2017020573 Sherman, Dallas (University of California, San Diego, Institute of Geophysics and Planetary Physics, La Jolla, CA); Kannberg, Peter and Constable, Steven. Surface towed electromagnetic system for mapping of subsea Arctic permafrost: Earth and Planetary Science Letters, 460, p. 97-104, illus. incl. sketch map, 24 ref., February 15, 2017.

Sea level has risen globally since the late Pleistocene, resulting in permafrost-bearing coastal zones in the Arctic being submerged and subjected to temperature induced degradation. Knowing the extent of permafrost and how it changes over time is important for climate change predictions and for planning engineering activities in the Arctic environment. We developed a controlled source electromagnetic (CSEM) method to obtain information on the depth, thickness, and lateral extent of marine permafrost. To operate in shallow water we used a surface towed electric dipole-dipole CSEM system suitable for deployment from small boats. This system was used to map permafrost on the Arctic shelf offshore Prudhoe Bay, Alaska. Our results show significant lateral variability in the presence of permafrost, with the thickest layers associated with a large river outflow where freshwater influx seems to have a preserving effect on relict subsea permafrost.

DOI: 10.1016/j.epsl.2016.12.002

2017018511 Gil, J. (University of Eastern Finland, Department of Environmental Science, Kuopio, Finland); Pérez, T.; Boering, K.; Martikainen, P. J. and Biasi, C. Mechanisms responsible for high N₂O emissions from subarctic permafrost peatlands studied via stable isotope techniques: Global Biogeochemical Cycles, 31(1), p. 172-189, illus. incl. 2 tables, 77 ref., January 2017.

Recent field studies have shown that there are habitats in the subarctic tundra emitting N₂O at exceptionally high rates. In this study, stable isotope techniques were applied to characterize the processes responsible for these high N₂O emissions which have been found from bare peat surfaces in permafrost peatlands. The results include the first data on the nitrogen and oxygen isotopic composition of N₂O emitted from arctic tundra. The emission-weighted average d¹⁵N^bulk value for N₂O of -13.0 ppm ± 2.0 ppm (mean ± SD; n = 8) from the bare peat surfaces falls within the range of the emission-weighted average values from other natural ecosystems but is distinct from those for managed/agricultural ecosystems. This implies that if in the future, a smaller rate in the overall decreasing trend of d¹⁵N^bulk N₂O tropospheric isotopic composition is found, it cannot be attributed only to agricultural N₂O emission reductions from mitigation actions but also to soils in natural ecosystems that may be emitting more N₂O to the atmosphere due to warmer conditions. The site preference (SP) values from emitted N₂O range from -30 ppm to 58 ppm, indicating a temporal shift of microbial production and consumption of N₂O during the sampling period. Soil emission SP data suggest that the N₂O emission in subarctic tundra are more likely to be produced by nitrifier denitrification in the drier study year, but due to variable published SP values for N₂O production processes in soils, this interpretation has to be taken with caution. According to SP values at depth, denitrification was the main N₂O production pathway. To better address the usefulness of SP in partitioning microbial mechanisms in soils, further studies in soils mesocosms are required. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015GB005370

2017017138 Langer, Moritz (Humboldt University of Berlin, Department of Geography, Berlin, Germany); Westermann, S.; Boike, J.; Kirillin, G.; Grosse, G.; Peng, S. and Krinner, G. Rapid degradation of permafrost underneath waterbodies in tundra landscapes; toward a representation of thermokarst in land surface models: Journal of Geophysical Research: Earth Surface, 121(12), p. 2446-2470, illus. incl. 1 table, 88 ref., December 2016.

Waterbodies such as lakes and ponds are abundant in vast Arctic landscapes and strongly affect the thermal state of the surrounding permafrost. In order to gain a better understanding of the impact of small- and medium-sized waterbodies on permafrost and the formation of thermokarst, a land surface model was developed that can represent the vertical and lateral thermal interactions between waterbodies and permafrost. The model was validated using temperature measurements from two typical waterbodies located within the Lena River delta in northern Siberia. Impact simulations were performed under current climate conditions as well as under a moderate and a strong climate-warming scenario. The performed simulations demonstrate that small waterbodies can rise the sediment surface temperature by more than 10°C and accelerate permafrost thaw by a factor of between 4 and 5. Up to 70% of this additional heat flux into the ground was found to be dissipated into the surrounding permafrost by lateral ground heat flux in the case of small, shallow, and isolated waterbodies. Under moderate climate warming, the lateral heat flux was found to reduce permafrost degradation underneath waterbodies by a factor of 2. Under stronger climatic warming, however, the lateral heat flux was too small to prevent rapid permafrost degradation. The lateral heat flux was also found to strongly impede the formation of thermokarst. Despite this stabilizing effect, our simulations have demonstrated that underneath shallow waterbodies (<1 m), thermokarst initiation happens 30 to 40 years earlier than in simulations without preexisting waterbody. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016JF003956

2017017127 O'Donnell, Jonathan A. (National Park Service, Arctic Network, Anchorage, AK); Aiken, George R.; Swanson, David K.; Panda, Santosh; Butler, Kenna D. and Baltensperger, Andrew P. Dissolved organic matter composition of Arctic rivers; linking permafrost and parent material to riverine carbon: Global Biogeochemical Cycles, 30(12), p. 1811-1826, illus. incl. 3 tables, sketch map, 90 ref., December 2016.

Recent climate change in the Arctic is driving permafrost thaw, which has important implications for regional hydrology and global carbon dynamics. Permafrost is an important control on groundwater dynamics and the amount and chemical composition of dissolved organic matter (DOM) transported by high-latitude rivers. The consequences of permafrost thaw for riverine DOM dynamics will likely vary across space and time, due in part to spatial variation in ecosystem properties in Arctic watersheds. Here we examined watershed controls on DOM composition in 69 streams and rivers draining heterogeneous landscapes across a broad region of Arctic Alaska. We characterized DOM using bulk dissolved organic carbon (DOC) concentration, optical properties, and chemical fractionation and classified watersheds based on permafrost characteristics (mapping of parent material and ground ice content, modeling of thermal state) and ecotypes. Parent material and ground ice content significantly affected the amount and composition of DOM. DOC concentrations were higher in watersheds underlain by fine-grained loess compared to watersheds underlain by coarse-grained sand or shallow bedrock. DOC concentration was also higher in rivers draining ice-rich landscapes compared to rivers draining ice-poor landscapes. Similarly, specific ultraviolet absorbance (SUVA₂₅₄, an index of DOM aromaticity) values were highest in watersheds underlain by fine-grained deposits or ice-rich permafrost. We also observed differences in hydrophobic organic acids, hydrophilic compounds, and DOM fluorescence across watersheds. Both DOC concentration and SUVA₂₅₄ were negatively correlated with watershed active layer thickness, as determined by high-resolution permafrost modeling. Together, these findings highlight how spatial variations in permafrost physical and thermal properties can influence riverine DOM. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GB005482

2017019883 Iijima, Yoshihiro (Japan Agency for Marine-Earth Science and Technology, Institute of Arctic Climate and Environment Research, Yokosuka, Japan); Nakamura, Tetsu; Park, Hotaek; Tachibana, Yoshihiro and Fedorov, Alexander N. Enhancement of Arctic storm activity in relation to permafrost degradation in eastern Siberia: International Journal of Climatology, 36(13), p. 4265-4275, illus., 44 ref., November 15, 2016.

In the last decade, increases in both soil temperature and active layer thickness have been observed in the central Lena River basin, an area located in the centre of continuous permafrost in the Eurasian continent. Increased soil temperatures have been accompanied by corresponding increases in soil moisture within the active layer at many sites throughout the region. These underground hydro-thermal changes are believed to be primarily due to perennially wet climate conditions, rather than the atmospheric warming alone that has resulted in abnormally large amounts of winter snow accumulation and late summer rainfall in the Lena River basin. This study aimed to clarify the linkage between atmospheric and land surface variations in regions of continuous permafrost in eastern Siberia based on in situ observation and atmospheric climatic data analyses. These wet conditions in 2004-2008 were likely caused by the enhancement of cyclones over the Arctic Ocean and eastward propagation of storm activity during late summer and early winter. Water vapour flux was enhanced in conjunction with the manifestation of precipitation in eastern Siberia. As a result, consecutive positive anomalies of winter snow accumulation and precipitation during the subsequent summers effectively humidified land surfaces in the permafrost region from 2005 onwards, which resulted in abrupt soil warming and wetting of both the active layer and the upper part of the permafrost. The positive effects on increasing soil temperatures of both snowfall in winter and rainfall in summer have been observed in eastern Siberia since the 1990s, and have also been demonstrated through land surface simulation. Results of these hydro-climatic changes indicated that the near-surface permafrost in eastern Siberia is vulnerable to the climatic conditions that have arisen due to the acceleration of the hydrological cycle that has resulted from the aforementioned period of warming. Abstract Copyright (2016), Royal Meteorological Society.

DOI: 10.1002/joc.4629

2017019574 Gisnas, Kjersti (University of Oslo, Department of Geosciences, Oslo, Norway); Westermann, Sebastian; Schuler, Thomas Vikhamar; Melvold, Kjetil and Etzelmuller, Bernd. Small-scale variation of snow in a regional permafrost model: The Cryosphere (Online), 10(3), p. 1201-1215, illus. incl. 3 tables, sketch maps, 47 ref., 2016.

The strong winds prevalent in high altitude and arctic environments heavily redistribute the snow cover, causing a small-scale pattern of highly variable snow depths. This has profound implications for the ground thermal regime, resulting in highly variable near-surface ground temperatures on the metre scale. Due to asymmetric snow distributions combined with the nonlinear insulating effect of snow, the spatial average ground temperature in a 1 km² area cannot be determined based on the average snow cover for that area. Land surface or permafrost models employing a coarsely classified average snow depth will therefore not yield a realistic representation of ground temperatures. In this study we employ statistically derived snow distributions within 1 km² grid cells as input to a regional permafrost model in order to represent sub-grid variability of ground temperatures. This improves the representation of both the average and the total range of ground temperatures. The model reproduces observed sub-grid ground temperature variations of up to 6 °C, and 98 % of borehole observations match the modelled temperature range. The mean modelled temperature of the grid cell reproduces the observations with an accuracy of 1.5 °C or better. The observed sub-grid variations in ground surface temperatures from two field sites are very well reproduced, with estimated fractions of sub-zero mean annual ground surface temperatures within ±10 %. We also find that snow distributions within areas of 1 km² in Norwegian mountain environments are closer to a gamma than to a lognormal theoretical distribution. The modelled permafrost distribution seems to be more sensitive to the choice of distribution function than to the fine-tuning of the coefficient of variation. When incorporating the small-scale variation of snow, the modelled total permafrost area of mainland Norway is nearly twice as large compared to the area obtained with grid-cell average snow depths without a sub-grid approach.

URL: http://www.the-cryosphere.net/10/1201/2016/tc-10-1201-2016.pdf

2017014852 Spencer, Robert G. M. (Florida State University, Department of Earth, Ocean and Atmospheric Science, Tallahassee, FL); Mann, Paul J.; Dittmar, Thorsten; Eglinton, Timothy I.; McIntyre, Cameron; Holmes, R. Max; Zimov, Nikita and Stubbins, Aron. Detecting the signature of permafrost thaw in Arctic rivers: Geophysical Research Letters, 42(8), p. 2830-2835, illus. incl. 1 table, 34 ref., April 28, 2015.

Climate change induced permafrost thaw in the Arctic is mobilizing ancient dissolved organic carbon (DOC) into headwater streams; however, DOC exported from the mouth of major arctic rivers appears predominantly modern. Here we highlight that ancient (>20,000 years B.P.) permafrost DOC is rapidly utilized by microbes (~50% DOC loss in <7 days) and that permafrost DOC decay rates (0.12 to 0.19 day^-1) exceed those for DOC in a major arctic river (Kolyma: 0.09 day^-1). Permafrost DOC exhibited unique molecular signatures, including high levels of aliphatics that were rapidly utilized by microbes. As microbes processed permafrost DOC, its distinctive chemical signatures were degraded and converged toward those of DOC in the Kolyma River. The extreme biolability of permafrost DOC and the rapid loss of its distinct molecular signature may explain the apparent contradiction between observed permafrost DOC release to headwaters and the lack of a permafrost signal in DOC exported via major arctic rivers to the ocean. Abstract Copyright (2015). American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015GL063498

2017017399 Deng, J. (University of New Hampshire, Earth Systems Research Center, Durham, NH); Li, C.; Frolking, S.; Zhang, Y.; Bäckstrand, K. and Crill, P. Assessing effects of permafrost thaw on C fluxes based on multiyear modeling across a permafrost thaw gradient at Stordalen, Sweden: Biogeosciences, 11(17), p. 4753-4770, illus. incl. 5 tables, 82 ref., 2014.

Northern peatlands in permafrost regions contain a large amount of organic carbon (C) in the soil. Climate warming and associated permafrost degradation are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is uncertain. We incorporated a permafrost model, Northern Ecosystem Soil Temperature (NEST), into a biogeochemical model, DeNitrification-DeComposition (DNDC), to model C dynamics in high-latitude peatland ecosystems. The enhanced model was applied to assess effects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen, Sweden. DNDC simulated soil freeze-thaw dynamics, net ecosystem exchange of CO₂ (NEE), and CH₄ fluxes across three typical land cover types, which represent a gradient in the process of ongoing permafrost thaw at Stordalen. Model results were compared with multiyear field measurements, and the validation indicates that DNDC was able to simulate observed differences in seasonal soil thaw, NEE, and CH₄ fluxes across the three land cover types. Consistent with the results from field studies, the modeled C fluxes across the permafrost thaw gradient demonstrate that permafrost thaw and the associated changes in soil hydrology and vegetation not only increase net uptake of C from the atmosphere but also increase the annual to decadal radiative forcing impacts on climate due to increased CH₄ emissions. This study indicates the potential of utilizing biogeochemical models, such as DNDC, to predict the soil thermal regime in permafrost areas and to investigate impacts of permafrost thaw on ecosystem C fluxes after incorporating a permafrost component into the model framework.

DOI: 10.5194/bg-11-4753-2014

2017019036 Hugelius, G. (Stockholm University, Department of Physical Geography and Quaternary Geology, Stockholm, Sweden); Strauss, J.; Zubrzycki, S.; Harden, J. W.; Schuur, E. A. G.; Ping, C. L.; Schirrmeister, L.; Grosse, G.; Michaelson, G. J.; Koven, C. D.; O'Donnell, J. A.; Elberling, B.; Mishra, U.; Camill, P.; Yu, Z.; Palmtag, J. and Kuhry, P. Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps: Biogeosciences, 11(23), p. 6573-6593, illus. incl. 6 tables, geol. sketch maps, 73 ref., 2014.

Soils and other unconsolidated deposits in the northern circumpolar permafrost region store large amounts of soil organic carbon (SOC). This SOC is potentially vulnerable to remobilization following soil warming and permafrost thaw, but SOC stock estimates were poorly constrained and quantitative error estimates were lacking. This study presents revised estimates of permafrost SOC stocks, including quantitative uncertainty estimates, in the 0-3 m depth range in soils as well as for sediments deeper than 3 m in deltaic deposits of major rivers and in the Yedoma region of Siberia and Alaska. Revised estimates are based on significantly larger databases compared to previous studies. Despite this there is evidence of significant remaining regional data gaps. Estimates remain particularly poorly constrained for soils in the High Arctic region and physiographic regions with thin sedimentary overburden (mountains, highlands and plateaus) as well as for deposits below 3 m depth in deltas and the Yedoma region. While some components of the revised SOC stocks are similar in magnitude to those previously reported for this region, there are substantial differences in other components, including the fraction of perennially frozen SOC. Upscaled based on regional soil maps, estimated permafrost region SOC stocks are 217 ± 12 and 472 ± 27 Pg for the 0-0.3 and 0-1 m soil depths, respectively (±95% confidence intervals). Storage of SOC in 0-3 m of soils is estimated to 1035 ± 150 Pg. Of this, 34 ± 16 Pg C is stored in poorly developed soils of the High Arctic. Based on generalized calculations, storage of SOC below 3 m of surface soils in deltaic alluvium of major Arctic rivers is estimated as 91 ± 52 Pg. In the Yedoma region, estimated SOC stocks below 3 m depth are 181 ± 54 Pg, of which 74 ± 20 Pg is stored in intact Yedoma (late Pleistocene ice- and organic-rich silty sediments) with the remainder in refrozen thermokarst deposits. Total estimated SOC storage for the permafrost region is ~1300 Pg with an uncertainty range of ~1100 to 1500 Pg. Of this, ~500 Pg is in non-permafrost soils, seasonally thawed in the active layer or in deeper taliks, while ~800 Pg is perennially frozen. This represents a substantial ~300 Pg lowering of the estimated perennially frozen SOC stock compared to previous estimates.

DOI: 10.5194/bg-11-6573-2014

2017020427 Lobkovsky, L. (Russian Academy of Sciences, P. P. Shirshov Institute of Oceanology, Moscow, Russian Federation); Ananyev, R.; Dmitrevskiy, N.; Dudarev, O.; Jakobsson, Martin; Nikiforov, S. and Roslyakov, A. Permafrost patterns in the SE Laptev Sea, East Siberian Arctic Ocean: in Atlas of submarine glacial landforms; modern, Quaternary and ancient (Dowdeswell, J. A., editor; et al.), Memoirs of the Geological Society of London, 46, p. 311-312, illus. incl. sects., sketch map, 9 ref., 2016.

DOI: 10.1144/M46.78

2017016575 Hu Guojie (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Cryosphere Research Station on Qinghai-Xizang Plateau, Lanzhou, China); Zhao Lin; Li Ren; Wu Tonghua; Wu Xiaodong; Pang Qiangqiang; Xiao Yao; Qiao Yongping and Shi Jianzong. Modeling hydrothermal transfer processes in permafrost regions of Qinghai-Tibet Plateau in China: Chinese Geographical Science, 25(6), p. 713-727, illus. incl. 4 tables, sketch map, 46 ref., December 2015.

DOI: 10.1007/s11769-015-0733-6

2017017132 Murton, Julian B. (University of Sussex, Department of Geography, Brighton, United Kingdom); Kuras, Oliver; Krautblatter, Michael; Cane, Tim; Tschofen, Dominique; Uhlemann, Sebastian; Schober, Sandra and Watson, Phil. Monitoring rock freezing and thawing by novel geoelectrical and acoustic techniques: Journal of Geophysical Research: Earth Surface, 121(12), p. 2309-2332, illus. incl. 1 table, 31 ref., December 2016.

Automated monitoring of freeze-thaw cycles and fracture propagation in mountain rockwalls is needed to provide early warning about rockfall hazards. Conventional geoelectrical methods such as electrical resistivity tomography (ERT) are limited by large and variable ohmic contact resistances, requiring galvanic coupling with metal electrodes inserted into holes drilled into rock, and which can be loosened by rock weathering. We report a novel experimental methodology that combined capacitive resistivity imaging (CRI), ERT, and microseismic event recording to monitor freeze-thaw of six blocks of hard and soft limestones under conditions simulating an active layer above permafrost and seasonally frozen rock in a nonpermafrost environment. Our results demonstrate that the CRI method is highly sensitive to freeze-thaw processes; it yields property information equivalent to that obtained with conventional ERT and offers a viable route for nongalvanic long-term geoelectrical monitoring, extending the benefits of the methodology to soft/hard rock environments. Contact impedances achieved with CRI are less affected by seasonal temperature changes, the aggregate state of the pore water (liquid or frozen), and the presence of low-porosity rock with high matrix resistivities than those achieved with ERT. Microseismic monitoring has the advantage over acoustic emissions that events were recorded in relevant field distances of meters to decameters from cracking events. For the first time we recorded about 1000 microcracking events and clustered them in four groups according to frequency and waveform. Compared to previous studies, mainly on ice-cracking in glaciers, the groups are attributed to single- or multiple-stage cracking events such as crack coalescence. Abstract Copyright (2016), . The Authors.

DOI: 10.1002/2016JF003948

2017020506 Throckmorton, Heather M. (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, Cambridge, MA); Newman, Brent D.; Heikoop, Jeffrey M.; Perkins, George B.; Feng, Xiahong; Graham, David E.; O'Malley, Daniel; Vesselinov, Velimir V.; Young, Jessica; Wullschleger, Stan D. and Wilson, Cathy J. Active layer hydrology in an arctic tundra ecosystem; quantifying water sources and cycling using water stable isotopes: Hydrological Processes, 30(26), p. 4972-4986, illus. incl. 3 tables, sketch map, 61 ref., December 30, 2016.

Climate change and thawing permafrost in the Arctic will significantly alter landscape hydro-geomorphology and the distribution of soil moisture, which will have cascading effects on climate feedbacks (CO₂ and CH₄) and plant and microbial communities. Fundamental processes critical to predicting active layer hydrology are not well understood. This study applied water stable isotope techniques (d²H and d¹⁸O) to infer sources and mixing of active layer waters in a polygonal tundra landscape in Barrow, Alaska (USA), in August and September of 2012. Results suggested that winter precipitation did not contribute substantially to surface waters or subsurface active layer pore waters measured in August and September. Summer rain was the main source of water to the active layer, with seasonal ice melt contributing to deeper pore waters later in the season. Surface water evaporation was evident in August from a characteristic isotopic fractionation slope (d²H vs d¹⁸O). Freeze-out isotopic fractionation effects in frozen active layer samples and textural permafrost were indistinguishable from evaporation fractionation, emphasizing the importance of considering the most likely processes in water isotope studies, in systems where both evaporation and freeze-out occur in close proximity. The fractionation observed in frozen active layer ice was not observed in liquid active layer pore waters. Such a discrepancy between frozen and liquid active layer samples suggests mixing of meltwater, likely due to slow melting of seasonal ice. This research provides insight into fundamental processes relating to sources and mixing of active layer waters, which should be considered in process-based fine-scale and intermediate-scale hydrologic models. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.10883

2017015188 Atchley, Adam L. (Los Alamos National Laboratory, Los Alamos, NM); Coon, Ethan T.; Painter, Scott L.; Harp, Dylan R. and Wilson, Cathy J. Influences and interactions of inundation, peat, and snow on active layer thickness: Geophysical Research Letters, 43(10), p. 5116-5123, illus. incl. 1 table, 60 ref., May 28, 2016.

Active layer thickness (ALT), the uppermost layer of soil that thaws on an annual basis, is a direct control on the amount of organic carbon potentially available for decomposition and release to the atmosphere as carbon-rich Arctic permafrost soils thaw in a warming climate. We investigate how key site characteristics affect ALT using an integrated surface/subsurface permafrost thermal hydrology model. ALT is most sensitive to organic layer thickness followed by snow depth but is relatively insensitive to the amount of water on the landscape with other conditions held fixed. The weak ALT sensitivity to subsurface saturation suggests that changes in Arctic landscape hydrology may only have a minor effect on future ALT. However, surface inundation amplifies the sensitivities to the other parameters and under large snowpacks can trigger the formation of near-surface taliks. Abstract Copyright Published 2016. This article is a US Government work and is in the public domain in the United States of America.

DOI: 10.1002/2016GL068550

2017019568 Darrow, Margaret M. (University of Alaska at Fairbanks, Department of Mining and Geological Engineering, Fairbanks, AK); Gyswyt, Nora L.; Simpson, Jocelyn M.; Daanen, Ronald P. and Hubbard, Trent D. Frozen debris lobe morphology and movement; an overview of eight dynamic features, southern Brooks Range, Alaska: The Cryosphere (Online), 10(3), p. 977-993, illus. incl. 1 table, sketch maps, 84 ref., 2016.

Frozen debris lobes (FDLs) are elongated, lobate permafrost features that mostly move through shear in zones near their bases. We present a comprehensive overview of eight FDLs within the Dalton Highway corridor (southern Brooks Range, Alaska), including their catchment geology and rock strengths, lobe soil characteristics, surface movement measurements collected between 2012 and 2015, and analysis of historic and modern imagery from 1955 to 2014. Field mapping and rock strength data indicate that the metasedimentary and metavolcanic bedrock forming the majority of the lobe catchments has very low to medium strength and is heavily fractured, thus easily contributing to FDL formation. The eight investigated FDLs consist of platy rocks typical of their catchments, organic debris, and an ice-poor soil matrix; massive ice, however, is present within FDLs as infiltration ice, concentrated within cracks open to the surface. Exposure of infiltration ice in retrogressive thaw slumps (RTSs) and associated debris flows leads to increased movement and various stages of destabilization, resulting in morphological differences among the lobes. Analysis of historic imagery indicates that movement of the eight investigated FDLs has been asynchronous over the study period, and since 1955, there has been an overall increase in movement rates of the investigated FDLs. The formation of surface features, such as cracks, scarps, and RTSs, suggests that the increased movement rates correlate to general instability, and even at their current distances, FDLs are impacting infrastructure through increased sediment mobilization. FDL-A is the largest of the investigated FDLs. As of August 2015, FDL-A was 39.2 m from the toe of the Dalton Highway embankment. Based on its current distance and rate of movement, we predict that FDL-A will reach the Dalton Highway alignment by 2023.

URL: http://www.the-cryosphere.net/10/977/2016/tc-10-977-2016.pdf

2017017665 Samsonov, Sergey V. (Natural Resources Canada, Canada Centre for Mapping and Earth Observation, Ottawa, ON, Canada); Lantz, Trevor C.; Kokelj, Steven V. and Zhang, Yu. Growth of a young pingo in the Canadian Arctic observed by RADARSAT-2 interferometric satellite radar: The Cryosphere (Online), 10(2), p. 799-810, illus. incl. 1 table, 40 ref., 2016.

Advancements in radar technology are increasing our ability to detect Earth surface deformation in permafrost environments. In this paper we use satellite Differential Interferometric Synthetic Aperture Radar (DInSAR) to describe the growth of a large, relatively young pingo in the Tuktoyaktuk Coastlands. High-resolution RADARSAT-2 imagery (2011-2014) analyzed with the Multidimensional Small Baseline Subset (MSBAS) DInSAR revealed a maximum 2.7 cm yr^-1 of domed uplift located in a drained lake basin. Satellite measurements suggest that this feature is one of the largest diameter pingos in the region that is presently growing. Observed changes in elevation were modeled as a 348 ´ 290 m uniformly loaded elliptical plate with clamped edge. Analysis of historical aerial photographs suggested that ground uplift at this location initiated sometime between 1935 and 1951 following drainage of the residual pond. Uplift is largely due to the growth of intrusive ice, because the 9 % expansion of pore water associated with permafrost aggradation into saturated sands is not sufficient to explain the observed short- and long-term deformation rates. The modeled thickness of ice-rich permafrost using the Northern Ecosystem Soil Temperature (NEST) was consistent with the maximum height of this feature. Modeled permafrost aggradation from 1972 to 2014 approximated elevation changes estimated from aerial photographs for that time period. Taken together, these lines of evidence indicate that uplift is at least in part a result of freezing of the sub-pingo water lens. Seasonal variations in the uplift rate seen in the DInSAR data closely match the modeled seasonal pattern in the deepening rate of freezing front. This study demonstrates that interferometric satellite radar can detect and contribute to understanding the dynamics of terrain uplift in response to permafrost aggradation and ground ice development in remote polar environments. The present-day growth rate is smaller than predicted by the modeling and no clear growth is observed at other smaller pingos in contrast with field studies performed mainly before the 1990s. Investigation of this apparent discrepancy provides an opportunity to further develop observation methods and models.

URL: http://www.the-cryosphere.net/10/799/2016/tc-10-799-2016.pdf

2017019436 Haberkorn, Anna (WSL Institute for Snow and Avalanche Research SLF, Davos, Switzerland); Phillips, Marcia; Kenner, Robert; Rhyner, Hansueli; Bavay, Mathias; Galos, Stephan P. and Hoelzle, Martin. Thermal regime of rock and its relation to snow cover in steep alpine rock walls; Gemsstock, Central Swiss Alps: Geografiska Annaler. Series A: Physical Geography, 97(3), p. 579-597, illus. incl. sect., 5 tables, sketch map, 59 ref., September 2015.

Snow cover influences the thermal regime and stability of frozen rock walls. In this study, we investigate and model the impact of the spatially variable snow cover on the thermal regime of steep permafrost rock walls. This is necessary for a more detailed understanding of the thermal and mechanical processes causing changes in rock temperature and in the ice and water contents of frozen rock, which possibly lead to rock wall instability. To assess the temporal and spatial evolution and influence of the snow, detailed measurements have been carried out at two selected points in steep north- and south-facing rock walls since 2012. In parallel, the one-dimensional energy balance model SNOWPACK is used to simulate the effects of snow cover on the thermal regime of the rock walls. For this, a multi-method approach with high temporal resolution is applied, combining meteorological, borehole rock temperature and terrain parameter measurements. To validate the results obtained for the ground thermal regime and the seasonally varying snowpack, the model output is compared with near-surface rock temperature measurements and remote snow cover observations. No decrease of snow depth at slope angles up to 70° was observed in rough terrain due to micro-topographic structures. Strong contrasts in rock temperatures between north- and south-facing slopes are due to differences in solar radiation, slope angle and the timing and depth of the snow cover. SNOWPACK proved to be useful for modelling snow cover-rock interactions in smooth, homogenous rock slopes. Abstract Copyright (2015), Swedish Society for Anthropology and Geography.

DOI: 10.1111/geoa.12101

2017016064 Krüger, J. P. (University of Basel, Environmental Geosciences, Basel, Switzerland); Leifeld, J. and Alewell, C. Degradation changes stable carbon isotope depth profiles in palsa peatlands: Biogeosciences, 11(12), p. 3369-3380, illus. incl. 3 tables, 51 ref., 2014.

Palsa peatlands are a significant carbon pool in the global carbon cycle and are projected to change by global warming due to accelerated permafrost thaw. Our aim was to use stable carbon isotopes as indicators of palsa degradation. Depth profiles of stable carbon isotopes generally reflect organic matter dynamics in soils with an increase of d¹³C values during aerobic decomposition and stable or decreasing d¹³C values with depth during anaerobic decomposition. Stable carbon isotope depth profiles of undisturbed and degraded sites of hummocks as well as hollows at three palsa peatlands in northern Sweden were used to investigate the degradation processes. The depth patterns of stable isotopes clearly differ between intact and degraded hummocks at all sites. Erosion and cryoturbation at the degraded sites significantly changes the stable carbon isotope depth profiles. At the intact hummocks the uplifting of peat material by permafrost is indicated by a turning in the d¹³C depth trend, and this assessment is supported by a change in the C / N ratios. For hollows isotope patterns were less clear, but some hollows and degraded hollows in the palsa peatlands show differences in their stable carbon isotope depth profiles indicating enhanced degradation rates. We conclude that the degradation of palsa peatlands by accelerated permafrost thawing can be identified with stable carbon isotope depth profiles. At intact hummocks d¹³C depth patterns display the uplifting of peat material by a change in peat decomposition processes.

DOI: 10.5194/bg-11-3369-2014

2017015189 Zhu, Dan (Université de Versailles Saint-Quentin-en-Yvelines, Laboratoire des Sciences du Climat et de l'Environnement, Gif sur Yvette, France); Peng, S.; Ciais, P.; Zech, R.; Krinner, G.; Zimov, S. and Grosse, G. Simulating soil organic carbon in yedoma deposits during the last glacial maximum in a land surface model: Geophysical Research Letters, 43(10), p. 5133-5142, illus. incl. 1 table, 47 ref., May 28, 2016.

Substantial quantities of organic carbon (OC) are stored in the thick, ice-rich, and organic-rich sediments called yedoma deposits, distributed in eastern Siberia and Alaska today. Quantifying yedoma carbon stocks during the glacial period is important for understanding how much carbon could have been decomposed during the last deglaciation. Yet processes that yield the formation of thick frozen OC in yedoma deposits are missing in global carbon cycle models. Here we incorporate sedimentation parameterizations into the Organizing Carbon and Hydrology In Dynamic Ecosystems (ORCHIDEE-MICT) land surface model, which leads to reasonable results in OC vertical distribution and regional budgets, compared with site-specific observations and inventories for today's nondegraded yedoma region. Simulated total soil OC stock for the northern permafrost region during the Last Glacial Maximum (LGM) is 1536-1592 Pg C, of which 390-446 Pg C is within today's yedoma region. This result is an underestimation since we did not account for the potentially much larger yedoma area during the LGM than the present day. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GL068874

2017016766 Xu, Guofang (University of Natural Resources and Life Sciences, Institute of Geotechnical Engineering, Vienna, Austria); Wu Wei and Qi Jilin. Modeling the viscous behavior of frozen soil with hypoplasticity: International Journal for Numerical and Analytical Methods in Geomechanics, 40(15), p. 2061-2075, illus. incl. 3 tables, 32 ref., October 25, 2016.

This paper presents a hypoplastic constitutive model for the viscous behavior of frozen soil. The model is composed of a "solid" part and a "fluid" part. The solid part is based on the extended hypoplastic model, and the fluid part is dependent on the second time derivative of strain. The performance of the model is demonstrated by simulating some uniaxial compression tests at different strain rates. Moreover, the model can describe in a unified way the three stages of typical creep tests, that is, primary, secondary, and tertiary stage. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/nag.2516

2017019041 Greene, S. (University of Chicago, Department of Chemistry, Chicago, IL); Walter Anthony, K. M.; Archer, D.; Sepulveda-Jauregui, A. and Martinez-Cruz, K. Modeling the impediment of methane ebullition bubbles by seasonal lake ice: Biogeosciences, 11(23), p. 6791-6811, illus. incl. 1 table, sketch map, 65 ref., 2014. Includes appendices.

Microbial methane (CH₄) ebullition (bubbling) from anoxic lake sediments comprises a globally significant flux to the atmosphere, but ebullition bubbles in temperate and polar lakes can be trapped by winter ice cover and later released during spring thaw. This "ice-bubble storage" (IBS) constitutes a novel mode of CH₄ emission. Before bubbles are encapsulated by downward-growing ice, some of their CH₄ dissolves into the lake water, where it may be subject to oxidation. We present field characterization and a model of the annual CH₄ cycle in Goldstream Lake, a thermokarst (thaw) lake in interior Alaska. We find that summertime ebullition dominates annual CH₄ emissions to the atmosphere. Eighty percent of CH₄ in bubbles trapped by ice dissolves into the lake water column in winter, and about half of that is oxidized. The ice growth rate and the magnitude of the CH₄ ebullition flux are important controlling factors of bubble dissolution. Seven percent of annual ebullition CH₄ is trapped as IBS and later emitted as ice melts. In a future warmer climate, there will likely be less seasonal ice cover, less IBS, less CH₄ dissolution from trapped bubbles, and greater CH₄ emissions from northern lakes.

DOI: 10.5194/bg-11-6791-2014

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2017015137 Jezek, Kenneth C. (Ohio State University, School of Earth Sciences, Columbus, OH). Airborne and space-borne remote sensing of cryosphere: in Earth system monitoring; selected entries from the encyclopedia of sustainability science and technology (Orcutt, John, editor), Springer, New York, NY, p. 7-34, 103 ref., 2013.

The cryosphere broadly constitutes all the components of the Earth system which contain water in a frozen state. As such, glaciers, ice sheets, snow cover, lake and river ice, and permafrost make up the terrestrial elements of the Cryosphere. Sea ice in all of its forms, frozen sea bed and icebergs constitute the oceanic elements of the Cryosphere while ice particles in the upper atmosphere and icy precipitation near the surface are the representative members of the Cryosphere in atmospheric systems.

DOI: 10.1007/978-1-4614-5684-1_2

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2017019672 Smirnov, A. N. (Institute for Geology and Mineral Resources of the Ocean, Academy Igor Gramberg, Saint Petersburg, Russian Federation); Zhurilova, M. A.; Bordukov, U. K.; Mironova, O. R. and Evdokimov, A. N. Fossil ivory deposits in the Arctic relic permafrost [abstr.]: in 35th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 35, Abstract 3584, 2016. Meeting: 35th international geological congress, Aug. 27-Sept. 4, 2016, Cape Town, South Africa.

Fossil ivory (tusks of Mammuthus primigenius) is a fossil analogue (Fl) of modern ivory. The only region in Russia (and in the entire World) of stable fossil mammoth ivory mining is the arctic part of Yakutia including the coasts of the Laptev Sea, East-Siberian seas, and the New Siberian Islands. 70-4 thousand years ago mammoths inhabited the entire area of the Late Pleistocene cryolithic zone in the northern hemisphere, which stretched from the coasts of the arctic seas far to the north. Yet the area of high-production FI collectors (deposits) are located only within the borders of the continuous modern cryoilithic zone in the continental part of the East Arctic sector of Eurasia. The basic conditions and the stages of formation of the fossil ivory deposits are caused by the major events in the natural processes in the arctic parts of the Earth in the Pleistocene-Holocene. One may mark out two basic stages of formation of FI deposits. The one stage (Late Pleistocene) is the stage of formation of the ivory-bearing collectors in the areas of active development of the Arctic cryolithic zone. The other one (Holocene-modern) is the stage of exposition of the deposits of FI and of formation of its placer concentrations caused by the global degradation of the Arctic cryolithic zone. In this case thermo-abrasive and other cryogenic processes became the active exogenic factors. The practical outcome of these processes is the occurrence of modern commercial FI deposits grouped in North Yakutia. The locations of the commercial deposits in this region are controlled by the following two main factors: bone-bearing collectors representing the continental covering cryogenic formations of the late Pleistocene-Holocene saturated with bone remains of fauna of the mammoth complex - origins of FI are located here; extensive outcrop of the collectors in the abrasion zone at the sea coasts, where their reworking, releasing a useful component and forming the FI concentrations take place.

URL: http://www.americangeosciences.org/sites/default/files/igc/3584.pdf

2017014992 Braverman, Michael (Wilfrid Laurier University, Waterloo, ON, Canada) and Quinton, William L. Lateral variations of ground temperatures along linear disturbances in the peatlands in the regions of discontinuous permafrost [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Réunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, p. 253-254, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.

2017015013 Hu Yalu (China University of Geosciences, Wuhan, China); Xing Wenle; Ma Rui and Sun Ziyong. Groundwater flow system in a permafrost area in the upper reaches of Heihe River [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Réunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, p. 270, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.

2017018012 Kielhofer, Jennifer R. (University of Arizona, Department of Geosciences, Tucson, AZ). Micromorphology of buried soils in central Alaska; a petrographic approach to understanding soil formation during the late Pleistocene and Holocene in interior subarctic lowlands [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 81-25, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.

Micromorphology is a valuable tool for identifying soil characteristics that are difficult or impossible to observe in the field. This technique has great potential to elucidate soil formation in high-latitude settings, where buried soils are often thin, discontinuous, and weakly developed. The Shaw Creek Flats (SCF) catchment and Delta River Valley (DRV) of interior Alaska are ideal regions for micromorphology, as they contain numerous buried soils in Late Pleistocene and Holocene aeolian deposits. However, little micromorphological research has been conducted in these regions, with most samples collected directly from archaeological excavations. In these cases, past human activity and cultural features could obscure the true soil-stratigraphic record. Therefore, previous samples may not accurately reflect the role of paleoenvironmental conditions on soil formation. To address such concerns, this micromorphology study examines soils from non-archaeological localities. Samples were collected from a deeply buried, stratified loess deposit near the Mead archaeological site in SCF and at the Hurricane Bluff loess exposure in the DRV. At Mead, buried soils dated to the Younger Dryas (12,120-11,850 cal BP) exhibit abundant and well-preserved organic matter, dusty clay coatings, and clay infillings, suggesting a moderate degree of pedogenesis. Abundant iron (Fe) oxide nodules and mottling indicate a fluctuating water table. In contrast to prior studies, frost action features are not observed, indicating that these soils were not strongly impacted by freeze/thaw processes. It is also possible that later soil formation under warmer Holocene climatic regimes obliterated such features. Hurricane Bluff samples show evidence of clay translocation, Fe oxide accumulation and moderate soil development throughout the Holocene, confirming field interpretations. Ultimately, soil micromorphology at these sites indicates moderate pedogenesis and weathering under relatively wet conditions or alternating wetting and drying cycles in the Late Pleistocene. Micromorphology also reveals the importance of vegetation growth in forming Late Pleistocene soils. Despite the modern prevalence of permafrost in this area, Late Pleistocene and most Holocene soils do not appear altered by frost action.

2017020043 Stewart, Alexander K. (Saint Lawrence University, Department of Geology, Canton, NY); Hubbard, Trent D. and Heinrich, Catherine. Analysis of frequent mass movement using dendrogeomorphology; Alaska Highway, Northway Junction, interior Alaska [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 277-4, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sep. 25-28, 2016, Denver, CO.

The more than 2,700-km-long Alaska Highway (AH) was built in less than one year (1942) through austere, wild environments, with inadequate design and maintenance. Aggravating this is the underlying permafrost that, with projected warming, will likely decrease the overall stability of portions of the roadway. In preparation for construction of a proposed natural-gas pipeline, a 4.8-hectare site was selected between Alaska Highway mileposts 1265 and 1267 near Northway Junction for dendrogeomorphic analysis. This section of the AH is affected by three large, retrogressive mass movements expanding headward from the bluffs of the Chisana River. We used a Swedish increment borer to sample 30 tilted Picea mariana (black spruce) trees in order to maximize the record of reaction wood growth as a result of tilting. After sample preparation, reaction wood events were characterized using microscopic analysis and recorded as modified skeleton plots of event-response phenomena, which resulted in a replication-summary plot. Of the 29 trees analyzed (56 cores), the chronology for these tilted specimens was 175 years (1840-2014). Visual and statistical analyses from 1900-2014 show that before 1989 (a period of 88 years), reaction wood accounted for only 5% of recorded tree growth; however, from 1989 onward (a period of 24 years), reaction wood accounted for 35% of recorded tree growth. Spatial evaluation of select reaction-wood years (1966, 1989, 1995, 2006 and 2011) reveals site-wide disturbance during each event. We propose that this section of the AH was stable from at least 1899 to 1987, with no recognized failure associated with the 1942 emplacement of the highway. In the late-growth or post-growth season of 1988-1989, a mass-movement event destabilized the site with continued, significant (re)mobilizations proposed in 1994, 2005, 2010 and, by extension, 2013. With climate impacting higher latitudes at greater rates, Alaskans can expect climate-induced effects on infrastructure; depending on the climate model and implemented adaptations, these could add up to 20% ($6.1 billion) to normal wear and tear costs from now until 2030 (Larsen et al., 2008).

2017015337 Wang, Y. (Jilin University, College of Construction Engineering, Changchun, China); Sun, Y. H.; Guo, W. and Jia, R. Development and experiments of hole-bottom freezing drilling tool for gas-hydrate-bearing sediments sampling [abstr.]: in 35th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 35, Abstract 4344, illus., 4 ref., 2016. Meeting: 35th international geological congress, Aug. 27-Sept. 4, 2016, Cape Town, South Africa.

World-wide natural gas hydrate (NGH) is a kind of notably large potential energy resource. Its reserves was estimated at over 15X10¹² tons of oil equivalent. In fact, when the utilization rate of this resource just reached 17%-20%, the world's energy requirements for 200 years would be satisfied [1]. NGHs are stable at low temperatures and high pressures and are usually located in permafrost regions, deepwater seas, and lake sediments [2,3]. The analysis of core samples is an essential component in the exploration-exploitation of natural gas hydrates (NGH). The condition precedent for investigations of NGH drilling core is a special sampling technique that prevents its volatilization in the sampling process. In this paper, we propose a hole-bottom freezing method for NGH sampling that uses the mixture of alcohol and dry ice as a cold source to decrease the temperature of the NGH drilling core. The low temperature reduces NGH's critical breakdown pressure and promotes the self-preservation of NGH. For example, gas hydrates were putted into the vessel that its temperature is -5°C, -10°C and -18°C, the gas hydrates almost didn't decompose in the time of ten days. When the temperature of vessel is -18°C, the decompose amount is only 0.85% [4]. We introduce the hole-bottom freezing drilling tool that allow for the recovery of gas-hydrate-bearing sediments, A schematic of the NGH hole-bottom freezing drilling tool is shown in Figure. 1. The hole-bottom freezing technique utilizes a sampling barrel and an outer pipe. The mixture of alcohol and dry ice is injected into the annular space between the sampling barrel and the outer pipe to reduce the NGH core to subzero temperatures during the sampling process. Then, functional tests using several different experiments such as hole-bottom storage experiment of cold source, freezing experiment of simulative NGH-core and application of the drilling tool. Laboratory tests and the application show that the hole-bottom freezing method are feasible for NGH sediments sampling.

URL: http://www.americangeosciences.org/sites/default/files/igc/4344.pdf

2017015012 Luo Dongliang (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Jin Huijun and Lu Lanzhi. Recent advances in monitoring of the unfrozen soil water in the source area of the Yellow River, China [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Réunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, p. 269-270, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.

2017019926 Banks, Maria E. (Planetary Science Institute, Tucson, AZ); Fenton, Lori K.; Bridges, Nathan T.; Geissler, Paul E.; Chojnacki, Matthew; Silvestro, Simone and Zimbelman, James R. Mobility in middle and high southern latitude dune fields [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 140-6, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sep. 25-28, 2016, Denver, CO.

Repeat images of martian aeolian features acquired by the High Resolution Imaging Science Experiment (HiRISE) have led to the detection of changes and migration of bedforms (dunes and ripples) in some locations, while other locations do not yet show evidence of change or movement. While all image pairs of bedforms in high northern latitudes (>60° N) show evidence of aeolian driven movement (likely due at least in part to strong katabatic winds from the high elevation polar cap), the same is not true for bedforms observed in high southern latitudes. Here we analyze all currently available HiRISE image pairs covering dune fields at latitudes south of 40° for evidence of movement. We also apply a dune stability index (SI) based on morphological characteristics (0-6, with higher numbers indicating more morphological indications of stability and erosion) based on previous work by Fenton and Hayward (2010). Of the 71 locations investigated, »65% show evidence of wind driven movement or bedform migration. Results indicate a general trend of decreasing sand mobility with increasing latitude and SI. Over 75% of the sites between 40-60° S latitude show changes while »50% of sites south of 60° S, and over 60% of sites south of 70° S show no detectable movement. This is consistent with previous morphological studies that have suggested that bedforms in high southern latitudes are stabilized by agents, such as ground ice, which likely limit sediment movement (i.e. sand availability). Bedforms also show a general decrease in migration rate in higher latitudes, although the highest rates occur in Noachis Terra and Icaria Planum and may be related more to regional trends in wind strength rather than the presence or absence of seasonal (polar) processes. Bedforms with lower (more active-appearing) SIs are more active while those with higher SIs (5-6, less active-appearing) are dominantly immobile. Migration rates also generally decrease with increasing SI. Interestingly, most ripples with an SI of 3 exhibit migration. This combination of actively migrating bedforms along with dune field morphologies consistent with both stability and activity suggests possible competing influences of aeolian and polar processes, or perhaps a shift from earlier conditions dominated by polar processes to a more recent increase in aeolian activity.

2017020061 Hon, Rudolph (Boston College, Department of Earth and Environmental Sciences, Chestnut Hill, MA); Rice, Mikaela; Schaudt, Barry; Andronache, Constantin and Besancon, James. Simulation of dynamics and mechanism of road salt brines migration in the subsurface [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 278-11, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sep. 25-28, 2016, Denver, CO.

Deicer brines (sodium chloride) running off the road surfaces during/after the winter snowstorms are significantly denser than the surrounding snow or ice. For temperatures ranging downward from 30 oF to 25 oF and 20 oF these solutions have densities increasing from 1.015 g/cm³ to 1.047 g/cm³ and 1.075 g/cm³ respectively. The brines will therefore accumulate at the bottom of the snow pile and even melt through the frozen ground to reach the subsurface and the underlying aquifer. Our interest is to investigate how these concentrated solutions interact with groundwater and the mechanism of modifying their initial high concentrations to the levels observed in natural waters in the northeastern US. In the same temperature range as above (30 oF to 20 oF) the brine concentrations increase from 2.1 wt% to near 10 wt% of NaCl whereas by contrast the NaCl concentration in natural waters is typically less than 0.2 wt%, more commonly 0.02 wt% to 0.08 wt%. We designed a series of benchtop experiments using plastic transparent boxes (12 x 12 x 21 cm) filed with a saturated single fraction fine sand and introduced blue dyed brine solutions (0.5 wt%, 1 wt%, and 5 wt%) alongside the transparent wall. Experimental progress was recorded by time lapse photography.

2017020071 King, Courtney C. (University of Maine, School of Earth and Climate Sciences, Orono, ME); Hillebrand, Trevor R.; Stone, John O. and Hall, Brenda L. History of the last glacial maximum and subsequent recession alongside Hatherton Glacier, Antarctica [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 279-7, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sep. 25-28, 2016, Denver, CO.

Well-constrained glacial geologic data from the maximum and termination of the last ice age afford key insights into the behavior of the Antarctic Ice Sheet (AIS) under a rapidly changing climate and offer benchmarks for model simulations. Here, we present new data on the timing and style of the local last glacial maximum and subsequent deglaciation of Hatherton Glacier, an outlet of the AIS in the Ross Sea sector. The current paradigm is that during the last glacial maximum (LGM), the expanded AIS grounded across what today is the Ross Sea. This grounded Ross Sea Ice Sheet caused inflowing ice from outlet glaciers and ice streams entering the embayment from East and West Antarctica, respectively, to thicken. Widespread deposits in the adjacent and now ice-free valleys provide evidence of these outlet glaciers achieving and then abandoning their LGM positions. However, previous chronologic information from Hatherton Glacier affords conflicting stories of the ice sheet's LGM history, with one interpretation casting doubt on whether the outlet glacier thickened at all during the maximum of the last glaciation. We re-evaluated the LGM history of Hatherton Glacier by carrying out our own systematic radiocarbon dating study using more than 150 dates of subfossil algae from glacial deposits and from former ice-dammed ponds associated with the ice-margin. Our work shows that the last high-stand of Hatherton Glacier occurred approximately 10 ka and subsequent ice recession was gradual throughout the Holocene. This new chronology, constructed from three sites along the glacier, is consistent with evidence elsewhere in the Transantarctic Mountains that suggests maximum ice levels during the last ice age were reached during the termination of the global ice age, possibly as a result of increased precipitation.

2017018000 Trzinski, Adam (University of Delaware, Department of Geological Sciences, Newark, DE) and O'Neal, Michael. Evaluating the physiographic and climatic controls on rock glaciers and protalus ramparts in the dry Andes, San Juan, Argentina [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 81-13, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.

Recent environmental legislation in Argentina protects ground ice, including that in rock glaciers and protalus ramparts, as important sources of water reserves in the Dry Andes. However, the true extent of ground ice coverage - and therefore its impact on regional hydrology is not well known in this remote and little-studied terrain. This study investigates the physiographic and climatic factors controlling the distribution of rock glaciers and protalus ramparts using a digital inventory from two different locations of the Dry Andes in the San Juan Province, Argentina. Principal components analysis of the inventory data indicates that south and west-trending slopes favor the formation of rock glaciers, whereas north and east-trending slopes favor the formation of protalus ramparts. These results, when coupled with other data, indicate that protalus ramparts and rock glaciers form in unique physiographic settings where slope, elevation, and solar radiation are the primarya controls on their presence/absence. Our methods and results can be applied to other areas in the Dry Andes to identify analogous conditions aiding land-use and environmental protection decisions.

2017017622 Merritts, Dorothy (Franklin and Marshall College, Earth and Environment, Lancaster, PA); Schulte, Kayla; Blair, Aaron; Potter, Noel; Walter, Robert; Markey, Erin; Weiserbs, Ben; Alter, Sam; Guillorn, Sally; Lewis, Evan; Kehne, Larissa and Xie, Yunan. Lidar analysis of periglacial landforms and their paleoclimatic significance, unglaciated Pennsylvania: in Guidebook for the 79th annual field conference of Pennsylvania geologists; Pennsylvania's Great Valley & bordering mountains near Carlisle (Anthony, Robin, editor; et al.), Guidebook for the Annual Field Conference of Pennsylvania Geologists, 79, p. 49-76, illus. incl. geol. sketch map, 45 ref., 2014. Meeting: 79th annual field conference of Pennsylvania geologists, Oct. 16-18, 2014, Pennsylvania.

URL: http://fcopg.org/wp-content/uploads/2014/06/FCOPG-14_GUIDEBOOK_001_083_Intro.pdf

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