations (shelf seas and oceanic waters) these relationships are difficult to derive, as there might be pools of similar concentration/intensity but different ratio of absorption to DOC (carbon specific absorption coefficient, a*). Here we present an algorithm to estimate DOC concentrations based on quantitative (a350) and qualitative (spectral absorption slope between 275 and 295nm, S275-295) properties of CDOM. The algorithm considers that there is a linear correlation between DOC and a350 but that the slope of the relationship (inverse of a*) varies depending on the exponent of the ultraviolet (UV) spectral slope (S275-295), that is, the character or source of DOM. We compiled a Pan-Arctic dataset (n=3607) from a wide range of aquatic systems spanning lakes, rivers, estuaries, coastal and shelf seas and open ocean with salinity ranging from 0 to 35.3. DOC ranged between 19 and 2304 mM, whereas a350 varied from 0.01-81.33 m-1 and S275-295 ranged 12-39 mm-1. The algorithm provided significant and robust (r2=0.93; p<0.0001) DOC estimates (pDOC), ranging 1-2598 mM (RMSE=64 mM). This indicates that, besides its simplicity, this method is capable of capturing the extremely high variability of DOC within the broad gradient of Arctic aquatic systems considered in this study. Apart from that, pDOC estimates could reproduce both DOC profiles and the DOC vs. salinity relationship across the Arctic Ocean (i.e., distinct sites with highly distinct hydrographic conditions). This potentially makes the method suitable for high-resolution and long-term in situ monitoring of DOC concentrations in Arctic aquatic systems from e.g., absorbance measurements from in situ nitrate sensors. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-12720

2021047947 Gornyy, Victor (Russian Academy of Sciences, Laboratory of Remote Sensing Methods and Geoinformatics, Saint Petersburg, Russian Federation); Kiselev, Andrei; Kritsuk, Sergei; Latypov, Iscander and Tronin, Andrei. Multiyear dynamics of remotely mapped characteristics of ecosystems in northern Eurasia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3090, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The climate change of the last decades has to be reflected in the ecosystems dynamics. By investigating the ecosystem dynamics one can get the information about climate change. One of the most suitable source of information about ecosystem dynamics is remote sensing satellite data. We used EOS multispectral images, gravimetric data of the GRACE satellite, and AURA satellite contents of sulfur dioxide data for the period of the last ~20 years. Daily and 8 days composites of different quantitative characteristics, reduced to the spatial resolution 1´1 km, were retrieved from standard products and raw data: - the daily averaged land surface temperature; - the duration of vegetation (the period of year when a land surface temperature is higher than +10°C); - the Enhanced Vegetation Index (EVI); - the effective water layer thickness (EWLT) according satellite gravimentry); - the concentration of sulphur dioxide in atmosphere. The speed of each characteristics change was estimated and mapped by using linear regression. As the result, the regular chain of isometric domains of land surface temperature rising and decreasing was noticed from the West edge to the East edge of Northern Eurasia. The presence of this chain was the reason to express hypothesis about more complex structure of the modern atmospheric circulation and interaction between the Ferrel and the Polar cells. Additionally we have noticed that domain of the land surface temperature growth at the Northern part of West Siberia coincides with decreasing of EWLT. We interpreted this phenomena as result of permafrost degradation. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3090

2021047952 Groenke, Brian (Alfred Wegener Institute, Permafrost, Potsdam, Germany); Langer, Moritz; Gallego, Guillermo and Boike, Julia. Learning soil freeze characteristic curves with universal differential equations [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13409, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Permafrost thaw is considered one of the major climate feedback processes and is currently a significant source of uncertainty in predicting future climate states. Coverage of in-situ meteorological and land-surface observations is sparse throughout the Arctic, making it difficult to track the large-scale evolution of the Arctic surface and subsurface energy balance. Furthermore, permafrost thaw is a highly non-linear process with its own feedback mechanisms such as thermokarst and thermo-erosion. Land surface models, therefore, play an important role in our ability to understand how permafrost responds to the changing climate. There is also a need to quantify freeze-thaw cycling and the incomplete freezing of soil at depth (talik formation). One of the key difficulties in modeling the Arctic subsurface is the complexity of the thermal regime during phase change under freezing or thawing conditions. Modeling heat conduction with phase change accurately requires estimation of the soil freeze characteristic curve (SFCC) which governs the change in soil liquid water content with respect to temperature and depends on the soil physical characteristics (texture). In this work, we propose a method for replacing existing brute-force approximations of the SFCC in the CryoGrid 3 permafrost model with universal differential equations, i.e. differential equations that include one or more terms represented by a universal approximator (e.g. a neural network). The approximator is thus tasked with inferring a suitable SFCC from available soil temperature, moisture, and texture data. We also explore how remote sensing data might be used with universal approximators to extrapolate soil freezing characteristics where in-situ observations are not available. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13409

2021048024 Gruber, Stephan (Carleton University, Ottawa, ON, Canada); Subedi, Rupesh and Kokelj, Steven V. Relict basal ice from the Laurentide ice sheet near Lac de Gras, Slave geological province, N.W.T., Canada [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3490, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

A 2015 drilling campaign near Lac de Gras has recovered permafrost core interpreted to contain preserved basal ice of the Laurentide Ice Sheet (Subedi et al., 2020). Previous samples of basal ice from ice sheets originate from coring, usually beneath modern ice divides, modern margins of Arctic icecaps that have preserved basal ice-sheet ice, or from studies near the margins of former ice sheets. The present study may be the first evidence of basal ice a few hundred kilometers from ice divides. In this intermediate zone, rates of erosion beneath an ice sheet increase and the thermal regime at the base varies. Our finding is of applied relevance because it highlights the mosaic character of a landscape that contains terrain types with non-negligible ground-ice content, poised for climate-driven thaw and landscape change. The occurrence and mosaic character of preserved ice may be reconciled with glaciological theory and observations from mineral prospecting using the theory on the genesis of dispersal plumes in till developed by Hooke et al. (2013). The existence of preserved basal ice opens basic-research opportunities alongside exploration, mining and infrastructure development in the area. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3490

2021048038 Gudmundsson, Lukas (ETH Zurich, Department of Environmental Systems Science, Zurich, Switzerland); Kirchner, Josefine; Gädeke, Anne; Burke, Eleanor; Biskaborn, Boris K. and Noetzli, Jeannette. Attributing the global increase in permafrost temperatures to human induced climate change [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8337, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Permafrost temperatures are increasing at the global scale, resulting in permafrost degradation. Besides substantial impacts on Arctic and Alpine hydrology and the stability of landscapes and infrastructure, permafrost degradation can trigger a large-scale release of carbon to the atmosphere with possible global climate feedbacks. Although increasing global air temperature is unanimously linked to human emissions into the atmosphere, the attribution of observed permafrost warming to anthropogenic climate change has so far mostly relied on anecdotal evidence. Here we apply a climate change detection and attribution approach to long permafrost temperature records from 15 boreholes located in the northern Hemisphere and simulated soil temperatures obtained from global climate models contributing to the sixth phase of the Coupled Model Intercomparison Project (CMIP6). We show that observed and simulated trends in permafrost temperature are only consistent if the effect of human emissions on the climate system is considered in the simulations. Moreover, the analysis also reveals that neither simulated pre-industrial climate variability nor the effects natural drivers of climate change (e.g. impacts of large volcanic eruptions) suffice to explain the observed trends. While these results are most significant for a global mean assessment, our analysis also reveals that simulated effects of anthropogenic climate change on permafrost temperature are also consistent with the observed record at the station scale. In summary, the quantitative combination of observed and simulated evidence supports the conclusion that anthropogenic climate change is the key driver of increasing permafrost temperatures with implications for carbon cycle-climate feedbacks at the planetary scale.

DOI: 10.5194/egusphere-egu21-8337

2021047957 Hessilt, Thomas Duchnik (Vrije Universiteit Amsterdam, Department of Earth Science, Amsterdam, Netherlands); van der Werf, Guido; Abatzoglou, John T.; Scholten, Rebecca C. and Veraverbeke, Sander. Future increases in lightning-ignited boreal fires from conjunct increases in dry fuels and lightning [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2218, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Fire is the most important landscape disturbance in the boreal forest of North America. The boreal region is the largest terrestrial biome and stores approximately 35% of the global soil carbon (C). Burned area has increased over the last decades and is projected to increase further in the future, potentially altering boreal forest ecosystems from a net sink of C to a source of C. Approximately 90% of the burned area in the region originates from wildfires ignited by lightning strikes. It is therefore important to understand the drivers of lightning-induced wildfires to evaluate the consequences of possible future changes in lightning activity and ignition efficiency. Here, we evaluated lightning ignition efficiency, i.e. the probability that a lightning strike starts a fire, for Alaska and Northwest Territories between 2001 and 2018 in function of three sets of drivers: lightning characteristics, topography, and fire weather. Further, we projected the lightning ignition efficiency under the RCP8.5 scenario and combined it with predictions of future lightning activity to assess future lightning ignition. The logistic model demonstrated an overwhelming influence of fire weather on lightning ignition efficiency (area under the curve >0.83), whereas lightning characteristics and topography contributed relatively little to the model performance. We found that short-term drying of the organic soils is the most important requirement for a lightning strike to start a fire. The average lightning ignition efficiency for Alaska and Northwest Territories increased with 54±32% and 44±44 by 2100. Combined with future projections of lightning activity, we predicted a total increase in lightning ignition of up to 230±20% and 92±56% for Alaska and Northwest Territories by 2100. Future increases in lightning ignitions in the boreal forest will likely induce additional burned areas in regions with C-rich peatland and permafrost soils. Our research showed that the increased availability of dry fuels and increases in lightning will reinforce each other leading to more boreal fires and consequent C emissions. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-2218

2021048039 Iwahana, Go (University of Alaska at Fairbanks, International Arctic Research Center, Fairbanks, AK); Cooper, Zachary; Carpenter, Shelly; Deming, Jody and Eicken, Hajo. Intra-ice and intra-sediment cryopeg brine occurrence in permafrost near Utqiagvik (Barrow) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8528, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Cryopeg is a volume of permafrost with a significant amount of cryotic unfrozen water as a result of freezing-point depression by dissolved salt content. Cryopeg and saline permafrost have been reported for coastal areas of the Arctic seas, and their current distribution and future changes are a great concern for the warming Arctic, as the state of permafrost controls ground stability and the functioning of ice cellars in Arctic villages. To describe the distribution and segregation of cryopeg lenses, and to explore the origin and development of the cryopeg and associated brines found near Utqia?vik, we conducted extensive sampling campaigns in the Barrow Permafrost Tunnel during May of 2017 and 2018. We found two types of cryopeg brines based on their distinctive spatial occurrences: (1) intra-ice brine (IiB), entirely bounded by massive ice; and (2) intra-sediment brine (IsB), found in unfrozen sediment lenses within permafrost. While two examples of IiB have been reported previously, they were each found within ice layers below ice-sealed lakes in the McMurdo Dry Valleys of Antarctica, geological settings very different from ours. In our study, the IiBs were at roughly atmospheric pressure and situated in small pockets of ellipsoidal or more complex shape (dimensions of up to about 30 cm wide and 3 cm height) within 17-41 cm above the underlying sediment layer. Several individual IiB pockets may have been connected by porous ice of low permeability. Radiocarbon dating suggests that, at the earliest, the IiB was segregated about 11 ka BP from IsB-bearing cryopeg underneath. IsB lenses were interpreted as having developed through repeated evaporation and cryoconcentration of seawater in a lagoonal environment, then isolated at the latest when the surrounding sediment froze up and became covered by an upper sediment unit around 40 ka BP or earlier. Considering the common characteristics among the cryopeg brines accessed from the tunnel and those found in brine-bearing marine sediment around Utqia?vik, all occurrences of cryopeg brine in the region may have experienced analogous development despite potentially contrasting salinities and estimated ages. An increase in permafrost temperature invariably will result in expansion of cryopeg lenses and may change movement of liquids within the permafrost, which potentially become threats to Arctic coasts, infrastructure, and food security.

DOI: 10.5194/egusphere-egu21-8528

2021048041 Jakober, Dan (bgeos, Korneuburg, Austria); Bergstedt, Helena; Kroisleitner, Christine and Bartsch, Annett. Comparison of permafrost mean annual ground temperature derived from two different satellite-based schemes; land surface temperature based (ESA CCI+ Permafrost) versus surface status (Metop ASCAT) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9824, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Different approaches exist for a satellite-based estimation of mean annual ground temperature (MAGT). Landsurface temperature can be ingested by transient models. Surface status information (frozen/unfrozen days) has been shown to be applicable for the estimation of ground temperature as well. Such approaches are based on an empirically defined relationship. Both approaches have been evaluated with in situ bore hole measurements, but not yet compared with each other. A comparison between yearly arctic mean temperatures, derived from the advanced scatterometer (ASCAT) and data from ESA's CCI+ Permafrost project was carried out. The used ASCAT record is available from 2008 (first full year) onwards while the latest CCI+ Permafrost data is available from 1997 to 2018. The ASCAT data was recorded by satellites whose measurements are only intermittently available as one flyover over the whole arctic north of 60°N takes two days on average. To fill in the missing values exponentially weighted moving averages (EWMA) were used. From the number of frozen days an expected average temperature was derived based on Kroisleitner et al. (2018). The CCI+ Permafrost data incorporates modelled MAGT for depths between the surface down to a depth of 10 meters. These data points were extracted from the raster files (~1km resolution) and averaged over polygons representing an approximation of the ASCAT grid (footprint approximation). Single polygon areas range from 150-160 km2. Only footprints for which data is available in both records (and thus permafrost presence) have been eventually compared. The CCI+ Permafrost data shows an average surface temperature of -1.42 °C for the areas analyzed between 2008 and 2018 while the statistically padded ASCAT data suggests a mean temperature of -1.18 °C over the same time period. The ASCAT retrieval corresponds to a general MAGT whereas CCI+ Permafrost values are available for certain depths. Water fraction within ASCAT footprint also affect the quality of the derivation of frozen days. New calibration considering certain depths and water fraction is suggested.

DOI: 10.5194/egusphere-egu21-9824

2021047979 Juhls, Bennet (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Morgenstern, Anne and Overduin, Pier Paul. Lena River biogeochemistry resolved by a high frequency monitoring; comparing a wet and a dry year [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14501, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

River biogeochemistry at any location integrates environmental processes over a definable upstream area of the river watershed. Therefore, biogeochemical parameters of river water are powerful indicators of the climate change impact on the entire watershed and smaller parts of it. The current warming of the Siberian Arctic is changing atmospheric forcing, precipitation, subsurface water storage, and runoff from rivers to the Arctic Ocean. A number of studies predict an increase of organic carbon export by rivers into the Arctic Ocean with further warming of the Arctic. Major potential drivers for this increase are the rise of river discharge and permafrost thaw, which mobilizes organic matter. Here, we present results of high frequency monitoring program of the Lena River waters in the central part of its delta at the Laptev Sea. For the first time, a number of biogeochemical parameters such as dissolved organic carbon (DOC), coloured dissolved organic matter, electrical conductivity, temperature, and d18O isotopes were measured at an interval of every few days throughout the entire season. Currently, the data set comprises two complete years from the spring 2018 until the spring 2020, which were characterized by extremely high and low summer discharges, respectively. While 2018 to 2019 was the fourth highest on record from 1936 to present, resulting in an annual DOC flux of 6.8 Tg C yr-1, 2019 was the sixth lowest discharge year with a significantly lower DOC flux of 4.5 Tg C yr-1. Endmember analysis using electrical conductivity and d18O isotopes showed that rainwater transported less DOC in 2019 (1.5 Tg C) than in 2018 (2.9 Tg C) although the winter base flow and the snow and ice meltwater transported similar amounts. The biogeochemical response of the Lena River water provides us with new insights into the catchment processes, including permafrost thaw and potential mobilization of previously frozen organic carbon. Our new monitoring program will serve 1) as a baseline to measure future changes and 2) as a training dataset to project changes under future climate scenarios. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-14501

2021047950 Karesdotter, Elisie (Stockholm University, Department of Physical Geography, Stockholm, Sweden) and Kalantari, Zahra. Vulnerability and importance of Arctic wetlands as large-scale nature-based solutions for sustainability in a changing climate [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3148, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Wetlands as large-scale nature-based solutions (NBS) provide multiple ecosystem services of local, regional, and global importance. Knowledge concerning location and vulnerability of wetlands, specifically in the Arctic, is vital to understand and assess the current status and future potential changes in the Arctic. Using available high-resolution wetland databases together with datasets on soil wetness and soil types, we created the first high-resolution map with full coverage of Arctic wetlands. Arctic wetlands' vulnerability is assessed for the years 2050, 2075, and 2100 by utilizing datasets of permafrost extent and projected mean annual average temperature from HadGEM2-ES climate model outputs for three change scenarios (RCP2.6, 4.5, and 8.5). With approximately 25% of Arctic landmass covered with wetlands and 99% being in permafrost areas, Arctic wetlands are highly vulnerable to changes in all scenarios, apart from RCP2.6 where wetlands remain largely stable. Climate change threatens Arctic wetlands and can impact wetland functions and services. These changes can adversely affect the multiple services this sort of NBS can provide in terms of great social, economic, and environmental benefits to human beings. Consequently, negative changes in Arctic wetland ecosystems can escalate land-use conflicts resulting from natural capital exploitation when new areas become more accessible for use. Limiting changes to Arctic wetlands can help maintain their ecosystem services and limit societal challenges arising from thawing permafrost wetlands, especially for indigenous populations dependent on their ecosystem services. This study highlights areas subject to changes and provides useful information to better plan for a sustainable and social-ecological resilient Arctic. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3148

2021048017 Keaveney, Evelyn (Queen's University, School of the Natural and Built Environment, Belfast, United Kingdom); Barrett, Gerard; Reimer, Paula and Blaauw, Maarten. Carbon sources and sequestration; 14C ramped pyroxidation in aquatic sediments [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12319, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Sequestration of organic carbon in aquatic sediments can depend on its source and potential lability. Studies have shown that bulk lake and marine sediment comprises carbon of different origin but its source has been difficult to attribute. A new Ramped Pyroxidation/Combustion (RPO) system in the 14CHRONO Centre has been established. RPO is a technique that incrementally heats a sample, and allows for collection of the CO2 produced for radiocarbon analyses. The results show its utility in partitioning carbon sources in lake sediment (Rostherne Mere, UK, Santa Maria del Orolake, Mexico), and arctic marine sediment (Chukchi Sea and Beaufort Shelf). RPO and 2-stepped combustion1. 14C indicated multiple carbon sources in Rostherne Mere sediment, some of which could be attributed to the construction of a sewage treatment works (STW) on the lake shore, and subsequently inputs from this STW. RPO identified 3 carbon fractions in Mexican Lake sediment, which provided a more accurate chronology, partitioning the contemporaneous sediment date from offsets induced from volcanic activity in the area. Results from Arctic marine sediment demonstrated inputs of carbon from ancient permafrost, providing a means to refine the chronologies and a basis for future research linked with carbon loss from thawing permafrost.

DOI: 10.5194/egusphere-egu21-12319

2021047968 Khadhraoui, Madiha (Université Laval, Département de Géologie et de Génie Géologique, Sainte-Foy, QC, Canada); Molson, John and Bhiry, Najat. Experimental and numerical investigation of microparticle transport and deposition in the context of permafrost thaw [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13611, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In natural porous environments, soil particle migration during flow plays an important role in soil stability and pollutant transport by affecting soil mechanical properties and water quality. In northern areas, permafrost degradation alters the subsurface connection pathways leading to mass movements and rearrangement of the soil. To date, few models have included the influence of temporal and spatial variations of flow velocity and porous media heterogeneity on the transport and deposition of suspended particles. In this study, laboratory column experiments and a numerical model were used to investigate these issues. The laboratory column experiments were carried out under different flow rates and the effect of porous media heterogeneity was investigated using different grain size distributions. The soil columns were reconstituted from several samples taken in the studied site, the Tasiapik Valley, located in the discontinuous permafrost zone near Umiujaq, Nunavik, Quebec. During the experiments, the spatio-temporal distribution of the porosity and the hydraulic conductivity was monitored using X-ray computed tomography imaging (CT-SCAN). Using the pore water velocity computed from the groundwater flow solution, the advection-dispersion transport equation with a first-order kinetic term for particle deposition was solved using the finite element model Heatflow/Smoker. The dependency of the attachment kinetics on the pore water velocity and on the porous media heterogeneity was included. The model was tested and validated with an analytical solution and calibrated with the experimental data. Our simulations highlight the roles of hydrodynamic conditions and soil characteristics on particle transport and deposition mechanisms and the susceptibility of the porous medium to thermo-suffosion in permafrost environments. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13611

2021047959 Kjaer, Sigrid Trier (Norwegian University of Life Sciences, Faculty of Environmental Sciences and Natural Resource Management, As, Norway); Nedkvitne, Nora; Westermann, Sebastian; Althuizen, Inge and Dorsch, Peter. Carbon degradation in subarctic organic permafrost (peat plateaus) after thawing; what constraints CO2 and CH4 production? [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-11121, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Rapid warming in Subarctic areas releases large amounts of frozen carbon which can potentially result in large CO2 and CH4 emissions to the atmosphere. In Northern Norway vast amount of carbon are stored in peat plateaus, but these landscape elements have been found to decrease laterally since at least the 1950s. Peat plateaus are very sensitive to climate change as the permafrost is relatively warm compared to permafrost found in the arctic. So far, only limited information is available about potential degradation kinetics of organic carbon in these ecosystems. We sampled organic matter from depth profiles along a well-documented chronosequence of permafrost degradation in Northern Norway. After thawing over-night, we incubated permafrost and active layer for up to 3 months at 10°C. To determine factors constraining degradation, we measured gas kinetics (O2, CO2, CH4) under different conditions (oxic/anoxic, loosely packed/stirred suspensions in water, with altered DOC content and nutrient amendments) and related them to pH, DOC, element (C, N, P, S) and d13C and d15N signatures of the peat. Organic matter degradation was strongly inhibited in the absence of oxygen. By contrast, CH4 production or release seemed to be related to soil depth rather than incubation conditions and was found to be highest in samples from the transition zone between active layer and permafrost. Degradation rates and their dependencies on peat characteristics will be compared with permafrost characteristics along the chronosequence and additional experiments exploring the role of O2, DOC and other nutrients for carbon degradation will be discussed. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-11121

2021048035 Ko, Nayeon (Seoul National University, Seoul, South Korea); Yang, Ji-Woong; Iwahana, Go; Fedorov, Alexandre; Shepelev, Andrei G.; Opel, Thomas; Wetterich, Sebastian and Ahn, Jinho. Paleoclimate inferred from concentration of greenhouse gas and ratios of O2/Ar and N2/Ar in ice wedges in northeastern Siberia and northern Alaska [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6965, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Global warming is drawing keen attention to people all over the people. Especially, the history of climate in permafrost area is of great interest to better understand greenhouse gas emission due to the thaw of permafrost in the future. In this context, formation of ice wedges and greenhouse gas was studied based on gas chemistry in permafrost ice wedges. The study areas are Batagay and Zyryanka in northeastern Siberia, and North Slope in Alaska. The gas was extracted using a dry extraction method that physically breaks down ice, and cryogenically collects gas in a stainless steel tube. The gas mixing ratios were analyzed by gas chromatography. N2 and Ar occluded in the air bubbles in the ice are relatively unaffected by microbial activity, but if liquid water contacted atmospheric air and froze, the N2/Ar ratio in the ice will differ from the atmospheric value due to difference in the gas solubility in water. On the other hand, if O2 was consumed by microorganisms in the ice, the concentration of O2 will decrease and consequently the O2/Ar ratio will also decrease. Our results show that the d(O2/Ar) and d(N2/Ar) of the ice wedges in Zyryanka and North Slope areas range from -86.5% to -12.2% and from -16.0% to 5.5%, respectively with regard to modern air. The 14C ages of Zyryanka and North Slope samples are 810±30 BP and 1920±30 BP, respectively, corresponding to the late Holocene. Because the late Holocene was a relatively warm period, it may be interpreted that the ice wedges formed predominantly from snow melt water, resulting in the negative values of d(N2/Ar). This is in contrast with our earlier study on ice wedges in Central Yakutia region (Syrdakh, Cyuie, and Churapcha) (Kim et al., 2019). The Central Yakutian ice wedges formed during the Last Glacial Maximum (LGM) and the d(N2/Ar) values of ~0% indicates that the ice did not form from snow melting. The d(O2/Ar) of the Zyryanka and North Slope is much less depleted than that of Central Yakutian (close to -100%). Oxygen consumption by microorganisms in the Central Yakutian ice is more completed probably by the longer time period for the biogeochemical reaction compared to the Zyranka and North Slope ice (>20,000 years vs. <2,000 years). The ages of Batagay ice wedges range to earlier part of the Late Pleistocene, and may allow us to study longer biogeochemical reactions in ice. The concentrations of CO2, N2O and CH4 in the Batagay ice range 260-71,000 ppm, 0.11-68 ppm and 4.7-130 ppm, respectively. Further geochemical analyses are in progress. Future study will include scrutinizing correlations among the three greenhouse gas concentrations. Our study shows that the gas mixing ratios in ice wedges may hlep us better understand the biogeochemical reactions in the ice and climate conditions when the permafrost formed.

DOI: 10.5194/egusphere-egu21-6965

2021048015 Koltai, Gabriella (Universität Innsbruck, Institute of Geology, Innsbruck, Austria); Spötl, Christoph; Jarosch, Alexander H. and Cheng Hai. Cryogenic cave carbonates in the Dolomites (northern Italy); insights into Younger Dryas cooling and seasonal precipitation [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7889, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In the European Alps, the Younger Dryas (YD) was characterized by the last major glacier advance with equilibrium line altitudes being ~220 to 290 m lower than during the Little Ice Age and also by the development of rock glaciers. Dating of these geomorphic features, however, is associated with substantial uncertainties leading to considerable ambiguities on the internal structure of this stadial, the most intensively studied one of the last glacial period. Our study utilizes a novel paleoclimate archive, coarse crystalline cryogenic cave carbonates (hereafter CCC), that allows to precisely constrain when ~ 0°C conditions prevailed in the shallow subsurface in the past, often related to permafrost thawing events. Here we presents the first record of CCC from the Dolomites (Southern Alps). In contrast to many studies from Central European caves these speleothems formed not during a major climate warming but within a prominent stadial. 230Th-dating of the CCC indicates sustained negative temperatures close to ~0°C between ~12.6 and ~12.2 ka BP at about 50 m below the surface, initiating the slow freezing of dripwater-induced meltwater pockets in perennial cave ice. This in combination with thermal modelling argues for a cooling of ≤&eq;3°C at the Allerod-YD transition at this high-alpine site in the Southern Alps. Our data suggest that autumns and early winters in the early part of the YD were relatively snow-rich, resulting in a stable winter snow cover at this site. The snow cover insulated the subsurface and allowed the cave interior to remain close to the freezing point (0°C) year-round, promoting CCC formation. The main phase of CCC precipitation at ~12.2 ka BP coincides with the mid-YD transition recorded in other archives across Europe. Based on thermal modelling we propose that CCC formation at ~12.2 ka BP was most likely associated with a slight warming of approximately +1°C in conjunction with drier autumns and early winters in the second half of the YD. These changes triggered CCC formation in this alpine cave as well as ice glacier retreat and rock glacier expansion in the Alps. Our study demonstrates that CCCs can provide quantitative constraints on paleotemperature and seasonally resolved precipitation changes.

DOI: 10.5194/egusphere-egu21-7889

2021047988 Kruse, Stefan (Alfred-Wegener-Institute, Helmholtz-Centre for Marine- and Polar Research, Potsdam, Germany); Stünzi, Simone M.; Langer, Moritz; Boike, Julia and Herzschuh, Ulrike. Assessing the impact of permafrost-vegetation interaction on treeline dynamics in Siberia with the individual-based, spatially explicit treeline model LAVESI coupled to the permafrost land-surface model CryoGrid [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-14119, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Tundra-taiga ecotone dynamics play a relevant role in the global carbon cycle. However, it is rather uncertain whether these ecosystems could develop into a carbon source rather than continuing atmospheric carbon sequestration under global warming. This knowledge gap stems from the complex permafrost-vegetation interactions, not yet fully understood. Consequently, shedding light on the role of current and future active layer dynamics is crucial for an accurate prediction of treeline dynamics, and thus for aboveground forest biomass and carbon stock developments. We make use of a coupled model version combining CryoGrid, a one-dimensional permafrost land-surface model, with LAVESI, an individual-based and spatially explicit forest model for larch species (Larix Mill.) in Siberia. Following a parametrization against an extensive field data set of 100+ forest inventories conducted along the Siberian treeline (97-169° E), we run simulations for the upcoming centuries forced by climatic change scenarios. The coupled model setup benefits from the detailed process implementation gained while developing the individual models. Therefore, we can reproduce the energy transfer and thermal regime in permafrost ground as well as the radiation budget, nitrogen and photosynthetic profiles, canopy turbulence, and leaf fluxes, while at the same time, predicting the expected establishment, die-off, and treeline movements of larch forests. In our analyses, we focus on vegetation and permafrost dynamics and reveal the magnitudes of different feedback processes between permafrost, vegetation, and current and future climate in Northern Siberia. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-14119

2021047987 Kulawska, Aleksandra (Univeristy of Birmingham, Department of Earth and Environmental Sciences, Birmingham, United Kingdom); MacKenzie, Angus Robert; Kettridge, Nicholas; Ullah, Sami and Pugh, Thomas A. M. On thin ice; contrasting responses of woody NPP to permafrost thaw [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-1579, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Boreal forests are located at latitudes that are predicted to experience some of the greatest warming on the planet. Forests growing on permafrost may be particularly vulnerable, with accelerated soil warming and permafrost degradation linked to changes in woody net primary productivity (NPPw). Recent evidence suggests that the responses of NPPw to permafrost thaw are mixed, with both increases and decreases in productivity observed following the onset of permafrost degradation. What determines these contrasting responses is currently poorly understood. This leads to uncertainties in predicting the future vegetation and carbon dynamics in permafrost regions, which propagate to climate projections in Earth System Models. Here, we propose a framework, and a set of hypotheses to explain the observed differences in the response of NPPw to permafrost thaw. We argue that the relationship between permafrost thaw and NPPw is non-linear and determined by a set of climatic and environmental variables. On this basis, we partition ecosystems into classes, and describe their relationships between permafrost thaw and NPPw. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-1579

2021047945 Leshyk, Victor (Northern Arizona University, Department of Biology, Flagstaff, AZ). The importance of an artistic lens to assess the Anthropocene [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7652, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

As the Anthropocene progresses into more and more dire territory, research continues to refine quantifiable, predictive narratives about the changes that will unfold in the very near future--heat waves, droughts, rising seas, and other shifts in climate that threaten aspects of human life worldwide, from agriculture and industry to medicine and human quality of life as a whole. This evolving, cross-referenced narrative should create a perfect warning to correct our course on carbon emissions, our ongoing ecosystem damage from modern agriculture, and other effects tied to current unsustainable practices such as overuse of fossil fuels and reliance on plastic materials. However, when these science narratives are placed directly in the spotlight of press and social media, they often merge into a large uncompelling whole, much as many unique and attractive bricks together might combine to create a uniform and ominous wall. The end result is audience disengagement in the face of daunting information. This effect is so substantiated that studies now recommend that science communicators should avoid "intimidating" and "demoralizing" global audiences with vivid Anthropocene scenarios, and instead focus on creating less-threatening "feel-good" engagement that can serve as a bridge to positive public action that supports renewable energy, organic agriculture, and other corrective changes to the societal footprint. As a professional science communicator, I reject the advice to avoid painting an ever more clear portrait of the Anthropocene: I believe the problem that "demoralizes" the public is not Anthropocene content, but poor presentation, often driven by journalistic trends to sensationalize future apocalyptic scenarios that create titillating fear. Through my work, I rely not so much on creating a fascination with doomsday scenarios but instead create a fascination with the detailed mechanisms by which the Anthropocene is forcing change: by thawing permafrost, threatening forests, destroying biodiversity, all the while showing how these processes fit within the context of deep time. With a rich deep time perspective, viewers can see why the Anthropocene is such a distortion of natural ecosystem services, and how human technology and habits could instead be changed to work within the carrying capacity of earth systems. In this presentation, I share my science illustration portfolio to explain my unique approach that fuses the charisma of "fine art" approaches using metaphor, hyper-realism, and didactic compositions with new research findings to reach beyond sensationalist Anthropocene imagery and create a new visual vocabulary for ecosystem research that unites experts and lay public with a common scientific worldview. I have given this personal philosophy of creative science illustration the name "Accurate Passion" and employ it for a range of topics and clients, including my in-house colleagues at a university research center focusing on ecosystem science, and graduate-level students of my university-level science illustration courses for the past three years. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-7652

2021047970 Lodi, Rachele (National Research Council, Institute of Polar Science, Venice, Italy); Wagner, Julia; Hugelius, Gustaf; Martin, Victoria Sophie; Speetjens, Niek; Richter, Andreas; Gabrieli, Jacopo and Barbate, Carlo. Persistent organic pollutants distribution of small coastal catchments at the Canadian Beaufort Coast [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-10165, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Recent decades have shown phases of very rapid warming in the Canadian Arctic. This raises a concern, also in reference to potential changes in permafrost active layer deepening, enhancing the fact that seawater, snow and soils are becoming important secondary sources remobilizing persistent organic pollutants (POPs). This work investigates the potential influence of permafrost on POPs distribution in the soils of two small coastal catchments at the Canadian Beaufort coast. One catchment is located south of Herschel Island on the mainland and was covered by the Laurentide ice sheet during the last glacial maximum (LGM), the second catchment is located westerly at Komakuk Beach and was ice-free during the LGM. Soils were sampled by horizon in the Active Layer from an open soil pit and by coring into the permafrost, near the top of the permafrost table and at 90 cm depth from the soil surface (99 samples form Ptarmigan Bay and 89 from Komakuk Beach). The total sampling depth was 1,0 m (including Active Layer and Permafrost). A random distribution of the points over the areas guaranteed the sampling over different Landforms, aiming to understand the contaminant concentration and distribution. Quantification of PAHs, PCBs, HCB was performed using GC-MS technique, a 7890A gas chromatographer coupled with a 5975C MSD System, Agilent Technologies, at CNR-ISP Venice, Italy. Preliminary results confirm that the mechanism responsible for the transport of POPs into the soil are believed to be gravity drainage and capillary suction into fissures and cracks. An accumulation of PAHs has been detected in the permafrost transient layer. It is probably related, as demonstrate in literature, to the accumulation and transport of soil organic carbon influence, as well as the changing in hydraulic barriers. The role of cryoturbation in the vertical transport and accumulation of POPs is also considered and discussed. The study has been conducted thanks to Grant Agreement number: 773421 - Nunataryuk - H2020-BG-2016-2017/H2020-BG-2017-1 'Permafrost thaw and the changing arctic coast: science for socio-economic adaptation - Nunataryuk' [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-10165

2021047985 Magnani, Marta (University of Turin, Turin, Italy); Baneschi, Ilaria; Gaimberini, Mariasilvia and Provenzale, Antonello. Drivers of carbon dioxide fluxes in High-Arctic tundra; data-driven models [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5665, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Arctic regions are extreme environments where ecosystems are undergoing significant changes induced by the temperature rise, that is progressing about twice faster than in the rest of the world. In the high-Arctic, the Critical Zone (CZ) has a thin above-ground component, consisting of tundra vegetation, and a highly seasonal below-ground component, with varying extension and chemical-physical characteristics. The complexity of this system makes future projections of the Arctic CZ a challenging goal. In particular, it is still unclear whether the system will turn from a carbon sink to a carbon source. On the one hand, the uptake of carbon dioxide (CO2) by vegetation is expected to increase in future years owing to the widening growing season and the shift in community composition but, on the other, increasing soil temperatures are fostering carbon release by thawing permafrost and degradation of organic matter through heterotrophic respiration in deglaciated soils. In this work, we identified the main biotic and abiotic drivers of CO2 emissions (Ecosystem Respiration, ER), and CO2 uptake (Gross Primary Production, GPP), in the Arctic tundra biome. During summer 2019 we extensively measured CO2 fluxes at the soil-vegetation-atmosphere interface, basic meteoclimatic variables and ecological descriptors at the Critical Zone Observatory of Bayelva river basin (CZO@Bayelva), Spitzbergen, in the Svalbard Archipelago (NO). Flux measurements were obtained by a portable accumulation chamber, allowing for the statistical analysis of fluxes variability at small scale. Together with flux measurements, we sampled soil temperature and humidity at the chamber base and local air temperature, pressure and humidity. In addition, the vegetation cover was obtained from digital RGB pictures of the sampled surfaces. By means of multi regression models, we related flux data to environmental parameters, vegetation cover extent and vegetation type, thus obtaining empirical data-driven models that describe the coupled dynamics of soil, vegetation, water and atmosphere that contribute to the present budgeting of the carbon cycle in the arctic CZ. This work may help in assessing the possible future evolution of high-Arctic environment under projected changes in vegetation community composition and abiotic parameters. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-5665

2021048020 Majdanski, Mariusz (Polish Academy of Sciences, Institute of Geophysics, Warsaw, Poland); Marciniak, Artur; Owoc, Bartosz; Dobinski, Wojciech; Wawrzyniak, Tomasz; Osuch, Marzena; Nawrot, Adam and Glazer, Michal. Surprisingly thick active layer of permafrost in the mountain slope in the SW Svalbard [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2206, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost along inclined profile between the coast and the mountain slope in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with continuous temperature monitoring in shallow boreholes. Joint interpretation of seismic data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the permafrost where apparent P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. Independent refraction seismic analysis in two seasons shows in average 10 m thick sedimentary layer on top of compacted bedrock. In sediments P wave velocity is changing from 1500 m/s to 4000 m/s between seasons. Velocities in the bedrock are also changing from 4000 m/s to 5500 m/s. Moreover, tomographic interpretation shows that significant change in P wave velocities is observed down to 30 meters. Such unusual active layer behavior is confirmed in in-situ thermal observations with above 0C temperatures at the depth of 19m. Those observations can be explained with strong underground flow during the frozen period confirmed with borehole.

DOI: 10.5194/egusphere-egu21-2206

2021047948 Makshtas, Alexander (Arctic and Antarctic Research Institute, Air - Sea Interaction, St. Petersburg, Russian Federation); Bogorodski, Petr and Jozhikov, Ilya. Thermal regime of soil active layer at the Bolshevik Island (Archipelago Severnaya Zemlya) during 2016-2020 years [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8838, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Investigations of active soil layer on the Research station "Ice Base Cape Baranova" had been started in February 2016 after installation on the meteorological site sensors of Finnish Meteorological Institute: thermochain with IKES PT00 temperature sensors at depths of 20, 40, 60, 80 and 100 cm, soil heat flux sensor HFP, and two ThetaProbe type ML3 soil moisture sensors. Based on the results of measurements annual cycle of soil temperature changes was revealed with amplitudes 10-15°C less than the amplitudes of surface air layer temperature (Ta) and especially the temperature of the soil upper surface (Tsrad), in great degree determined by short-wave radiation heating and long-wave radiation cooling. Approximation by linear fittings shows average rates of increase Ta -0.4°C/year, Tsrad -0.3°C/year, and temperatures of active soil layer -0.2°C/year. The data on thermal regime of active soil layer and characteristics of energy exchange in atmospheric surface layer make it possible to draw the conclusion about the reason for the abnormally warm state of the upper meter soil layer in summer 2020, despite in March during the whole period under study active soil layer was the warmest in 2017. Comparison in temperatures of the underlying surface and characteristics of surface heat balance during period under study showed that in 2020 the temperature of the soil surface at the end of May for a short time reached the temperature of snow melting. It is happened 25 days earlier than in 2017 as well as other years and led to radical decrease in surface albedo, sharp increase of heat flux to the underlying surface, and increased duration of active soil layer heating. Additionally, permafrost thawing studies using a manual contact method were carried out on the special site, organized according to CALM standards. These studies showed significant variety of soil active layer thicknesses in the relatively small area (~0.12 km2), which indicates significant spatial variability of microrelief, structure and thermophysical properties of soil, as well as vegetation, typical for Arctic desert. Calculations carried out with version of the well-known thermodynamic Leibenzon model for various parameterizations of vegetation and soil properties partly described peculiarities of spatial variability of observed thawing depths. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-8838

2021047981 Martens, Jannik (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Wild, Birgit; Semiletov, Igor; Dudarev, Oleg V. and Gustafsson, Orjan. Patterns of terrestrial carbon distribution in the Arctic Ocean deduced from the Circum-Arctic Sediment CArbon DatabasE (CASCADE) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5401, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Climate change is expected to affect the release of organic carbon (OC) from Arctic permafrost systems and other terrestrial deposits. In addition to greenhouse gas emissions on land, a fraction of the organic matter is liberated to the aquatic cycle and migrates to the Arctic Ocean where it is either degraded or buried in sediments, foremost on the vast continental shelves. The Arctic Ocean basin represents a large footprint for contemporary and past land-ocean transport of terrestrial OC. To this end, the Circum-Arctic Sediment CArbon DatabasE (CASCADE; URL: was established to curate and harmonize data on OC and total nitrogen concentrations, carbon isotopes (d13C, D14C) and terrestrial biomarkers (long-chain n-alkanes, n-alkanoic acids and lignin phenols) in an openly accessible data collection. CASCADE was populated using carbon data from both published records and unpublished data from a large community collaboration. The first release of CASCADE includes observations at thousands of oceanographic stations distributed over the shelves and the central basins of the Arctic Ocean, and also includes hundreds of sediment cores, representing a range of time scales (decadal to orbital). Mapping CASCADE data provides an overview to start deducing sources, pathways and deposition of carbon in different regions of the Arctic Ocean. Dual-isotope (d13C, D14C) source apportionment of OC and 210Pb dating of centennial-scale sediment cores permit quantitative analysis of sequestration of carbon transported from permafrost systems and other deposits to the Arctic Ocean. Preliminary results suggest that surface soils (incl. permafrost active layer) are the dominating terrestrial carbon source to Circum-Arctic shelf sediments. The second largest terrestrial source are Pleistocene ice-rich permafrost compartments (Ice Complex Deposits), which stretch along coastlines of the Laptev, East Siberian, Chukchi and Beaufort Seas and are highly vulnerable to coastal erosion and thermal collapse in a warming climate. Climate change is likely to cause permafrost thawing by further deepening of the seasonal active layer and accelerated coastal erosion of permafrost, as well as disturbance of the vast boreal peatlands. CASCADE provides an integrated perspective and benchmark for lateral carbon remobilization and will fuel further empirical and modelling studies of Arctic biogeochemical cycles. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-5401

2021047994 Marushchak, Maija E. (University of Jyvaskyla, Department of Biological and Environmental Science, Jyvaskyla, Finland); Nykanen, Hannu; Pumpanen, Jukka; Sannel, A. Britta K.; Strom, Lena; White, Joel and Biasi, Christina. Effects of labile carbon on anaerobic decomposition processes in permafrost wetlands [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9656, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Climate warming and permafrost thaw are exposing the large carbon (C) pools of northern wetlands to enhanced decomposition, potentially increasing the release of the greenhouse gases carbon dioxide (CO2) and methane (CH4). Permafrost thaw is usually associated with changes in hydrology and vegetation: Ground collapse leads to the formation of new, productive thermokarst wetlands, and active layer deepening allows plant roots to penetrate to deeper soil layers. These processes promote interaction between old permafrost carbon and recent plant-derived carbon, but the effect of this interaction on anaerobic decomposition processes is poorly known. Here, we report the preliminary results of a 1+-year-long soil incubation experiment where we investigated the role of fresh organics on anaerobic decomposition in arctic wetlands. We sampled mineral subsoil of Greenlandic wetland sites and the active layer and permafrost peat in a Swedish palsa mire, and incubated them with and without repeated amendments of 13C enriched glucose and cellulose. We determined the rate and isotopic composition of CO2 and CH4 with an isotopic laser, and estimated the contribution of soil organic matter decomposition vs. added carbon to the total C gas release. These results represent new understanding on how plant-derived organics change the magnitude and composition of C gas, thus affecting the climatic feedbacks from permafrost wetland C pool. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9656

2021047982 Matsubara, Felipe (Stockholm Univeristy, Department of Environmental Science, Stockholm, Sweden); Wild, Birgit; Martens, Jannik; Wennstrom, Rickard; Dudarev, Oleg; Semiletov, Igor and Gustafsson, Orjan. Multi-proxy evaluation of terrestrial organic matter degradation across the east Siberian Arctic seas [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12328, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Ongoing global warming is expected to accelerate the thaw of permafrost on land and to increase the input of terrigenous organic matter (terrOM) into the Arctic Ocean through coastal erosion and river discharge. Large remobilization of terrOM into the East Siberian Arctic Shelf (ESAS) dominates the organic matter in surface sediments over large parts of the shelf and its degradation contributes to ocean acidification. Previous studies have focused on the source apportionment of terrOM and the releases of CO2 and CH4 to the atmosphere from terrOM degradation; this study focuses on its diagenetic state during cross-shelf transport, since degradation is the link between permafrost thawing and greenhouse gases emissions. This study probes the degradation status of different terrOM components across the ESAS using various molecular and isotopic proxies and hence evaluates their differences to infer degradation. High-molecular weight (HMW) lipid compounds and lignin phenols are exclusively produced by terrestrial plants, providing protection, strength and rigidity to the plant structure. Owing to diagenesis, microbial degradation leads to 1) loss of functional groups, thus the ratios of HMW n-alkanoic acids, HMW n-alkanols and sterols relative to HMW n-alkanes decrease; 2) reduction of unsaturated to saturated carbons, so ratios of stanols relative to stenols increase; 3) a higher formation of carboxylic acids in the lignin polymer and hence ratios of acids to aldehydes of vanillyl (Vd and Vl) and syringyl (Sd and Sl) increase. The concentrations of lipid- and lignin-derived products per sediment specific surface area decreased with offshore distance of the samples. During cross-shelf transport, the biomarker degradation proxies showed an increasing degradation for Sd/Sl, Vd/Vl, the "tannin-like" compound 3,5-dihydrobenzoic acid to vanillyl (3,5-Bd/V), b-sitostanol/b-sitostenol and Carbon Preference Index (CPI) of HMW n-alkanes. Some other proxies showed no clear trend from inner to outer shelf and such inconsistent patterns are currently being investigated to better understand both the usefulness/response of different proxies and of the lability of terrOM in the ESAS. While b-sitostanol/b-sitostenol and CPI HMW n-alkane did not show strong differences between the East Siberian Sea and the Laptev Sea, Vd/Vl and Sd/Sl ratios indicated stronger degradation on the outer Laptev Sea and 3,5-Bd/V ratios indicated stronger degradation in the outer eastern East Siberian Sea. Such differences could reflect source properties of terrOM entering the ESAS, such as differences in source vegetation or transport pathway, i.e. coastal erosion or river discharge. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-12328

2021047986 Murchie, Tyler J. (McMaster University, McMaster Ancient DNA Centre, Hamilton, ON, Canada); Monteath, Alistair J.; Long, George S.; Karpsinski, Emil; Cocker, Scott; Zazula, Grant; MacPhee, Ross; Froese, Duane and Poinar, Hendrik. Ecological turnover and megafaunal ghost ranges during the Pleistocene-Holocene transition in central Yukon, Canada as revealed by palaeoenvironmental DNA [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-372, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The multitude of factors alleged to have contributed to the late Quaternary mass extinction of some two-thirds of Earth's megafauna is complicated by the coarse record of buried macro-fossils. In response, micro-methods such as ancient DNA have been increasingly able to augment discontinuous palaeontological records to investigate the relative timings of vegetation turnover versus megafaunal extirpations-all in the absence of biological tissues. Here, we present sedimentary ancient DNA data retrieved using the PalaeoChip Arctic-1.0 bait-set diachronically identifying fauna and flora from permafrost cores recovered from the Klondike region of central Yukon, Canada dating between 30,000-6000 calendar years BP. We observe a substantial turnover in ecosystem composition between 13,000-10,000 BP with the rise of woody shrubs and the disappearance of mammoth-steppe vegetation. We also identify a lingering signal of Equus sp. (North American horse) and Mammuthus primigenius (woolly mammoth) from multiple samples thousands of years after their last dated macro-fossils, possibly as late as the mid-Holocene. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-372

2021047969 Nedkvitne, Nora (Norwegian University of Life Sciences, Environmental Sciences and Natural Resource Management, As, Norway); Kjaer, Sigrid Trier; de Wit, Heleen; Westermann, Sebastian and Dorsch, Peter. Mercury in permafrost landscapes in the Norwegian subarctic; current status and potential for increased release and methylation by permafrost thaw [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-11126, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

A vast amount of global mercury is believed to be stored in the Arctic, much of which is frozen in permafrost. Increasing temperatures in the Subarctic, leading to permafrost thaw, alter the global mercury cycle by mobilizing and releasing stored mercury. This is of concern since it allows mercury to spread though air- and waterways. Moreover, mobilized mercury in combination with increased microbial activity can increase the production of methyl mercury (MeHg), a highly potent neurotoxin which readily bioaccumulates throughout food webs. We report current levels of total mercury (HgT) and MeHg for permafrost cores, ambient surface waters, and active layer pore waters across a gradient of sporadic permafrost (peat plateaus) ranging from coastal-mild to inland-cold climate in the northernmost part of continental Europe (Finnmark, Norway). To investigate the effect of microbial activity on mercury methylation, permafrost samples were thawed and subjected to long-term incubation under oxic, and oxic/anoxic conditions, with and without additional native DOC and extraneous C, N, P, S, and Hg additions. Microbial activity was monitored by CO2 and CH4 production. Our field samples indicate that the %MeHg of HgT are higher in the outlet of the peat plateau than in the inlet and that streams have a significantly higher %MeHg of HgT than ponds. In contrast, thermokarst ponds (collapsed peat plateaus) have a significantly higher concentration of HgT than streams. In the incubation experiments, presence or absence of oxygen had the largest impact on DOC and dissolved HgT accumulation; soil slurries incubated under anoxic conditions yielded higher concentrations of both DOC and dissolved HgT compared to oxic conditions. Selected results from ongoing experiments will be presented. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-11126

2021047949 Nehren, Udo (Technische Hochschule Köln, University of Applied Sciences, Institute for Technology and Resources Management in the Tropics and Subtropics, Cologne, Germany) and Mojica, Teresa Arce. Nature-based solutions to mitigate the risk of shallow landslides; a global analysis [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5586, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Landslides claim many lives and cause high financial losses in mountainous regions around the world every year. Especially in high mountain regions, the landslide risk is likely to increase further in the coming years due to the thawing of permafrost soils and the associated activation of slope dynamics. However, a higher landslide risk is also expected regionally in tropical and subtropical mountainous regions, namely where an increase in extreme weather events is projected and at the same time, there is a higher socio-ecological vulnerability and exposure due to population growth, land use pressure and other factors. To mitigate the risk to people and their assets, various hard and soft infrastructure measures are available. Especially in the European Alps, the concept of protection forests (German: Schutzwalder) in combination with hard infrastructure has been used for years as an ecosystem-based or hybrid measure. Based on a systematic global literature review (275 papers), we investigated which Nature-based Solutions (NbS) to mitigate the risk of shallow landslides are in place worldwide, in which countries and regions they were implemented, and which approaches under the NbS umbrella concept were applied (e.g. Green Infrastructure, Ecological Engineering, Eco-DRR, etc.). As a result of this comprehensive analysis, we present a portfolio of measures to mitigate the risk of shallow landslides that are being applied in various (eco)regions and cultural contexts around the world and discuss the success of these measures as well as potential risks, uncertainties, and failures. We also emphasize the need for further research particularly on the effectiveness of ecosystem-based landslide risk reduction in different mountain ecosystems, as well as the cost-effectiveness of NbS compared to hard infrastructure. We conclude that despite a successful implementation in the Alps and few other mountain regions, the protection forest concept has hardly been applied so far, especially in the Global South. In addition, we emphasize the particular challenge of establishing protection forests due to the rapid climatic and ecological changes and related geomorphological process dynamics in mountain regions in the course of global climate change. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-5586

2021047972 Nielsen, David Marcolino (University of Hamburg, Center for Earth System Research and Sustainability, Hamburg, Germany); Pieper, Patrick; Brovkin, Victor; Overduin, Paul; Ilyina, Tatiana; Baehr, Johanna and Dobrynin, Mikhail. Sensitivity of organic carbon fluxes from Arctic coastal erosion to climate change [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13268, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

When unprotected by sea-ice and exposed to the warm air and ocean waves, the Arctic coast erodes and releases organic carbon from permafrost to the surrounding ocean and atmosphere. This release is estimated to deliver similar amounts of organic carbon to the Arctic Ocean as all Arctic rivers combined, at the present-day climate. Depending on the degradation pathway of the eroded material, the erosion of the Arctic coast could represent a positive feedback loop in the climate system, to an extent still unknown. In addition, the organic carbon flux from Arctic coastal erosion is expected to increase in the future, mainly due to surface warming and sea-ice loss. In this work, we aim at addressing the following questions: How is Arctic coastal erosion projected to change in the future? How sensitive is Arctic coastal erosion to climate change? To address these questions, we use a 10-member ensemble of climate change simulations performed with the Max Planck Institute Earth System Model (MPI-ESM) for the Coupled Model Intercomparison Project phase 6 (CMIP6) to make projections of coastal erosion at a pan-Arctic scale. We use a semi-empirical approach to model Arctic coastal erosion, assuming a linear contribution of its thermal and mechanical drivers. The pan-Arctic carbon release due to coastal erosion is projected to increase from 6.9±5.4 TgC/year (mean estimate±two standard deviations from the distribution of uncertainties) during the historical period (mean over 1850-1950) to between 13.1±6.7 TgC/year and 17.2±8.2 TgC/year in the period 2081-2100 following an intermediate (SSP2.4-5) and a high-end (SSP5.8-5) climate change scenario, respectively. The sensitivity of the organic carbon release from Arctic coastal erosion to climate warming is estimated to range from 1.52 TgC/year/K to 2.79 TgC/year/K depending on the scenario. Our results present the first projections of Arctic coastal erosion, combining observations and Earth system model (ESM) simulations. This allows us to make first-order estimates of sensitivity and feedback magnitudes between Arctic coastal erosion and climate change, which can lay out pathways for future coupled ESM simulations. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13268

2021047958 Novenko, Elena (Moskovskiy Pedagogicheskiy Gosudarstvennyy Universitet, Department of Landscape Science, Moscow, Russian Federation); Mazei, Natalia; Kupryanov, Dmitry and Prokushkin, Anatoly. The late Holocene forest fire history in continuous permafrost zone of central Siberia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5509, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Understanding the long-term fire history of larch forests in the permafrost zone of Central Siberia is essential for an assessment of the possible responses and feedbacks of forest ecosystems to climate change. The multi-proxy record from the area of the Evenkian field station of the Sukachev Institute of Forest SB RAS, located in the middle part of the Lower Tunguska river basin provides important new data on the fire frequency, vegetation changes and paludification dynamics in the Central Evenkia over the last 3.5 ka BP. The new results of radiocarbon dating, loss on ignition, plant macrofossil and macro charcoal analyses from a sediment core taken in the waterlogged larch forest (N64°09'56.1" E100°31'43.9") are presented. The obtained data have shown that fires were an important factor in the evolution of forest ecosystems in this continuous permafrost regions and acted as a trigger for the paludification process in the study area. The reconstruction of fire frequency demonstrated that the fire return period in the warm epochs of the late Holocene (3.6-2.7 ka BP, 1.5-0.7 ka BP, including the Medieval Climate Anomaly) varied from 115 to 150 years, and increased to 275-300 years during the periods of cooling (2.7-1.5 ka BP; the Little Ice Age, 0.7-0.15 ka BP). We suggested that the shorter and possibly colder summers during the cold epochs led to a decreased evaporation and a rise of ground moisture in many habitats, which was unfavorable for the occurrence and extension of forest fires. During the last 200 years the frequency of forest fires in the study area increased significantly, the fire return period reduced to a minimum value for the entire period under consideration (i.e. the last 3.5 ka BP) and reached 80 years. The fire free interval revealed from the macro charcoal analyses for the last 200 years is close to the average fire free interval reconstructed by dendrochronological data from the study area for the same period. The low human impact on forest ecosystems due to remote location of study area from settlements and mining regions suggests the natural causes of these fires. This work was supported by the Russian Science Foundation, project No. 20-17-00043. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-5509

2021047978 Ogneva, Olga (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany); Mollenhauer, Gesine; Fuchs, Matthias; Palmtag, Juri; Sanders, Tina; Grotheer, Hendrik; Mann, Paul and Strauss, Jens. Particulate and dissolved organic carbon composition in the Lena River and its delta, from Yakutsk to the Arctic Ocean [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8005, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Rapid climate warming in the Arctic intensifies permafrost thaw, increases active layer depth in summer and enhances riverbank and coastal erosion. All of these cause additional release of organic matter (OM) into streams and rivers. OM will be (1) transformed and modified during transport and subsequently discharged into the Arctic Ocean, or (2) removed from the active cycling by sedimentation. Here, the nearshore zone (which includes deltas, estuaries and coasts) is of great importance, where the major transformation processes of terrestrial material take place. Despite the importance of deltas for the biogeochemical cycle, their functioning is poorly understood. For our study we examined the Lena River nearshore, which represents the world's third largest delta and supplies the second highest annual water and sediment discharge into the Arctic Ocean. Running through almost the entirety of East Siberia from Lake Baikal to the Laptev Sea, the Lena River drains an area of ~2,61´106 km2 with approximately 90% underlain by permafrost. Our aims were to investigate the spatial variation of OM concentration and isotopic composition during transit from terrestrial permafrost source to the ocean interface, and to compare riverine and deltaic OM composition. We measured particulate and dissolved organic carbon (POC and DOC) concentrations and their associated d13C and D14C values in water samples collected along a ~1500 km long Lena River transect from Yakutsk downstream to the river outlet into the Laptev Sea. We find significant qualitative and quantitative differences between the OM composition in the Lena River main channel and its delta. Further, we found suspended matter and POC concentrations decreased during transit from river to the Arctic Ocean. DOC concentrations in the Lena delta were almost 50% lower than OM from the main channel. We found that deltaic POC is depleted in 13C relative to fluvial POC, and that its 14C signature suggests a modern composition indicating phytoplankton origin. This observation likely reflects the difference in hydrological conditions between the delta and the river main channel, caused by lower flow velocity and average water depth. We propose that deltaic environments provide favorable growth conditions for riverine primary producers such as algae and aquatic plants. Deltaic DOC is depleted in 14C compared to riverine, especially in samples taken from the water surface, which indicates contributions from an additional old carbon stock source, specific for the Lena Delta. We suggest that this C is released from deltaic bank erosion and partly stays floating on the surface. In conclusion, we found a strong impact of deltaic processes on the fate and dominant signatures of OM discharged into the Arctic Ocean. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-8005

2021048004 Olid, Carolina (Umea University, Department of Ecology and Environmental Science, Abisko, Sweden); Zannella, Alberto and Lau, Danny C. P. The role of methane transport from the active layer in sustaining methane emissions and food chains in subarctic ponds [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15327, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Shallow groundwater flow from the seasonally thawed active layer is increasingly recognized as an important pathway for delivering methane (CH4) into Arctic lakes and streams, but its contribution to CH4 emissions from thaw ponds has not been evaluated. Furthermore, the potential influence of the shallow groundwater-derived CH4 on the trophic support and nutritional quality of thaw pond food chains remains unexplored. In this study, we used a radon-mass balance approach to quantify the CH4 transport from the active layer into thaw ponds in a sub-Arctic catchment. We analysed stable isotopes and fatty acids of pond macroinvertebrates to evaluate the potential effects of CH4 inputs through active layer groundwater flows on the aquatic food chains. Our results indicate that CH4 fluxes from the active layer can sustain CH4 emissions from the ponds. Consumers in ponds receiving greater CH4 inputs from the active layer had lower stable carbon isotope signatures that indicates a greater trophic reliance on methane oxidizing bacteria (MOB), and they had lower nutritional quality as indicated by their lower tissue concentrations of polyunsaturated fatty acids. Accurate predictions of CH4 release from small thaw ponds will thus require improved knowledge of the contributions from various processes including internal production, flow paths of active layer groundwater, and MOB-consumer interactions. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-15327

2021047961 Palmtag, Juri (Northumbria university, Department of Geography and Environmental Science, Newcastle-Upon-Tyne, United Kingdom); Manning, Cara; Bedington, Michael; Fuchs, Matthias; Göckede, Mathias; Grosse, Guido; Juhls, Bennet; Lefebvre, Paul; Mollenhauer, Gesine; Ogneva, Olga; Overduin, Paul; Polimene, Luca; Strauss, Jens; Torres, Ricardo; Zimov, Nikita and Mann, Paul. Seasonal methane and carbon dioxide emissions from the coastal nearshore of the Kolyma River, Siberia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9535, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Arctic rivers deliver ~11% of global river discharge into the Arctic Ocean, while this ocean represents only ~1% of the global ocean volume. Ongoing climate warming across the Arctic, and specifically Siberia, has led to regional-scale changes in precipitation patterns, greater rates of permafrost thaw and active layer deepening, as well as enhanced riverbank and coastal erosion. Combined, these climatic and cryospheric perturbations have already resulted in increased freshwater discharge and changes to constituent loads (e.g. dissolved organic carbon - OC) supplied from land to the Arctic Ocean. To date, the majority of studies examining terrestrial organic matter (OM) delivery to the Arctic Ocean have focused almost entirely on freshwater (riverine) or fully-marine environments and been conducted during late summer seasons - often due to logistical constraints. Despite this, an improved understanding of how OC is transformed, mineralised and released during transit through the highly reactive nearshore estuarine environment is critical for examining the fate and influence of terrestrial OM on the Arctic Ocean. Capturing seasonality over the open water period is also necessary to identify current OM fluxes to the ocean vs the atmosphere, and aid in constraining how future changes may modify them. Here we focus upon carbon dioxide (CO2) and methane (CH4) measurements collected during six repeated transects of the Kolyma River and nearshore zone (covering ~120 km) from 2019. Transects spanned almost the entirety of the riverine open water season (June to September). We use these results, in parallel with gas concentrations derived from prior studies, to develop and validate a simple box-model of gas emissions from the nearshore zone. Observations and model-derived output data reveal that more than 50% of the cumulative gross delivery of CH4 and CO2 to the coastal ocean occurred during the freshet period with dissolved CH4 concentrations in surface water reaching 660 Nanomole per liter [nmol/l]. These results demonstrate the relevance of seasonal dynamics and its spatial variability which are needed in order to estimate greenhouse gas fluxes on an annual basis. More accurate understanding of land-ocean carbon fluxes in the Arctic is therefore crucial to mitigate the effects of climate change and to support the decisions of policy makers. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9535

2021048003 Pan, Mengdi (Helmholtz Center Potsdam GFZ German Research Center for Geosciences, Inorganic and Isotope Geochemistry, Potsdam, Germany) and Schicks, Judith. Experimental simulations of mixed gas hydrates dissociation in response to temperature changes in Qilian Mountain permafrost, China [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7791, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Gas hydrates are ice-like crystalline solids consisting of water and gas (predominantly methane). The methane gas bound in hydrate structures and their worldwide occurrence make them interesting not only as a potential energy source but also as a possible climate-relevant factor. Estimations predict that a certain amount of atmospheric CH4 may originate through dissociation of global gas hydrates, which may exacerbate global warming (Ruppel and Kessler, 2017). In turn, climate warming is not only directly affecting the hydrate distribution, but also perturbing the hydrate stability field, leading to the release of CH4 from hydrate-bearing sediments. Gas hydrates, particularly those associated within or below shallow permafrost, are likely to be affected by the climate processes. For instance, gas hydrates in Qilian Mountain permafrost (QMP) are found below thin permafrost layers at a shallow depth of around 133-396 m. They might be vulnerable to dissociation due to global warming resulting in a possible higher CH4 gas emission in this area. Considering the environmental effect, a proper understanding of hydrate dissociation behavior under specific conditions is important for the stability of natural gas hydrate deposits with respect to climate change. This study focuses on the potential dissociation process of gas hydrates in QMP. Before the observation of hydrate dissociation, mixed gas hydrates are synthesized from pure water and gas mixtures containing CH4, C2H6, C3H8, CO2 at conditions close to those in QMP (3.0 MPa, 278 K) with respect to feed gas composition, pressure and temperature. Formed hydrate crystals are analyzed in x-y-z directions applying confocal in situ Raman spectroscopic measurements to identify structures and guest compositions. The dissociation process is based on the thermal conduction simulating global warming and the results are discussed under several isobaric conditions. The Raman spectra continuously record changes in the hydrate phase for each selected crystal over the whole dissociation period. Preliminary results show that the Raman peak intensities for all components start to decrease when the temperature approaches 287 K, indicating the release of gas from hydrate structures. Interestingly, the varying hydrate composition for the measured crystals suggests a heterogeneous dissociation behavior of each single crystal. The results indicate a faster release of CH4 molecules from the hydrate phase than other components. In addition, the Raman signals of CH4 gas molecules that trapped in large cages of sII hydrate disappear first during the dissociation process. After a limited time, mixed gas hydrates decompose completely without evidence of self-preservation effects. These results provide essential information for the estimation of possible methane release from this area in response to future climate warming. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-7791

2021047976 Pan Yanxi (China University of Geosciences, School of Environmental Studies, Water Resources, and Hydrogeology, Wuhan, China) and Sun Ziyong. The effect of permafrost area and types on flux and composition of dissolved organic matter in stream from alpine catchments, northeastern Qinghai-Tibet Plateau [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-4288, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Understanding optical characteristics, composition and source of dissolved organic matter (DOM) i n rivers is important for region and global carbon cycle, especially in the inland rivers of the Qinghai-Tibet Plateau. In order to understand the impact of permafrost degradation on river DOM output under the background of climate warming, we selected 34 typical sub-basins in the upper reaches of the Heihe River basin on the Qinghai-Tibet Plateau according to the different proportion of permafrost area in the basin. Water samples were collected at the outlet of each sub-basin in October 2018, January, April and July 2019, respectively. The variations of DOM structure and source identification in different permafrost basin were investigated using UV-visible absorbance and fluorescence spectroscopy. The results showed that: (1) The concentration of C1 and C2 components and the values of SUVA254, HIX and FI increased with the decrease of the percentage of permafrost area. Indicating that with the degradation of frozen soil, the runoff path deepens, and more terrestrial organic matter is dissolved into the water body, which increases the terrestrial DOM in the river water, which in turn leads to the increase of DOM concentration, humification degree and aromaticity; (2) As the proportion of permafrost area decreases, the SR value shows a decreasing trend, indicating that the DOM of rivers in permafrost regions has the characteristics of low molecular weight and low humic acid, while the DOM of rivers in seasonally frozen soil regions is the opposite, indicating a frozen soil Melting may lead to the increase of terrestrial DOM in river water, and the increase in the depth of freeze-thaw cycle may release aromatic substances containing fused ring structure in frozen soil, which will enter the river with runoff, resulting in increased aromaticity and molecular weight of DOM in river water; (3) The concentrations of C1 and C2 components are positively correlated with vegetation coverage, and vegetation coverage is negatively correlated with the percentage of permafrost area. It shows that the degradation of frozen soil will increase the coverage of vegetation, thereby increasing the DOM from terrestrial sources. This study shows that the optical characteristics, composition and source of DOM have important indications for the degradation of permafrost under the background of global warming. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-4288

2021047946 Panov, Alexey (Russian Academy of Sciences, Siberian Branch, V. N. Sukachev Institute of Forest, Krasnoyarsk, Russian Federation); Prokushkin, Anatoly; Lavric, Jost; Kübler, Karl; Korets, Mikhail; Urban, Anastasiya; Sidenko, Nikita; Zrazhevskaya, Galina; Bondar, Mikhail and Heimann, Martin. Accurate continuous observations of carbon dioxide and methane dry mole fractions in the Arctic atmosphere near the Dikson settlement, Siberia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9773, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Measurements of the atmospheric sources and sinks of carbon dioxide (CO2) and methane (CH4) in the pan-Arctic domain are extremely sparse that limits our knowledge of carbon cycling over this dramatically sensitive environment and making predictions about a fate of carbon conserved in currently frozen ground. Especially critical are the gaps in the arctic latitudes of Siberia, covered by the vast permafrost underlain tundra, where only few continuous atmospheric observation stations are currently operational. We present the first two years of accurate continuous observations of atmospheric CO2 and CH4 dry mole fractions at the new atmospheric carbon observation station located near the Dikson settlement (73.33°N, 80.34°E) on the seashore of the western part of the Taimyr Peninsula in Siberia. Data quality control of trace gas measurements is achieved by regular calibrations against WMO-traceable reference gases from pressurized dry air tanks filled at the Max Planck Institute for Biogeochemistry (Jena, Germany). Associated meteorological variables permit evaluation of the climate variability of the local environment and provide a background for screening and interpreting the greenhouse gases (GHG) data records. Here we summarize the scientific rationale of the new site, give technical details of the instrumental setup, analyse the local environments and present CO2 and CH4 fluctuations in the arctic atmosphere. Along with the temporal variability of GHG's, we provide an overview of the angular distribution of detected GHG signals in the region and their input to the atmospheric fluctuations on the measurement site. Observation records deal with the daytime mixed layer and may be considered as representative throughout the vast area (~500-1000 km), and cover the period from September 2018 to September 2020. The reported study was funded by Russian Foundation for Basic Research, Krasnoyarsk Territory and Krasnoyarsk Regional Fund of Science, project number 20-45-242908, RFBR project 18-05-60203 and by the Max Planck Society (Germany) [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9773

2021048027 Philippe, Meven (Université de Nantes, Laboratoire de Planétologie et Géodynam, Nantes, France); Conway, Susan J.; Font-Ertlen, Marianne; Morino, Costanza and Bourgeois, Olivier. Link between molards and permafrost degradation; an experimental study [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8268, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Molards are cones of loose debris, from ~50 cm to ~15 m in height, and are the remnants of formerly ice-cemented blocks that moved within a landslide, then degraded progressively. Thus, presence of molards in landslide deposits implies an involvement of both ice-cemented and non-ice-cemented ground within the mass movement, and so the presence of an area of discontinuous permafrost at the level of the detachment zone. Permafrost is frozen or unfrozen ground that remains <0°C for at least two consecutive years, and it can be sensitive to temperature variations. Increasing temperatures can cause its degradation, which can create areas of discontinuous permafrost and enhance slope instability, which represents a threat for populations in polar and mountainous regions. Therefore, accurately identifying areas of discontinuous permafrost is a contemporary challenge for assessments of the state and evolution of permafrost, and for understanding landslide-related hazards to protect local populations. In this context, we will carry out physical modelling of the degradation of initial ice-cemented blocks made of sediments into molards. The M2C laboratory contains two cold rooms -- the largest one >12 m2 -- that can go down to -20°C, allowing near-field-scale simulations to be performed. We are developing an experimental protocol that consists in freezing mixes of sediment and water in 30 cm cubes, and then observing their degradation under controlled conditions. We identified grain size of the sediment and its ice content as the main two parameters that should influence the degradation process. Therefore, we will vary these parameters in the first series of experiments. We will observe the degradation processes that occur (e.g. grain falls, gravitational collapses, debris flows) using video cameras. The thaw-front propagation will be monitored by thermocouples within the frozen blocks. An array of time-lapse cameras will be used to produce time series of elevation models to monitor the 3D morphological evolution from blocks to molards. Air temperature and humidity will be monitored. Data on grain size, ice content, degradation processes and temperature/humidity will be used to calibrate a numerical model, which will allow us to explore a parameter space inaccessible/impractical for the laboratory (e.g. bigger scales, or realistic diurnal/seasonal thermal cycles). The final 3D shape (e.g. height, slope, basal area covered) of experimental molards should vary according to the initial parameters (i.e. grain size and ice content) and these measurements will inform the criteria used to distinguish molards from other similar landforms, such as hummocks or hummocky moraine, in the field and/or from remote sensing data.

DOI: 10.5194/egusphere-egu21-8268

2021047980 Polosukhina, Daria (Siberian Federal University, Krasnoyarsk, Russian Federation); Prokushkin, Anatoly and Steinhof, Axel. Radiocarbon patterns of dissolved and particulate organic carbon in the Yenisei River and its major tributaries [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9734, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

There is the significant progress in recent decades in the quantification of terrigenous carbon release to the rivers of the Arctic Ocean basin and characterization of its chemical properties, origin and age (e.g. Amon et al., 2012, Holmes et al., 2012). As warming accelerates the thawing permafrost may potentially increase the release the ancient carbon (Wild et al., 2019, Estop-Aragones et al., 2020). However, more detailed analysis is still needed particularly in regard of the age of carbon exported from the diverse landscapes of large Arctic rivers and its transformation during the transport to the Arctic ocean. In this study we analyzed D14C in dissolved organic carbon (DOC) and particulate organic carbon (POC) of the Yenisei River main channel and its major tributaries between 56°N and 68°N at freshet, summer and fall seasons. D14C was measured in Max Planck Institute for Biogeochemistry (Germany) by the accelerator mass spectrometry (AMS) system based on a 3MV Tandetron accelerator as described earlier (Steinhof et al., 2017). The oldest DOC in the Yenisei main stem was detected right after the Krasnoyarsk dam (56°N) and varied during a year without clear seasonal pattern in the range of the fraction of modern C (fMC) from 0.868 to 1.028. At freshet the fMC increased down stream up to 1.12 at 60°N and then remained relatively stable between 61° and 67.4°N (1.097±0.014). The major tributaries released DOC with fMC ranging from 1.0869 (Angara, 58°N) to 1.1046 (Kurejka (66.5°N), demonstrating more modern C with latitude. During the summer-fall season the Yenisei main channel and main Eastern tributaries contained older DOC (fMC=0.968-1.054 and 0.949-1.045, respectively). The POC of the Yenisei River was sufficiently older (fMC=0.83-0.92) than DOC at all seasons and showed similar latitudinal pattern, i.e. the youngest POC was detected near 60-61°N (fMC >0.90). The D14C-POC values in analyzed tributaries were increasing with latitude at freshet (R2=0.53) and summer lowflow (R2=0.33), except the largest Eastern tributaries, demonstrating the slight opposite pattern. On the other hand, increasingly more ancient POC was releasing by permafrost-dominated Eastern tributaries with increasing basin size. In opposite, D14C-POC of Western tributaries showed increased input of more recently fixed carbon. Our findings provided new data on the formation of terrigenic carbon fluxes to the Arctic Ocean from one of the largest river basins in the Arctic. This study was supported by RFBR grants -05-60203-Arktika. The radiocarbon analyses were kindly supported by Max-Plank Institute for biogeochemistry (ZOTTO project). [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-9734

2021048013 Preusker, Rene (Freie Universität Berlin, Institute for Space Sciences, Berlin, Germany); El-Kassar, Jan and Juhls, Bennet. Evaluating dissolved organic carbon retrieval in the Lena River delta using Sentinel 3 OLCI data [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15997, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

As air temperatures in the Arctic continue to rise, permafrost thaw intensifies, and discharge from the Arctic rivers increases. These drastic changes are likely to accelerate mobilization of organic matter and its export through rivers into the Arctic Ocean. Therefore, thorough monitoring of these processes becomes increasingly important. The Lena River with its large catchment area is one of the major sources of the organic carbon in the Arctic Ocean and, therefore, plays a crucial role in the Arctic carbon cycle. To observe current and future changes of carbon transport via the Lena River, a new monitoring program has been initiated in 2018. In situ water samples are collected from the one of the Lena Delta branches every several days. Since generally the in situ sampling in the Arctic is challenging and costly, in this study, we test the potential of remote sensing to complement the field observations. Remote sensing provides synoptic spatial coverages and high temporal resolution at high latitudes. We test the retrieval of dissolved organic carbon (DOC) from satellite-derived chromophoric dissolved organic matter (CDOM). For this, we use measurements of the Ocean & Land Colour Instrument (OLCI) on board the Sentinel-3 satellites in combination with beforehand tested atmospheric correction algorithms and CDOM retrieval algorithms. The quality of the satellite retrieved DOC of the Lena River water is assessed by DOC, measured in the in situ samples. Remotely sensed DOC contributes to an improvement of DOC fluxes monitoring, which can potentially be extended to all big Arctic rivers.

DOI: 10.5194/egusphere-egu21-15997

2021048014 Prud'homme, Charlotte (Max Planck Institute for Chemistry, Research Group for Terrestrial Palaeoclimates, Mainz, Germany); Fischer, Peter; Jöris, Olaf; Hatté, Christine; Vinnepand, Mathias; Vonhof, Hubert; Moine, Olivier; Vött, Andreas and Fitzsimmons, Kathryn. Millennial-timescale reconstruction of upper Pleistocene temperature and precipitation derived from earthworm calcite granules in Western European loess profiles [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-7071, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Loess-Palaeosol Sequences (LPS) represent the most extensive Quaternary terrestrial archives. Although researchers have long been able to identify short-lived climatic changes in LPS through stratigraphy, until recently we have lacked the tools to 1) identify how continuous loess archives may be, and to what extent short-lived, millennial-timescale climatic events were recorded in loess sediments, and to 2) quantitatively reconstruct past climate parameters from loess proxies. Stratigraphically, the impact of short-lived climatic cycles can be observed in the form of primary loess deposits reflecting cold stadial conditions, intercalated with arctic and boreal brown soils and tundra gley horizons indicating milder interstadials. Short-term establishment and subsequent degradation of an active permafrost layer can also be identified in temperate-latitude loess such as that found in the Rhine Valley of central-western Europe. Recently developed proxy methods can now be used to quantify climatic parameters such as temperature and precipitation in these regions. Associated with radiocarbon dating, these new approaches will vastly improve our understanding of continental environmental changes through the Upper Pleistocene, which can now be compared at high temporal resolution with marine and ice core records. In particular, the quantity and stable isotope ratios of crystalline calcite granules (>0.8 mm), secreted by earthworms (Lumbricus sp.) at the soil surface, preserve climate information contemporaneous with deposition of the loess sediment. In this study, we assess the utility of the earthworm calcite granules (ECG) approach by reconstructing temperature and precipitation at high resolution between 50 and 15 ka from two temporally overlapping loess sequences, Schwalbenberg and Nussloch, situated approximately 200 km apart in the German Rhine Valley. ECG counts down the two profiles reveal millennial-timescale climatic variations; high ECG concentrations associated with pedogenetic horizons suggest milder climatic with increasing biological activity and vegetation cover. Using empirical equations based on 1) observations of modern earthworm response to temperature and 2) the linear relationship between D13C values of plants and precipitation, the stable oxygen and carbon isotope compositions from ECGs can be used as direct proxies for warm season temperature and annual soil moisture, respectively. We embed our climate reconstructions within Bayesian age models based on radiocarbon dating of ECG in order to establish precise correlations between the two sequences and with other climatic archives. We find that ECGs provide valuable proxies able to meaningfully quantify palaeoclimate variations from terrestrial deposits over millennial timescales. Our results further show periods of quasi-simultaneous climatic change in the Northern Hemisphere, closely linking the climatic signatures recorded in the Upper Pleistocene of Schwalbenberg and Nussloch to the Greenland ice core records.

DOI: 10.5194/egusphere-egu21-7071

2021047984 Queiroz Alves, Eduardo (Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany); Wang, Yunyi; Hefter, Jens; Grotheer, Hendrik; Zonneveld, Karin A. F. and Mollenhauer, Gesine. Uncovering the contribution of permafrost thaw to the enhanced terrestrial organic matter input into the Bay of Biscay during the last deglaciation [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3398, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The thawing of permafrost in the polar regions has important implications for climate on Earth. Indeed, permafrost degradation results in a positive climate feedback which is currently aggravated by human action. The dynamic character of Earth's climate means that past trends and variability can be examined to improve future projections of this effect. Notably, the permafrost zone that covered parts of Europe during the Last Glacial Maximum (LGM) is currently absent, indicating that this region is a crucial area for the study of permafrost carbon remobilization during the last deglacial warming. Here, we investigate the mobilization of permafrost material to the Bay of Biscay, off the English Channel. Although this location has been shown to have experienced an enhanced deposition of terrigenous material during the last deglaciation, the contribution of permafrost thaw is unknown. We have established an accurate and robust chronological framework for this deposition, showing enhanced rates of sediment accumulation from approximately 20.2 to 15.8 kcal BP. Biomarker analysis has revealed periods of marked increases in terrigenous input, namely from approximately 20.5 to 19 and from 19 to 16.5 kcal BP. Moreover, by performing compound specific radiocarbon dating on n-alkanoic acids isolated from the sedimentary archive, we have been able to determine the origin of organic matter deposited at the core location. Our results will help researchers to assess to what extent permafrost thaw contributed to the peak of organic matter deposition present in the marine sediment, allowing us to sharpen our understanding of the mechanisms of permafrost carbon mobilization. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3398

2021047966 Raab, Sandra (Max Planck Institute for Biogeochemistry, Department of Biogeochemical Systems, Jena, Germany); Goeckede, Mathias; Vonk, Jorien; Hildebrandt, Anke and Heimann, Martin. Links between hydrological patterns and lateral carbon fluxes; a comparison between a wet and a drained site on a Siberian permafrost floodplain tundra [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-15020, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

As a major reservoir for organic carbon, permafrost areas play a pivotal role in global climate change. Vertical carbon fluxes as well as lateral transport from land to groundwaters and surface waters towards the ocean are highly dependent on various abiotic and biotic factors. These include for example temperature, groundwater depth, or vegetation community. During summer months, when soils thaw and lateral carbon transport within suprapermafrost groundwater bodies and surface waters occurs, flow patterns and therefore carbon redistribution may differ significantly between dry and wet conditions. Since dry soil conditions are expected to become more frequent in the future, associated shifts in carbon transport patterns play an important role in quantifying the carbon input into the water body linked to permafrost degradation. This study focuses on hydrological and carbon transport patterns within a floodplain tundra site near Chersky, Northeast Siberia. We compared a wet control site with a site affected by a drainage ring built in 2004 to study the effect of water availability on carbon production and transport. Water table depths at both sites were continuously monitored with a distributed sensor network over the summer seasons 2016-2020. At several locations, water samples were collected in 2016 and 2017 to determine organic carbon concentrations (DOC) as well as carbon isotopes (e.g. D14C-DOC). Suprapermafrost groundwater and surface water from the drainage ditch and the nearby Ambolikha river were included in the analysis. Our results focus on the physical hydrological conditions as well as on DOC and D14C-DOC observations. The spatio-temporal dynamics of water table depth revealed systematic differences between control and drained sites. The drained area showed a stronger decrease in water tables towards peak summer season in July and stronger reactions to precipitation events. The control area responded less pronounced to short-term changes. At the drained site, the main groundwater flow direction was stable throughout the measurement period. The control site was characterized by a shift in water flow confluence depending on increasing and decreasing water levels. DOC and D14C-DOC data showed that the highest concentrations of organic carbon and oldest DOC can be found in late summer. DOC concentrations were higher at the drained site compared to the wet site. We will show that the distribution of dissolved carbon can be directly related to hydrological flow patterns, and that understanding of these redistribution processes is essential for interpreting the carbon budget in disturbed permafrost. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-15020

2021047960 Rehder, Zoé (International Max Planck Research School on Earth System Modelling, Hamburg, Germany); Kleinen, Thomas; Kutzbach, Lars; Stepanenko, Victor and Brovkin, Victor. Sensitivity of pond methane emissions in the Lena River delta to climate changes in new model MeEP [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8387, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Permafrost ponds are a steady source of methane. However, it is difficult to assess the sensitivity of pond methane emissions to ongoing warming and climate-change-induced drainage, because pond methane emissions show large temporal and spatial variability already on local scale. We study this sensitivity on the landscape level with a new process-based model for Methane Emissions from Ponds (MeEP model), which simulates the three main pathways of methane emissions (diffusion, plant-mediated transport and ebullition) as well as the temperature profile of the water column and the surrounding soils. The model was set up for the polygonal tundra in the Lena River Delta. Due to a temporal resolution of one hour, it is capable of capturing the diurnal, day-to-day and seasonal variability in methane fluxes. MeEP also considers one of the main drivers of spatial variability - ground heterogeneity. Depending on where ponds form in the polygonal tundra, they can be classified as ice-wedge, polygonal-centre or merged-polygonal ponds. In MeEP, each of these pond types is simulated separately and the representation of these ponds was informed by dedicated measurements. The model performance is validated against eddy-covariance measurements of methane fluxes and against in-situ measurements of the aqueous methane concentration, both obtained on Samoylov Island. We will present results regarding the sensitivity of modeled methane emissions from ponds to warming and drainage on the landscape scale. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-8387

2021048001 Ridolfi, Emilia (Université Libre de Bruxelles, Brussels, Belgium); Wilkenskjeld, Stiig; Miesner, Frederieke; Brovkin, Victor; Overduin, Paul and Arndt, Sandra. Modeling methane production and emission from thawing sub-sea permafrost on the warming Arctic shelf [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-176, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The Arctic shelf hosts a large, yet poorly quantified reservoir of relic permafrost. It has been suggested that global warming, which is amplified in polar regions, will accelerate the thawing of this subsea permafrost, thus potentially unlocking large stocks of comparably reactive organic matter (OM). The microbial degradation of OM in the thawing and generally anoxic permafrost layer has the potential of producing and, ultimately, releasing important fluxes of CH4 to the atmosphere. Because CH4 is a potent greenhouse gas, such a release would further intensify global warming. However, the potential role of subsea permafrost thaw on microbial CH4 production and CH4 emissions from Arctic sediments currently remains unconstrained. Here, we use a nested model approach to address this critical knowledge gap. We developed a pseudo-three-dimensional reaction-transport model for permafrost bearing sediments on the Arctic shelf to estimate the production, consumption, and, efflux of CH4 on the Arctic shelf in response to projected subsea permafrost thaw. The model accounts for the most pertinent biogeochemical processes affecting methane and sulfur cycling in permafrost bearing marine sediments. It is initialized based on a published submarine permafrost map (SuPerMap) and forced by a range of projected thawing rate scenarios derived from the Max Planck Institute Earth System Model (MPI-ESM) simulation results for the period 1850-2100. Critical model parameters, such as permafrost OM content and its apparent reactivity are chosen based on a comprehensive analysis of published experimental data. Here, we present the output of this environmental scenario ensemble. Simulation results reveal that CH4 production rates are highly sensitive to changes in the apparent reactivity of permafrost OM. Although simulated CH4 production rates vary over a large range (0.001-130 PgC produced over 250 years), they generally highlight the potential for producing and, thus releasing large amounts of methane from thawing subsea permafrost on the warming Arctic Shelf. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-176

2021047954 Rogers, Brendan M. (Woodwell Climate Research Center, Falmouth); Elder, Molly; Frumhoff, Peter; Gasser, Thomas; Kukavskaya, Elena; MacDonald, Erin; Mack, Michelle; Natali, Susan; Phillips, Carly; Scholten, Rebecca; Treharne, Rachael; Veraverbeke, Sander and Walker, Xanthe. Intensifying fire regimes in the Arctic-boreal zone; recent changes, global implications, and possible solutions [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6404, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Across much of the high latitudes, wildfires have been increasing in frequency, area burned, and severity in response to longer fire seasons, more severe fire weather, and increased ignitions. These fires not only affect the tundra and boreal forests they burn, but also global climate due to the high levels of carbon emitted during combustion that take decades to re-aggrade. Carbon emissions from high latitude fires are generally not included in global models that inform policy nor emissions reductions commitments from relevant countries. In this presentation we describe recent progress and critical unknowns related to intensifying fire regimes in high latitude ecosystems, with a particular focus on (i) trends in burned area and large fire years; (ii) changing ignitions sources including lightning, human, and overwintering fires; (iii) patterns and drivers of carbon emissions, including interactions with permafrost; (iv) implications for global carbon budgets; and (v) potential climate mitigation through increased resources for carbon-focused fire management. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-6404

2021048021 Romeyn, Rowan (University of Tromso, Department of Geosciences, Tromso, Norway); Hanssen, Alfred; Kohler, Andreas; Ruud, Bent Ole; Stemland, Helene Meling and Johansen, Tor Arne. Frost quakes; the sound of a dynamic cryosphere and a convenient source for passive surface wave imaging of permafrost [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8617, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

A class of short-duration seismic events were recorded on dense, temporary geophone arrays deployed in Adventdalen, Svalbard in spring and autumn 2019. A similar class of events have also been detected in seismic records from the SPITS seismic array located on Janssonhaugen in Adventdalen, that has been in continuous operation since the 1990's. In both cases, estimated source positions are dominantly local and cluster around frost polygon, ice-wedge geomorphologies. Correlation with periods of rapidly cooling air temperature and consequent thermal stress build-up in the near surface are also observed. These events are consequently interpreted as frost quakes, a class of cryoseism. The dense, temporary arrays allowed high quality surface-wave dispersion images to be generated, that show potential to monitor structure and change in permafrost through passive seismic deployments. While the lower wavenumber resolution of the sparser SPITS array is less suited to imaging the near-surface in detail, the long continuous recording period gives us a unique insight into the temporal occurrence of frost quakes. This allows us, for example, to better understand the dynamic processes leasing to frost quakes by correlating temporal occurrence with models of thermal stress in the ground, constrained by thermistor temperature measurements from a nearby borehole. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-8617

2021047974 Ruben, Manuel (Alfred-Wegener Institut, Marine Geoscience, Bremerhaven, Germany); Schubotz, Florence; Marchant, Hannah; Hefter, Jens; Grotheer, Hendik; Forwick, Matthias; Szczucinski, Witold and Mollenhauer, Gesine. Microbial utilization of terrigenous ancient carbon released to marine environments traced by compound specific radiocarbon dating [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-1030, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Until two decades ago, ancient carbon was regarded as non-bioavailable substrate for organisms because it was synthesised, deposited, and once before (partially) degraded thousands to millions of years ago. Such aged organic matter is stored in terrestrial permafrost deposits or sedimentary bedrock, where it is locked up and remains disconnected from the active global carbon cycle. However, with changing climatic conditions, these organic matter reservoirs are being remobilised at faster rates by receding glaciers or permafrost thaw. During transport and after redeposition in newly formed sediments, the ancient carbon can be accessed by micro-organisms, but whether or not the micro-organisms can utilize the ancient carbon is highly debated. Using a combined approach of lipid biomarker analysis, lipidology, and radiocarbon dating of bulk organic matter as well as single compounds targeting intact polar lipid fatty acids (IPL-FAs), our research demonstrates that microbial communities utilise supposedly non-bioavailable ancient carbon for biosynthesis in Arctic marine fjord sediments. The availability of ancient carbon to the sub-surface microbes represents a carbon source that has not been accounted for in today's climate models. These implications are of major importance concerning the increased thawing of high latitude permafrost soils, permafrost mobilization and coastal erosion due to anthropogenic climate change, catalysing associated positive feedback loops. In future research, we will use this approach to study the utilization of ancient carbon derived from North American and Siberian permafrost soils in Arctic shelf sediments to assess its importance in the global carbon budgets. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-1030

2021047977 Sanders, Tina (Helmholtz-Zentrum Geesthacht, Institute für Küstenforschung, Geesthacht, Germany); Fiencke, Claudia; Fuchs, Matthias; Haugk, Charlotte; Mollenhauer, Gesine; Ogneva, Olga; Palmtag, Juri; Strauss, Jens; Tuerena, Robyn and Dahnke, Kirstin. Seasonal variations in the transport and biogeochemical turnover of mainly dissolved organic nitrogen from the Lena Delta to the nearshore Laptev Sea [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-8191, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Pan-arctic rivers transport a huge amount of nitrogen to the Arctic Ocean. The permafrost-affected soils around the Arctic Ocean contain a large reservoir of organic matter including carbon and nitrogen, which partly reach the river after permafrost thaw and erosion. Our study aims to estimate the load of nitrogen supplied from terrestrial sources into the Arctic Ocean. Therefore, water, suspended particulate matter (SPM) and sediment samples were collected in the Lena Delta along a (~200 km) transect from the center of the Lena Delta to the open Laptev Sea in late winter (April) and in summer (August) 2019. In winter, 21 sample from 13 stations and in summer, 51 samples from 18 stations were taken. 9 of these sampling stations in the outer delta region were sampled in both seasons. We measured organic and inorganic nitrogen and the 15N stable isotopes composition of all three sample types to determine sources, sinks and processes of nitrogen transformation during transport. In winter, the nitrogen transported from the delta to the Laptev Sea were mainly dissolved organic nitrogen (DON) and nitrate, which occur in similar amounts. The load of nitrate increased slightly in the delta, while no changes to the isotope values of DON and nitrate were observe indicating a lack of biological activity in the winter season. However, lateral transport from soils was a likely source. In summer, nitrogen was mainly transported as DON and particulate nitrogen in the SPM fraction, including phytoplankton. The nitrogen stable isotope values of the different nitrogen components ranges between 0.5 and 4.5 ppm, and were subsequently enriched from the soils via SPM/sediment and DON to nitrate. This indicates that nitrogen in the soils mainly originates from nitrogen fixation from the atmosphere. During transport and remineralisation, biogeochemical recycling via nitrification and assimilation by phytoplankton led to an isotopic enrichment in summer from organic to inorganic components. In the coastal waters of the Laptev Sea, the river waters are slowly mixed with marine nitrate containing waters from the Arctic Ocean, and a part of the riverine organic nitrogen is buried in the sediments. We assume that the ongoing permafrost thawing and erosion will intensify and increase the transport of reactive nitrogen to coastal waters and will affect the biogeochemical cycling, e.g. the primary production. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-8191

2021048025 Savi, Sara (Universität Potsdam, Potsdam, Germany); Comiti, Francesco and Strecker, Manfred. Global warming, slope stability, and the dynamization of geological hazards in high mountain regions; a case study from the Eastern Alps [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2070, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

In recent decades, slope instability in high-mountain regions has often been linked to the increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small to medium-size rockfalls and debris flows in a small catchment of the Italian Alps (Sulden/Solda basin). We found that rockfall events have been increasing since the 1990s, whereas debris flows have increased only since 2010. The current warming trend of mountain regions such as the Southern Alps is leading to an increased elevation of rockfall detachment areas (altitudinal shift of ca. 300-400 m in the study site), mostly controlled by frost-cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity-duration rainfall distribution. The possible occurrence of a debris-flow event in this environment may be additionally influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden basin (above ca. 2500 m asl), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 1990s and that an increase in rockfalls and debris flows during spring and summer can be observed. Our study thus confirms that "forward-looking" hazard mapping should be undertaken in these increasingly frequented areas of the Alps, as these environmental changes have elevated the overall hazard level in these high-elevation regions.

DOI: 10.5194/egusphere-egu21-2070

2021048019 Scandroglio, Riccardo (Technical University Munich, Chair of Landslide Research, Munich, Germany); Rehm, Till; Limbrock, Jonas K.; Kemna, Andreas; Heinze, Markus; Pail, Roland and Krautblatter, Michael. Decennial multi-approach monitoring of thermo-hydro-mechanical processes, Kammstollen outdoor laboratory, Zugspitze (Germany) [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13815, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The warming of alpine bedrock permafrost in the last three decades and consequent reduction of frozen areas has been well documented. Its consequences like slope stability reduction put humans and infrastructures at high risk. 2020 in particular was the warmest year on record at 3000 m a.s.l. embedded in the warmest decade. Recently, the development of electrical resistivity tomography (ERT) as standard technique for quantitative permafrost investigation allows extended monitoring of this hazard even allowing including quantitative 4D monitoring strategies (Scandroglio et al., in review). Nevertheless thermo-hydro-mechanical dynamics of steep bedrock slopes cannot be totally explained by a single measurement technique and therefore multi-approach setups are necessary in the field to record external forcing and improve the deciphering of internal responses. The Zugspitze Kammstollen is a 850 m long tunnel located between 2660 and 2780 m a.s.l., a few decameters under the mountain ridge. First ERT monitoring was conducted in 2007 (Krautblatter et al., 2010) and has been followed by more than one decade of intensive field work. This has led to the collection of a unique multi-approach data set of still unpublished data. Continuous logging of environmental parameters such as rock/air temperatures and water infiltration through joints as well as a dedicated thermal model (Schroder and Krautblatter, in review) provide important additional knowledge on bedrock internal dynamics. Summer ERT and seismic refraction tomography surveys with manual and automated joints' displacement measurements on the ridge offer information on external controls, complemented by three weather stations and a 44 m long borehole within 1 km from the tunnel. Year-round access to the area enables uninterrupted monitoring and maintenance of instruments for reliable data collection. "Precisely controlled natural conditions", restricted access for researchers only and logistical support by Environmental Research Station Schneefernerhaus, make this tunnel particularly attractive for developing benchmark experiments. Some examples are the design of induced polarization monitoring, the analysis of tunnel spring water for isotopes investigation, and the multi-annual mass monitoring by means of relative gravimetry. Here, we present the recently modernized layout of the outdoor laboratory with the latest monitoring results, opening a discussion on further possible approaches of this extensive multi-approach data set, aiming at understanding not only permafrost thermal evolution but also the connected thermo-hydro-mechanical processes. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13815

2021047997 Schulze, Christopher (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Olefeldt, David; Kljun, Natascha; Chasmer, Laura; Hopkinson, Chris; Helbig, Manuel; Gosselin, Gabriel Hould and Sonnentag, Oliver. Effects of warming and permafrost thaw on carbon dioxide fluxes from boreal peatlands in northwestern Canada [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13882, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The Taiga Plains ecozone in northwestern Canada is warming rapidly which alters the carbon dioxide (CO2) fluxes of the boreal peat landscape in two ways: 1) directly by increasing temperatures going along with increasing fluxes and 2) indirectly via permafrost thaw and resulting wetland expansion. However, we still lack an understanding of how direct and indirect effects vary across a latitudinal climate gradient covering different extents of permafrost. In this study, we will compare two years of concurrent eddy covariance measurements made over forested permafrost peat plateaus at Smith Creek (discontinuous permafrost) and Scotty Creek (sporadic permafrost) to assess differences in net CO2 exchange and its two component fluxes, gross primary productivity (GPP) and ecosystem respiration (ER). Footprint analysis will be used to assess the net CO2 balance of peat plateaus and thermokarst wetlands at both sites. We hypothesize that GPP and ER will be higher at the warmer Scotty Creek site, due to both, more abundant thermokarst wetlands and higher GPP and ER of peat plateaus at this southern site. We also hypothesize that the effects of warming on GPP are greater than on ER and thus that the warmer Scotty Creek site is a greater net CO2 sink. Our study will conclude on the carbon feedback of warming peat landscapes near the southern limit of permafrost in northwestern Canada in response to Climate Change. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13882

2021047944 Schweitzer, Peter (Universität Wien, Department of Social and Cultural Anthropology, Vienna, Austria) and Povoroznyuk, Olga. Ignoring environmental change in Bykovskiy, Yakutia? Thawing permafrost, indigenous knowledge and modernization ideologies in northern Russia [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6765, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The town of Tiksi and the nearby indigenous village of Bykovskiy are located in northern Yakutia, where the Lena River meets the Arctic Ocean. Both owe their existence to Soviet policies and development plans, one tied to the Northern Sea Route, and the other to a fishing enterprise based on the labor of political prisoners. Post-Soviet transformations since the 1990s have severely altered the economic base of these communities, typically resulting in social, cultural and economic shocks and hardships. At the same time, both communities are affected by environmental change, most visibly in Bykovskiy, where coastal erosion caused by permafrost thaw has been destructing the local graveyard and endangers the housing infrastructure. Interestingly, when we conducted fieldwork there in 2019, our interlocutors seemed to pay very little attention to these environmental problems in the narratives they shared with us. While it might be tempting to accuse local residents of ignoring permafrost thaw and other environmental changes, the situation, we argue, is more complex. In fact, indigenous residents, especially, those making a living by practicing "traditional" activities, such as fishing and reindeer herding, have been observing extreme weather events, shifts in seasonal patterns, and changes in the behavior of land animals and fish for a long time. Similarly, to other parts of the Arctic, this accumulated traditional ecological knowledge has been helpful for adapting to the dramatically changing environment. At the same time, on the discursive and political level, this knowledge has been devalued or, at best, rated as a secondary source of information in relation to a more "advanced" institutionalized expert knowledge. Moreover, the Soviet modernization ideologies and discourses about human-environmental relations have impacted local knowledge, ethics and perceptions of the changing environment. This presentation calls for attention to historical and regional contexts and explores how hierarchical relations between different knowledge systems and how state modernization ideologies inform the ways in which indigenous communities in northern Russia relate to the effects of climate change today. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-6765

2021047996 Sim, Thomas (University of Leeds, School of Geography, Leeds, United Kingdom); Swindles, Graeme; Morris, Paul; Baird, Andy; Cooper, Claire; Gallego-Sala, Angela; Charman, Dan; Roland, Thomas; Borken, Werner; Mullan, Donal; Aquino-López, Marco and Galka, Mariusz. Divergent responses of permafrost peatlands to recent climate change [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-3220, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Permafrost peatlands are found in high-latitude regions and store globally-important amounts of soil organic carbon. These regions are warming at over twice the global average rate, causing permafrost thaw and exposing previously inert carbon to decomposition and emission to the atmosphere as greenhouse gases. However, it is unclear how peatland hydrological behaviour, vegetation structure and carbon balance, and the linkages between them, will respond to permafrost thaw in a warming climate. Here we show that permafrost peatlands follow divergent ecohydrological trajectories in response to recent climate change within the same rapidly warming region (northern Sweden). Whether a site becomes wetter or drier depends on local factors and the autogenic response of individual peatlands. We find that bryophyte-dominated vegetation demonstrates resistance, and in some cases resilience, to climatic and hydrological shifts. Drying at four sites is clearly associated with reduced carbon sequestration, while no clear relationship at wetting sites is observed. We highlight the complex dynamics of permafrost peatlands and warn against an overly-simple approach when considering their ecohydrological trajectories and role as C sinks under a warming climate. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-3220

2021047953 Smith, Thomas (London School of Economics, Department of Geography & Environment, London, United Kingdom); McCarty, Jessica; Turetsky, Merritt and Parrington, Mark. Geospatial analysis of Arctic fires in the MODIS era; 2003-2020 [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16198, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

MODIS has provided an 18-year continuous record of global fire activity. Here we present a geospatial analysis of MODIS hotspots in the high latitudes of the northern hemisphere from 2003 through to 2020. By combining the hotspot data with multiple land-cover datasets relating to vegetation cover, permafrost, and peat, we investigate boreal and tundra wildfire regimes, including an assessment of a significant northwards shift and increase in fire activity in 2019 and 2020. We focus on the distribution of hotspots on high latitude peatlands and permafrost and the associated difficulties in confirming residual smouldering combustion of peat soils using current remote sensing technology. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-16198

2021047943 Sparks, Donald (University of Delaware, Wilmington, DE). Impact of environmental change on biogeochemical cycling in soil systems [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-435, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Environmental change, particularly the impact of climate change, is having a profound impact on humankind. Rising seas and temperatures are causing increasing flooding and melting of ice and permafrost soils. The impact of these processes on biogeochemical cycling of metals, carbon, and nutrients in soils and water is not well understood. For example, how do rising seas, which cause inundation of soils with saline water, followed by retrenchment, and salinization of groundwater, affect cycling of redox active elements such as arsenic and iron as well as nutrients such as phosphorus. Complexation of carbon with iron-bearing minerals is a major mechanism for carbon retention. Under changing climatic conditions, how will carbon cycling be impacted, particularly in permafrost soils, which are sinks for a large portion of terrestrial carbon? This presentation will explore these questions, and others, over a range of spatial and temporal scales. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-435

2021048040 Stimmler, Peter (Leibniz Centre for Agricultural Landscape Research, Silicon Biogeochemistry, Bayreuth, Germany) and Schaller, Jörg. Amorphous Si and Ca affect microbial community structure in Arctic permafrost soils [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-9486, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Arctic warming affects the permafrost soils in different ways. Increase soil temperature and thawing of deeper horizons modifies the release of greenhouse gases (GHG) by release of nutrients. A lot of research was done about nutrient cycling of C, N and P, but little is known about the influence of Ca and amorphous Si (ASi) on this elements. To show the potential of this two elements in the Arctic systems, we analysed the effect of ASi and Ca on microbial community structure with next generation sequencing and qPCR. We analyzed fungal and bacterial community structure in two different soils from Greenland after incubation with different levels of ASi and Ca. Microbial community reacted differently in the high Arctic (Peary Land) and low Arctic soil (Disko Island) to changing concentrations of ASi and Ca. We found a significant change with linear correlation from gram-negative to gram-positive bacteria classes with increasing Ca and/or ASi levels. Further, abundance of Ascomycota and Basidiomycota changed. We postulate this changes as an important factor for changed GHG production as potential response to modified nutrient availability.

DOI: 10.5194/egusphere-egu21-9486

2021048006 Treat, Claire C. (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Potsdam, Germany); Jones, Miriam C.; Brosius, Laura S.; Grosse, Guido; Anthony, Katey Walter and Frolking, Steve. Methane emissions from high-latitude peatlands during the Holocene from a synthesis of peatland records [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-6224, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The sources of atmospheric methane (CH4) during the Holocene remain widely debated, including the role of high latitude wetland and peatland expansion and fen-to-bog transitions. We reconstructed CH4 emissions from northern peatlands from 13,000 before present (BP) to present using an empirical model based on observations of peat initiation (>3600 14C dates), peatland type (>250 peat cores), and contemporary CH4 emissions in order to explore the effects of changes in wetland type and peatland expansion on CH4 emissions over the end of the late glacial and the Holocene. We find that fen area increased steadily before 8000 BP as fens formed in major wetland complexes. After 8000 BP, new fen formation continued but widespread peatland succession (to bogs) and permafrost aggradation occurred. Reconstructed CH4 emissions from peatlands increased rapidly between 10,600 BP and 6900 BP due to fen formation and expansion. Emissions stabilized after 5000 BP at 42±25 Tg CH4 y-1 as high-emitting fens transitioned to lower-emitting bogs and permafrost peatlands. Widespread permafrost formation in northern peatlands after 1000 BP led to drier and colder soils which decreased CH4 emissions by 20% to 34±21 Tg y-1 by the present day. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-6224

2021047998 Ulyantsev, Alexander (Russian Academy of Sciences, Shirshov Institute of Oceanology, Moscow, Russian Federation); Bratskaya, Svetlana; Belyaev, Nikolay; Dudarev, Oleg and Semiletov, Igor. Compositional pattern of lignin derived phenols of sediments as a proxy of accumulation of terrestrial organic matter in coastal zone of the Laptev Sea [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-4726, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The modern East Siberian Arctic shelf represents a fascinating area with a vast expansion of subsea permafrost that holds a large pool of frozen immobilised organic carbon (OC). Amplified climate change at high latitudes has raised growing concerns about potential positive carbon-climate feedbacks. Degradation of permafrost in the Arctic could constitute a positive feedback to climate change due to activation of this OC stock, while recognizing the origin and peculiarities of organic matter (OM) is useful for predicting the potential for involving the ancient OC in modern carbon cycling. This paper emphasises the molecular composition of lignin-derived phenols (LDP) in bottom sediments and subsea permafrost from the Laptev Sea shelf as a proxy to describe the main sources, distribution, and preservation of terrestrial OM. The compositional pattern and concentration of LDP revealed irregular dynamics of terrigenous OM supply in the study area, that were governed primarily by continental flows. The OC concentration in the studied sediments varied from 0.04% to 23.1% (mean 1.74%, median 1.07%). The concentration of LDP in the studied 126 samples from five sediment cores obtained from Buor-Khaya Bay varied from 0.7 to 13191 (mean 539, median 63.5) mg/g of dry sediment as the sum of vanillyl, syringyl, and cinnamyl (VSC) compounds and from 0.03 to 27.6 (mean 1.61, median 0.76) mg/100 mg of OC content. All OC-rich samples showed higher concentrations of LDP and virtually non-oxidized lignin. Vegetation proxies suggested that vascular plant tissues account for a significant fraction of the lignin in the examined samples, with a strong share of gymnosperms. The concentration of LDP correlates to OC content, indicating a strong supply of terrestrial OC to the study area. Degradation proxies indicate a predominant supply of wood-rich non-oxidized terrestrial OM. The well-preserved lignin revealed in the studied deposits represents a specific feature of Quaternary lithodynamics of the Laptev Sea and is not typical for the majority of bottom sediments of the World Ocean. Good correlation between OC and lignin concentration suggests that terrigenous fluxes were the main contributor to OM supply. Distribution of specific lignin phenols and related ratios coupled with lithology and grain size revealed that fluvial processes have been leading here. This research was supported through the Russian Scientific Foundation (grant no. 19-77-10044) within the framework of the state assignment of the Shirshov Institute of Oceanology RAS (grant no. 0149-2019-0006). [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-4726

2021047956 Veraverbeke, Sander (Vrije Universiteit Amsterdam, Faculty of Science, Amsterdam, Netherlands); Delcourt, Clement; Granath, Gustaf; Kukavskaya, Elena; Mack, Michelle; Strengbom, Joachim; Walker, Xanthe; Hessilt, Thomas; Rogers, Brendan and Scholten, Rebecca. Carbon emissions from fires in permafrost peatlands [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-2355, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Increases in arctic and boreal fires can switch these biomes from a long-term carbon (C) sink to a source through direct fire emissions and longer-term emissions from soil respiration. Landscapes of intermediate drainage tend to experience the highest C combustion, dominated by soil C emissions, because of relatively thick and periodically dry organic soils. These landscapes may also induce a climate warming feedback through combustion and post-fire respiration of legacy C -- soil C that had escaped burning in the previous fire -- including from permafrost thaw and degradation. Data shortages from fires in tundra ecosystems and Eurasian boreal forests limit our understanding of C emissions from arctic-boreal fires. Interactions between fire, topography, vegetation, soil and permafrost need to be considered when estimating climate feedbacks of arctic-boreal fires. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-2355

2021047962 Wild, Birgit (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Shakhova, Natalia; Dudarev, Oleg; Ruban, Alexey; Kosmach, Denis; Tumskoy, Vladimir; Tesi, Tommaso; Joss, Hanna; Nybom, Inna; Alexanderson, Helena; Jakobsson, Martin; Mazurov, Alexey; Semiletov, Igor and Gustafsson, Orjan. Potential greenhouse gas production by organic matter decomposition in thawing subsea permafrost [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-5766, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Subsea permafrost extends over vast areas across the East Siberian Arctic Ocean shelves and might harbor a large and vulnerable organic matter pool. Field campaigns have observed strongly elevated concentrations of CH4 in seawater above subsea permafrost that might stem from microbial degradation of thawing subsea permafrost organic matter, from release of CH4 stored within subsea permafrost, from shallow CH4 hydrates or from deeper thermogenic/petrogenic CH4 pools. We here assess the potential production of CH4, as well as CO2 and N2O by organic matter degradation in subsea permafrost after thaw. To that end, we employ a set of subsea permafrost drill cores from the Buor-Khaya Bay in the south-eastern Laptev Sea where previous studies have observed a rapid deepening of the ice-bonded permafrost table. Preliminary data from an ongoing laboratory incubation experiment suggest the production of both CH4 and CO2 by decomposition of thawed subsea permafrost organic matter, while N2O production was negligible. These data will be combined with detailed biomarker analysis to constrain the vulnerability of subsea permafrost organic matter to degradation to greenhouse gases upon thaw. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-5766

2021047983 Wu, Junjie (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany); Mollenhauer, Gesine; Stein, Ruediger; Hefter, Jens; Fahl, Kirsten; Grotheer, Hendrik; Wei Bingbing and Nam, Seung-Il. Mobilization of aged carbon via meltwater floods and coastal erosion in the Canadian Arctic during the last deglaciation [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-448, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

It is consensus that the deglacial changes in ocean carbon storage and circulation play a role in regulating atmospheric CO2. However, emerging evidence suggests that the rapid deglacial CO2 rises can in part be attributed to large quantities of pre-aged carbon being released from degrading permafrost. In this study, we apply a radiocarbon approach on both terrestrial compounds (high molecular weight fatty acids; HWM-FA) and bulk organic carbon from a well-studied core ARA04C/37 from the Canadian Beaufort Sea. Based on our records, substantial amounts of ancient carbon were supplied from land to the ocean during the mid-late deglaciation (14.5-10 cal. kyr BP) by frequent high sediment flux events. Because the core location is strongly influenced by the Mackenzie River discharge, sediments only contain minor contributions from marine organic matter, allowing to consider mainly two terrestrial sources to explain the characteristics of bulk sedimentary organic matter. The terrestrial HMW-FA are taken to represent the biospheric carbon, and their age differences from the bulk organic carbon are explained by petrogenic carbon input. During the Younger Dryas, ice-sheet melting and meltwater outbursts enhanced petrogenic carbon contributions, suggesting a major source in the hinterland drainage system. During the rapid sea-level rise (meltwater pulses 1a and 1b), the very old organic carbon and comparable ages between biospheric carbon and bulk organic carbon indicate the occurrence of permafrost carbon remobilization primarily via coastal erosion while petrogenic carbon from the drainage system was found negligible. Remobilized ancient permafrost carbon is commonly regarded to be highly bioavailable, while petrogenic carbon is likely more recalcitrant to biological degradation. Our records thus suggest that the release of ancient carbon to the Beaufort Sea had the strongest impact on the atmospheric CO2 level and contributed to its rapid increases during the B/A and Pre-Boreal when permafrost deposits along the coast were eroded. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-448

2021047964 Wu, Weichao (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Holmstrand, Henry; Wild, Birgit; Shakhova, Natalia; Kosmach, Denis; Semiletov, Igor and Gustafsson, Orjan. Methane oxidation processes in sediment of the Laptev and East Siberian Seas indicated from microbial lipids and carbon isotope composition [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-13428, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The East Siberian Arctic Shelf is an integrated coastal sea system with complex biogeochemical processes influenced by underlying subsea permafrost, hydrates and thermogenic compartments. Methane is released from the marine sediments to the water column, which serves as an interphase between the lithosphere and the atmosphere. Before escaping into water column and atmosphere, methane has potentially experienced extensive aerobic and anaerobic oxidation by microbes in the marine sediment. In particular, the aerobic process is assumed to be dominant in the surface oxic/suboxic marine sediment (upper 1 cm) after anaerobic processes in deeper zones. However, these processes are insufficiently understood in sediments of the Arctic Ocean. To probe these, we investigated the microbial lipids and their stable carbon composition in surface marine sediment (upper 1 cm) from two active methane seep areas in the Laptev Sea and the East Siberian Sea. The microbial fatty acids (C12 to C18 fatty acids) were relatively enriched in 13C (d13C -18.8 to -31.2 ppm) compared to that of dissolved CH4 in nearby bottom water (-54.6 to -29.7 ppm). This contrasts to previous reports of strongly depleted d13C signals in microbial lipids (e.g., -100 ppm) at active marine mid-ocean ridges and mud volcanoes, from quite different ocean areas. The absence of a depleted d13C signal in these general microbial biomarkers suggest that these reflect substrates other than methane such as other parts of the sediment organic matter, indicated by the stronger correlation of d13C between fatty acids and bulk organic carbon than that between fatty acid and CH4. However, the putatively more specific biomarkers for aerobic methanotrophic bacteria (mono-unsaturated C16 and C18 fatty acids) show a distinct pattern in the Laptev Sea and East Siberian Sea: C16:1 and C18:1 were enriched in 13C (up to 4.5 ppm) relative to their saturated analogs in the Laptev Sea; whereas, C18:1 was depleted in 13C (up to 4.5 ppm) compared to C18 in the East Siberian Sea. This could be because the relative populations of Type I and II methanotrophs were different in the two areas with different carbon assimilation pathways. Our results cannot exclude a slowly active aerobic methanotrophs at methane seeps in the East Siberian Arctic Ocean and thus call for more information from molecular microbiology. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-13428

2021047990 Yang Yuanhe; Yang Guibiao; Peng Yunfeng; Abbott, Benjamin W.; Biasi, Christina; Wei Bin; Zhang Dianye; Wang Jun; Yu Jianchun; Li Fei; Wang Guanqin; Kou Dan and Liu FutingPhosphorus regulates ecosystem carbon dynamics after permafrost thaw [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-376, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

The ecosystem carbon (C) dynamics after permafrost thaw depends on more than just climate change since soil nutrient status may also impact ecosystem C balance. It has been advocated that the potential nitrogen (N) release upon permafrost thaw could promote plant growth and thus offset soil C loss. However, compared with the widely accepted C-N interactions, little is known about the potential role of soil phosphorus (P) availability. Here we combined two-year field observations along a permafrost thaw sequence (constituted by four thaw stages, i.e., non-collapse and 5, 14, and 22 years since collapse) with an in-situ fertilization experiment (included N and P additions at the level of 10 g N m-2 yr-1 and 10 g P m-2 yr-1, respectively) in a Tibetan swamp meadow to evaluate ecosystem C-nutrient interactions upon permafrost thaw. Our results showed that changes in soil P availability rather than N availability played an important role in regulating the increases in gross primary productivity and the decreases in net ecosystem exchange along the thaw sequence. The fertilization experiment further confirmed that P addition had stronger effects on plant growth than N addition in this permafrost ecosystem. These two lines of evidence highlight the crucial role of soil P availability in altering the trajectory of permafrost C cycle under climate warming. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-376

2021048018 Yu Zhitong (China Academy of Space Technology, Qian Xuesen Laboratory of Space Technology, Beijing, China); Hu Luojia; Huang Yan; Ma Rong; Xiao Peng and Yao Wei. New space observation of the global cryosphere [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-12871, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Quantifying changes in Earth's ice sheets and identifying the climate drivers are central to improving sea level projections. But it is a pity that the future sea level is difficult to predicted. Space observation can provide global multiscale long-term continuous monitoring data. And it is very important for understanding intrinsic mechanisms, improve models and projections and analyze the impacts on human civilization. Several satellites are applied for Global Cryosphere Watch, including sea ice extent and concentration, ice sheet elevation, glacier area and velocity. Although there are many variable can be measured by satellite sensors. But several variables need to improve the observing capability and developing new methods. Such as snow depth on ice, ice sheets thickness, and permafrost parameters. China has established high-resolution earth observation system to realize stereopsis and dynamic monitoring of the lands, the oceans and the atmosphere. Currently, Qian Xuesen Laboratory working together with Sun Yat-sen University, is trying to design a new space observation system to support Three Poles Environment and Climate Changes project. We are conceptualizing two series satellites including FluxSats and BingSats for carbon/water cycle and cryosphere observations, respectively. To clarify the mechanism of the cryosphere carbon release and carbon sink effects of the oceans and ecosystems. We are developing a new lidar system for detecting the concentration and wind speed, and then atmospheric boundary layer flux exchange can be estimated. To understand the rapid change of the sea ice, such as drift, fragmentation and freeze. We need a short revisit and wide swath system capabilities. InSAR technology gives the digital elevation of the ice surface. And temporal difference InSAR (DInSAR) shows the changes of elevation. BingSAT-Tomographic Observation of Polar Ice Sheets (TOPIS) achieves the tomographic observation of polar ice sheets with a wide swath and short revisit time. Over the polar regions, the CubeSats form a large cross-track baseline with the master satellite to realize the high two-dimensional spatial resolution with the along-track synthetic aperture. The MirrorSAR technology is utilized in BingSat-TOPIS to achieve time and phase synchronization more economically than the traditional bistatic radar. Sparse array and digital beamforming are also considered to significantly reduce the number of microsatellites, and achieve tomographic images of polar ice sheets. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-12871

2021048002 Zadorozhnaia, Nataliia (Russian Academy of Sciences, Siberian Branch, Earth's Cryosphere Institute, Tyumen, Russian Federation); Oblogov, Gleb; Vasiliev, Alexander and Streletskaya, Irina. Methane in frozen and thawed soils of the western sector of Russian Arctic [abstr.]: in European Geosciences Union general assembly 2021, Geophysical Research Abstracts, 23, Abstract EGU21-16558, 2021. Meeting: European Geosciences Union general assembly 2021, April 19-30, 2021, World Wide Web.

Many researchers study the Earth's climate change and the impact of the greenhouse effect on this process. The large amount of methane (CH4) is preserved in permafrost. In this regard, scientists recently pay a great attention to the problem of methane emission during the permafrost degradation in the Arctic zone. Until now, the methane content in underground ice, frozen Quaternary sediments has been studied insufficiently. The methane content in the active layer is especially poorly studied. The authors researched methane content in frozen grounds of the upper permafrost horizon (transition zone) and in thawed sediments of the active layer for different tundra landscapes near the Marre-Sale polar station on the western coast of the Yamal peninsula and for landscapes of the Pechora river estuary area (Russia). More than 420 samples of gas from sediments in active and transient layer were collected in Marre-Sale and 36 samples in Pechora area. To determine the methane content, the samples were placed in syringes and degassed using the "head space" technique. CH4 measurements were carried out on a chromatograph with flame ionization detector (FID) Shimadzu GC-2014 (Japan) in the laboratory of Federal State Institution "VNIIOkeangeologiya" (Saint-Petersburg, Russia). Methane content in the frozen and thawed sediments of different dominant landscapes of typical tundra on Yamal peninsula and landscapes of southern tundra on Pechora area is extremely variable. The greatest amount of methane is typical for the most wet landscapes with primarily of silt loam soils. In dry primarily sandy well-drained landscapes, the methane content is low. The highest methane content is measured within the low floodplain of river, water tracks, swampy depressions of polygonal relief, and lake basins landscapes (mean varied from 0.8 to 2.5 ml [CH4]/kg, with a maximum of 9.0 ml [CH4]/kg). For landscapes of the moist surface of typical tundra, the average values of methane content were approximately 0.4 ml [CH4]/kg (with a maximum of 3.4 ml [CH4]/kg). The lowest methane contents in soils were characteristic of the landscapes of well-drained tundra, and sand fields where the average values do not exceed 0.2 ml [CH4]/kg. Mean methane content in soils of Pechora river mouth landscapes varied from 0.05 to 4.5 ml [CH4]/kg, with a maximum of 15.8 ml [CH4]/kg. Determined that methane contents in the frozen soils of the transition zone is 2 to 5 times higher than in the soils of the active layer. High content of methane in upper layers of permafrost should be considered as a significant source of methane, which can be involved in emission of greenhouse gases into the atmosphere during permafrost degradation. [Copyright Author(s) 2021. CC Attribution 4.0 License:]

DOI: 10.5194/egusphere-egu21-16558

2021047332 Torres, Marta (Oregon State University, College of Earth, Ocean, and Atmospheric Sciences, Corvallis, OR); Kim, JiHoon; Hong, Wei-Li; Ryu, Jong-Sik; Kang, Moo-Hee; Han, Dukki; Nam, Seung-Il; Koh, Dong-Chan; Niessen, Frank; Lee, Dong-Hun; Jang, Kwangchul; Rae, James and Chen Meilian. Geochemical evidence for the discharge of meteoric flow to the Chukchi Sea suggestive of a subsurface flow pulse during the early Holocene thermal maximum (EHTM) [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 242-1, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

The impact of permafrost thaw on the discharge of subsurface flow in the Arctic Ocean and its connection to (bio-)geochemical interactions in this critical zone of our planet are still poorly understood. We present geochemical data collected on the Chukchi Shelf, where chloride and water isotope data reveal a meteoric source enriched in cations with a radiogenic fingerprint. The postulated subsurface fluid is enriched in dissolved inorganic carbon and methane; the isotopic composition of the carbon reservoirs is consistent with discharge of fluids affected by diagenetic reactions in a closed system. This scenario is in accordance with published reports of high abundance of a terrestrial humic-like fluorescent dissolved organic matter at this shelf site. These fluid characteristics are in stark contrast with those from other sites in the Chukchi Sea, where fluid discharge does not impact regional biogeochemical reactions in marine sediment. Numerical simulations indicate that the observed data at the investigated site in the shelf cannot be attributed to a water discharge that occurred during the past centuries and thus suggest no association with anthropogenically-induced climate change. Alternatively, we attribute our observations to paleo-subsurface flow resulting from permafrost thaw during the Early Holocene Thermal Maximum (EHTM).

DOI: 10.1130/abs/2020AM-356187

2021047113 Andreeva, V. V. (Russian Academy of Sciences, Siberian Branch, Institute of Permafrost, Yakutsk, Russian Federation); Maksimov, G. T.; Spector, V. V.; Kholodov, A. L.; Davydov, S. P. and Lobanov, A. L. Cryolithological section of ice-rich sediments of the annual heat circulation layer in post-pyrogenic sections of the Kolyma Lowland north-eastin International science and technology conference; Earth science, IOP Conference Series. Earth and Environmental Science, 459(3), Article 032051, illus. incl. 1 table, geol. sketch maps, 25 ref., April 2020. Meeting: International science and technology conference; Earth science, Dec. 10-12, 2019, Russky Island, Russian Federation.

The article provides the results of cryolithological studies of ice-rich sediments in post-pyrogenic areas in the Nizhnekolymsky district of Sakha Republic (Yakutia) near Chersky village. Two boreholes were drilled, and a comprehensive analysis of core material was carried out. The results of the work reflect various cryogenic structure for relatively similar cryogenic landscapes. Copyright Published under license by IOP Publishing Ltd

DOI: 10.1088/1755-1315/459/3/032051

2021047103 Ivanov, V. A. (Institute of Oil and Gas Problems SB RAS, Yakutsk, Russian Federation) and Rozhin, I. I. Estimating thermal effect of a group of gas wells on permafrost rockin International science and technology conference; Earth science, IOP Conference Series. Earth and Environmental Science, 459(3), Article 032005, 12 ref., April 2020. Meeting: International science and technology conference; Earth science, Dec. 10-12, 2019, Russky Island, Russian Federation.

The article is devoted to a computational experiment on forecasting the thermal interaction of a group of gas wells and permafrost. In connection with the spread of cluster drilling, it becomes necessary to study the thermal effect of a cluster of wells on frozen soils in the specific conditions of Central Yakutia. As input data for the numerical survey, field data on thermal logging, production rates, physicochemical properties of gas, rock properties and parameters of the developed deposits were used. Quantitative results were obtained on the extent and pattern of thawing of frozen rocks in the vicinity of the group of wells, and on well operation modes. The results of the work can be used in planning the development of gas fields in the considered area. Copyright Published under license by IOP Publishing Ltd

DOI: 10.1088/1755-1315/459/3/032005

2021047110 Spektor, V. B. (Russian Academy of Sciences, Melnikov Permafrost Institute, Laboratory of General Geocryology, Yakutsk, Russian Federation); Shestakova, A. A. and Torgovkin, Ya I. Temperature field of the permafrost zone in northeastern Siberiain International science and technology conference; Earth science, IOP Conference Series. Earth and Environmental Science, 459(3), Article 032032, illus. incl. 1 table, 23 ref., April 2020. Meeting: International science and technology conference; Earth science, Dec. 10-12, 2019, Russky Island, Russian Federation.

The Northeastern Siberia includes the coasts of the Sea of Okhotsk, part of the North Siberian Lowland, the Central Siberian Plateau and the Lena Delta. Based on field measurements and calculations, this study characterizes the regional distribution of permafrost temperature in the layer of zero annual amplitude (ZAA). Permafrost temperatures vary over a wide range from -2 to -13°C. Analysis of ZAA temperatures indicates that permafrost is transient in much of the study region. In its northern part, especially where diluvial deposits are present, temperature profiles are isothermal or have inverse (negative) gradients. The temperature field in the areas of pre-Quaternary carbonate rocks is characterized by wide scatter of the values and often by higher ZAA temperatures. This is due to the karst process in carbonate rocks which is associated with heat release. This process likely occurred below the bottom of post-catastrophic basins, resulting in greater heat flow and disturbance of the equilibrium state of permafrost. The layers of dolomite flour over the pre-Quaternary carbonate rocks provide additional evidence of the high water contents in upper permafrost during deposition of the diluvial sequence. Temperatures below ZAA in these areas may reach -4°C, while similar settings without carbonate rocks have temperatures below ZAA as low as -8 to -11°C. This study has confirmed the high variability of ZAA temperatures in the region. Copyright Published under license by IOP Publishing Ltd

DOI: 10.1088/1755-1315/459/3/032032

Back to the Top


© American Geosciences Institute 2021