2017042114 Dou, Shan (Lawrence Berkeley National Laboratory, Earth & Environmental Sciences Area, Berkeley, CA); Nakagawa, Seiji; Dreger, Douglas Scott and Ajo-Franklin, Jonathan. An effective-medium model for P-wave velocities of saturated, unconsolidated saline permafrost: Geophysics, 82(3), p. EN33-EN50, illus. incl. 4 tables, 65 ref., May 2017.
To better understand the relationship between P-wave velocities and ice content in saturated, unconsolidated saline permafrost, we constructed an effective-medium model based upon ultrasonic P-wave data that were obtained from earlier laboratory studies. The model uses a two-end-member mixing approach in which an ice-filled, fully frozen end member and a water-filled, fully unfrozen end member are mixed together to form the effective medium of partially frozen sediments. This mixing approach has two key advantages: (1) It does not require parameter tuning of the mixing ratios, and (2) it inherently assumes mixed pore-scale distributions of ice that consist of frame-strengthening (i.e., cementing and/or load-bearing) ice and pore-filling ice. The model-predicted P-wave velocities agree well with our laboratory data, demonstrating the effectiveness of the model for quantitatively inferring ice content from P-wave velocities. The modeling workflow is simple and is largely free of calibration parameters - attributes that ease its application in interpreting field data sets.
2017050360 Duan Liangliang (Northeast Forestry University, School of Forestry, Harbin, China); Man Xiuling; Kurylyk, Barret L.; Cai Tijiu and Li, Qiang. Distinguishing streamflow trends caused by changes in climate, forest cover, and permafrost in a large watershed in northeastern China: Hydrological Processes, 31(10), p. 1938-1951, illus. incl. 6 tables, geol. sketch map, 80 ref., May 15, 2017.
Understanding how rivers respond to changes in land cover, climate, and subsurface conditions is critical for sustainably managing water resources and ecosystems. In this study, long-term hydrologic, climate, and satellite data (1973-2012) from the Upper Tahe River watershed (2359 km2) in the Da Hinggan Mountains of northeast China were analysed to quantify the relative hydrologic effects of climate variability (system input) and the combined influences of forest cover change and permafrost thaw (system characteristics) on average annual streamflow (system response) using 2 methods: the sensitivity-based method and the Kendall-Theil robust line method. The study period was subdivided into a forest harvesting period (1973-1987), a forest stability period (1988-2001), and a forest recovery period (2002-2012). The results indicated that the combined effects of forest harvesting and permafrost thaw on streamflow (+ 47.0 mm) from the forest harvesting period to the forest stability period was approximately twice as large as the effect associated with climate variability (+20.2 mm). Similarly, from the forest stability period to the forest recovery period, the decrease in average annual streamflow attributed to the combined effects of forest recovery and permafrost thaw (-38.0 mm) was much greater than the decrease due to climate variability (-22.2 mm). A simple method was used to separate the distinct impacts of forest cover change and permafrost thaw, but distinguishing these influences is difficult due to changes in surface and subsurface hydrologic connectivity associated with permafrost thaw. The results highlight the need to consider multiple streamflow drivers in future watershed and aquatic ecosystem management. Due to the ecological and hydrological susceptibility to disturbances in the Da Hinggan Mountains, forest harvesting will likely negatively impact ecohydrological processes in this region, and the effects of forest species transition in the forest recovery process should be further investigated. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2017049999 Mueller, Carsten W. (Technische Universitát München, Lehrstuhl für Bodenkunde, Germany); Hoeschen, Carmen; Steffens, Markus; Buddenbaum, Henning; Hinkel, Kenneth; Bockheim, James G. and Kao-Kniffin, Jenny. Microscale soil structures foster organic matter stabilization in permafrost soils: Geoderma, 293, p. 44-53, illus. incl. 3 tables, 41 ref., May 2017.
Organic carbon (OC) stored in permafrost affected soils of the higher northern latitudes is known to be highly vulnerable to ongoing climatic change. Although the ways to quantify soil OC and to study connected C dynamics from ecosystem to global scale in the Arctic has improved substantially over the last years, the basic mechanisms of OC sequestration are still not well understood. Here we demonstrate a first approach to directly study micro scale soil structures mainly responsible for soil OC (SOC) stabilization using nano scale secondary ion mass spectrometry (NanoSIMS). A cross section from a permafrost layer of a Cryosol from Northern Alaska was analysed using a cascade of imaging techniques from reflectance light microscopy (RLM) to scanning electron microscopy (SEM) to NanoSIMS. This allowed for the direct evaluation of micro scale soil structures known to be hot spots for microbial activity and SOC stabilization in temperate soils. The imaging techniques were supported by classical soil analyses. Using this unique set of techniques we are able to evidence the formation of micro-aggregate structures in the vicinity of plant residues in permafrost soils. This clearly indicates biogeochemical interfaces at plant surfaces as important spheres for the formation of more complex soil structures in permafrost soils. Organo-mineral associations from these hot spots of microbial activity were recovered from plant residues (free particulate organic matter, fPOM) as fine grained mineral fraction with a typically low C/N ratio. This nicely illustrates the link between classical bulk analysis and state of the art spectromicroscopic techniques.
2017045918 Zhang Zhongqiong (Chinese Academy of Science, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Qingbai; Gao Siru and Hou Yandong. Response of the soil hydrothermal process to difference underlying conditions in the Beiluhe permafrost region: Environmental Earth Sciences, 76(5), Article 194, illus. incl. 3 tables, sketch map, 30 ref., March 2017.
The changes in hydrothermal dynamics under different underlying conditions are the important aspect of hydrological and ecological processes, and engineering stability in permafrost regions. This study monitored the temperature and moisture of soil at a depth range from 0 to 80 cm beneath the barren, alpine steppe, and alpine meadow at the Beiluhe Basin on the Qinghai-Tibet Plateau. The freezing and thawing process and hydrothermal dynamic changes were analyzed within the test range. In a year, the freezing and thawing process controlled the pattern of hydrothermal changes. The properties of ground surface affected the hydrothermal change process in various stages. In the freeze stages, moisture and the absolute value of ground temperature showed an exponential relationship. In the thawing stages, moisture may increase, decrease, or remain stable in different temperature ranges. This process is affected by precipitation, solar radiation, and so on. At a 0-30 cm depth range, moisture increased linearly with precipitation. At 0-20 cm depth range, precipitation had a significant effect on the ground temperature changes. With the same rainfall condition, the decline of ground temperature corresponds with solar radiation flux. Results confirmed that ground properties were important factors that control the soil moisture and temperature change in the permafrost region. Copyright 2017 Springer-Verlag Berlin Heidelberg
2017050065 Rogger, M. (Vienna University of Technology, Institute for Hydraulic Engineering and Water Resources Management, Vienna, Austria); Chirico, G. B.; Hausmann, H.; Krainer, K.; Brückl, E.; Stadler, P. and Blöschl, G. Impact of mountain permafrost on flow path and runoff response in a high alpine catchment: Water Resources Research, 53(2), p. 1288-1308, illus. incl. 3 tables, 110 ref., February 2017.
Permafrost in high alpine catchments is expected to disappear in future warmer climates, but the hydrological impact of such changes is poorly understood. This paper investigates the flow paths and the hydrological response in a 5 km2 high alpine catchment in the Otztal Alps, Austria, and their changes resulting from a loss of permafrost. Spatial permafrost distribution, depth to the permafrost table, and depth to the bedrock were mapped by geophysical methods. Catchment runoff and meteorological variables were monitored from June 2008 to December 2011. These data were used along with field experience to infer conceptual schemes of the dominant flow paths in four types of hillslopes that differ in terms of their unconsolidated sediment characteristics and the presence of permafrost. The four types are: talus fans, rock glaciers, Little Ice Age (LIA) till, and pre-LIA till. Permafrost tends to occur in the first three types, but is absent from pre-LIA till. Based on these flow path concepts, runoff was simulated for present conditions and for future conditions when permafrost has completely disappeared. The simulations indicate that complete disappearance of permafrost will reduce flood peaks by up to 17% and increase runoff during recession by up to 19%. It is argued that change modeling needs to account for flow path types and their changes based on geophysical surveys and field investigations. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2017050059 Ulrich, Mathias (Leipzig University, Institute for Geography, Leipzig, Germany); Matthes, H.; Schirrmeister, L.; Schütze, J.; Park, H.; Iijima, Y. and Fedorov, A. N. Differences in behavior and distribution of permafrost-related lakes in central Yakutia and their response to climatic drivers: Water Resources Research, 53(2), p. 1167-1188, illus. incl. 2 tables, sketch map, 66 ref., February 2017.
The Central Yakutian permafrost landscape is rapidly being modified by land use and global warming, but small-scale thermokarst process variability and hydrological conditions are poorly understood. We analyze lake-area changes and thaw subsidence of young thermokarst lakes on ice-complex deposits (yedoma lakes) in comparison to residual lakes in alas basins during the last 70 years for a local study site and we record regional lake size and distribution on different ice-rich permafrost terraces using satellite and historical airborne imagery. Statistical analysis of climatic and ground-temperature data identified driving factors of yedoma- and alas-lake changes. Overall, lake area is larger today than in 1944 but alas-lake levels have oscillated greatly over 70 years, with a mean alas-lake-radius change rate of 1.6 ± 3.0 m/yr. Anthropogenic disturbance and forest degradation initiated, and climate forced rapid, continuous yedoma-lake growth. The mean yedoma lake-radius change rate equals 1.2 ± 1.0 m/yr over the whole observation period. Mean thaw subsidence below yedoma lakes is 6.2 ± 1.4 cm/yr. Multiple regression analysis suggests that winter precipitation, winter temperature, and active-layer properties are primary controllers of area changes in both lake types; summer weather and permafrost conditions additionally influence yedoma-lake growth rates. The main controlling factors of alas-lake changes are unclear due to larger catchment areas and subsurface hydrological conditions. Increasing thermokarst activity is currently linked to older terraces with higher ground-ice contents, but thermokarst activity will likely stay high and wet conditions will persist within the near future in Central Yakutian alas basins. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2017045431 Wang Junfeng (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Jia Kun; Rafique, Rashid; Guo Lei; Yu Qihao; Yue Yongyu and Yuan Chang. Changes of backfill soil of tower foundation in the permafrost regions with warm ice-rich frozen soil on the Qinghai-Tibet Plateau: Environmental Earth Sciences, 75(21), Article 1416, illus. incl. 2 tables, 30 ref., November 2016.
In permafrost regions with warm ice-rich frozen soil, the changes in backfill soil of the cast-in-place bulb pile and the precast footing are studied over 2 years. The study results show that the freezing period is longer, but the thawing period is shorter for the backfill soil compared with those at the natural control sites. Depths of permafrost table at the backfill sites decrease apparently. The freeze-thaw actions accelerate the improvement of backfill soil, especially in the middle and upper layers. The increasing rates of backfill soil compactness at 3.0 m (middle layer) and at 5.0 m (bottom layer) are the fastest (39.2 and 13.1%) and the slowest (3.4 and 1.1%), respectively. The freeze-thaw actions also improve the backfill soil moisture, especially at the bottom layer. Soil temperature, compactness and moisture are found to be the most important factors affecting the freezing intensity of backfill soil. The improvement of soil compactness and moisture contributes to enhancing the freezing intensity of backfill soil, which benefits the stability of tower foundations. The cast-in-place bulb pile, with the backfill soil characteristics of lower temperature, shorter thawed period, longer frozen period, shallower permafrost table and greater frozen intensity, is more suitable for the warm ice-rich frozen soil. Copyright 2016 Springer-Verlag Berlin Heidelberg
2017043043 Li Jing (Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Sheng Yu; Wu Jichun; Feng Ziliang; Ning Zuojun; Hu Xiaoying and Zhang Xiumin. Landform-related permafrost characteristics in the source area of the Yellow River, eastern Qinghai-Tibet Plateau: Geomorphology, 269, p. 104-111, illus. incl. 3 tables, sketch maps, 33 ref., September 15, 2016.
The source area of the Yellow River (SAYR) lies in the eastern part of the Qinghai-Tibet Plateau (QTP). Glaciers are absent in the area, but permafrost is widespread because of the high elevations, typically 4200-5000 m a.s.l. Landforms in the SAYR were classified into seven basic types, based on their morphological characteristics and genesis, and further divided into 12 sub-classes based on geomorphic processes. Permafrost development and ground temperature in boreholes were analyzed on representative landforms in the SAYR. Permafrost was discontinuously distributed at 4300-4400 m a.s.l. in fluvial plains because of variations in local topography, sediments, vegetation and water content. In hills and low-relief mountains in the western part of the study area, permafrost is continuous above 4400 m a.s.l. even on unshaded south-facing slopes. In contrast, permafrost in the central part of the study area is discontinuous over this elevation range. Analysis of ground temperature measurements revealed that three macro-scale factors, latitude, longitude, and elevation, explain 72.8% of the variation in the measured mean annual ground temperature (MAGT). The remaining 27.2% can potentially be explained by variations in topography and land cover within the SAYR.
2017044822 Liu Shengqian (China University of Geosciences, School of Energy Resources, Beijing, China); Jiang Zaixing; Liu Hui; Pang Shouji; Xia Zhongyuan; Jin Zhonghui; Wang Junhui and Wei Xiaojie. The natural-gas hydrate exploration prospects of the Nayixiong Formation in the Kaixinling-Wuli permafrost, Qinghai-Tibet Plateau: Marine and Petroleum Geology, 72, p. 179-192, illus. incl. 4 tables, geol. sketch map, 81 ref., April 2016.
Critical components of the Qinghai-Tibet Plateau natural-gas hydrate (NGH) petroleum system has been examined in this study. The results demonstrate that the Kaixinling-Wuli permafrost region contains viable prospects for gas hydrate exploration within favorable temperature and pressure stability conditions. In the study area, the average annual temperature of ground surface is -4.2°C, the thickness of permafrost ranges from 40 to 150 m (average 84 m), and the geothermal gradient beneath the permafrost is between 1.54°C/100 m and 2.67°C/100 m (average 2.03°C/100 m). The thickness of the methane-gas hydrate stability zone (GHSZ) is approximately 240-450 m. The Upper Permian Nayixiong Formation is dominated by braided delta and shallow shelf facies under mostly reducing conditions. The potential swamp deposited source rocks have a high total organic carbon (TOC) content that features a mixture of kerogen types II or III and an average vitrinite reflectance (Ro) of 2.04%. Overall, the thick sedimentary column in this region, its abundance of organic matter and its high thermal maturity suggest that the Nayixiong Formation source rocks have a high gas-generation potential. An effective fault-fracture-pore system also provides migration channels for deeper gas and also act as a reservoir for vein-type gas hydrate occurrences. The Kaixinling-Wuli area, when compared to other regions in the Qinghai-Tibet Plateau, exhibits greater gas hydrate petroleum system exploration potential as a result of the favorable temperature/pressure stability conditions and effective gas and gas-hydrate migration-storage system. Abstract Copyright (2016) Elsevier, B.V.
2017040459 Tyszkowski, Sebastian (Polish Academy of Sciences, Department of Environmental Resources and Geohazards, Torun, Poland); Kaczmarek, Halina; Slowinski, Michal; Kozyreva, Elena; Brykala, Dariusz; Rybchenko, Artiom and Babicheva, Viktoria A. Geology, permafrost, and lake level changes as factors initiating landslides on Olkhon Island (Lake Baikal, Siberia): Landslides, 12(3), p. 573-583, illus. incl. 1 table, geol. sketch map, 47 ref., June 2015.
Permafrost decline, observed in the last few decades as a result of climate change, causes an activation of cryogenic landslide processes. This study on Olkhon Island in Lake Baikal (Eastern Siberia), located within the discontinuous permafrost zone, was aimed to determine how strongly the landslide forms found there are associated with climatic conditions and if they can react to climate change. It was also important to identify which type of landslides in this area is the most sensitive indicator of the observed changes and to what extent they can react to them. For this purpose, landslides were identified, and their morphology, geological structure, and thermal parameters were assessed. The results show that the key process is the increase in thickness of the active layer, partly due to the presence of Miocene lake clays and changes in water level in Lake Baikal. Copyright 2014 Springer-Verlag Berlin Heidelberg
2017047880 Schuur, Ted (Northern Arizona University, Flagstaff, AZ). The permafrost prediction; thawing Arctic tundra will likely speed up climate change for a century or more; the question is, how drastically?: Scientific American, 315(6), p. 56-61, illus., December 2016.
2017042713 Stackhouse, Brandon T. (Princeton University, Department of Geosciences, Princeton, NJ); Vishnivetskaya, Tatiana A.; Layton, Alice; Chauhan, Archana; Pfiffner, Susan; Mykytczuk, Nadia C.; Sanders, Rebecca; Whyte, Lyle G.; Hedin, Lars; Saad, Nabil; Myneni, Satish and Onstott, Tullis C. Effects of simulated spring thaw of permafrost from mineral Cryosol on CO2 emissions and atmospheric CH4 uptake: Journal of Geophysical Research: Biogeosciences, 120(9), p. 1764-1784, illus. incl. 2 tables, 76 ref., September 2015.
Previous studies investigating organic-rich tundra have reported that increasing biodegradation of Arctic tundra soil organic carbon (SOC) under warming climate regimes will cause increasing CO2 and CH4 emissions. Organic-poor, mineral cryosols, which comprise 87% of Arctic tundra, are not as well characterized. This study examined biogeochemical processes of 1 m long intact mineral cryosol cores (1-6% SOC) collected in the Canadian high Arctic. Vertical profiles of gaseous and aqueous chemistry and microbial composition were related to surface CO2 and CH4 fluxes during a simulated spring/summer thaw under light versus dark and in situ versus water saturated treatments. CO2 fluxes attained 0.8 ± 0.4 mmol CO2 m-2 h-1 for in situ treatments, of which 85 ± 11% was produced by aerobic SOC oxidation, consistent with field observations and metagenomic analyses indicating aerobic heterotrophs were the dominant phylotypes. The Q10 values of CO2 emissions ranged from 2 to 4 over the course of thawing. CH4 degassing occurred during initial thaw; however, all cores were CH4 sinks at atmospheric concentration CH4. Atmospheric CH4 uptake rates ranged from -126 ± 77 to -207 ± 7 nmol CH4 m-2 h-1 with CH4 consumed between 0 and 35 cm depth. Metagenomic and gas chemistry analyses revealed that high-affinity Type II methanotrophic sequence abundance and activity were highest between 0 and 35 cm depth. Microbial sulfate reduction dominated the anaerobic processes, outcompeting methanogenesis for H2 and acetate. Fluxes, microbial community composition, and biogeochemical rates indicate that mineral cryosols of Axel Heiberg Island act as net CO2 sources and atmospheric CH4 sinks during summertime thaw under both in situ and water saturated states. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
2017044900 Kedzia, Stanislaw (Polska Akademia Nauk, Instytut Geografii i Przestrzennego Zagospodarowania im. Stanislawa Leszczyckiego, Warsaw, Poland). Zarys historii badan przemarzania gruntu i wieloletniej zmarzliny w polskiej czesci Tatr [An overview of the history of research on frozen ground and permafrost in the Polish Tatra Mountains]: Przeglad Geograficzny = Polish Geographical Review, 87(1), p. 53-69 (English sum.), illus., 60 ref., 2015.
2017042112 Sato, Hedison Kiuity (Universidade Federal da Bahia, Instituto de Geociencias, Salvador, Brazil) and de Souza Prates, Jose Humberto. The magnetometric resistivity method in a stratified medium having resistivities varying exponentially with depth: Geophysics, 82(3), p. E121-E127, illus., 16 ref., May 2017.
Using a known solution for the electric potential and Ampere's law, the azimuthal component of the magnetic field is deduced in a horizontally layered medium with a current point source placed anywhere, considering that the resistivity in each layer varies exponentially with depth. This theoretical result contributes to model the magnetometric resistivity method, which had been applied onshore, e.g., for mineral exploration, offshore to investigate the permafrost layer at bottom sea, hydrothermal flux, and natural resources. We have numerically tested the obtained formulation against previous results found in the literature that use distinct electrode and sensor dispositions, with models having three and four layers. Introducing the exponential variation, it verified the sensitivity to physical and geometric parameters comparing the exponential and homogeneous models.
2017050376 Larsen, A. S. (National Park Service, Yukon-Charley Rivers National Preserve and Gates of the Arctic National Park and Preserve, Fairbanks, AK); O'Donnell, J. A.; Schmidt, J. H.; Kristenson, H. J. and Swanson, D. K. Physical and chemical characteristics of lakes across heterogeneous landscapes in arctic and subarctic Alaska: Journal of Geophysical Research: Biogeosciences, 122(4), p. 989-1008, illus. incl. 3 tables, sketch map, 104 ref., April 2017.
Lakes are an important component of high-latitude regions, providing habitat for fish and wildlife and playing a critical role in biogeochemical and global carbon cycles. High-latitude lakes are sensitive to climate change, in part due to their development within permafrost soils. Considerable heterogeneity exists across arctic and subarctic landscapes, yet little is known about how this landscape variability influences chemical and physical attributes of lakes. We investigated the physical and chemical limnology of 617 lakes in Alaska's boreal forest and boreal-arctic transition zone. We categorized lakes into 10 basin types based on parent material, topography, genesis, and permafrost characteristics. Physical parameters varied across lake basin types, with the deepest lakes occurring in ice-poor glacial deposits and ice-rich terrain, while the shallowest lakes were observed in floodplain deposits and coastal lowlands. Dissolved inorganic nitrogen (N) and phosphorous (P) concentrations were generally low across all landscapes, whereas total N and P were highest in lakes underlain by ice-rich Pleistocene loess. Total N and P concentrations were significantly correlated with chlorophyll a, indicating a possible colimitation of primary productivity in these systems. Base cation concentrations helped elucidate lake basin hydrology and the relative influence of shallow versus deep groundwater inputs to surface water. Using these results, we developed a simple conceptual model for each lake and landscape type based on differences in physical and chemical parameters. Overall, we expect that the vulnerability of lake ecosystems to climate change will vary across lake basin types and will be mediated by spatial patterns in permafrost characteristics and subsurface hydrology. Abstract Copyright (2017), . The Authors.
2017050372 Zhang, Xiaowen (University of Florida, Department of Geological Sciences, Gainesville, FL); Hutchings, Jack A.; Bianchi, Thomas S.; Liu, Yina; Arellano, Ana R. and Schuur, Edward A. G. Importance of lateral flux and its percolation depth on organic carbon export in Arctic Tundra soil; implications from a soil leaching experiment: Journal of Geophysical Research: Biogeosciences, 122(4), p. 796-810, illus. incl. sketch map, 87 ref., April 2017.
Temperature rise in the Arctic is causing deepening of active layers and resulting in the mobilization of deep permafrost dissolved organic matter (DOM). However, the mechanisms of DOM mobilization from Arctic soils, especially upper soil horizons which are drained most frequently through a year, are poorly understood. Here we conducted a short-term leaching experiment on surface and deep organic active layer soils, from the Yukon River basin, to examine the effects of DOM transport on bulk and molecular characteristics. Our data showed a net release of DOM from surface soils equal to an average of 5% of soil carbon. Conversely, deep soils percolated with surface leachates retained up to 27% of bulk DOM while releasing fluorescent components (up to 107%), indicating selective release of aromatic components (e.g., lignin and tannin), while retaining nonchromophoric components, as supported by spectrofluorometric and ultrahigh-resolution mass spectroscopic techniques. Our findings highlight the importance of the lateral flux of DOM on ecosystem carbon balance as well as processing of DOM transport through organic active layer soils en route to rivers and streams. This work also suggests the potential role of leachate export as an important mechanism of C losses from Arctic soils, in comparison with the more traditional pathway from soil to atmosphere in a warming Arctic. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2017046373 Cao Bin (Lanzhou University, Key Laboratory of Western China's Environmental Systems, Lanzhou, China); Gruber, Stephan; Zhang Tingjun; Li Lili; Peng Xiaoqing; Wang Kang; Zheng Lei; Shao Wanwan and Guo Hong. Spatial variability of active layer thickness detected by ground-penetrating radar in the Qilian Mountains, western China: Journal of Geophysical Research: Earth Surface, 122(3), p. 574-591, illus. incl. 3 tables, sketch maps, 68 ref., March 2017.
The active layer plays a key role in geomorphic, hydrologic, and biogeochemical processes in permafrost regions. We conducted a systematic investigation of active layer thickness (ALT) in northeastern Qinghai-Tibetan Plateau by using ground-penetrating radar (GPR) with 100 and 200 MHz antennas. We used mechanical probing, pit, and soil temperature profiles for evaluating ALT derived from GPR. The results showed that GPR is competent for detecting ALT, and the error was ±0.08 m at common midpoint co-located sites. Considerable spatial variability of ALT owing to variation in elevation, peat thickness, and slope aspect was found. The mean ALT was 1.32 ± 0.29 m with a range from 0.81 to 2.1 m in Eboling Mountain. In Yeniu Gou, mean ALT was 2.72 ± 0.88 m and varied from 1.07 m on the north-facing slope to 4.86 m around the area near the lower boundary of permafrost. ALT in peat decreased with increasing elevation at rates of -1.31 m/km (Eboling Mountain) and -2.1 m/km (Yeniu Gou), and in mineral soil in Yeniu Gou, the rate changed to -4.18 m/km. At the same elevation, ALT on the south-facing slope was about 0.8 m thicker than that on the north-facing slopes, while the difference was only 0.18 m in peat-covered area. Within a 100 m2 area with a local elevation difference of 0.8 m, ALT varied from 0.68 m to 1.25 m. Both field monitoring and modeling studies on spatial ALT variations require rethinking of the current strategy and comprehensive design. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2017046385 Ruppel, Carolyn D. (U. S. Geological Survey, Woods Hole, MA) and Kessler, John D. The interaction of climate change and methane hydrates: Reviews of Geophysics, 55(1), p. 126-168, illus. incl. 2 tables, 368 ref., March 2017.
Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors-the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases-mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future. Abstract Copyright (2016), . The Authors.
2017043044 Colucci, R. R. (Institute of Marine Sciences Trieste, Department of Earth System Sciences and Environmental Technology, Trieste, Italy); Boccali, C.; Zebre, M. and Guglielmin, M. Rock glaciers, protalus ramparts and pronival ramparts in the southeastern Alps: Geomorphology, 269, p. 112-121, illus. incl. 1 table, sketch maps, 61 ref., September 15, 2016.
Rock glaciers and protalus ramparts are characteristic landforms of the periglacial domain often used as markers for the occurrence of permafrost in mountain terrains. As such, relict rock glaciers can be used for paleoclimate reconstructions. We present here the first previously unreported rock glacier inventory of the south-eastern Alps (including the north-eastern-most region of Italy and Slovenia), interpreted from high resolution orthophotos and a high resolution digital terrain model interpolated from airborne laser scanning (LiDAR). We mapped 53 rock glaciers covering a total area of 3.45 km2. The majority of rock glaciers are classified as relict and distributed between 1708 and 1846 m a.s.l. with slope ranging between 19° and 27°. In addition to rock glaciers we observed 66 protalus (pronival) ramparts, having median elevation of 1913 m a.s.l. and covering 0.48 km2. More than half of the inventoried protalus ramparts are located in the more maritime area of the Alps with higher precipitation compared to the location of rock glaciers. Using paleoclimate reconstruction based on the 1981-2010 climatological record of the area, we infer that the rock glaciers formed during one of the dry and cold periods of the late Pleistocene and early Holocene. Possible evolution of the active pronival forms observed in the most maritime area of this alpine sector is also discussed.
2017049772 Colombo, Nicola (Universita di Torino, Dipartimento di Scienze della Terra, Turin, Italy); Giaccone, Elisa; Paro, Luca; Buffa, Giorgio and Fratianni, Simona. The recent transition from glacial to periglacial environment in a high altitude Alpine basin (Sabbione Basin, northwestern Italian Alps); preliminary outcomes from a multidisciplinary approach: Geografia Fisica e Dinamica Quaternaria (Testo Stampato), 39(1), p. 21-36 (Italian sum.), illus. incl. 4 tables, geol. sketch map, 115 ref., 2016.
High Alps are characterised by glacial and periglacial environments, which change sensitively in response to climatic changes. The global warming that has been witnessed over the last few decades has caused remarkable effects on high altitude mountain zones. In order to assess the ongoing transition from glacial to periglacial environments, due to climate change, and its effects on cryosphere, geosphere and biosphere, a multidisciplinary approach has been applied in the Sabbione Basin (Italy). In this study, attention has mainly been paid to two selected areas (pilot sites) representative of glacial-periglacial interactions in the investigated basin. Climatological and geomorphological studies have been conducted, together with analyses on the potential permafrost distribution. Furthermore, floristic surveys have been carried out to characterise the vegetation within the periglacial sites and Artemisia genipi has been selected as the monitoring species because of its abundance and its late flowering season. The climatic analyses have indicated that, over the last decades, air temperatures have increased and snow cover duration and thickness have decreased, thus causing a substantial regression of the glaciers. Periglacial processes and new permafrost-related landforms have been developing in recently deglaciated areas. The distribution, reproductive state and phenology of the monitoring species show a clear relationship with the permafrost-related landforms (i.e. rock glaciers). Moreover, the phenological delay observed in some of the Artemisia genipi individuals shows that micro-morphology and cold water sources have a considerable influence on their development. Finally, it has been found that lower altitude plant species have been colonising the basin, indicating an upward shift due to global warming conditions.
2017046011 Mangelsdorf, Kai (German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam, Germany); Bajerski, Felizitas; Karger, Cornelia and Wagner, Dirk. Identification of a novel fatty acid in the cell membrane of Chryseobacterium frigidisoli PB4T isolated from an East Antarctic glacier forefield: Organic Geochemistry, 106, p. 68-75, illus., 41 ref., April 2017.
The cell membrane phospholipid fatty acid (PLFA) inventory of Chryseobacterium frigidisoli PB4T, a psychrotolerant, non-motile, gram-negative, aerobic bacterium isolated from ice free permafrost deposits in continental Antarctica contains a FA with a novel methyl ester mass spectrum. In a temperature cultivation experiment of C. frigidisoli at 0 °C this unknown FA was the dominant PLFA. The molecular mass indicates a C17 FA with two double bond equivalents (DBEs). A 3-pyridylcarbinol derivatization experiment as well as hydrogenation of the double bonds allowed structural assignment of the respective FA as 14-methyl-hexadeca-9,13-dienoic acid (anteiso-heptadeca-9,13-dienoic acid or ai-17:2D9,13) an unusual anteiso-w3-FA with bis-methylene interrupted double bonds (ai-17:2w3,7 or ai-17:2n-3,7). The iso-counterpart of this unsaturated FA also occurred in trace amount. The close vicinity of the w3 double bond to the anteiso branch and also to the iso branch seems to be responsible for a shift in the gas chromatography retention times of these compounds, resulting in elution shortly after the saturated counterparts. The dominance of the ai-17:2w3,7 at 0 °C cultivation temperature suggests its importance for cell membrane adaptation of C. frigidisoli with respect to low ambient temperature conditions.
2017049926 Andrieux, Eric (Université de Bordeaux, Pessac, France); Bertran, Pascal; Antoine, Pierre; Deschodt, Laurent; Lenoble, Arnaud and Coutard, Sylvie. Database of Pleistocene periglacial features in France; description of the online version: Quaternaire (Paris), 27(4), p. 329-339 (French sum.), illus., 65 ref., December 2016.
A database of Pleistocene periglacial features in France has been compiled from a review of academic literature and reports of rescue archaeology, the analysis of aerial photographs and new field surveys. Polygons, soil stripes, ice-wedge pseudomorphs, sand wedges and composite wedge pseudomorphs are included in the database together with their geographic coordinates, geological context, description and associated references. It is hoped that this database, which aim is to be integrated in broader studies, will stimulate further work on past permafrost reconstruction and will favour greater understanding of the climatic events that lead to the formation of the periglacial features. The database is available online on the AFEQ-CNF INQUA website (URL: https://afeqeng.hypotheses.org/487). A folder that contains photographs and sketches of the features is also available on request.
2017041192 Szymanski, Wojciech (Jagiellonian University, Institute of Geography and Spatial Management, Department of Pedology and Soil Geography, Cracow, Poland); Siwek, Janusz; Wascinska, Joanna and Wojtun, Bronislaw. Texture and geochemistry of surface horizons of Arctic soils from a non-glaciated catchment, SW Spitsbergen: Polish Polar Research, 37(3), p. 361-377, illus. incl. 2 tables, sketch map, 51 ref., 2016.
Physical and chemical properties of Arctic soils and especially the properties of surface horizons of the soils are very important because they are responsible for the rate and character of plant colonization, development of vegetation cover, and influence the rate and depth of thawing of soils and development of active layer of permafrost during summer. The main aim of the present study is to determine and explain the spatial diversity of selected physical and chemical properties of surface horizons of Arctic soils from the non-glaciated Fuglebekken catchment located in the Hornsund area (SW Spitsbergen) by means of geostatistical approach. Results indicate that soil surface horizons in the Fuglebekken catchment are characterized by highly variable physical and chemical properties due to a heterogeneous parent material (marine sediments, moraine, rock debris), tundra vegetation types, and non-uniform influence of seabirds. Soils experiencing the strongest influence of seabird guano have a lower pH than other soils. Soils developed on the lateral moraine of the Hansbreen glacier have the highest pH due to the presence of carbonates in the parent material and a lack or presence of a poorly developed and discontinuous A horizon. The soil surface horizons along the coast of the Hornsund exhibit the highest content of the sand fraction and SiO2. The surface of soils occurring at the foot of the slope of Ariekammen Ridge is characterized by the highest content of silt and clay fractions as well as Al2O3, Fe2O3, and K2O. Soils in the central part of the Fuglebekken catchment are depleted in CaO, MgO, and Na2O in comparison with soils in the other sampling sites, which indicates the highest rate of leaching in this part of the catchment.
2017047285 Rowley, Taylor (Texas A&M University, High Alpine and Arctic Research Program, College Station, TX); Giardino, John R.; Granados-Aguilar, Raquel and Vitek, John D. Periglacial processes and landforms in the critical zone: in Principles and dynamics of the critical zone (Giardino, John R., editor; et al.), Developments in Earth Surface Processes, 19, p. 397-447, illus. incl. sketch map, 220 ref., 2015.
2017048218 Ulven, O. I. (University of Oslo, Physics of Geological Processes, Oslo, Norway); Beinlich, A.; Hovelmann, J.; Austrheim, H. and Jamtveit, B. Subarctic physicochemical weathering of serpentinized peridotite: Earth and Planetary Science Letters, 468, p. 11-26, illus. incl. 2 tables, geol. sketch map, 76 ref., June 15, 2017.
Frost weathering is effective in arctic and subarctic climate zones where chemical reactions are limited by the reduced availability of liquid water and the prevailing low temperature. However, small scale mineral dissolution reactions are nevertheless important for the generation of porosity by allowing infiltration of surface water with subsequent fracturing due to growth of ice and carbonate minerals. Here we combine textural and mineralogical observations in natural samples of partly serpentinized ultramafic rocks with a discrete element model describing the fracture mechanics of a solid when subject to pressure from the growth of ice and carbonate minerals in surface-near fractures. The mechanical model is coupled with a reaction-diffusion model that describes an initial stage of brucite dissolution as observed during weathering of serpentinized harzburgites and dunites from the Feragen Ultramafic Body (FUB), SE-Norway. Olivine and serpentine are effectively inert at relevant conditions and time scales, whereas brucite dissolution produces well-defined cm to dm thick weathering rinds with elevated porosity that allows influx of water. Brucite dissolution also increases the water saturation state with respect to hydrous Mg carbonate minerals, which are commonly found as infill in fractures in the fresh rock. This suggests that fracture propagation is at least partly driven by carbonate precipitation. Dissolution of secondary carbonate minerals during favorable climatic conditions provides open space available for ice crystallization that drives fracturing during winter. Our model reproduces the observed cm-scale meandering fractures that propagate into the fresh part of the rock, as well as dm-scale fractures that initiate the breakup of larger domains. Rock disintegration increases the reactive surface area and hence the rate of chemical weathering, enhances transport of dissolved and particulate matter in the weathering fluid, and facilitates CO2 uptake by carbonate precipitation. Our observations have implications for element cycling and CO2 sequestration in natural gravel and mine tailings.
2017048444 Roundy, Bruce A. (Brigham Young University, Department of Plant and Wildlife Science, Provo, UT) and Madsen, Matthew D. Frost dynamics of sagebrush steppe soils: Soil Science Society of America Journal, 80(5), p. 1403-1410, illus. incl. 3 tables, 39 ref., October 2016.
Sagebrush (Artemisia spp.) steppe rangelands in the western United States are converting to weedy landscapes after large-scale wildfires. To restore ecosystem function, perennial grasses, shrubs, and forbs are sown in fall after summer wildfires or in association with mechanical fuel reduction projects. Recent research has indicated that seeds may germinate too soon after fall sowing and seedlings suffer high mortality from frost during the winter. To help determine the length of germination delay needed to avoid seedling frost mortality and to help guide frost-tolerance experiments, we analyzed fall to spring soil temperatures from 2010 to 2014 on six sagebrush-bunchgrass sites and eight woodland sites where conifers had invaded sagebrush communities. Soil temperatures were measured using thermocouples attached to microloggers, with stations placed in untreated, prescribed burned, and mechanically treated plots. Soil freezing differed with site, year of measurement, and soil depth but was relatively unaffected by fire and mechanical fuel reduction treatments. The 2-cm depth experienced much more freezing than lower depths (14-29 cm) and had >60 freeze-thaw cycles from late October into late March. Although maximum continuously frozen periods ranged from 11 to 45 d, most frost periods were <1 d long. Additional field and laboratory research is needed to determine the effects of different seed coatings on germination delay and frost dynamics on seedling mortality to best avoid frost mortality.
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2017040816 Fritz, Michael (Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Potsdam, Germany); Couture, Nicole and Lantuit, Hugues. Erosion of Arctic permafrost coasts and mobilization of dissolved organic carbon (DOC) from ground ice [abstr.]: in PAGES Goa 2013; 4th open science meeting on The past; a compass for future Earth; program and abstracts, PAGES (Past Global Changes) Open Science Meeting (OSM) - Abstract Book, 4, p. 156, February 2013. Meeting: PAGES 4th open science meeting; the past; a compass for future Earth, Feb. 13-16, 2013, Goa, India.
URL: http://pages-igbp.org/download/docs/meeting-products/abstracts/osm4ysm2/OSM2013a ...
2017040869 Ilyashuk, Boris (University of Innsbruck, Institute of Ecology, Innsbruck, Australia); Koinig, Karin; Ilyashuk, Elena; Tessadri, Richard and Psenner, Roland. Permafrost melting and ecotoxicological consequences in a periglacial lake in the Eastern Alps; answers from the past and present [abstr.]: in PAGES Goa 2013; 4th open science meeting on The past; a compass for future Earth; program and abstracts, PAGES (Past Global Changes) Open Science Meeting (OSM) - Abstract Book, 4, p. 196, February 2013. Meeting: PAGES 4th open science meeting; the past; a compass for future Earth, Feb. 13-16, 2013, Goa, India.
URL: http://pages-igbp.org/download/docs/meeting-products/abstracts/osm4ysm2/OSM2013a ...
2017040776 Rudaya, Natalia (Russian Academy of Sciences, Institute of Archaeology & Ethnography, Russian Federation); Andreev, Andrei; Wetterich, Sebastian; Tumskoy, Vladimir and Schirrmeister, Lutz. Environmental records in permafrost of east Siberian Arctic during the MIS2 stadial and the MIS3 interstadial: in PAGES Goa 2013; 4th open science meeting on The past; a compass for future Earth; program and abstracts, PAGES (Past Global Changes) Open Science Meeting (OSM) - Abstract Book, 4, p. 128-129, February 2013. Meeting: PAGES 4th open science meeting; the past; a compass for future Earth, Feb. 13-16, 2013, Goa, India.
URL: http://pages-igbp.org/download/docs/meeting-products/abstracts/osm4ysm2/OSM2013a ...
2017045148 Lee, Sung-rock (Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea) and Lee, Joo-yong. International gas hydrate research program; key findings and perspectives [abstr.]: in 35th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 35, Abstract 904, illus., 4 ref., 2016. Meeting: 35th international geological congress, Aug. 27-Sept. 4, 2016, Cape Town, South Africa.
Gas hydrates occur globally through deep-water continental margins and in areas overlain by thick permafrost deposits. Due to the growing consensus that gas hydrate resources hosted in sand-rich sediments are the technologically amenable for production, resource assessment efforts have focused on sand bearing deposits. Estimated gas-in-place in hydrate-bearing sand came up with median estimate of 43,311 tcf utilizing a petroleum system approach, which are consistent with other studies and correspond to substantial resource potential (HEI, 2011). The Asian countries including Japan, Korea, China, India have been conducting their own national gas hydrate research program since late 1990's. Main exploratory drilling campaigns have been relatively rare and have been conducted around the world, especially in Asia and North America (Collett, 2014). Academic projects have also been conducted in the U.S., notably the ODP and IODP Legs in North American offshore areas. The most important research sites and areas are highlighted in Mallik (Canada), Alaska North Slope (US), Blake Ridge and Cascadia (ODP & IODP), Gulf of Mexico (JIP, US), Nankai Trough (MH21, Japan), Ulleung Basin (UBGH, Korea), Indian Ocean (NGHP, India), Shenhu Basin (GMGS, China), Gumusut-Kakap (Malaysia), New Zealand, Taiwan, and so on(Fig.1). The recently launched MIGRATE project in European countries also deserves attention. Notably Arctic Mallik production test in Canada was the first dedicated hydrate-research site, and the location of a thermal-stimulation test in 2002 and depressurization test in 2007-2008. And the first and only CO2-injected field production trial was conducted in 2012 in the Alaska Ignik Sikumi site operated by ConocoPhillips. For marine gas hydrates, the world's first offshore production test was successfully conducted in 2013 using depressurization method in Nankai Trough, Japan. It is expected that 2nd production test will be performed in early 2017 in Nankai Trough for a month operation with much improved production technologies of depressurization method (MH21, 2014). Gas hydrate production raises significant operational challenges in sand-rich sediments which will arise from dissociation. The challenges will be concerned with produced water discharge, stimulation, flow assurance, geomechanical stability, sand control, subsurface monitoring, and etc. And the long-duration field production tests are the next prerequisite for assessing production profiles. But early commercial production is likely to come from Asia when less gas availability and higher gas prices (SBC, 2015).
2017046056 Martin, Eileen Rose (Stanford University, Stanford, CA); Dou, Shan; Lindsey, Nate; Chang, Jason P.; Biondi, Biondo C.; Ajo Franklin, Jonathan Blair; Wagner, Anna M.; Bjella, Kevin; Daley, Thomas M.; Freifeld, Barry M.; Robertson, Michelle; Ulrich, Craig and Williams, Ethan F. Analysis and attenuation of artifacts caused by spatially and temporally correlated noise sources in Green's function estimates [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract S13B-2550, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.
Localized strong sources of noise in an array have been shown to cause artifacts in Green's function estimates obtained via cross-correlation. Their effect is often reduced through the use of cross-coherence. Beyond independent localized sources, temporally or spatially correlated sources of noise frequently occur in practice but violate basic assumptions of much of the theory behind ambient noise Green's function retrieval. These correlated noise sources can occur in urban environments due to transportation infrastructure, or in areas around industrial operations like pumps running at CO2 sequestration sites or oil and gas drilling sites. Better understanding of these artifacts should help us develop and justify methods for their automatic removal from Green's function estimates. We derive expected artifacts in cross-correlations from several distributions of correlated noise sources including point sources that are exact time-lagged repeats of each other and Gaussian-distributed in space and time with covariance that exponentially decays. Assuming the noise distribution stays stationary over time, the artifacts become more coherent as more ambient noise is included in the Green's function estimates. We support our results with simple computational models. We observed these artifacts in Green's function estimates from a 2015 ambient noise study in Fairbanks, AK where a trenched distributed acoustic sensing (DAS) array was deployed to collect ambient noise alongside a road with the goal of developing a permafrost thaw monitoring system. We found that joints in the road repeatedly being hit by cars travelling at roughly the speed limit led to artifacts similar to those expected when several points are time-lagged copies of each other. We also show test results of attenuating the effects of these sources during time-lapse monitoring of an active thaw test in the same location with noise detected by a 2D trenched DAS array.
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