Permafrost Monthly Alerts (PMAs)

2018057262 Fu Qiang (Northeast Agricultural University, School of Water Conservancy & Civil Engineering, Harbin, China); Hou Renjie; Li Tianxiao; Wang Min and Yan Jiawen. The functions of soil water and heat transfer to the environment and associated response mechanisms under different snow cover conditions: Geoderma, 325, p. 9-17, illus. incl. 5 tables, sketch map, 33 ref., September 1, 2018.

This study investigates the response mechanisms between soil water-heat transfer and environmental factors during freeze-thaw periods and establishes soil water-heat transfer functions in a cold region. Based on field-measured values of soil temperature and liquid-phase water content collected at an automatic weather station in the black soil area of the Songnen plain, the influence of the cumulative negative temperature on the soil freezing depth was analyzed under different snow cover conditions. A gray correlation analysis method was used to screen the environmental factors and determine those with the most influence on changes in soil water-heat transfer processes. Then, soil water-heat transfer functions were established between the selected environmental factors and soil temperature, the liquid-phase soil water content. The results showed that during the freezing and thawing period, snow cover hindered the effects of the cumulative temperature on the thickness of the frozen soil layer. Additionally, the time of occurrence of the maximum freezing depth under natural snow (NS), compacted snow (CS) and thickened snow (TS) treatments was delayed 7, 12 and 20 days, respectively, compared with that under bare land (BL). The correlation between atmospheric temperature, total radiation and soil temperature was relatively high, and this effect decreased with the increasing of snow cover. The main driving factors of variations in the liquid-phase water content were ambient humidity and saturated vapor pressure, and the effects of these factors decreased with increasing soil depth and snow cover thickness, similarly. In the active frozen layer, the correlation coefficients of the soil water-heat transfer functions were relatively high, and the function model can be tested by the significance (P < 0.05) test. However, the R² values of functions below the active layer were relatively low, and the soil water-heat transfer in the area below the active layer was less affected by the environment. This study reveals the characteristics of energy transfer and mass transfer in a composite system of atmospheric factors and frozen soil under snow cover conditions. It provides a reference for accurate forecasting and the efficient utilization of soil water and heat resources in cold and arid regions.

DOI: 10.1016/j.geoderma.2018.03.022

2018055444 Jutebring Sterte, Elin (Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umea, Sweden); Johansson, Emma; Sjoberg, Ylva; Huseby Karlsen, Reinert and Laudon, Hjalmar. Ground water-surface water interactions across scales in a boreal landscape investigated using a numerical modelling approach: Journal of Hydrology, 560, p. 184-201, illus. incl. 7 tables, sketch map, 66 ref., May 2018. Includes appendices.

Groundwater and surface-water interactions are regulated by catchment characteristics and complex inter- and intra-annual variations in climatic conditions that are not yet fully understood. Our objective was to investigate the influence of catchment characteristics and freeze-thaw processes on surface and groundwater interactions in a boreal landscape, the Krycklan catchment in Sweden. We used a numerical modelling approach and sub-catchment evaluation method to identify and evaluate fundamental catchment characteristics and processes. The model reproduced observed stream discharge patterns of the 14 sub-catchments and the dynamics of the 15 groundwater wells with an average accumulated discharge error of 1% (15% standard deviation) and an average groundwater-level mean error of 0.1 m (0.23 m standard deviation). We show how peatland characteristics dampen the effect of intense rain, and how soil freeze-thaw processes regulate surface and groundwater partitioning during snowmelt. With these results, we demonstrate the importance of defining, understanding and quantifying the role of landscape heterogeneity and sub-catchment characteristics for accurately representing catchment hydrological functioning.

DOI: 10.1016/j.jhydrol.2018.03.011

2018055445 Wang Weihua (Northwest Institute of Eco-Environment and Resources, Cryosphere Research Station on the Qinghai-Tibet Plateau, Lanzhou, China); Wu Tonghua; Zhao Lin; Li Ren; Zhu Xiaofan; Wang Wanrui; Yang Shuhua; Qin Yanhui and Hao Junmin. Exploring the ground ice recharge near permafrost table on the central Qinghai-Tibet Plateau using chemical and isotopic data: Journal of Hydrology, 560, p. 220-229, illus. incl. 5 tables, sketch map, 81 ref., May 2018.

Thawing permafrost on the Qinghai-Tibet Plateau (QTP) has great impacts on the local hydrological process by way of causing ground ice to thaw. Until now there is little knowledge on ground ice hydrology near permafrost table under a warming climate. This study applied stable tracers (isotopes and chloride) and hydrograph separation model to quantify the sources of ground ice near permafrost table in continuous permafrost regions of the central QTP. The results indicated that the ground ice near permafrost table was mainly supplied by active layer water and permafrost water, accounting for 58.9 to 87.0% and 13.0 to 41.1%, respectively, which implying that the active layer was the dominant source. The contribution rates from the active layer to the ground ice in alpine meadow (59 to 69%) was less than that in alpine steppe (70 to 87%). It showed well-developed hydrogeochemical depth gradients, presenting depleted isotopes and positive chemical gradients with depth within the soil layer. The effects of evaporation and freeze-out fractionation on the soil water and ground ice were evident. The results provide additional insights into ground ice sources and cycling near permafrost table in permafrost terrain, and would be helpful for improving process-based detailed hydrologic models under the occurring global warming.

DOI: 10.1016/j.jhydrol.2018.03.032

2018055812 Zhang Xuanwen (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Liu Xiaohong; Wang Wenzhi; Zhang Tingjun; Zeng Xiaomin; Xu Guobao; Wu Guoju and Kang Huhu. Spatiotemporal variability of drought in the northern part of northeast China: Hydrological Processes, 32(10), p. 1449-1460, illus. incl. 1 table, sketch map, 66 ref., May 15, 2018.

The thermal and moisture balance of permafrost regions has been altered by global warming, profoundly influencing vegetation dynamics and forest carbon cycling. To understand the spatial and temporal characteristics and driving forces responsible for changes in moisture conditions in the permafrost region of the Greater and Lesser Hinggan Mountains, northeastern China, we assessed long-term trends for temperature, precipitation, and the standardized precipitation-evapotranspiration index. From 1951 to 2014, annual mean temperature had a significant increase trend and the annual precipitation was not with significant trend. Since 1951, the annual standardized precipitation-evapotranspiration index has decreased significantly at the boundary between regions with seasonal soil freezing and permafrost, suggesting that conspicuous permafrost degradation and moisture loss has occurred. The study area can be divided into 4 parts with a different balance between thermal and moisture conditions: the northern Songnen Plains, the Hulun Buir Sand Land, the middle reaches of the Heilongjiang River, and the Mohe region. However, only the middle reaches of the Heilongjiang River showed an obvious long-term drying trend. The 4 areas showed quasi-periodic oscillation and sea surface temperature during the winter half-year affected drought intensity in the northern of Songnen Plains. When El Nino strengthened, moisture conditions increased in the northern of Songnen Plains, whereas stronger La Nina events decreased water availability. The result of this study will be beneficial for regional water resource management and prepare for potential drought hazards in the northeastern China. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.11503

2018055829 Lyu, Zhou (Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN) and Zhuang, Qianlai. Quantifying the effects of snowpack on soil thermal and carbon dynamics of the arctic terrestrial ecosystems: Journal of Geophysical Research: Biogeosciences, 123(4), p. 1197-1212, illus. incl. 4 tables, 86 ref., April 2018.

Snow insulation effects modify soil and carbon dynamics in northern middle to high latitudes (45°-90°N). This study incorporates these effects by introducing a snow model into an existing soil thermal model in a biogeochemistry modeling framework, the Terrestrial Ecosystem Model. The coupled model is used to quantify snow insulation effects on carbon and soil thermal dynamics in 45°-90°N region for the historical period (2003-2010) and the future period (2017-2099) under two climate scenarios. The revised model captures the snow insulation effects and improves the estimates of soil thermal dynamics and the land freeze-thaw as well as terrestrial ecosystem carbon dynamics. Historical mean cold-season soil temperature at 5 cm depth driven with satellite-based snow data is 6.4°C warmer in comparison with the original model simulation. Frozen area in late spring is estimated to shrink mainly over eastern Siberia, in central to eastern Europe, and along southern Canada in November. During each nongrowing season in the historical period, 0.41 Pg more soil C is released due to warmer soil temperature estimated using the new model. During 2003-2010, the revised model estimates that the region accumulated 0.86 Pg less C due to weaker gross primary production, leading to a regional C loss at 0.19 PgC/year. The revised model projects that the region will lose 38-51% permafrost area by 2100 and continue to be a C source under the low-emission scenario (Representative Concentration Pathway 2.6) but to be gradually transitioning into a weak sink in the latter half of the 21st century under the high-emission scenario (Representative Concentration Pathway 8.5). Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JG003864

2018059543 O'Neill, H. Brendan (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Norway) and Christiansen, Hanne H. Detection of ice wedge cracking in permafrost using miniature accelerometers: Journal of Geophysical Research: Earth Surface, 123(4), p. 642-657, illus. incl. 3 tables, sketch map, 56 ref., April 2018.

Determining the exact timing of ice wedge cracking in permafrost is challenging. Five miniature accelerometers were installed near the ground surface in the trough of a primary ice wedge within a network of low-centered polygons in Adventdalen, Svalbard, to test whether these instruments could be used to detect dynamics of thermal contraction cracking. Data from 2003 to 2013 were analyzed to characterize cryoseismic signals in the ice wedge trough. High-magnitude accelerations (from 5 g to at least 100 g) were typically registered in late winter, when the top of permafrost had cooled to about -10°C; these likely correspond to ice wedge cracking in permafrost. Tensile stresses calculated from temperatures measured in the ice wedge trough are near laboratory strengths reported for ice and mineral active layer sediments, supporting the interpretation that large accelerations are caused by thermal contraction cracking. Lower magnitude accelerations occurred throughout the freezing season, usually coinciding with rapid cooling at the ground surface. These small accelerations may be associated with (i) the initiation of small cracks in the active layer of the trough or (ii) the horizontal and vertical propagation of existing ice wedge cracks. The results of this investigation indicate that miniature accelerometers are an effective, inexpensive, and simple method to determine the timing of ice wedge cracking and rates of crack propagation along ice wedge troughs. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JF004343

2018055834 Wu, Yuxin (Lawrence Berkeley National Laboratory, Climate and Ecosystem Sciences Division, Berkeley, CA); Ulrich, Craig; Kneafsey, Timothy J.; Lopez, Robin; Chou, Chunwei; Geller, Jil; McKnight, Katie; Dafflon, Baptiste; Soom, Florian; Peterson, John and Hubbard, Susan S. Depth-resolved physicochemical characteristics of active layer and permafrost soils in an arctic polygonal tundra region: Journal of Geophysical Research: Biogeosciences, 123(4), p. 1366-1386, illus. incl. 3 tables, 111 ref., April 2018.

Permafrost physicochemical parameters play a key role in controlling the response of permafrost carbon to climate change. We studied the physicochemical parameters of permafrost in an Arctic tundra region to evaluate (1) how soil parameters vary with depth and whether and how they are interrelated, (2) whether and how permafrost soil differs from its overlaying active layer, and (3) whether soil property-depth relationships are different across geomorphic features (e.g., low, flat, and high centered polygons). We also explored the possible biogeochemical processes that led to these soil characteristics and how they may affect biogeochemical reactions upon permafrost thaw. We observed (1) consistent relationships between soil property and depth and between major parameters, (2) large contrasts of key soil parameters between active layer and permafrost, indicative of potentially different response of the permafrost carbon to warming when compared to the active layer, and (3) a correlation between soil hydraulic conductivity and topographic features that impacts soil hydrologic processes. Our analysis suggests that the permafrost has a marine-derived chemical signature that differs from the active layer and shapes the physicochemical fingerprints of the different geomorphic features. Specifically, we revealed the unique signatures of the high center polygons, indicative of possible microbial activity at depth (>1 m). Our study suggested consistent key soil parameter-depth correlations while demonstrating complex lateral and vertical variabilities. These results are valuable for identifying approaches to upscale point-based measurements and for improving model parameterization to predict permafrost carbon behavior and feedback under future climate. Abstract Copyright (2018), . The Authors.

DOI: 10.1002/2018JG004413

2018057304 Evans, Sarah G. (Appalachian State University, Department of Geological and Environmental Sciences, Boone, NC); Ge, Shemin; Voss, Clifford I. and Molotch, Noah P. The role of frozen soil in groundwater discharge predictions for warming alpine watersheds: Water Resources Research, 54(3), p. 1599-1615, illus. incl. sketch map, 77 ref., March 2018.

Climate warming may alter the quantity and timing of groundwater discharge to streams in high alpine watersheds due to changes in the timing of the duration of seasonal freezing in the subsurface and snowmelt recharge. It is imperative to understand the effects of seasonal freezing and recharge on groundwater discharge to streams in warming alpine watersheds as streamflow originating from these watersheds is a critical water resource for downstream users. This study evaluates how climate warming may alter groundwater discharge due to changes in seasonally frozen ground and snowmelt using a 2-D coupled flow and heat transport model with freeze and thaw capabilities for variably saturated media. The model is applied to a representative snowmelt-dominated watershed in the Rocky Mountains of central Colorado, USA, with snowmelt time series reconstructed from a 12 year data set of hydrometeorological records and satellite-derived snow covered area. Model analyses indicate that the duration of seasonal freezing in the subsurface controls groundwater discharge to streams, while snowmelt timing controls groundwater discharge to hillslope faces. Climate warming causes changes to subsurface ice content and duration, rerouting groundwater flow paths but not altering the total magnitude of future groundwater discharge outside of the bounds of hydrologic parameter uncertainties. These findings suggest that frozen soil routines play an important role for predicting the future location of groundwater discharge in watersheds underlain by seasonally frozen ground. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017WR022098

2018057322 Lininger, Katherine B. (Colorado State University, Department of Geosciences, Fort Collins, CO); Wohl, E. and Rose, J. R. Geomorphic controls on floodplain soil organic carbon in the Yukon Flats, interior Alaska, from reach to river basin scales: Water Resources Research, 54(3), p. 1934-1951, illus. incl. 1 table, 92 ref., March 2018.

Floodplains accumulate and store organic carbon (OC) and release OC to rivers, but studies of floodplain soil OC come from small rivers or small spatial extents on larger rivers in temperate latitudes. Warming climate is causing substantial change in geomorphic process and OC fluxes in high latitude rivers. We investigate geomorphic controls on floodplain soil OC concentrations in active-layer mineral sediment in the Yukon Flats, interior Alaska. We characterize OC along the Yukon River and four tributaries in relation to geomorphic controls at the river basin, segment, and reach scales. Average OC concentration within floodplain soil is 2.8% (median = 2.2%). Statistical analyses indicate that OC varies among river basins, among planform types along a river depending on the geomorphic unit, and among geomorphic units. OC decreases with sample depth, suggesting that most OC accumulates via autochthonous inputs from floodplain vegetation. Floodplain and river characteristics, such as grain size, soil moisture, planform, migration rate, and riverine DOC concentrations, likely influence differences among rivers. Grain size, soil moisture, and age of surface likely influence differences among geomorphic units. Mean OC concentrations vary more among geomorphic units (wetlands = 5.1% versus bars = 2.0%) than among study rivers (Dall River = 3.8% versus Teedrinjik River = 2.3%), suggesting that reach-scale geomorphic processes more strongly control the spatial distribution of OC than basin-scale processes. Investigating differences at the basin and reach scale is necessary to accurately assess the amount and distribution of floodplain soil OC, as well as the geomorphic controls on OC. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017WR022042

2018059814 Sun Zhizhong (Chinese Academy of Sciences, Cold and Arid Regions Environmental Research Institute, Lanzhou, China); Ma Wei; Zhang Shujuan; Wen Zhi and Wu Guilong. Embankment stability of the Qinghai-Tibet Railway in permafrost regions: Journal of Cold Regions Engineering, 32(1), March 2018. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000153

2018055767 Wang Yinghui (Shanghai Ocean University, Shanghai Engineering Research Center of Hadal Science and Technology, Shanghai, China); Xu Yunping; Spencer, Robert G. M.; Zito, Phoebe; Kellerman, Anne; Podgorski, David; Xiao Wenjie; Wei Dandan; Rashid, Harunur and Yang Yuanhe. Selective leaching of dissolved organic matter from alpine permafrost soils on the Qinghai-Tibetan Plateau: Journal of Geophysical Research: Biogeosciences, 123(3), p. 1005-1016, illus. incl. 3 tables, 62 ref., March 2018.

Ongoing global temperature rise has caused significant thaw and degradation of permafrost soils on the Qinghai-Tibetan Plateau (QTP). Leaching of organic matter from permafrost soils to aquatic systems is highly complex and difficult to reproduce in a laboratory setting. We collected samples from natural seeps of active and permafrost layers in an alpine swamp meadow on the QTP to shed light on the composition of mobilized dissolved organic matter (DOM) by combining optical measurements, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry, radiocarbon (¹⁴C), and solid-state ¹³C nuclear magnetic resonance spectroscopy. Our results show that even though the active layer soils contain large amounts of proteins and carbohydrates, there is a selective release of aromatic components, whereas in the deep permafrost layer, carbohydrate and protein components are preferentially leached during the thawing process. Given these different chemical characteristics of mobilized DOM, we hypothesize that photomineralization contributes significantly to the loss of DOM that is leached from the seasonally thawed surface layer. However, with continued warming, biodegradation will become more important since biolabile materials such as protein and carbohydrate are preferentially released from deep-layer permafrost soils. This transition in DOM leachate source and associated chemical composition has ramifications for downstream fluvial networks on the QTP particularly in terms of processing of carbon and associated fluxes. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JG004343

2018059810 Zhang Xiong (Missouri University of Science and Technology, Department of Civil, Architectural and Environmental Engineering, Rolla, MO); Li Lin; McHattie, Robert and Oswell, Jim. Experimental study of ice-rich permafrost cut slope protection: Journal of Cold Regions Engineering, 32(1), March 2018. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000149

2018054086 Couture, Nicole J. (Canadian Geological Survey, Ottawa, ON, Canada); Irrgang, Anna; Pollard, Wayne; Lantuit, Hugues and Fritz, Michael. Coastal erosion of permafrost soils along the Yukon coastal plain and fluxes of organic carbon to the Canadian Beaufort Sea: Journal of Geophysical Research: Biogeosciences, 123(2), p. 406-422, illus. incl. 3 tables, sketch maps, 111 ref., February 2018.

Reducing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from coastal erosion. Different terrain units were assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, SOC contents were reduced by 19% and sediment contents by 16%. The SOC content in a 1 m² column of soil varied according to the height of the bluff, ranging from 30 to 662 kg, with a mean value of 183 kg. Forty-four per cent of the SOC was within the top 1 m of soil and values varied based on surficial materials, ranging from 30 to 53 kg C/m³, with a mean of 41 kg. Eighty per cent of the shoreline was erosive with a mean annual rate of change of -0.7 m/yr. This resulted in a SOC flux per meter of shoreline of 132 kg C/m/yr, and a total flux for the entire 282 km of the Yukon coast of 35.5 ´ 10⁶ kg C/yr (0.036 Tg C/yr). The mean flux of sediment per meter of shoreline was 5.3 ´ 10³ kg/m/yr, with a total flux of 1,832 ´ 10⁶ kg/yr (1.832 Tg/yr). Sedimentation rates indicate that approximately 13% of the eroded carbon was sequestered in nearshore sediments, where the overwhelming majority of organic carbon was of terrestrial origin. Abstract Copyright (2018), . American Geophysical Union and Her Majesty the Queen in Right of Canada. Reproduced with the permission of the Minister of Natural Resources Canada.

DOI: 10.1002/2017JG004166

2018054084 Faucherre, Samuel (University of Copenhagen, Center for Permafrost, Copenhagen, Denmark); Jorgensen, Christian Juncher; Blok, Daan; Weiss, Niels; Siewert, Matthias Benjamin; Bang-Andreasen, Toke; Hugelius, Gustaf; Kuhry, Peter and Elberling, Bo. Short and long-term controls on active layer and permafrost carbon turnover across the Arctic: Journal of Geophysical Research: Biogeosciences, 123(2), p. 372-390, illus. incl. 2 tables, 83 ref., February 2018.

Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (C_loss) five times during a 1 year incubation. The incubated material consisted of near-surface active layer (AL_NS), subsurface active layer (AL_SS), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, d¹³C, d¹⁵N, and dry bulk density (DBD). While no significant differences were observed between total AL_SS and permafrost C_loss over 1 year incubation (2.3 ± 2.4% and 2.5 ± 1.5% C_loss, respectively), AL_NS samples showed higher C_loss (7.9 ± 4.2%). DBD was the best explanatory parameter for active layer C_loss across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial C_loss between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO₂ production by providing representative mean values of CO₂ production rates and identifying standard parameters or proxies for upscaling potential CO₂ production from site to regional scales. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JG004069

2018057247 Schuster, Paul F. (U. S. Geological Survey, National Research Program, Boulder, CO); Schaefer, Kevin M.; Aiken, George R.; Antweiler, Ronald C.; Dewild, John F.; Gryziec, Joshua D.; Gusmeroli, Alessio; Hugelius, Gustaf; Jafarov, Elchin; Krabbenhoft, David P.; Liu Lin; Herman-Mercer, Nicole; Mu Cuicui; Roth, David A.; Schaefer, Tim; Striegl, Robert G.; Wickland, Kimberly P. and Zhang Tingjun. Permafrost stores a globally significant amount of mercury: Geophysical Research Letters, 45(3), p. 1463-1471, illus. incl. 1 table, 60 ref., February 16, 2018.

Changing climate in northern regions is causing permafrost to thaw with major implications for the global mercury (Hg) cycle. We estimated Hg in permafrost regions based on in situ measurements of sediment total mercury (STHg), soil organic carbon (SOC), and the Hg to carbon ratio (R_HgC) combined with maps of soil carbon. We measured a median STHg of 43 ± 30 ng Hg g soil^-1 and a median R_HgC of 1.6 ± 0.9 mg Hg g C^-1, consistent with published results of STHg for tundra soils and 11,000 measurements from 4,926 temperate, nonpermafrost sites in North America and Eurasia. We estimate that the Northern Hemisphere permafrost regions contain 1,656 ± 962 Gg Hg, of which 793 ± 461 Gg Hg is frozen in permafrost. Permafrost soils store nearly twice as much Hg as all other soils, the ocean, and the atmosphere combined, and this Hg is vulnerable to release as permafrost thaws over the next century. Existing estimates greatly underestimate Hg in permafrost soils, indicating a need to reevaluate the role of the Arctic regions in the global Hg cycle. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL075571

2018050543 Kutasov, Izzy M. (BYG Consulting Company, Boston, MA) and Eppelbaum, Lev V. Utilization of the Horner plot for determining the temperature of frozen formations; a novel approach: Geothermics, 71, p. 259-263, illus. incl. 4 tables, 22 ref., January 2018.

The most important data on the thermal regime of the Earth's interior come from temperature measurements in deep boreholes. The drilling process greatly alters the temperature field of formations surrounding the wellbore. In permafrost regions, due to thawing of the formation surrounding the wellbore during drilling, representative data can be obtained only by repeated observations over a long period of time (up to 10 years). Usually a number of temperature logs (3-10) are taken after the well's shut-in. Significant expenses are required to monitor the temperature regime of deep wells. In this paper, we introduce a new approach in predicting the undisturbed formations temperatures from shut-in temperature logs in deep wells. The main features of the suggested method are following: the refreezing of the thawed formations (around the wellbore) is completed, the temperature logs are taken after refreezing, the starting point in the well thermal recovery is moved from the end of well completion to the moment of time when the first shut-in temperature log was conducted. It is shown that after refreezing the further cooling of a well can be approximated by a constant (per unit of length) linear heat source. Hence, the Horner equation can be used for predicting the temperature of frozen formations for estimation of the formation temperature. A simple method to process field temperature data is presented. To demonstrate this approach, temperature shut-in time data for four depths from four wells in Alaska were successfully used.

DOI: 10.1016/j.geothermics.2017.10.005

2018050573 Wei Rongqiang (Chinese Academy of Sciences, Key Laboratory of Computational Geodynamics, Beijing, China); Zeng Qingli; Davies, Tim; Yuan Guangxiang; Wang Kaiyang; Xue Xinyu and Yin Qianfeng. Geohazard cascade and mechanism of large debris flows in Tianmo gully, SE Tibetan Plateau and implications to hazard monitoring: Engineering Geology, 233, p. 172-182, illus. incl. sect., geol. sketch maps, 66 ref., January 31, 2018.

Alpine glaciers and permafrost are sensitive to climate change, and their degradation due to annual temperature increasing has already induced many mass movements such as debris flows. On September 4 of 2007, July 25-31 and September 5-8 of 2010, three large debris flows took place in Tianmo gully, a left-bank tributary of Parlung River, southeast Tibetan Plateau. The debris flows blocked the river, and a section of highway 450 m long including a bridge 76 m long were destroyed by the subsequent outburst flood. This paper, based on post-event investigations, witness accounts, news reports and satellite image interpretation, systematically analyses the geo-environments, climate conditions and sources of these debris flow events. Their differences in flow process, surge numbers and velocity suggest that they resulted from different geohazard processes, cascades and initiation mechanisms. The 2007 debris flow originated from a bare rock/moraine collapse next to the cirque due to strong alternation of wet and dry conditions. The mass moved down the gully with velocity of 30-40 m/s estimated by back-calculation using superelevation and run-up. It entrained moraine, avalanched snow-ice and water from the channel, and transformed into high-speed debris flow, crossing the Parlung River and finally depositing onto the highway. The other two events in July and September of 2010 initiated from two channel-bank landslides triggered by melt-water and concentrated rainfall, which dammed the channel. The subsequent landslide dam failure generated debris flows over several days, with velocities of 12-14 m/s, that temporally blocked Parlung River. The initiation mechanisms of most large debris flows recorded in Parlung region are similar to the events in Tianmo gully, originating either from rock/moraine avalanches or from the collapse of a landslide dam. This implies that the periglacial degradation of bedrock and moraine is the key process to be monitored and assessed under climate warming. The paper applies the geohazard mechanisms and cascade to hazard monitoring in order to protect the existing Sichuan-Tibet highway and the forthcoming railway.

DOI: 10.1016/j.enggeo.2017.12.013

2018053881 Wlostowski, A. N. (University of Colorado at Boulder, Institute of Arctic and Alpine Research, Boulder, CO); Gooseff, M. N. and Adams, B. J. Soil moisture controls the thermal habitat of active layer soils in the McMurdo dry valleys, Antarctica: Journal of Geophysical Research: Biogeosciences, 123(1), p. 46-59, illus. incl. 2 tables, 60 ref., January 2018.

Antarctic soil ecosystems are strongly controlled by abiotic habitat variables. Regional climate change in the McMurdo Dry Valleys is expected to cause warming over the next century, leading to an increase in frequency of freeze-thaw cycling in the soil habitat. Previous studies show that physiological stress associated with freeze-thaw cycling adversely affects invertebrate populations by decreasing abundance and positively selecting for larger body sizes. However, it remains unclear whether or not climate warming will indeed enhance the frequency of annual freeze-thaw cycling and associated physiological stresses. This research quantifies the frequency, rate, and spatial heterogeneity of active layer freezing to better understand how regional climate change may affect active layer soil thermodynamics, and, in turn, affect soil macroinvertebrate communities. Shallow active layer temperature, specific conductance, and soil moisture were observed along natural wetness gradients. Field observations show that the frequency and rate of freeze events are nonlinearly related to freezable soil moisture (q_f). Over a 2 year period, soils at q_f < 0.080 m³/m³ experienced between 15 and 35 freeze events and froze rapidly compared to soils with q_f > 0.080 m³/m³, which experienced between 2 and 6 freeze events and froze more gradually. A numerical soil thermodynamic model is able to simulate observed freezing rates across a range of q_f, reinforcing a well-known causal relationship between soil moisture and active layer freezing dynamics. Findings show that slight increases in soil moisture can potentially offset the effect of climate warming on exacerbating soil freeze-thaw cycling. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JG004018

2018053875 Grant, R. F. (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Mekonnen, Z. A.; Riley, W. J.; Wainwright, H. M.; Graham, D. and Torn, M. S. Mathematical modelling of arctic polygonal tundra with Ecosys; 1, Microtopography determines how active layer depths respond to changes in temperature and precipitation: Journal of Geophysical Research: Biogeosciences, 122(12), p. 3161-3173, illus. incl. 5 tables, 53 ref., December 2017.

Microtopographic variation that develops among features (troughs, rims, and centers) within polygonal landforms of coastal arctic tundra strongly affects movement of surface water and snow and thereby affects soil water contents (q) and active layer depth (ALD). Spatial variation in ALD among these features may exceed interannual variation in ALD caused by changes in climate and so needs to be represented in projections of changes in arctic ALD. In this study, increases in near-surface q with decreasing surface elevation among polygon features at the Barrow Experimental Observatory (BEO) were modeled from topographic effects on redistribution of surface water and snow and from lateral water exchange with a subsurface water table during a model run from 1981 to 2015. These increases in q caused increases in thermal conductivity that in turn caused increases in soil heat fluxes and hence in ALD of up to 15 cm with lower versus higher surface elevation which were consistent with increases measured at BEO. The modeled effects of q caused interannual variation in maximum ALD that compared well with measurements from 1985 to 2015 at the Barrow Circumpolar Active Layer Monitoring (CALM) site (R² = 0.61, RMSE = 0.03 m). For higher polygon features, interannual variation in ALD was more closely associated with annual precipitation than mean annual temperature, indicating that soil wetting from increases in precipitation may hasten permafrost degradation beyond that caused by soil warming from increases in air temperature. This degradation may be more rapid if increases in precipitation cause sustained wetting in higher features. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JG004035

2018059268 Karelin, D. V. (Lomonosov Moscow State University, Moscow, Russian Federation); Goryachkin, S. V.; Zamolodchikov, D. G.; Dolgikh, A. V.; Zazovskaya, E. P.; Shishkov, V. A. and Kraev, G. N. Human footprints on greenhouse gas fluxes in cryogenic ecosystems: Doklady Earth Sciences, 477(2), p. 1467-1469, illus., 9 ref., December 2017.

Various human footprints on the flux of biogenic greenhouse gases from permafrost-affected soils in Arctic and boreal domains in Russia are considered. Tendencies of significant growth or suppression of soil CO₂ fluxes change across types of human impact. Overall, the human impacts increase the mean value and variance of local soil CO₂ flux. Human footprint on methane exchange between soil and atmosphere is mediated by drainage. However, all the types of human impact suppress the sources and increase sinks of methane to the land ecosystems. N₂O flux grew under the considered types of human impact. Based on the results, we suggest that human footprint on soil greenhouse gases fluxes is comparable to the effect of climate change at an annual to decadal timescales. Copyright 2017 Pleiades Publishing, Ltd.

DOI: 10.1134/S1028334X17120133

2018050936 Liu, Yong (National University of Singapore, Department of Civil and Environmental Engineering, Singapore, Singapore); Hu Jun; Xiao, Huawen and Chen, Elton J. Effects of material and drilling uncertainties on artificial ground freezing of cement-admixed soils: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 54(12), p. 1659-1671, illus. incl. 5 tables, 63 ref., December 2017.

The artificial ground freezing method can be used jointly with the deep cement mixing method during break-in and break-out processes of shield machines in a tunnel shaft. The frozen ground can fully cut off groundwater seepage, thus ensuring a watertight working platform. Cement-admixed soils can restrict frost heave and thaw-induced settlement because of the decreased permeability. Both methods can also enhance mechanical strength of the soil to enable construction to proceed. Two main sources of heterogeneity are likely to influence the freezing effect: spatial variability in in situ water content in natural soil and spatial variability in binder concentration in cement-admixed soils. Furthermore, positioning error when installing freeze pipes can also affect freezing efficiency. This study simulates in situ water content and binder concentration as Gaussian random fields, whereby variations in the thermophysical properties are estimated. Positioning error is also assessed by prescribing an incline angle in freeze pipes. The influences of those two sources of spatial variability as well as positioning error are examined with random finite-element analyses and statistical characteristics are estimated based on the results. Results are tabulated to offer practitioners a rule of thumb for estimating additional efforts needed in artificial ground freezing, accounting for variations in the thermophysical properties and positioning errors in installing freeze pipes.

DOI: 10.1139/cgj-2016-0707

2018053535 Scotti, Riccardo (University of Bologna, Department of Biological, Geological and Environmental Sciences, Bologna, Italy); Brardinoni, Francesco; Crosta, Giovanni Battista; Cola, Giuseppe and Mair, Volkmar. Time constraints for post-LGM landscape response to deglaciation in Val Viola, central Italian Alps: Quaternary Science Reviews, 177, p. 10-33, illus. incl. 6 tables, geol. sketch map, 200 ref., December 1, 2017.

Across the northern European Alps, a long tradition of Quaternary studies has constrained post-LGM (Last Glacial Maximum) landscape history. The same picture remains largely unknown for the southern portion of the orogen. In this work, starting from existing ¹⁰Be exposure dating of three boulders in Val Viola, Central Italian Alps, we present the first detailed, post-LGM reconstruction of landscape (i.e., glacial, periglacial and paraglacial) response south of the Alpine divide. We pursue this task through Schmidt-hammer exposure-age dating (SHD) at 34 sites including moraines, rock glaciers, protalus ramparts, rock avalanche deposits and talus cones. In addition, based on the mapping of preserved moraines and on the numerical SHD ages, we reconstruct the glacier extent of four different stadials, including Egesen I (13.1±1.1 ka), Egesen II (12.3±0.6 ka), Kartell (11.0±1.4 ka) and Kromer (9.7±1.4 ka), whose chronologies agree with available counterparts from north of the Alpine divide. Results show that Equilibrium Line Altitude depressions (DELAs) associated to Younger Dryas and Early Holocene stadials are smaller than documented at most available sites in the northern Alps. These findings not only support the hypothesis of a dominant north westerly atmospheric circulation during the Younger Dryas, but also suggest that this pattern could have lasted until the Early Holocene. SHD ages on rock glaciers and protalus ramparts indicate that favourable conditions to periglacial landform development occurred during the Younger Dryas (12.7±1.1 ka), on the valley slopes above the glacier, as well as in newly de-glaciated areas, during the Early Holocene (10.7±1.3 and 8.8±1.8 ka). The currently active rock glacier started to develop before 3.7±0.8 ka and can be associated to the Lobben oscillation. Four of the five rock avalanches dated in Val Viola cluster within the Early Holocene, in correspondence of an atmospheric warming phase. By contrast, the timing of the main Val Viola rock avalanche, 7.7±0.3 ka during the Holocene Thermal Optimum, suggests a possible causal linkage to permafrost degradation. Overall, Schmidt-hammer proved to be an effective, inexpensive and versatile tool for improving the spatial resolution of Val Viola post-LGM landscape history, starting from existing numerical age constrains.

DOI: 10.1016/j.quascirev.2017.10.011

2018053495 Zaborska, Agata (Polish Academy of Sciences, Institute of Oceanology, Sopot, Poland). Sources of ¹³⁷Cs to an Arctic fjord (Hornsund, Svalbard): Journal of Environmental Radioactivity, 180, p. 19-26, illus. incl. 1 table, sketch maps, 47 ref., December 2017.

Although primary sources of anthropogenic ¹³⁷Cs have decreased nowadays, the Arctic is exposed to a variety of secondary sources. These include riverine run-off, oceanic currents, drifting sea ice, melting glaciers and permafrost. Recent reports underline the role of glaciers, specifically cryoconite holes, in radionuclide accumulation. Therefore, this study investigates the hypothesis that melting glaciers are an important means of delivering ¹³⁷Cs for Arctic fjord (Hornsund, Svalbard). As marine sediments are the final sink for most contaminants, seven 30-40 cm long sediment cores collected in 2016 were investigated for ¹³⁷Cs activity concentration. Five were collected in a transect from the central to the outer part of the fjord while two were collected within one km of the different melting tidewater glaciers. Sediment layers were dated using ²¹⁰Pb to reveal the history of ¹³⁷Cs accumulation. The measured ¹³⁷Cs activity concentrations ranged from <0.1 to 7.7 Bq kg^-1. The activity concentrations ranging from 0.3 to 3.1 Bq kg^-1 were measured in surface (0-2 cm) sediments. The total ¹³⁷Cs inventories were calculated for five station and ranged from 322 to 908 Bq m^-2, of which 29-34 Bq m^-2 were deposited within the last decade. At two stations characterized by largest sediment accumulation rates only the last decade inventories were calculated and they ranged from 13 to 444 Bq·m^-2. The mean of ¹³⁷Cs fluxes calculated for last decade ranged from 2.7 to 44.1 Bq m^-2yr^-1. The history of ¹³⁷Cs environmental inputs was well revealed in the sediments as the ¹³⁷Cs penetration depth agreed with the time of its introduction to the Arctic and the most pronounced ¹³⁷Cs activity concentration peak was found in sediments dated for circa 1963. Although ¹³⁷Cs fluxes and inventories were largest in the glacial bay (Brepollen), the ¹³⁷Cs was diluted in a large amount of sedimenting material. Based on the results in this study, the glaciers do not appear to act as important sources of ¹³⁷Cs to the marine environment in the Hornsund fjord.

DOI: 10.1016/j.jenvrad.2017.09.021

2018057791 Chen Ji (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Gansu, China); Feng Ziliang; Sheng Yu; Liu Lei and Li Jing. Long-term use of diatomite slope embankments in warm permafrost regions: Journal of Cold Regions Engineering, 31(3), September 2017. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000124

2018053422 Bugaets, A. N. (Russian Academy of Sciences, Pacific Institute of Geography, Vladivostok, Russian Federation); Pschenichnikova, N. F.; Tereshkina, A. A.; Krasnopeev, S. M.; Gartsman, B. I.; Golodnaya, O. M. and Oznobikhin, V. I. Digital soil map of the Ussuri River basin: Eurasian Soil Science, 50(8), p. 907-916, 32 ref., August 2017. Based on Publisher-supplied data.

On the basis of digital soil, topographic, and geological maps; raster topography model; forestry materials; and literature data, the digital soil map of the Ussuri River basin (24400 km²) was created on a scale of 1: 100000. To digitize the initial paper-based maps and analyze the results, an ESRI ArcGIS Desktop (ArcEditor) v.10.1 (URL: http://www.esri.com) and an open-code SAGA GIS v.2.3 (System for Automated Geoscientific Analyses, URL: http://www.saga-gis.org) were used. The spatial distribution of soil areas on the obtained digital soil map is in agreement with modern cartographic data and the SRTM digital elevation model (SRTM DEM). The regional soil classification developed by G. I. Ivanov was used in the legend to the soil map. The names of soil units were also correlated with the names suggested in the modern Russian soil classification system. The major soil units on the map are at the soil subtypes that reflect the entire vertical spectrum of soils in the south of the Far East of Russia (Primorye region). These are mountainous tundra soils, podzolic soils, brown taiga soils, mountainous brown forest soils, bleached brown soils, meadow-brown soils, meadow gley soils, and floodplain soils). With the help of the spatial analysis function of GIS, the comparison of the particular characteristics of the soil cover with numerical characteristics of the topography, geological composition of catchments, and vegetation cover was performed. Copyright 2017 Pleiades Publishing, Ltd.

DOI: 10.1134/S1064229317080038

2018053421 Okoneshnikova, M. V. (Russian Academy of Sciences, Institute of Biological Problems of the Cryolithozone, Yakutsk, Russian Federation) and Desyatkin, R. V. Soils of northern spurs of the Cherskii Ridge in the area of the northern pole of cold; morphology, properties, and classification: Eurasian Soil Science, 50(8), p. 898-906, 28 ref., August 2017. Based on Publisher-supplied data.

The soils in the area of the northern pole of cold located on the interfluve between the Yana and Adycha Rivers within the spurs of Kisilyakh Ridge included in the mountain system of Cherskiy Ridge have been studied for the first time. The profile-genetic approach has been applied to describe the soils and determine their classification position. It is found that the major soil types in this region are the soils of the postlithogenic trunk belonging to the orders of lithozems (Cryic Leptosols), gley soils (Gleyic Skeletic Cryosols), and Al-Fe-humus soils (Spodic Skeletic Cryosols). The ecological ranges of altitudinal zones--the taiga zone with various types of lithozems below 630-700 m a.s.l. and the tundra zone with combinations of gley and nongley cryogenic soils above these heights-have been established. The development of gley or nongley soils is specified by the local orogenic and lithological conditions and slope aspect, which, in turn, control the degree of drainage and the presence and character of permafrost. In the profile of mountainous gley soils (gleyzems) with shallow ice-rich permafrost, cryogenic processes and features typical of the analogues of these soils on plains-cryogenic cracking, cryoturbation, solifluction, thixotropy, oxiaquic features above permafrost, saturation of the soil profile with mobile humus, etc.-are typical. Copyright 2017 Pleiades Publishing, Ltd.

DOI: 10.1134/S1064229317080099

2018052816 Dadfar, Behrang (University of Western Ontario, Department of Civil and Environmental Engineering, London, ON, Canada); El Naggar, M. Hesham and Nastev, Miroslav. Quantifying exposure of linear infrastructures to earthquake-triggered transverse landslides in permafrost thawing slopes: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 54(7), p. 1002-1012, illus. incl. 6 tables, 53 ref., July 2017.

Seismic shaking can cause slope instability in otherwise relatively stable permafrost terrains. In addition, rapid ice melting in low-permeability fine-grained soils can lead to excess pore-water pressure build-up and cause instability in slopes even at small angles. This study addresses the active-layer detachment (ALD) slope instability hazard and develops a systematic risk assessment framework for existing and future linear infrastructures, such as energy pipelines, bridges, and roads traversing permafrost regions. Mild slopes, with average gradient of 7°, are considered in this study as the most representative of actual field conditions. The potential for earthquake-triggered ALD is analytically quantified. State-of-the-art ALD morphological statistics for northern Canada are combined with seismic slope stability analyses to determine (i) the probability of linear infrastructure exposure to permanent ground deformations (PGDs) caused by ALD and (ii) the extent of the potential PGD that the linear infrastructure may be subjected to. The Monte Carlo technique is applied to simulate and assess the sensitivity of the model to parameters such as earthquake magnitude and source-to-site distance. Findings from this study can be used to evaluate the vulnerability of linear infrastructures exposed to the ALD hazard.

DOI: 10.1139/cgj-2017-0076

2018051582 Liljedahl, A. K. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Gädeke, A.; O'Neel, S.; Gatesman, T. A. and Douglas, T. A. Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska: Geophysical Research Letters, 44(13), p. 6876-6885, illus. incl. 1 table, sketch map, 81 ref., July 16, 2017.

Arctic river discharge has increased in recent decades although sources and mechanisms remain debated. Abundant literature documents permafrost thaw and mountain glacier shrinkage over the past decades. Here we link glacier runoff to aquifer recharge via a losing headwater stream in subarctic Interior Alaska. Field measurements in Jarvis Creek (634 km²), a subbasin of the Tanana and Yukon Rivers, show glacier meltwater runoff as a large component (15-28%) of total annual streamflow despite low glacier cover (3%). About half of annual headwater streamflow is lost to the aquifer (38 to 56%). The estimated long-term change in glacier-derived aquifer recharge exceeds the observed increase in Tanana River base flow. Our findings suggest a linkage between glacier wastage, aquifer recharge along the headwater stream corridor, and lowland winter discharge. Accordingly, glacierized headwater streambeds may serve as major aquifer recharge zones in semiarid climates and therefore contributing to year-round base flow of lowland rivers. Abstract Copyright (2017), . The Authors.

DOI: 10.1002/2017GL073834

2018051506 James, S. R. (University of Florida, Department of Geological Sciences, Gainesville, FL); Knox, Hunter A.; Abbott, R. E. and Screaton, E. J. Improved moving window cross-spectral analysis for resolving large temporal seismic velocity changes in permafrost: Geophysical Research Letters, 44(9), p. 4018-4026, illus., 50 ref., May 16, 2017.

Cross correlations of seismic noise can potentially record large changes in subsurface velocity due to permafrost dynamics and be valuable for long-term Arctic monitoring. We applied seismic interferometry, using moving window cross-spectral analysis (MWCS), to 2 years of ambient noise data recorded in central Alaska to investigate whether seismic noise could be used to quantify relative velocity changes due to seasonal active-layer dynamics. The large velocity changes (>75%) between frozen and thawed soil caused prevalent cycle-skipping which made the method unusable in this setting. We developed an improved MWCS procedure which uses a moving reference to measure daily velocity variations that are then accumulated to recover the full seasonal change. This approach reduced cycle-skipping and recovered a seasonal trend that corresponded well with the timing of active-layer freeze and thaw. This improvement opens the possibility of measuring large velocity changes by using MWCS and permafrost monitoring by using ambient noise. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GL072468

2018054897 Draebing, D. (Technische Universität München, Landslide Research Group, Munich, Germany); Krautblatter, M. and Hoffmann, T. Thermo-cryogenic controls of fracture kinematics in permafrost rockwalls: Geophysical Research Letters, 44(8), p. 3535-3544, illus., 64 ref., April 28, 2017.

Thermo-cryogenic processes prepare and trigger rockfalls and rockslides in alpine environments. Temporal occurrence, controls, and applied stresses of Thermo-cryogenic processes on rock masses are poorly understood. This paper reports annual crackmeter measurements with 3 h resolution across perennially ice-filled fractures in an unstable rock permafrost crestline. Thermo-cryogenic processes are controlled by snow cover onset and duration. Thermal changes in snow-free periods control expansion and contraction coincident temperature gradients on a daily to seasonal scale. We can show how snow cover promotes sustained temperatures from -9 to -1°C and boosts ice segregation-related fracture opening up to 1 cm in 8 months. During snowmelt, meltwater induces ice erosion and ice relaxation, which occur in the freeze-thaw window close to the thawing point. We hypothesize that Thermo-cryogenic processes and their cyclic repetition can lead to Thermo-cryogenic fatigue preparing rock slope failure and can control type and location of rockfalls in a changing climate. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GL072050

2018057790 Crowther, G. Scott (Crowther Associates, Anchorage, AK). Northern exposure in Nome: Journal of Cold Regions Engineering, 31(1), March 2017. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000109

2018057789 Sveen, Svein-Erik (University of Tromso - Arctic University of Norway, Institute of Building, Energy and Material Technology, Norway); Nguyen, Hung Thanh and Sorensen, Bjorn Reidar. Thaw penetration in frozen ground subjected to hydronic heating: Journal of Cold Regions Engineering, 31(1), March 2017. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000117

2018058391 Zimmermann, Heike Hildegard (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Unit, Potsdam, Germany); Raschke, Elena; Epp, Laura Saskia; Stoof-Leichsenring, Kathleen Rosmarie; Schwamborn, Georg; Schirrmeister, Lutz; Overduin, Pier Paul and Herzschuh, Ulrike. Sedimentary ancient DNA and pollen reveal the composition of plant organic matter in late Quaternary permafrost sediments of the Buor Khaya Peninsula (north-eastern Siberia): Biogeosciences, 14(3), p. 575-596, illus. incl. 3 tables, 111 ref., 2017.

Organic matter deposited in ancient, ice-rich permafrost sediments is vulnerable to climate change and may contribute to the future release of greenhouse gases; it is thus important to get a better characterization of the plant organic matter within such sediments. From a Late Quaternary permafrost sediment core from the Buor Khaya Peninsula, we analysed plant-derived sedimentary ancient DNA (sedaDNA) to identify the taxonomic composition of plant organic matter, and undertook palynological analysis to assess the environmental conditions during deposition. Using sedaDNA, we identified 154 taxa and from pollen and non-pollen palynomorphs we identified 83 taxa. In the deposits dated between 54 and 51 kyr BP, sedaDNA records a diverse low-centred polygon plant community including recurring aquatic pond vegetation while from the pollen record we infer terrestrial open-land vegetation with relatively dry environmental conditions at a regional scale. A fluctuating dominance of either terrestrial or swamp and aquatic taxa in both proxies allowed the local hydrological development of the polygon to be traced. In deposits dated between 11.4 and 9.7 kyr BP (13.4-11.1 cal kyr BP), sedaDNA shows a taxonomic turnover to moist shrub tundra and a lower taxonomic richness compared to the older samples. Pollen also records a shrub tundra community, mostly seen as changes in relative proportions of the most dominant taxa, while a decrease in taxonomic richness was less pronounced compared to sedaDNA. Our results show the advantages of using sedaDNA in combination with palynological analyses when macrofossils are rarely preserved. The high resolution of the sedaDNA record provides a detailed picture of the taxonomic composition of plant-derived organic matter throughout the core, and palynological analyses prove valuable by allowing for inferences of regional environmental conditions.

DOI: 10.5194/bg-14-575-2017

2018057787 Flynn, David (KGS Group, Winnipeg, MB, Canada); Kurz, David; Alfaro, Marolo; Graham, Jim and Arenson, Lukas U. Forecasting ground temperatures under a highway embankment on degrading permafrost: Journal of Cold Regions Engineering, 30(4), December 2016. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000106

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2018058756 Beylich, Achim A. (Geological Survey of Norway (NGU), Trondheim, Norway). The DYNAFLUX / DYNACOLD (dynamics, fluxes, stability, succession and landscape formation in cold environments) network (2004-2017) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10025, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

There is a wide range of high-latitude and high-altitude cold climate landscapes within Europe, covering a significant proportion of the total land surface area. This spectrum of defined cold-climate landscapes represents a variety of stages of deglaciation history and landscape formation. We can find landscapes at different levels of postglacial stabilization which is providing the unique opportunity to study the interactions between geo-, bio-, social and socio-economic systems at the land surface. The DYNAFLUX / DYNACOLD Network (2004-2017) bridges across the geo-, bio-, social and socioeconomic sciences in order to analyze the complex dynamics of adjustment, stabilization, succession and landscape formation during and after ice retreat and under ongoing anthropogenic influences. The network provides a multidisciplinary forum where researchers come together and discuss. In addition, this network is linking a number of other scientific networks, working groups and programs and creates an umbrella network and a forum for sharing knowledge and experience. The scientific focus of DYNAFLUX / DYNACOLD is also relevant for a number of end users, including risk and vulnerability assessment, sustainable land use, land management and conservation. In addition, present key questions related to environmental change like, e.g., hazards, permafrost degradation and loss of biodiversity are addressed and discussed. Further information is found under URL: http://www.ngu.no/sediflux. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10025.pdf

2018050398 Draebing, Daniel (Technische Universität München, Department of Civil, Geo and Environmental Engineering, Munich, Germany). The application of refraction seismics in alpine permafrost studies [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7430, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Permafrost studies in alpine environments focus on landslides from permafrost-affected rockwalls, landslide deposits or periglacial sediment dynamics. Mechanical properties of soils or rocks are influenced by permafrost and changed strength properties affect these periglacial processes. To assess the effects of permafrost thaw and degradation, monitoring techniques for permafrost distribution and active-layer thaw are required. Seismic wave velocities are sensitive to freezing and, therefore, refraction seismics presents a valuable tool to investigate permafrost in alpine environments. In this study, (1) laboratory and field applications of refraction seismics in alpine environments are reviewed and (2) data are used to quantify effects of rock properties (e.g. lithology, porosity, anisotropy, saturation) on p-wave velocities. In the next step, (3) influence of environmental factors are evaluated and conclusions drawn on permafrost differentiation within alpine periglacial landforms. This study shows that p-wave velocity increase is susceptible to porosity which is pronounced in high-porosity rocks. In low-porosity rocks, p-wave velocity increase is controlled by anisotropy decrease due to ice pressure (Draebing and Krautblatter, 2012) which enables active-layer and permafrost differentiation at rockwall scale (Krautblatter and Draebing, 2014; Draebing et al., 2016). However, discontinuity distribution can result in high anisotropy effects on seismic velocities which can impede permafrost differentiation (Phillips et al., 2016). Due to production or deposition history, porosity can show large spatial differences in deposited landforms. Landforms with large boulders such as rock glaciers and moraines show highest p-wave velocity differences between active-layer and permafrost which facilitates differentiation (Draebing, 2016). Saturation with water is essential for the successful application of refraction seismics for permafrost detection and can be controlled at laboratory scale. At landform scale, saturation shows temporal and spatial variation which is partially reflected in variation of seismic velocities of the active-layer (Draebing, 2016). Environmental factors result in a high spatial variation of rock or soil properties that affect seismic velocities. However, in landforms such as rock glaciers and moraines active-layer and permafrost can be distinguished based on seismic velocities alone while p-wave velocity differences of these layers in talus slopes and debris-covered slopes decrease and, therefore, require additional geophysical techniques or boreholes for layer differentiation (Draebing, 2016). Draebing, D., Krautblatter, M. 2012. P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model. The Cryosphere 6, 1163-1174. Draebing, D. 2016. Application of refraction seismics in alpine permafrost studies: a review. Earth-Science Reviews 155, 136-152. Draebing, D., Haberkorn, A., Krautblatter, M., Kenner, R., Phillips, M. 2016. Spatial and temporal snow cover variability and resulting thermal and mechanical response in a permafrost rock wall. Permafrost and Periglacial Processes. Krautblatter, M., Draebing, D. 2014. Pseudo 3D-P-wave refraction seismic monitoring of permafrost in steep unstable bedrock. Journal of Geophysical Research: Earth Surface 119, 287-99. Phillips, M., Haberkorn, A., Draebing, D., Krautblatter, M., Rhyner, H., Kenner, R. 2016. Seasonally intermittent water flow through deep fractures in an Alpine rock ridge: Gemsstock, central Swiss Alps. Cold Regions Science and Technology 125, 117-127. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7430.pdf

2018058810 Duvillard, Pierre-Allain (Université Savoie Mont Blanc, CNRS, EDYTEM Laboratoire, Le Bourget du Lac, France); Magnin, Florence; Mörtl, Christian; Ravanel, Ludovic and Deline, Philip. Thermal conditions of rock slopes below unstable infrastructure in Alpine permafrost area; the cases of the Cosmiques hut and the Grands Montets cable-car station (Mont Blanc massif) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10142, 3 ref., 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Thermal state of steep permafrost-affected rock faces is crucial to assess the safety and reliability of mountain infrastructure as current permafrost degradation affects the rock slope stability. In the Mont-Blanc massif, 23 infrastructures are built on such a rock face with 13 of them that are characterized by a high risk of destabilization (Duvillard et al., 2015), including the upper station of the Grands Montets cable car (3325 m a.s.l.) as well as the Cosmiques hut (3613 m a.s.l.) on which we will focus. These two buildings have already been affected by different geomorphological processes. A rockfall event (600 m3) occurred for example on the SE face on the Arête inférieure des Cosmiques on the 21st of August 1998 (Ravanel et al., 2013) and the Grands Montets case shows a slow subsidence of the stairway over the last decade. In order to better assess the role of the permafrost in these processes and to gain insight on possible future geomorphic activity, we characterized the current permafrost conditions and simulated its changes up to the end of the 21st century using two complementary approaches: (i) the result of ERT (Electrical Resistivity Tomography) surveys carried out in October 2016 on the northern and southern faces right below the Cosmiques hut (at the level of the foundations) and at the Aiguilles des Grands Montets; (ii) the modeling of mean annual rock surface temperature for 2016 and at the end of the 21st century (Magnin et al., in rev.). Duvillard P.-A., Ravanel L., Deline P. (2015). Risk assessment of infrastructure destabilisation due to global warming in the high French Alps. Journal of Alpine Research, 103 (2). Magnin F., Josnin J.-Y., Ravanel L., Pergaud J., Pohl B., Deline P. (in rev.). Modelling rock wall permafrost degradation in the Mont Blanc massif from the LIA to the end of the 21st century. The Cryosphere Discuss., doi:10.5194/tc-2016-132. Ravanel L., Deline P., Lambiel C. and Vincent C. (2013). Instability of a high alpine rock ridge: the lower arête des Cosmiques, Mont-Blanc massif, France. Geografiska Annaler A, 95 : 51-66. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10142.pdf

2018053792 Farzamian, Mohammad (Universidade de Lisboa, Lisbon, Portugal); Vieira, Goncalo; Yaghoobi, Borhan; Monteiro Santos, Fernando A.; Hauck, Christian; Bernando, Ivo and Ramos, Miguel. Application of time-lapse ERT in active layer monitoring at Crater Lake, Deception Island, Antarctica [abstr.]: in GELMON 2017; 4th international workshop on Geoelectrical monitoring; book of abstracts (Hoyer, Stefan, editor), Berichte der Geologischen Bundesanstalt, 124, p. 22, illus., 1 ref., 2017. Meeting: 4th international workshop on Geoelectrical monitoring; GELMON 2017, Nov. 22-24, 2017, Vienna, Austria.

2018057145 Frampton, Andrew (Stockholm University, Department of Physical Geography, Stockholm, Sweden). Subsurface flow pathway dynamics in the active layer of coupled permafrost-hydrogeological systems under seasonal and annual temperature variability [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9289, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

There is a need for improved understanding of the mechanisms controlling subsurface solute transport in the active layer in order to better understand permafrost-hydrological-carbon feedbacks, in particular with regards to how dissolved carbon is transported in coupled surface and subsurface terrestrial arctic water systems under climate change. Studying solute transport in arctic systems is also relevant in the context of anthropogenic pollution which may increase due to increased activity in cold region environments. In this contribution subsurface solute transport subject to ground surface warming causing permafrost thaw and active layer change is studied using a physically based model of coupled cryotic and hydrogeological flow processes combined with a particle tracking method. Changes in subsurface water flows and solute transport travel times are analysed for different modelled geological configurations during a 100-year warming period. Results show that for all simulated cases, the minimum and mean travel times increase non-linearly with warming irrespective of geological configuration and heterogeneity structure. The timing of the start of increase in travel time depends on heterogeneity structure, combined with the rate of permafrost degradation that also depends on material thermal and hydrogeological properties. These travel time changes are shown to depend on combined warming effects of increase in pathway length due to deepening of the active layer, reduced transport velocities due to a shift from horizontal saturated groundwater flow near the surface to vertical water percolation deeper into the subsurface, and pathway length increase and temporary immobilization caused by cryosuction-induced seasonal freeze cycles. The impact these change mechanisms have on solute and dissolved substance transport is further analysed by integrating pathway analysis with a Lagrangian approach, incorporating considerations for both dissolved organic and inorganic carbon releases. Further model development challenges are also highlighted and discussed, including coupling between subsurface and surface runoff, soil deformations, as well as site applications and larger system scales. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-9289.pdf

2018058759 Gallach, Xavi (Université Savoie Mont Blanc, CNRS, EDYTEM Laboratoire, Le Bourget du Lac, France); Ogier, Christophe; Ravanel, Ludovic; Deline, Philip and Carcaillet, Julien. Reconstruction of the rock fall/avalanche frequency in the Mont Blanc massif since the last glacial maximum; new results using 10Be cosmogenic dating and reflectance spectroscopy [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10030, 2 ref., 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Rockfalls and rock avalanches are active processes in the Mont Blanc massif, with infrastructure and alpinists at risk. Thanks to a network of observers (hut keepers, mountain guides, alpinists) set up in 2007 present rockfalls are well surveyed and documented. Rockfall frequency over the past 150 years has been studied by comparison of historical photographs, showing that it strongly increased during the three last decades, especially during hot periods like the summer of 2003 and 2015, due to permafrost degradation driven by the climate change. In order to decipher the possible relationship between rockfall occurrence and the warmest periods of the Lateglacial and the Holocene, we start to study the morphodynamics of some selected high-elevated (>3000 m a.s.l.) rockwalls of the massif on a long timescale. Contrary to low altitude, deglaciated sites where study of large rockfall deposits allows to quantify frequency and magnitude of the process, rockfalls that detached from high-elevated rockwalls are no more noticeable as debris were absorbed and evacuated by the glaciers. Therefore, our study focuses on the rockfall scars. Their 10Be dating gives us the rock surface exposure age from present to far beyond the Last Glacial Maximum, interpreted as the rockfall ages. TCN dating of rockfalls has been carried out at the Aiguille du Midi in 2007 (Boehlert et al., 2008), and three other sites in the Mont Blanc massif in 2011 (Gallach et al., submitted). Here we present a new data set of rockfall dating carried out in 2015 that improves the 2007 and 2011 data. Furthermore, a relationship between the colour of the Mont Blanc granite and its exposure age has been shown: fresh rock surface is light grey (e.g. in recent rockfall scars) whereas weathered rock surface is in the range grey to orange/red: the redder a rock surface, the older its age. Here, reflectance spectroscopy is used to quantify the granite surface colour. Böhlert, R., Gruber, S., Egli, M., Maisch, M., Brandová, D., Haeberli, W., Ivy-Ochs, S., Christl, M., Kubik, P.W., Deline, P. (2008). Comparison of exposure ages and spectral properties of rock surfaces in steep, high alpine rock walls of Aiguille du Midi, France. Proceedings of the 9th International Conference on Permafrost, 143-148. Gallach, X. et al. (submitted). Timing of rockfalls in the Mont Blanc massif (western Alps). Evidences from surface exposure dating with cosmogenic 10Be. Landslides. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10030.pdf

2018052027 Gillespie, Alan R. (University of Washington at Seattle, Quaternary Research Center, Seattle, WA); Batbaatar, J.; Sletten, Ronald S.; Trombotto, Dario; O'Neal, Michael; Hanson, Brian and Mushkin, Amit. Monitoring and mapping soil ice/water phase transitions in arid regions [abstr.]: in Geological Society of America, 2017 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 49(6), Abstract no. 372-14, 2017. Meeting: Geological Society of America, 2017 annual meeting & exposition, Oct. 22-25, 2017, Seattle, WA.

Water resources in many arid regions are inadequate to support increasing populations and may become more so due to onrushing climate changes. Water in these regions comes from three main sources: precipitation, meltwater streams from nearby mountains, and shallow and deep aquifers, and it makes sense to monitor each of these using remote sensing for mapping where possible. It is important to track the changing extent of ground ice - seasonal as well as permafrost - as one measure of the effect of climate change. We are developing a method with which to map near-surface ground ice thermally, using time series of long-wave infrared (8-12 mm) satellite images to detect freeze-up (or thaw) from the signature "zero curtain." The zero curtain is a well understood phenomenon that occurs when ground temperatures seasonally cool (or warm) through 0°C but stall for a week or more as available energy is used to freeze (or melt) groundwater in Fall (or Spring) instead of changing its temperature. Detecting the zero curtain is not the only way to infer the presence of ground ice: for example, surficial soil moisture has been be detected with side-looking RADAR backscatter because the dielectric constant differs for soil, ice and water. However, the zero curtain is a distinctive signature. Our method appears to be effective as thermal imagers survey Earth's surface daily (e.g., MODIS) or more frequently (e.g., AVHRR), albeit at low resolution (km scale). We have measured ground temperature profiles in the Atacama Andes (Barrancas Blancas on Ojos de Salado) and in the San Juan Province of the Argentinean Andes for periods of up to 6 years, and obtained daily and 8-day MODIS thermal images with which we can detect and verify the zero curtain. Mapping ice-rich permafrost is an obvious goal, but in the Andes the coarse km-scale spatial resolution has prevented us from detecting the small patches of intermittent permafrost mapped in the field. We have therefore tested the MODIS data over coarsely mapped ice-rich permafrost regions in the Mongolian steppes. Factors that appear to limit the detection of the zero curtain from space include vegetation, the depth to permafrost and the active layer, as well as the tradeoff between spatial and temporal resolution available from current spaceborne sensors.

2018058868 Gruber, Stephan (Carleton University, Ottawa, ON, Canada); Riddick, Julia; Brown, Nick; Karunaratne, Kumari and Kokelj, Steve V. Strong lateral variation of ground temperature revealed by a large network of boreholes in the Slave geological province of Canada [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11257, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The Slave Geological Province is a key region in the Canadian North. Its tundra areas form a large and resource-rich landscape in which comparably few systematic permafrost observations exist. Because the region contains layers of ice-rich till, the ground is susceptible to subsidence during thaw. Consequently, possible impacts of permafrost thawing on infrastructure and the natural environment motivate baseline investigations and simulation studies. In this context, the spatial variation of ground temperatures is relevant: How well can we extrapolate from one or few locations of observation? How well can we describe permafrost characteristics with coarse-grid (e.g., 50 km) models assuming relatively homogenous conditions? In July 2015, an observation network of more than 40 plots was installed to monitor ground thermal regime and to detect surface subsidence. Plots are within few tens of meters to few tens of kilometers from each other and were chosen to represent a distinct combination of surficial geology, vegetation, drainage conditions, and snow accumulation. In each plot (15 m x 15 m), temperatures are recorded in a borehole as well as about 10 cm deep at four locations. Data on surface and subsurface properties has been recorded as well. In September 2016, data was downloaded from the loggers and the conditions of the instruments were described. This contribution presents the first year of temperature data. In the annual averages, it reveals more than 7°C lateral variation between plots as well as within-plot variations of more than 2.5°C. This underscores the need for carefully designing measurement campaigns and methods when aiming to test coarse-scale permafrost simulations, even in gentle topography. The data resulting from this observational network will be made available publicly in the near future. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11257.pdf

2018050488 Hauck, Christian (University of Fribourg, Department of Geosciences, Fribourg, Switzerland) and Hilbich, Christin. Electrical and seismic mixing rules for detecting changes in ground ice content in permafrost studies [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-12167, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Geophysical methods are now widely used in permafrost research to detect and monitor frozen ground and potentially quantify the ground ice content in the soil. Hereby, often a combination of different methods is used to reduce the ambiguities inherent with the indirect nature of geophysical surveys. Geophysical mixing rules and petrophysical relationships originally developed by exploration industry may help to quantitatively relate geophysical variables such as the electrical resistivity or the seismic P-wave velocity to the physical properties of the subsurface. Two of these mixing rules were combined by Hauck et al. (2011) in a so-called 4-phase model to attempt to quantify the ground ice, air- and water content and their changes with time in permafrost environments (e.g. Pellet et al. 2016). However, these mixing rules are often either empirically derived (making use of a large number of borehole samples) or based on a simplified mixing model, i.e. an equal weighting of each phase component (ice, water, soil/rock, air) depending on the actual fractional content of each phase. There is thus no obvious 'best choice' model from the available geophysical approaches. Stimulated by recent theoretical work by Glover (2010), who analysed the relationships between the empirical and theory-derived mixing models, this contribution aims to analyse the applicability of various mixing models for electrical and seismic data sets in the context of detecting and monitoring permafrost degradation. Input data stem from various geophysical surveys around the world and ground truth data for validation is available from corresponding permafrost boreholes from the PERMOS and GTN-P data bases. Glover, P. W. (2010). A generalized Archie's law for n phases. Geophysics, 75(6), E247-E265. Hauck, C., Bottcher, M. and Maurer, H. (2011): A new model for estimating subsurface ice content based on combined electrical and seismic data sets. The Cryosphere, 5, 453-468. Pellet, C., Hilbich, C., Marmy, A. and Hauck, C. (2016): Soil moisture data for the validation of permafrost models using direct and indirect measurement approaches at three alpine sites. Front. Earth Sci. 3:91. doi: 10.3389/feart.2015.00091. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-12167.pdf

2018053790 Kemna, Andreas (University of Bonn, Bonn, Germany); Weigand, Maximilian; Orozco, Adrian Flores; Wagner, Florian; Hilbich, Christin and Hauck, Christian. Use of geoelectrical monitoring methods for characterizing thermal state, ice content and water flow in permafrost environments [abstr.]: in GELMON 2017; 4th international workshop on Geoelectrical monitoring; book of abstracts (Hoyer, Stefan, editor), Berichte der Geologischen Bundesanstalt, 124, p. 19-20, 2017. Meeting: 4th international workshop on Geoelectrical monitoring; GELMON 2017, Nov. 22-24, 2017, Vienna, Austria.

2018058794 Kraushaar, Sabine (University of Vienna, Institute of Geography and Regional Research, Physical Geography, Vienna, Austria); Kamleitner, Sarah; Czarnowsky, Verena; Blöthe, Jan; Morche, David; Knöller, Kay and Lachner, Johannes. Hydro-chemical detection of permafrost degradation in the Eastern European Alps; implications for geomorphological process studies and natural hazard assessment [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10104, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The Gepatschferner glacier in the Upper Kaunertal valley is one of the fastest melting glaciers in the Eastern European Alps. With a retreat rate of around 110 m a-1 since the hydrological year 2012/ 2013, unconsolidated sediments of steep lateral moraines have been exposed to erosion, from which nowadays episodic and perennial springs well. We hypothesize that the springs indicate the melt out of dead ice lenses in areas below 2500 m, causing a potential significant morphological change in the moraines and a decrease of slope stability in the proglacial long after glacier retreat. However, permafrost degradation has not been considered so far in contemporary erosion measurements. The present study aims to identify the spring water's origin and displays first attempts of quantifying thermal erosion, which describes the matrix volume loss due to melting and drainage of ice water. Samples were routinely analyzed for temperature, electrical conductivity, d2H, and d18O. Results support the hypothesis that certain springs derive from melting ice of similar isotopic signature as the glacier. In a second step, chosen samples were examined for the long-lived anthropogenic nuclide 129I. Since the 1950s the atmospheric abundance of 129I has significantly increased. Its occurrence in the water samples hints a surface contact of the waters in the last 65 years. Springs of ice origin show little 129I content and are believed to derive from dead ice by the glacier. First electric resistivity measurements support the hydro-chemical results and suggest the existence of ice lenses in the subsurface. Ice ablation and discharge measurements allowed first estimates of the thermal erosion volume caused by the melt out and drainage of ice lenses. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-10104.pdf

2018050527 Lewkowicz, Antoni G. (University of Ottawa, Ottawa, ON, Canada); Douglas, Thomas and Hauck, Christian. Towards a Global Permafrost Electrical Resistivity Survey (GPERS) database [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-12241, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Hundreds, and perhaps thousands, of Electrical Resistivity Tomography (ERT) surveys have been undertaken over the past two decades in permafrost areas in North America, Europe, and Asia. Two main types of ERT configurations have been conducted: galvanic surveys using metallic rods as conductors and capacitive-coupled surveys using towed cable arrays. ERT surveys have been carried out in regions with mountain permafrost, lowland permafrost, and coastal saline permafrost, and in undisturbed, naturally-disturbed (e.g. fire-affected), and anthropogenically-affected sites (e.g. around buildings and infrastructure). Some surveys are associated with local validation of frozen ground conditions, through borehole temperatures, frost probing or creep phenomena. Others are in locations without boreholes or with clast-rich or bedrock active layers which preclude this direct confirmation. Most surveys have been carried out individually on particular dates but there are increasing numbers of repeated ERT measurements being made to detect change, either at intervals using a fixed array of electrodes, or at high frequency with a fixed and automated measurement apparatus. Taken as a group, ERT profiles represent an untapped knowledge base relating to permafrost presence, absence, or partial presence (i.e. discontinuous permafrost), and in some cases to the thickness of permafrost and ice content. When combined with borehole information, ERT measurements can identify massive ice features and provides information on soil stratigraphy. The Global Permafrost Electrical Resistivity Survey (GPERS) database is planned as a freely available on-line repository of data from two-dimensional electrical resistivity surveys undertaken in permafrost regions. Its development is supported by the Permafrost Carbon Network and an application for an International Permafrost Association (IPA) Action Group is also underway. When the future GPERS records are compared with the GTN-P database it will be possible to see which boreholes or CALM sites are associated with ERT surveys and which are not. This can be used to target particular sites for ERT surveys to provide a more holistic view of what GTN-P measurements represent. GPERS data will permit empirical analyses of relationships between measured resistivities and permafrost conditions, including ground temperature, ice and liquid water content, and sediment type. These analyses will assist researchers in interpreting their local surveys. The spatial coordinates of the surveys in the database will also permit reacquisition of data in the future to examine changes over years or decades. The purpose of this presentation is to communicate the initiation of GPERS, to explore the level of interest in its development, and to help guide its maturation. In particular, we wish to discuss whether the database should initially focus on meta-data, including site location, vegetation type, and frozen ground conditions, or whether researchers would be willing to supply measurement data immediately which would lead to a more rapid development of GPERS but would also require more resources. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-12241.pdf

2018051984 Lorenson, Thomas D. (U. S. Geological Survey, Santa Cruz, CA); Conaway, Christopher H.; Fitzpatrick, John; Choy, Doug; Oberle, Ferdinand; Johnson, Cordell; Richmond, Bruce; Gibbs, Ann and Swarzenski, Peter W. Chemistry of cryopegs on Barter Island, North Slope Alaska [abstr.]: in Geological Society of America, 2017 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 49(6), Abstract no. 367-5, 2017. Meeting: Geological Society of America, 2017 annual meeting & exposition, Oct. 22-25, 2017, Seattle, WA.

On Barter Island, NE Alaska, a large basal cryopeg extending from the coast to at least 300 m inland was recently discovered. The cryopeg was detected from surface penetrating multichannel electrical resistivity tomography (ERT) that imaged and characterized shallow subsurface permafrost. The ERT surveys revealed extensive subsurface regions of low resistivity at 5 meter depths suggesting the presence of hypersaline water underlying a much more resistive layer above. Borehole temperature data from a nearby inland location was -8°C at 10 m depth, too cold to for liquid fresh water needed to explain a less resistive layer below the frozen layer. The presence of the cryopeg was confirmed by coring as deep as 8 m in four locations. Extracted pore water from the cores were fresh in the upper 2 m, and showed increasing salinity with depth. Enhanced chlorine, bromine, and other anions and cations were found below 2.5 m. Chlorinity of up to 31 g/kg was extracted from stiff clay at 7 m depth. Pore water sulfate concentrations were depleted relative to seawater ratios of chloride to sulfate. X-ray diffraction analyses of the sediment revealed the presence of gypsum and anhydrite (CaSO₄ minerals), minerals that removed sulfate from the pore water when formed. Pore water ^87/86Sr isotopic measurements of 0.7111 - 0.7161, and water oxygen isotopic compositions of -20 to -26 permil strongly suggest that groundwater rather than seawater is the source of the pore water. Currently it is unknown if basal cryopegs are a prominent feature of northern Alaska permafrost, however genesis from groundwater as evidenced by this new data, suggests they might be extensive. Erosion rates are accelerating along portions of Northern Alaska due to recent warming trends and associated ice-free days along the coastline. If non-icebonded permafrost cryopegs are commonly present at elevations near present-day sea level, then we might expect these to enhance erosion as they become exposed by chemical and mechanical weathering of the ground surface. Enhanced erosion rates will contribute to greater releases of permafrost constituents into the atmosphere and the ocean.

2018053793 Mollaret, Coline (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Wagner, Florian; Hilbich, Christin and Hauck, Christian. Joint inversion of electric and seismic data applied to permafrost monitoring [abstr.]: in GELMON 2017; 4th international workshop on Geoelectrical monitoring; book of abstracts (Hoyer, Stefan, editor), Berichte der Geologischen Bundesanstalt, 124, p. 23, 4 ref., 2017. Meeting: 4th international workshop on Geoelectrical monitoring; GELMON 2017, Nov. 22-24, 2017, Vienna, Austria.

2018054979 Morse, Peter (Geological Survey of Canada, Ottawa, ON, Canada); Wolfe, Stephen and McWade, Taylor. Influence of terrain and highway construction on thermokarst distribution, North Slave region, NWT, Canada [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9864, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Permafrost degradation has been observed throughout the north and is expected to have broad reaching effects on the land and its people. Nevertheless, for much of Northern Canada little quantified information about thermokarst exists. For example, in the southern North Slave region, NWT, thermokarst distribution has never been assessed though permafrost is in thermal disequilibrium and modelling suggests permafrost extent will decline. Additionally, differential subsidence has been observed in the subarctic city of Yellowknife and along highway infrastructure connecting it to the south. To better understand present and future permafrost conditions, we mapped the location and size of thermokarst ponding (a change from forest cover to water) in the study area by comparing historic and modern remotely sensed data sets available from 1945, 1961, and 2005. These data were used to evaluate the dominant terrain controls on the distribution of thermokarst in the region, and the potential influence that highway construction may have had on thermokarst development. Historically, discontinuous permafrost developed in a time-transgressive manner during the Holocene as lake-level receded from glacial Lake McConnell to present-day Great Slave Lake (5 mm·a^-1 over the last 8000 years). As a consequence of inundation the upland areas are characterized by extensive wave-washed bedrock outcrops with glaciolacustrine (GL) sediments and glaciofluvial materials occurring between them, whereas the lowland areas feature prominent GL deposits that cover nearly 70% of the exposed surface. Throughout much of the region ground ice accumulation likely accompanied permafrost aggradation into fine-grained sediments, as is evident by lithalsa growth in particular. Highway 3, constructed during the mid-1960s, was preferentially aligned to crossed terrain underlain by fine-grained sediments to avoid bedrock and waterbodies. Local silt and clay used for highway embankment construction was sourced from shallow borrow pits developed along the right-of-way. Following construction, many borrow pits developed into ponds. Thermokarst ponding is widespread in the study area (n = 3138). The transition of approximately 3.57 km² of land cover from forested permafrost terrain to ponds is different than in the low subarctic where permafrost peatlands degrade to fens. Most ponds are small (< 5000 m²), but range up to nearly 45 000 m². Pond distribution relates to surficial geology and elevation, with ponds dominantly constrained to GL deposits, and decreased pond counts with increased elevation. Highway construction has substantially affected thermokarst development. Compared to pond density within undisturbed GL deposits, pond density is an order of magnitude greater in the vicinity of Highway 3, where about half of the borrow pits have developed thermokarst ponds within them. In contrast, only 6.5% of ponds within 200 m of the highway developed before 1961. Thermokarst is likely widespread throughout the region as GL deposits are extensive. Reduced thermokarst ponding at higher elevation is likely related to reduced GL extent, but may also be related to more time for past thermokarst development given the landscape history. Regardless, future thermokarst development will continue to be associated with permafrost in low lying forested GL deposits that should be avoided by new infrastructure construction. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-9864.pdf

2018058887 Musselman, Keith (National Center for Atmospheric Research, Boulder, CO); Clark, Martyn; Endalamaw, Abraham; Bolton, W. Robert; Nijssen, Bart and Arnold, Jeffrey. Effects of modeling decisions on cold region hydrological model performance; snow, soil and streamflow [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11305, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Cold regions are characterized by intense spatial gradients in climate, vegetation and soil properties that determine the complex spatiotemporal patterns of snowpack evolution, frozen soil dynamics, catchment connectivity, and streamflow. These spatial gradients pose unique challenges for hydrological models, including: 1) how the spatial variability of the physical processes are best represented across a hierarchy of scales, and 2) what algorithms and parameter sets best describe the biophysical and hydrological processes at the spatial scale of interest. To address these topics, we apply the Structure for Unifying Multiple Modeling Alternatives (SUMMA) to simulate hydrological processes at the Caribou - Poker Creeks Research Watershed in the Alaskan sub-arctic Boreal forest. The site is characterized by numerous gauged headwater catchments ranging in size from 5 sq. km to 106 sq. km with varying extents (3% to 53%) of discontinuous permafrost that permits a multi-scale paired watershed analysis of the hydrological impacts of frozen soils. We evaluate the effects of model decisions on the skill of SUMMA to simulate observed snow and soil dynamics, and the spatial integration of these processes as catchment streamflow. Decisions such as the number of soil layers, total soil column depth, and vertical soil discretization are shown to have profound impacts on the simulation of seasonal active layer dynamics. Decisions on the spatial organization (lateral connectivity, representation of riparian response units, and the spatial discretization of the hydrological landscape) are shown to be as important as accurate snowpack and soil process representation in the simulation of streamflow. The work serves to better inform hydrological model decisions for cold region hydrologic evaluation and to improve predictive capacity for water resource planning. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11305.pdf

2018053795 Pfeiler, S. (Geological Survey of Austria, Vienna, Austria); Schöner, W.; Reisenhofer, S.; Ottowitz, David; Jochum, Birgit; Kim, J. H.; Supper, R. and Hoyer, Stefan. Data quality analysis of ERT data of geoelectrical permafrost monitoring on Hoher Sonnblick and on Kitzsteinhorn (Austrian Central Alps) [abstr.]: in GELMON 2017; 4th international workshop on Geoelectrical monitoring; book of abstracts (Hoyer, Stefan, editor), Berichte der Geologischen Bundesanstalt, 124, p. 25, 1 ref., 2017. Meeting: 4th international workshop on Geoelectrical monitoring; GELMON 2017, Nov. 22-24, 2017, Vienna, Austria.

2018050388 Saemundsson, Thorsteinn (University of Iceland, Faculty of Life and Environmental Sciences, Department of Geography and Tourism, Reykjavik, Iceland); Morino, Costanza; Helgason, Jon Kristinn; Conway, Susan J. and Petursson, Halldor G. The triggering factors of the Moafellshyrna debris slide in northern Iceland; intense precipitation, earthquake activity and thawing of mountain permafrost [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7417, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

On the 20th of September in 2012, a large debris slide occurred in the Moafellshyrna Mountain in the Trollaskagi Peninsula, central north Iceland. Three factors are likely to have contributed to the failure of the slope: intense precipitation, earthquake activity and thawing of ground ice. The weather conditions prior the slide were somewhat unusual, with a warm and dry summer. From the 20th of August to the 20th of September, about 440 mm of precipitation fell in the area, where the mean annual precipitation at the nearest station is around 670 mm. The slide initiated after this thirty day period of intense precipitation, followed by a seismic sequence in the Eyjafjargarall Graben, located about 60 km NNE of Moafellshyrna Mountain, a sequence that started on the 19th of September. The slide originated at elevation of 870 m a.s.l. on the NW-slope of the mountain. The total volume of the debris slide is estimated around 500,000 m3 and that its primary cause was intense precipitation. We cannot exclude the influence of the seismic sequence as a secondary contributing factor. The presence of ice-cemented blocks of talus immediately after the debris slide shows that thawing of ground ice could also have played an important role as a triggering factor. Ice-cemented blocks of talus have been observed in the deposits of two other recent landslides in northern Iceland, in the Torfufell Mountain and the Arnesfjall Mountain. The source areas for both the Moafellshyrna and the Torfufell slides are within the lower elevation limit of mountain permafrost in northern Iceland but the source area of the Arnesfjall slide is at much lower elevation, around 350 m a.s.l. The fact that there are now three documented landslides which are linked to ground ice-melting suggests that discontinuous permafrost is degrading in Iceland, consistent with the decadal trend of increasing atmospheric temperature in Iceland due to climate change. This study highlights that ground ice thaw could represent a new source of hazard in Iceland. The knowledge of the detailed distribution of mountain permafrost on the island is poorly constrained, making it is hard to predict where the next hazardous slide could occur in the future--therefore a making this a priority for future research. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7417.pdf

2018050415 Schicks, Judith (GFZ German Research Centre for Geosciences, Geochemistry, Potsdam, Germany); Heeschen, Katja; Spangenberg, Erik; Luzi-Helbing, Manja; Beeskow-Strauch, Bettina; Priegnitz, Mike; Giese, Ronny; Abendroth, Sven and Thaler, Jan. The assessment of different production methods for hydrate bearing sediments; results from small and large scale experiments [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7459, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Natural gas hydrates occur at all active and passive continental margins, in permafrost regions, and deep lakes. Since they are supposed to contain enormous amounts of methane, gas hydrates are discussed as an energy resource. For the production of gas from hydrate bearing sediments, three different production methods were tested during the last decade: depressurization, thermal and chemical stimulation as well as combinations of these methods. In the framework of the SUGAR project we developed a Large Scale Reservoir Simulator (LARS) with a total volume of 425L to test these three methods in a pilot plant scale. For this purpose we formed hydrate from methane saturated brine in sediments under conditions close to natural gas hydrate deposits. The obtained hydrate saturations varied between 40-90%. Hydrate saturation and distribution were determined using electrical resistivity tomography (ERT). The volumes of the produced gas and water were determined and the gas phase was analyzed via gas chromatography. Multi-step depressurization, thermal stimulation applying in-situ combustion as well as chemical stimulation via the injection of CO₂ and a CO₂-N2-mixture were tested. Depressurization and thermal stimulation appear to be less complicated compared to the chemical stimulation. For the understanding of the macroscopically observed processes on a molecular level, we also performed experiments on a smaller scale using microscopic observation, Raman spectroscopy and X-ray diffraction. The results of these experiments are of particular importance for the understanding of the processes occurring during the CO₂-CH₄ swapping. Under the chosen experimental conditions the observations indicate a (partial) decomposition and reformation of the hydrate structure rather than a diffusion-controlled exchange of the molecules. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7459.pdf

2018057119 Schuh, Carina (Stockholm University, Physical Geography, Stockholm, Sweden); Frampton, Andrew and Christiansen, Hanne. Effects of soil moisture retention on ice distribution and active layer thickness subject to seasonal ground temperature variations in a dry loess terrace in Adventdalen, Svalbard [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9242, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The active layer constitutes an important part of permafrost environments. Thermal and hydrological processes in the active layer determine local phenomena such as erosion and hydrological and ecosystem changes, and can have important implications for the global carbon-climate feedback. Permafrost degradation usually starts with a deepening of the active layer, followed by the formation of a talik and the subsequent thawing of permafrost. An increasing active layer thickness is therefore regarded as an indicator of permafrost degradation. The importance of hydrology for active layer processes is generally well acknowledged on a conceptual level, however the in general non-linear physical interdependencies between soil moisture, subsurface water and heat fluxes and active layer thaw progression are not fully understood. In this study, high resolution field data for the period 2000-2014 consisting of active layer and permafrost temperature, active layer soil moisture, and thaw depth progression from the UNISCALM research site in Adventdalen, Svalbard, is combined with a physically-based coupled cryotic and hydrogeological model to investigate active layer dynamics. The site is a loess-covered river terrace characterized by dry conditions with little to no summer infiltration and an unsaturated active layer. A range of soil moisture characteristic curves consistent with loess sediments is considered and their effects on ice and moisture redistribution, heat flux, energy storage through latent heat transfer, and active layer thickness is investigated and quantified based on hydro-climatic site conditions. Results show that soil moisture retention characteristics exhibit notable control on ice distribution and circulation within the active layer through cryosuction and are subject to seasonal variability and site-specific surface temperature variations. The retention characteristics also impact unfrozen water and ice content in the permafrost. Although these effects lead to differences in thaw progression rates, the resulting inter-annual variability in active layer thickness is not large. Field data analysis reveals that variations in summer degree days do not notably affect the active layer thaw depths; instead, a cumulative winter degree day index is found to more significantly control inter-annual active layer thickness variation at this site. A tendency of increasing winter temperatures is found to cause a general warming of the subsurface down to 10 m depth (0.05 to 0.26°C/yr, observed and modelled) including an increasing active layer thickness (0.8 cm/yr, observed and 0.3 to 0.8 cm/yr, modelled) during the 14-year study period. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-9242.pdf

2018050427 Talbot, Julie (Université de Montréal, Canada); Pelletier, Nicolas; Olefeldt, David; Turetsky, Merritt; Blodau, Christian; Sonnentag, Oliver and Quinton, William. The paleoecology, peat chemistry and carbon storage of a discontinuous permafrost peatland [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11115, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Permafrost in peatlands strongly influences ecosystem biogeochemical functioning, vegetation composition and hydrological functions. Permafrost peatlands of northwestern Canada store large amounts of carbon but the peatlands located at the southern margin of the permafrost zone are thawing rapidly. This thaw triggers changes in vegetation, hydrology and peat characteristics, and may affect carbon stocks. We present data from a permafrost plateau to thermokarst bog chronosequence located in the southern portion of the Scotty Creek watershed near Fort Simpson, Northwest Territories, Canada. We assessed changes in plant communities, hydrology, biogeochemistry and permafrost status over 9000 years of peatland development using plant macrofossil, testate amoeba and peat chemical characteristics. Peat accumulation started after the infilling of a lake 8500 cal. yr BP. Minerotrophic peat prevailed at the site until permafrost formed around 5000 cal. yr BP. Permafrost apparently formed three times, although there is spatial variability in the permafrost aggradation - degradation cycles. Permafrost thawed 550 cal. yr BP in the center of the thermokarst bog. Ombrotrophic peat is a fairly recent feature of the peat profiles, only appearing after the most recent permafrost thaw event. Both allogenic (temperature/precipitation/snow cover changes and wildfire) and autogenic (peat accumulation, Sphagnum growth) processes likely influenced permafrost aggradation and thaw. While apparent carbon accumulation rates were lower during present and past permafrost periods than during non-permafrost periods, long term carbon accumulation remained similar between cores with different permafrost period lengths. Deep peat was more decomposed in the thermokarst bog peat profile than in the permafrost plateau profile, highlighting the importance of considering potential deep peat carbon losses to project the fate of thawing permafrost peat carbon stores. Average long-term carbon accumulation derived from the peat cores (n=3, 20.6 1.9 g C m-2 a-1) is in the same range than the contemporary landscape-scale carbon balance measured from eddy covariance at the site (~15 g C m-2 a-1). While the carbon to nitrogen ratio tends to decrease with peat depth, the carbon to phosphorus ratio tends to increase, perhaps indicating a preferential uptake of phosphorus over nitrogen by plants. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11115.pdf

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2018055378 McNeil, R. J.; Day, S. J. A. and Williamson, Marie-Claude. Geochemical, mineralogical and indicator-mineral data for stream silt sediment, water and heavy-mineral concentrates, East Fiord area, western Axel Heiberg Island, Nunavut (part of NTS 59-G): Open-File Report - Geological Survey of Canada, Rep. No. 7779, 30 p., illus. incl. tables, 23 ref., 2018.

Stream sediment and water sampling programs such as the Geological Survey of Canada's (GSC) National Geochemical Reconnaissance (NGR) program are used to efficiently obtain systematic geochemical information, which is key in establishing the mineral potential over a large area. One of the basic assumptions of reconnaissance stream surveys is that the sediment chemistry and mineralogy reflect the bedrock and surficial geology of the catchment area upstream from the sample site. Fluvial and stream sediments form by the physical and chemical weathering of bedrock within the catchment basin. In the absence of mineralization, the sediment chemistry reflects normal or background element concentrations typical of the source bedrock. Mineralized bedrock, if present, will be revealed by the presence of elevated metal and/or indicator mineral contents in stream sediments. We report the results of a stream sediment and water study that was carried out as part of an environmental geoscience project on gossans in Canada's High Arctic. The survey was complementary to bedrock mapping and sampling of gossans found within permafrost in the down-drainage environment in the East Fiord area of western Axel Heiberg Island, Nunavut (NTS 59-G). The objectives were to characterize bedrock lithologies in the study area and to evaluate the economic mineral potential. The sampling strategy undertaken targeted drainages with known gossans and were within a day by foot traverse, from base camp. Stream silt and water samples were collected from 26 sites. At 14 of these sites, bulk sediment samples were collected for the heavy mineral concentrate (HMC) component in the <2 mm fraction. Silt and water samples were analyzed by ICP-MS and ICP-ES as well as for carbon content. Water samples were also submitted for alkalinity, anions by ion-chromatography and in-situ physico-chemical measurements. Bulk sediment samples were processed and the resulting HMC samples were picked for indicator minerals of various deposit types. Sampling and analytical techniques followed established NGR methodologies, ensuring data compatibility with the NGR database. The results suggest that the study area is prospective, potentially for Ni-Cu PGE, Cu-Pb-Zn mineralization and also for other types of economic deposits.

DOI: 10.4095/306606

2018055317 Sladen, W. E.; Morse, P. D. and Wolfe, S. A. Report on 2012-2017 shallow ground thermal investigations on the Tibbitt to Contwoyto Winter Road portages, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 8274, 23 p., illus. incl. 7 tables, 15 ref., 2018.

A field campaign was conducted in 2012-2017 to collect baseline geoscience data to determine air, surface, and near-surface ground temperature conditions along the Tibbitt to Contwoyto Winter Road (TCWR), Great Slave region, Northwest Territories. This field initiative was conducted in support of Natural Resources Canada's Climate Change Geoscience Program project entitled Transportation Risk in the Arctic to Climatic Sensitivity. Thermal data are presented in a digital format that can be utilized for assessments of permafrost sensitivity to climate change and for infrastructure planning.

DOI: 10.4095/306454

2018054007 Wolfe, Stephen A. (Geological Survey of Canada, Ottawa, ON, Canada); Duchesne, C.; O'Neill, H. B. and Parker, R. J. H. Modelling ground ice potential in Canada: Scientific Presentation - Geological Survey of Canada, Rep. No. 77, 1 sheet, illus. incl. sketch maps, 9 ref., 2018. Poster presented at the 45th annual Yellowknife geoscience forum 2017, Yellowknife, NT, Nov. 14-16, 2017.

DOI: 10.4095/306461

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