2016094441 Lenz, Josefine (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Department of Periglacial Research, Potsdam, Germany); Wetterich, Sebastian; Jones, Benjamin M.; Meyer, Hanno; Bobrov, Anatoly and Grosse, Guido. Evidence of multiple thermokarst lake generations from an 11 800-year-old permafrost core on the northern Seward Peninsula, Alaska: Boreas, 45(4), p. 584-603, illus. incl. sect., 3 tables, sketch map, 98 ref., October 2016. NSF Grant ARC-0732735.

Permafrost degradation influences the morphology, biogeochemical cycling and hydrology of Arctic landscapes over a range of time scales. To reconstruct temporal patterns of early to late Holocene permafrost and thermokarst dynamics, site-specific palaeo-records are needed. Here we present a multi-proxy study of a 350-cm-long permafrost core from a drained lake basin on the northern Seward Peninsula, Alaska, revealing Lateglacial to Holocene thermokarst lake dynamics in a central location of Beringia. Use of radiocarbon dating, micropalaeontology (ostracods and testaceans), sedimentology (grain-size analyses, magnetic susceptibility, tephra analyses), geochemistry (total nitrogen and carbon, total organic carbon, d¹³C_org) and stable water isotopes (d¹⁸O, dD, d excess) of ground ice allowed the reconstruction of several distinct thermokarst lake phases. These include a pre-lacustrine environment at the base of the core characterized by the Devil Mountain Maar tephra (22 800 ± 280 cal. a BP, Unit A), which has vertically subsided in places due to subsequent development of a deep thermokarst lake that initiated around 11 800 cal. a BP (Unit B). At about 9000 cal. a BP this lake transitioned from a stable depositional environment to a very dynamic lake system (Unit C) characterized by fluctuating lake levels, potentially intermediate wetland development, and expansion and erosion of shore deposits. Complete drainage of this lake occurred at 1060 cal. a BP, including post-drainage sediment freezing from the top down to 154 cm and gradual accumulation of terrestrial peat (Unit D), as well as uniform upward talik refreezing. This core-based reconstruction of multiple thermokarst lake generations since 11 800 cal. a BP improves our understanding of the temporal scales of thermokarst lake development from initiation to drainage, demonstrates complex landscape evolution in the ice-rich permafrost regions of Central Beringia during the Lateglacial and Holocene, and enhances our understanding of biogeochemical cycles in thermokarst-affected regions of the Arctic. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1111/bor.12186

2016094152 Mavromatis, Vasileios (Observatoire Midi-Pyrénées, Géosciences Environnement Toulouse, Toulouse, France); Rinder, Thomas; Prokushkin, Anatoly S.; Pokrovsky, Oleg S.; Korets, Mikhail A.; Chmeleff, Jérôme and Oelkers, Eric H. The effect of permafrost, vegetation, and lithology on Mg and Si isotope composition of the Yenisey River and its tributaries at the end of the spring flood: Geochimica et Cosmochimica Acta, 191, p. 32-46, illus. incl. 2 tables, sketch map, 85 ref., October 15, 2016. Includes appendices.

This work focuses on the behavior of the stable Mg and Si isotope compositions of the largest Arctic river, the Yenisey River and 28 of its major and minor tributaries during the spring flood period. Samples were collected along a 1500 km latitudinal profile covering a wide range of permafrost, lithology, and vegetation. Despite significant contrasts in the main physico-geographical, climate, and lithological parameters of the watersheds, the isotope composition of both dissolved Mg and Si was found to be only weakly influenced by the degree of the permafrost coverage, type of vegetation (forest vs. tundra), and lithology (granites, basalts, carbonates or terrigenous rocks). This observation is generally consistent with the lack of chemical uptake of Mg and Si by soil mineral formation and vegetation during the early spring. The radiogenic Sr isotope composition of the Yenisey and its tributaries varied within a narrow range (0.708 ≤&eq; ⁸⁷Sr/⁸⁶Sr ≤&eq; 0.711) reflecting the dominance of Phanerozoic rock weathering and/or atmospheric deposition on these compositions. The Mg and Si isotopic compositions of riverine samples reflect two main processes with distinct isotopic signatures. First, isotopically heavier Mg (d²⁶Mg = -1.0 ± 0.2 ppm) and isotopically lighter Si (d³⁰Si = 1.0 ± 0.25 ppm) are added to the waters by river suspended matter dissolution and leaching from vegetation biomass/topsoil litter. Second, isotopically lighter Mg (d²⁶Mg = -1.5 to -1.75 ppm) and isotopically heavier Si (d³⁰Si = 1.75-2.0 ppm) are delivered to the Yenisey's tributaries from deep underground water feeding the rivers via taliks. This lighter Mg and heavier Si isotopic composition is interpreted to originate from Precambrian dolomite dissolution and aluminosilicate dissolution coupled with authigenic mineral precipitation, respectively, in deep underground water reservoirs. Taking account of the isotopic composition evolution over the course of the year established earlier on mono-lithological watersheds of the Yenisey basin, the average annual isotopic signatures of the Yenisey river arriving to the Arctic Ocean are estimated to be d²⁶Mg = -1.58 ± 0.30 ppm and d³⁰Si = +1.60 ± 0.25 ppm. As the Yenisey is the largest river feeding the Arctic Ocean and as it samples a large variety of environments and lithologies, these values may be reasonable estimates for the average Mg and Si isotopic composition of the dissolved riverine flux to the Arctic Ocean.

DOI: 10.1016/j.gca.2016.07.003

2016098985 Way, Robert G. (University of Ottawa, Department of Geography, Environment and Geomatics, Ottawa, ON, Canada) and Lewkowicz, Antoni G. Modelling the spatial distribution of permafrost in Labrador-Ungava using the temperature at the top of permafrost: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 53(10), p. 1010-1028 (French sum.), illus. incl. 4 tables, sketch map, 86 ref., October 2016.

Permafrost zonation in Labrador-Ungava ranges from very isolated patches through to continuous permafrost. Here we present a new estimate of the distribution of permafrost at high resolution (250 m ´ 250 m) using spatial numerical modelling supported by station data from 29 air and ground climate monitoring stations. Permafrost presence was estimated using a modified version of the temperature at the top of permafrost (TTOP) model. Mean ground surface temperatures were modelled using gridded air temperatures and a novel n-factor parameterization scheme that compensates for regional differences in continentality, snowfall, and land cover and is transferable to other Subarctic environments. The thermal offset was modelled using land cover and surficial material datasets. Predicted TTOP values for the average climate range regionally from -9 °C (for high elevations in northern Quebec) to +5 °C (for southeastern Labrador - Quebec). Modelling for specific temporal windows (1948-1962, 1982-1996, 2000-2014) suggests that permafrost area increased from the middle of the 20th century to a potential peak extent (36% of the total land area) in the 1990s. Subsequent warming is predicted to have caused a decrease in permafrost extent of one-quarter (95 000 km²), even if air temperatures rise no further, providing air and ground temperatures equilibrate. Zonal boundaries derived by upscaling the high-resolution model are highly scale dependent, precluding direct comparison with the Permafrost Map of Canada that was generated without the use of geographic information system based analyses.

DOI: 10.1139/cjes-2016-0034

2016096667 Gordon, J. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Quinton, W.; Branfireun, B. A. and Olefeldt, D. Mercury and methylmercury biogeochemistry in a thawing permafrost wetland complex, Northwest Territories, Canada: Hydrological Processes, 30(20), p. 3627-3638, illus. incl. 1 table, sketch map, 54 ref., September 30, 2016.

In arctic and sub-arctic environments, mercury (Hg), more specifically toxic methylmercury (MeHg), is of growing concern to local communities because of its accumulation in fish. In these regions, there is particular interest in the potential mobilization of atmospherically deposited Hg sequestered in permafrost that is thawing at unprecedented rates. Permafrost thaw and the resulting ground surface subsidence transforms forested peat plateaus into treeless and permafrost-free thermokarst wetlands where inorganic Hg released from the thawed permafrost and draining from the surrounding peat plateaus may be transformed to MeHg. This study begins to characterize the spatial distribution of MeHg in a peat plateau-thermokarst wetland complex, a feature that prevails throughout the wetland-dominated southern margin of thawing discontinuous permafrost in Canada's Northwest Territories. We measured pore water total Hg, MeHg, dissolved organic matter characteristics and general water chemistry parameters to evaluate the role of permafrost thaw on the pattern of water chemistry. A gradient in vegetation composition, water chemistry and dissolved organic matter characteristics followed a toposequence from the ombrotrophic bogs near the crest of the complex to poor fens at its downslope margins. We found that pore waters in poor fens contained elevated levels of MeHg, and the water draining from these features had dissolved MeHg concentrations 4.5 to 14.5 times higher than the water draining from the bogs. It was determined through analysis of historical aerial images that the poor fens in the toposequence had formed relatively recently (early 1970s) as a result of permafrost thaw. Differences between the fens and bogs are likely to be a result of their differences in groundwater function, and this suggests that permafrost thaw in this landscape can result in hotspots for Hg methylation that are hydrologically connected to downstream ecosystems. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.10911

2016096796 Iwahana, Go (University of Alaska at Fairbanks, International Arctic Research Center, Fairbanks, AK); Harada, Koichiro; Uchida, Masao; Tsuyuzaki, Shiro; Saito, Kazuyuki; Narita, Kenji; Kushida, Keiji and Hinzman, Larry D. Geomorphological and geochemistry changes in permafrost after the 2002 tundra wildfire in Kougarok, Seward Peninsula, Alaska: Journal of Geophysical Research: Earth Surface, 121(9), p. 1697-1715, illus. incl. 2 tables, sketch maps, 63 ref., September 2016.

Geomorphological and thermohydrological changes to tundra, caused by a wildfire in 2002 on the central Seward Peninsula of Alaska, were investigated as a case study for understanding the response from ice-rich permafrost terrain to surface disturbance. Frozen and unfrozen soil samples were collected at burned and unburned areas, and then water isotope geochemistry and cryostratigraphy of the active layer and near-surface permafrost were analyzed to investigate past hydrological and freeze/thaw conditions and how this information could be recorded within the permafrost. The development of thermokarst subsidence due to ice wedge melting after the fire was clear from analyses of historical submeter-resolution remote sensing imagery, long-term monitoring of thermohydrological conditions within the active layer, in situ surveys of microrelief, and geochemical signals recorded in the near-surface permafrost. The resulting polygonal relief coincided with depression lines along an underground ice wedge network, and cumulative subsidence to 2013 was estimated as at least 10.1 to 12.1 cm (0.9-1.1 cm/year 11 year average). Profiles of water geochemistry in the ground indicated mixing or replenishment of older permafrost water with newer meteoric water, as a consequence of the increase in active layer thickness due to wildfire or past thaw event. Our geocryological analysis of cores suggests that permafrost could be used to reconstruct the permafrost degradation history for the study site. Distinct hydrogen and oxygen isotopic compositions above the Global Meteoric Water Line were found for water from these sites where permafrost degradation with geomorphological change and prolonged surface inundation were suggested. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016JF003921

2016096391 McGuire, A. David (University of Alaska at Fairbanks, Faibanks, AK); Koven, Charles; Lawrence, David M.; Clein, Joy S.; Xia Jiangyang; Beer, Christian; Burke, Eleanor; Chen, Guangsheng; Chen, Xiaodong; Delire, Christine; Jafarov, Elchin; MacDougall, Andrew H.; Marchenko, Sergey; Nicolsky, Dmitry; Peng, Shushi; Rinke, Annette; Saito, Kazuyuki; Zhang, Wenxin; Alkama, Ramdane; Bohn, Theodore J.; Ciais, Philippe; Decharme, Bertrand; Ekici, Altug; Gouttevin, Isabelle; Hajima, Tomohiro; Hayes, Daniel J.; Ji Duoying; Krinner, Gerhard; Lettenmaier, Dennis P.; Luo, Yiqi; Miller, Paul A.; Moore, John C.; Romanovsky, Vladimir; Schädel, Christina; Schaefer, Kevin; Schuur, Edward A. G.; Smith, Benjamin; Sueyoshi, Tetsuo and Zhuang, Qianlai. Variability in the sensitivity among model simulations of permafrost and carbon dynamics in the permafrost region between 1960 and 2009: Global Biogeochemical Cycles, 30(7), p. 1015-1037, illus. incl. 9 tables, 121 ref., July 2016.

A significant portion of the large amount of carbon (C) currently stored in soils of the permafrost region in the Northern Hemisphere has the potential to be emitted as the greenhouse gases CO₂ and CH₄ under a warmer climate. In this study we evaluated the variability in the sensitivity of permafrost and C in recent decades among land surface model simulations over the permafrost region between 1960 and 2009. The 15 model simulations all predict a loss of near-surface permafrost (within 3 m) area over the region, but there are large differences in the magnitude of the simulated rates of loss among the models (0.2 to 58.8 ´ 10³ km² yr^-1). Sensitivity simulations indicated that changes in air temperature largely explained changes in permafrost area, although interactions among changes in other environmental variables also played a role. All of the models indicate that both vegetation and soil C storage together have increased by 156 to 954 Tg C yr^-1 between 1960 and 2009 over the permafrost region even though model analyses indicate that warming alone would decrease soil C storage. Increases in gross primary production (GPP) largely explain the simulated increases in vegetation and soil C. The sensitivity of GPP to increases in atmospheric CO₂ was the dominant cause of increases in GPP across the models, but comparison of simulated GPP trends across the 1982-2009 period with that of a global GPP data set indicates that all of the models overestimate the trend in GPP. Disturbance also appears to be an important factor affecting C storage, as models that consider disturbance had lower increases in C storage than models that did not consider disturbance. To improve the modeling of C in the permafrost region, there is the need for the modeling community to standardize structural representation of permafrost and carbon dynamics among models that are used to evaluate the permafrost C feedback and for the modeling and observational communities to jointly develop data sets and methodologies to more effectively benchmark models. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GB005405

2016090017 Mu Cuicui (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Zhang Tingjun; Zhang Xiankai; Li Lili; Guo Hong; Zhao Qian; Cao Lin; Wu Qingbai and Cheng Guodong. Carbon loss and chemical changes from permafrost collapse in the northern Tibetan Plateau: Journal of Geophysical Research: Biogeosciences, 121(7), p. 1781-1791, illus. incl. 1 table, 54 ref., July 2016.

Permafrost collapse, known as thermokarst, can alter soil properties and carbon emissions. However, little is known regarding the effects of permafrost collapse in upland landscapes on the biogeochemical processes that affect carbon balance. In this study, we measured soil carbon and physiochemical properties at a large thermokarst feature on a hillslope in the northeastern Tibetan Plateau. We categorized surfaces into three different microrelief patches based on type and extent of collapse (control, drape, and exposed areas). Permafrost collapse resulted in substantial decreases of surface soil carbon and nitrogen stocks, with losses of 29.6 ± 4.2% and 28.9 ± 3.1% for carbon and nitrogen, respectively, in the 0-10 cm soil layer. Laboratory incubation experiments indicated that control soil had significantly higher CO₂ production rates than that of drapes. The results from Fourier transform infrared spectroscopy analysis showed that exposed soils accumulated some organic matter due to their low position within the feature, which was accompanied by substantial changes in the chemical structure and characteristics of the soil carbon. Exposed soils had higher hydrocarbon and lignin/phenol backbone content than in control and drape soils in the 0-10 cm layer. This study demonstrates that permafrost collapse can cause abundant carbon and nitrogen loss, potentially from mineralization, leaching, photodegradation, and lateral displacement. These results demonstrate that permafrost collapse redistributes the soil organic matter, changes its chemical characteristics, and leads to losses of organic carbon due to the greenhouse gas emission. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015JG003235

2016096393 Tanski, George (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Couture, Nicole; Lantuit, Hugues; Eulenburg, Antje and Fritz, Michael. Eroding permafrost coasts release low amounts of dissolved organic carbon (DOC) from ground ice into the nearshore zone of the Arctic Ocean: Global Biogeochemical Cycles, 30(7), p. 1054-1068, illus. incl. 5 tables, 95 ref., July 2016.

Ice-rich permafrost coasts in the Arctic are highly sensitive to climate warming and erode at a pace that exceeds the global average. Permafrost coasts deliver vast amounts of organic carbon into the nearshore zone of the Arctic Ocean. Numbers on flux exist for particulate organic carbon (POC) and total or soil organic carbon (TOC, SOC). However, they do not exist for dissolved organic carbon (DOC), which is known to be highly bioavailable. This study aims to estimate DOC stocks in coastal permafrost as well as the annual flux into the ocean. DOC concentrations in ground ice were analyzed along the ice-rich Yukon coast (YC) in the western Canadian Arctic. The annual DOC flux was estimated using available numbers for coast length, cliff height, annual erosion rate, and volumetric ice content in different stratigraphic horizons. Our results showed that DOC concentrations in ground ice range between 0.3 and 347.0 mg L^-1 with an estimated stock of 13.6 ± 3.0 g m^-3 along the YC. An annual DOC flux of 54.9 ± 0.9 Mg yr^-1 was computed. These DOC fluxes are low compared to POC and SOC fluxes from coastal erosion or POC and DOC fluxes from Arctic rivers. We conclude that DOC fluxes from permafrost coasts play a secondary role in the Arctic carbon budget. However, this DOC is assumed to be highly bioavailable. We hypothesize that DOC from coastal erosion is important for ecosystems in the Arctic nearshore zones, particularly in summer when river discharge is low, and in areas where rivers are absent. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015GB005337

2016093830 Frederick, Jennifer M. (Sandia National Laboratories, Albuquerque, NM) and Buffett, Bruce A. Submarine groundwater discharge as a possible formation mechanism for permafrost-associated gas hydrate on the circum-Arctic continental shelf: Journal of Geophysical Research: Solid Earth, 121(3), p. 1383-1404, illus. incl. 1 table, 30 ref., March 2016.

Submarine groundwater discharge (SGD) is a large-scale, buoyancy-driven, offshore flow of terrestrial groundwater. If SGD occurs within the permafrost-bearing sediments of the circum-Arctic shelf, such fluid circulation may transport large amounts of dissolved methane to the circum-Arctic shelf, aiding the formation of permafrost-associated gas hydrate. We investigate the feasibility of this new permafrost-associated gas hydrate formation mechanism with a 2-D, multiphase fluid flow model, using the Canadian Beaufort Shelf as an example. The numerical model includes freeze/thaw permafrost processes and predicts the unsteady, 2-D methane solubility field for hydrate inventory calculations. Model results show that widespread, low-saturation hydrate deposits accumulate within and below submarine permafrost, even if offshore-flowing groundwater is undersaturated in methane gas. While intrapermafrost hydrate inventory varies widely depending on permafrost extent, subpermafrost hydrate stability remains largely intact across consecutive glacial cycles, allowing widespread subpermafrost accumulation over time. Methane gas escape to the sediment surface (atmosphere) is predicted along the seaward permafrost boundary during the early to middle years of each glacial epoch; however, if free gas is trapped within the forming permafrost layer instead, venting may be delayed until ocean transgression deepens the permafrost table during interglacial periods, and may be related to the spatial distribution of observed pingo-like features (PLFs) on the Canadian Beaufort Shelf. Shallow, gas-charged sediments are predicted above the gas hydrate stability zone at the midshelf to shelf edge and the upper slope, where a gap in hydrate stability allows free gas to accumulate and numerous PLFs have been observed. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015JB012627

2016093572 Kanevskiy, Mikhail (University of Alaska, Institute of Northern Engineering, Fairbanks, AK); Shur, Yuri; Strauss, Jens; Jorgenson, Torre; Fortier, Daniel; Stephani, Eva and Vasiliev, Alexander. Patterns and rates of river bank erosion involving ice-rich permafrost (yedoma) in northern Alaska: Geomorphology, 253, p. 370-384, illus. incl. 5 tables, sketch maps, 88 ref., January 15, 2016. Includes appendices.

Yedoma, a suite of syngenetically frozen silty ice- and organic-rich deposits with large ice wedges that accumulated during the late Pleistocene, is vulnerable to thermal degradation and erosion because of the extremely high ice contents. This degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution, infrastructure damage, and water quality. We used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35-m-high active yedoma bluff along the Itkillik River in northern Alaska. The total volumetric ground-ice content-including wedge, segregated, and pore ice-was estimated to be ~ 86%. The process of riverbank erosion and stabilization include three main stages typical of the areas with ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. Active riverbank erosion at the main study site started in July 1995, when the Itkillik River changed its channel. The total retreat of the riverbank during 1995-2010 within different segments of the bluff varied from 180 to 280 m; the average retreat rate for the most actively eroded part of the riverbank was almost 19 m/y. From August 2007 to August 2011, the total retreat varied from 10 to almost 100 m. The average retreat rate for the whole 680-m-long bluff was 11 m/y. For the most actively eroded central part of the bluff (150 m long) it was 20 m/y, ranging from 16 to 24 m/y. More than 180,000 m³ of ground ice and organic-rich frozen soil, or almost 70,000 metric tons (t) of soil solids including 880 t of organic carbon, were transported to the river from the retreating bank annually. This study reports the highest long-term rates of riverbank erosion ever observed in permafrost regions of Eurasia and North America. Abstract Copyright (2016) Elsevier, B.V.

DOI: 10.1016/j.geomorph.2015.10.023

2016097429 Riedel, Michael (Geological Survey of Canada-Pacific, Sidney, BC, Canada); Goldberg, David S. and Guerin, G. Compressional and shear-wave velocities from gas hydrate bearing sediments; examples from the India and Cascadia margins as well as Arctic permafrost regions: in Geologic implications of gas hydrates in the offshore of India; results of the National Gas Hydrate Program Expedition 01 (Ramana, M. V., editor; et al.), Marine and Petroleum Geology, 58(Part A), p. 292-320, illus. incl. 4 tables, sketch map, 54 ref., December 2014.

Shear wave velocity data have been acquired at several marine gas hydrate drilling expeditions, including the India National Gas Hydrate Program Expedition 1 (NGHP-01), the Ocean Drilling Program (ODP) Leg 204, and Integrated Ocean Drilling Program (IODP) Expedition 311 (X311). In this study we use data from these marine drilling expeditions to develop an understanding of general grain-size control on the P- and S-wave properties of sediments. A clear difference in the downhole trends of P-wave (Vp) and S-wave (Vs) velocity and the Vp/Vs ratio from all three marine regions was observed: the northern Cascadia margin (IODP X311) shows the highest P-wave and S-wave velocity values overall and those from the India margin (Expedition NGHP-01) are the lowest. The southern Cascadia margin (ODP Leg 204) appears to have similar low P-wave and S-wave velocity values as seen off India. S-wave velocity values increase relative to the sites off India, but they are not as high as those seen on the northern Cascadia margin. Such regional differences can be explained by the amount of silt/sand (or lack thereof) occurring at these sites, with northern Cascadia being the region of the highest silt/sand occurrences. This grain-size control on P-wave and S-wave velocity and associated mineral composition differences is amplified when compared to the Arctic permafrost environments, where gas hydrate predominantly occurs in sand- and silt-dominated formations. Using a cross-plot of gamma ray values versus the Vp/Vs ratio, we compare the marine gas hydrate occurrences in these regions: offshore eastern India margin, offshore Cascadia margin, the Ignik-Sikumi site in Alaska, and the Mallik 5L-38 site in the Mackenzie Delta. The log-data from the Arctic permafrost regions show a strongly linear Vp-Vs relationship, similar to the previously defined empirical relationships by Greenberg and Castagna (1992). P- and S-wave velocity data from the India margin and ODP Leg 204 deviate strongly from these linear trends, whereas data from IODP X311 plot closer to the trend of the Arctic data sets and previously published relationships. Three new linear relationships for different grain size marine sediment hosts are suggested: a) mud-dominated (Mahanadi Basin, ODP Leg 204 & NGHP-01-17): Vs = 1.5854 ´ Vp - 2.1649 b) silty-mud (KG Basin): Vs = 0.8105 ´ Vp - 1.0223 c) silty-sand (IODP X311): Vs = 0.5316 ´ Vp - 0.4916 We investigate the relationship of gas hydrate saturation determined from electrical resistivity on the Vp/Vs ratio and found that the sand-dominated Arctic hosts show a clearly decreasing trend of Vp/Vs ratio with gas hydrate saturation. Though limited due to lower overall GH saturations, a similar trend is seen for sites from IODP X311 and at the ash-dominated NGHP-01-17 sediment in the Andaman Sea. Gas hydrate that occurs predominantly in fractured clay hosts show a different trend where the Vp/Vs ratio is much higher than at sand-dominated sites and remains constant or increases slightly with increasing gas hydrate saturation. This trend may be the result of anisotropy in fracture-dominated systems, where P- and S-wave velocities appear higher and Archie-based saturations of gas hydrate are overestimated. Gas hydrate concentrations were also estimated in these three marine settings and at Arctic sites using an effective medium model, combining P- and S-wave velocities as equally weighted constraints on the calculation. The effective medium approach generally overestimates S-wave velocity in high-porosity, clay-dominated sediments, but can be accurately used in sand-rich formations. Abstract Copyright (2014) Elsevier, B.V.

DOI: 10.1016/j.marpetgeo.2014.07.028

2016095135 Severskiy, E. V. (Russian Academy of Sciences, Research Institute of the Permafrost, Kazakhstan Highland Geocryological Laboratory, Almaty, Kazakhstan); Olenchenko, V. V. and Gorbunov, A. P. Vliyaniye lokal'nykh faktorov na rasprostraneniye tolshchi merzlykh porod perevala Zhosalykezen' (Severnyy Tyan'-Shan') [Influence of local factors on permafrost distribution in the Zhosalykezen Pass (northern Tien Shan)]: Kriosfera Zemli = Earth Cryosphere, 18(4), p. 13-22 (English sum.), illus. incl. sect., 9 ref., December 2014.

The results of studies of mountain permafrost of the alpine type by the methods of thermometry and geoelectrical survey are presented. The influence of natural and anthropogenic local factors on the structure of permafrost is demonstrated using the geoelectric models. Such factors include the exposition of the slope, the tectonics, the warming and cooling effects of the foundations of buildings. Changing slope exposure is expressed in geoelectric models by the decreasing of resistivity of high-resistance horizon, the violation of its continuity and the decreasing of its thickness. In the area of faults the discontinuous or island character of the high-resistance horizon (permafrost) is observed. During the seismic events the temperature of rocks increases here up to the positive values. According to geophysical data, the formation of taliks occurs in the base of deformed buildings, in the places of accumulation of snow as snow barriers and under the sites with asphalt covering.

2016095141 Korniyenko, S. G. (Russian Academy of Sciences, Institute of Oil and Gas, Moscow, Russian Federation). Otsenka pogreshnosti izmereniya ploshchadi vodoyemov v kriolitozone po dannym kosmicheskoy s"yemki razlichnogo prostranstvennogo razresheniya [Errors of aquatic area measurement in the permafrost zone based on satellite images of variable resolution]: Kriosfera Zemli = Earth Cryosphere, 18(4), p. 86-93 (English sum.), illus. incl. 5 tables, sketch maps, 12 ref., December 2014.

In the example of the inland water bodies of the west coast of the Yamal Peninsula (Marre-Sale District) the error of measurement of their area according to the shooting from the satellites GeoEye-1 and Landsat 5 has been examined. It has been demonstrated that in the classification of a water body on multispectral space images the measurement error of their areas depends substantially on the specified number of classes' types of the Earth's surface. Empirical equations of the dependence of the error from the water body square and spatial resolution of the data satellite imagery have been defined.

2016096671 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK). Lateral and subsurface flows impact Arctic Coastal Plain lake water budgets: Hydrological Processes, 30(21), p. 3918-3931, illus. incl. 4 tables, sketch map, 64 ref., October 15, 2016.

Arctic thaw lakes are an important source of water for aquatic ecosystems, wildlife, and humans. Many recent studies have observed changes in Arctic surface waters related to climate warming and permafrost thaw; however, explaining the trends and predicting future responses to warming is difficult without a stronger fundamental understanding of Arctic lake water budgets. By measuring and simulating surface and subsurface hydrologic fluxes, this work quantified the water budgets of three lakes with varying levels of seasonal drainage, and tested the hypothesis that lateral and subsurface flows are a major component of the post-snowmelt water budgets. A water budget focused only on post-snowmelt surface water fluxes (stream discharge, precipitation, and evaporation) could not close the budget for two of three lakes, even when uncertainty in input parameters was rigorously considered using a Monte Carlo approach. The water budgets indicated large, positive residuals, consistent with up to 70% of mid-summer inflows entering lakes from lateral fluxes. Lateral inflows and outflows were simulated based on three processes; supra-permafrost subsurface inflows from basin-edge polygonal ground, and exchange between seasonally drained lakes and their drained margins through runoff and evapotranspiration. Measurements and simulations indicate that rapid subsurface flow through highly conductive flowpaths in the polygonal ground can explain the majority of the inflow. Drained lakes were hydrologically connected to marshy areas on the lake margins, receiving water from runoff following precipitation and losing up to 38% of lake efflux to drained margin evapotranspiration. Lateral fluxes can be a major part of Arctic thaw lake water budgets and a major control on summertime lake water levels. Incorporating these dynamics into models will improve our ability to predict lake volume changes, solute fluxes, and habitat availability in the changing Arctic. Abstract Copyright Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

DOI: 10.1002/hyp.10917

2016096795 Normandeau, Alexandre (Canadian Geological Survey, Bedford Institute of Oceanography, Dartmouth, NS, Canada); Lamoureux, S. F.; Lajeunesse, P. and Francus, P. Sediment dynamics in paired High Arctic lakes revealed from high-resolution swath bathymetry and acoustic stratigraphy surveys: Journal of Geophysical Research: Earth Surface, 121(9), p. 1676-1696, illus. incl. sects., sketch maps, 65 ref., September 2016.

High Arctic lakes are commonly used for paleoclimatic reconstructions because they are particularly sensitive to climate variability. However, the processes leading to sediment deposition and distribution in these lakes are often poorly understood. Here for the first time in the Canadian High Arctic, we present original data resulting from swath bathymetry and subbottom surveys carried out on two lakes at Cape Bounty, Melville Island. The results reveal the dynamic nature of the lakes, in which mass movement deposits and bedforms on the deltas reflect frequent slope instabilities and hyperpycnal flow activity. The analysis of the mass movement deposits reveals that small blocky debris flows/avalanches, debris flows, and a slide occurred during the Holocene. These mass movements are believed to have been triggered by earthquakes and potentially by permafrost thawing along the shoreline. Altogether, these mass movement deposits cover more than 30% of the lake floors. Additionally, the river deltas on both lakes were mapped and reveal the presence of several gullies and bedforms. The presence of gullies along the delta front indicates that hyperpycnal flows generated at the river mouth can transport sediment in different trajectories downslope, resulting in a different sediment accumulation pattern and record. The dynamic nature of these two lakes suggests that further analysis on sediment transport and distribution within Arctic lakes is required in order to improve paleoclimatic reconstructions. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016JF003873

2016095136 Konstantinov, P. Ya. (Russian Academy of Sciences, Siberian Division, P. Melnikov Permafrost Institute, Yakutsk, Russian Federation); Fedorov, A. N.; Ugarov, I. S.; Argunov, R. N.; Suzdalov, D. A. and Yinzhima, Y. Rezul'taty issledovaniy mezhgodovoy izmenchivosti glubiny sezonnogo protaivaniya okolo Yakutska [Analysis of annual variations of seasonal thawing depth in the Yakutsk area]: Kriosfera Zemli = Earth Cryosphere, 18(4), p. 23-32 (English sum.), illus. incl. table, 44 ref., December 2014.

The results of 16 years of seasonal thaw depth observations in permafrost landscapes near Yakutsk have been presented. For the first time in central Yakutia, the observations at two sites have been carried out following the CALM program protocol on a dense grid of frost/thaw tubes. Measurements have provided new data on the effects of landscape conditions, winter season and rainfall on interannual variations in seasonal thaw depth.

2016094455 Dietze, Elisabeth (German Research Centre for Geosciences, Section 5.2 Climate Dynamics and Landscape Evolution, Potsdam, Germany); Slowinski, Michal; Zawiska, Izabela; Veh, Georg and Brauer, Achim. Multiple drivers of Holocene lake level changes at a lowland lake in northeastern Germany: Boreas, 45(4), p. 828-845, illus. incl. sect., strat. cols., 3 tables, sketch maps, 90 ref., October 2016.

Many German lakes experienced significant water level declines in recent decades that are not fully understood due to the short observation period. At a typical northeastern German groundwater-fed lake with a complex basin morphology, an acoustic sub-bottom profile was analysed together with a transect of five sediment cores, which were correlated using multiple proxies (sediment facies, m-XRF, macrofossils, subfossil Cladocera). Shifts in the boundary between sand and mud deposition were controlled by lake level changes, and hence, allowed the quantification of an absolute lake level amplitude of ~8 m for the Holocene. This clearly exceeded observed modern fluctuations of 1.3 m (AD 1973-2010). Past lake level changes were traced continuously using the calcium-record. During high lake levels, massive organic muds were deposited in the deepest lake basin, whereas lower lake levels isolated the sub-basins and allowed carbonate deposition. During the beginning of the Holocene (>9700 cal. a BP), lake levels were high, probably due to final melting of permafrost and dead-ice remains. The establishment of water-use intensive Pinus forests caused generally low (3-4 m below modern) but fluctuating lake levels (9700-6400 cal. a BP). Afterwards, the lake showed an increasing trend and reached a short-term highstand at c. 5000 cal. a BP (4 m above modern). At the transition towards a cooler and wetter late Holocene, forests dominated by Quercus and Fagus and initial human impact probably contributed more positively to groundwater recharge. Lake levels remained high between 3800 and 800 cal. a BP, but the lake system was not sensitive enough to record short-term fluctuations during this period. Lake level changes were recorded again when humans profoundly affected the drainage system, land cover and lake trophy. Hence, local Holocene water level changes reflect feedbacks between catchment and vegetation characteristics and human impact superimposed by climate change at multiple temporal scales. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1111/bor.12190

2016089085 D'Amico, Michele (Universita degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Grugliasco, Italy); Gorra, Roberta and Freppaz, Michele. Small scale variability of soil properties and soil-vegetation relationships in patterned ground on different lithologies (NW Italian Alps): Catena (Giessen), 135, p. 47-58, illus. incl. 7 tables, sketch map, 45 ref., December 2015.

Cryogenic patterned ground represents spectacular periglacial landscapes. On the Alps, sorted/nonsorted patterned ground features larger than 1 m, formed by deep seasonal cryoturbation with or without permafrost, occupy exposed, stable surfaces at high altitudes and represent a particularly harsh habitat for plant life. We analyzed soils across transects through typical active patterned ground features (sorted/nonsorted circles and stripes) on four common lithotypes (calcschists, serpentinite, gabbros and gneiss) in the Western Italian Alps, in order to observe the small-scale lateral and depth variability in physico-chemical properties, and their association with cryoturbation, plant cover and species distribution. Cryoturbation was correlated with lateral/vertical textural sorting across features, mostly visible on silt and coarse sand, but with opposite trends on sorted and nonsorted patterned ground types. A strong lateral variability in organic carbon was detected, with high values near the better vegetated rims and low contents in the centers. Exchangeable bases, heavy metals and nutrients followed the same distribution. However, the differences inherited from the parent materials were overwhelming. Climate is the main driver of high altitude ecosystems, reducing total plant cover and causing cryoturbation, which in turn creates strong edaphic gradients over small distances. Plant species and communities are well correlated with edaphic properties inherited from the parent materials, such as exchangeable Ca and heavy metals. Abstract Copyright (2015) Elsevier, B.V.

DOI: 10.1016/j.catena.2015.07.005

2016095138 Vasil'chuk, Yu. K. (Moscow State University, Department of Geography, Moscow, Russian Federation); Budantseva, N. A.; Vasil'chuk, A. K.; Yoshikava, K.; Podbornyy, Ye. Ye. and Chizhova, Yu. N. Izotopnyy sostav ledyanogo yadra pozdnegolotsenovogo bulgunnyakha na mestorozhdenii Pestsovoye v doline reki Yevoyakha na yuge Tazovskogo poluostrova [Isotope composition of upper Holocene pingo ice core in the Pestsovoye Field, Yevoyakha Valley, southern Taz Peninsula]: Kriosfera Zemli = Earth Cryosphere, 18(4), p. 47-58 (English sum.), illus. incl. 3 tables, sketch map, 25 ref., December 2014.

The ice core of Pestsovoye pingo in the Yevoyakha River valley in northwestern Siberia has been studied. Thickness of the pingo ice is more than 15 m. The d¹⁸O value of the pingo ice varies from -11.6 to -15.8ppm, dD from -93.2 to -123.0ppm. Comparison with isotope data of the ice core of Weather pingo (Alaska) has been carried out. In Weather pingo ice d¹⁸O values range from -15.5 to -22.0ppm, dD values change from -132 to -170ppm. Both isotope profiles of pingo ice are contrasting and arcuate-shaped as a result of isotope fractionation during freezing of sub-pingo waters in closed system. Fractionation leads to isotopic contrast of ice: by 4-6ppm of d¹⁸O and by 20-25 ppm of dD values. Radiocarbon dating of the covering peat at Pestsovoye pingo evidences that the heaving occurred in two stages. At the first stage the heaving began at about 5 kyr BP in the distal part of the mound. At the second stage about 2.5 kyr BP the heaving recommenced actively in the central part of the pingo. The heaving rate was very high--more than 2-3 cm per year. As a result a pingo of 17 m has been formed.

2016096461 Rempel, Alan W. (University of Oregon, Department of Geological Sciences, Eugene, OR); Marshall, Jill A. and Roering, Joshua J. Modeling relative frost weathering rates at geomorphic scales: Earth and Planetary Science Letters, 453, p. 87-95, illus. incl. 1 table, 45 ref., November 1, 2016. Includes appendix.

Frost damage is a powerful agent of geomorphic change. Cracks can grow when the ice pressure in pores reaches a threshold that depends on matrix properties and crack geometry. Mineral surfaces that are preferentially wetted by liquid water rather than ice are coated by premelted liquid at a pressure that is lower than the ice pressure. Because this pressure difference increases as the temperature cools, when the ice pressure is effectively pinned at the cracking threshold, temperature gradients induce gradients in liquid pressure that draw water towards colder temperatures. Porosity increases and frost damage accumulates in regions where water supplies crack growth. To apply this understanding over the large spatial and temporal scales that are relevant to evolving landscapes, we develop a simple model that tracks porosity changes. Our central assumption is that frost damage is correlated with porosity increases under conditions where frost cracking takes place. Accordingly, we account for the permeability reductions with decreased temperature that accompany ice growth along porous pathways and derive general expressions for the porosity change through time at particular depths, as well as the total porosity increase through all depths beneath a point at the ground surface over the time during which cracking occurs each year. To illustrate the resulting patterns of frost weathering, we consider a general case in which the permeability has a power law dependence on temperature and the annual surface-temperature variation is sinusoidal. We find that the degree of frost damage generally decreases with depth, except at localized depths where damage is elevated because the rock spends longer times near the threshold for cracking, leading to enhanced water supply in comparison with neighboring regions. The magnitude of the net expansion that results from porosity changes at all depths beneath the ground surface is increased for seasonal thermal cycles with larger amplitudes, with a broad maximum centered on a mean annual temperature near the threshold required for crack growth. Warmer mean annual temperatures lead to less damage because of the reduction in time during which it is cold enough for cracking, whereas colder mean annual temperatures are accompanied by reduced water supply due to the temperature dependence of permeability. All of the controlling parameters in our model are tied explicitly to physical properties that can in principle be measured independently, which suggests promise for informing geomorphic interpretations of the role of frost weathering in evolving landforms and determining erosion rates.

DOI: 10.1016/j.epsl.2016.08.019

2016090395 Mezbahuddin, M. (Alberta Agriculture and Forestry, Environmental Stewardship Branch, Edmonton, AB, Canada); Grant, R. F. and Flanagan, L. B. Modeling hydrological controls on variations in peat water content, water table depth, and surface energy exchange of a boreal western Canadian fen peatland: Journal of Geophysical Research: Biogeosciences, 121(8), p. 2216-2242, illus. incl. 2 tables, 75 ref., August 2016.

Improved predictive capacity of hydrology and surface energy exchange is critical for conserving boreal peatland carbon sequestration under drier and warmer climates. We represented basic processes for water and O₂ transport and their effects on ecosystem water, energy, carbon, and nutrient cycling in a process-based model ecosys to simulate effects of seasonal and interannual variations in hydrology on peat water content, water table depth (WTD), and surface energy exchange of a Western Canadian fen peatland. Substituting a van Genuchten model (VGM) for a modified Campbell model (MCM) in ecosys enabled a significantly better simulation of peat moisture retention as indicated by higher modeled versus measured R² and Willmot's index (d) with VGM (R² ~ 0.7, d ~ 0.8) than with MCM (R² ~ 0.25, d ~ 0.35) for daily peat water contents from a wetter year 2004 to a drier year 2009. With the improved peat moisture simulation, ecosys modeled hourly WTD and energy fluxes reasonably well (modeled versus measured R²: WTD ~ 0.6, net radiation ~ 0.99, sensible heat > 0.8, and latent heat > 0.85). Gradually declining ratios of precipitation to evapotranspiration and of lateral recharge to discharge enabled simulation of a gradual drawdown of growing season WTD and a consequent peat drying from 2004 to 2009. When WTD fell below a threshold of ~ 0.35 m below the hollow surface, intense drying of mosses in ecosys caused a simulated reduction in evapotranspiration and an increase in Bowen ratio during late growing season that were consistent with measurements. Hence, using appropriate water desorption curve coupled with vertical-lateral hydraulic schemes is vital to accurately simulate peatland hydrology and energy balance. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016JG003501

2016092346 Lu Yang (Hohai University, College of Water Conservancy and Hydropower, Nanjing, China); Liu Sihong; Weng Liping; Wang Liujiang; Li Zhuo and Xu Lei. Fractal analysis of cracking in a clayey soil under freeze-thaw cycles: Engineering Geology, 208, p. 93-99, illus. incl. 2 tables, 64 ref., June 24, 2016.

Under extreme climate conditions, clayey soils experience not only seasonal drying and wetting but also frequent freezing and thawing. Cracking would also occur in clayey soils under freeze-thaw cycles, but now less academic attention has been paid on this issue. In this study, a series of laboratory tests were conducted on a clayey soil to investigate the cracking behaviors under freeze-thaw cycles. Water loss, surface crack initiation and propagation processes were monitored after each freeze-thaw cycle. By using the image processing technique, the crack patterns were described and then quantitatively analyzed on the basis of the fractal dimension concept. It was found that for the tested clayey soil subjected to freeze-thaw cycles, the surface crack pattern slowly evolves from an irregularly rectilinear pattern towards a polygonal or quasi-hexagonal one; and the water loss, closely related to the sample thickness, plays a significant role in the process of the clay cracking; Upon cyclic freezing-thawing, the fractal dimension is well correlated to the surface crack ratio in a logarithmic equation. Fractal dimension concept can offer a new perspective on the quantitative understanding of cracking initiation and propagation in clayey soils under freeze-thaw cycles.

DOI: 10.1016/j.enggeo.2016.04.023

2016089145 Li Zongxing (Chinese Academy of Sciences, Cold and Arid Region Environment and Engineering Research Institute, Lanzhou, China); Feng Qi; Wang, Q. J.; Song, Yong; Cheng Aifang and Li Jianguo. Contribution from frozen soil meltwater to runoff in an in-land river basin under water scarcity by isotopic tracing in northwestern China: Global and Planetary Change, 136, p. 41-51, illus. incl. 1 table, sketch map, 96 ref., January 2016. Includes appendices.

Cryosphere meltwater has been recognized as an important source of local water resources. However, there are few assessments on the contribution from frozen soil meltwater. In this study, we quantify the fraction from frozen soil meltwater and glacier snow meltwater to runoff in Shiyang River, an in-land river basin of northwestern China, where glaciers were disappearing and frozen soil was in degradation. A large number of samples for precipitation, surface water, groundwater, frozen soil meltwater and glacier snow meltwater have been collected and analyzed for their isotopic compositions. Results indicated that runoff was mainly generated from the cryosphere belt, and it was found that frozen soil meltwater was responsible for 20%, on average, of the outlet river water during flood season in the basin. The contribution rates from frozen soil meltwater to the outlet river runoff changed among the seven sub-basins. The results confirmed that frozen soil meltwater has played an important role in runoff of in-land river basins, and evaluating its influence on the hydrological process under a climate warming scenario is of great significance. Abstract Copyright (2016) Elsevier, B.V.

DOI: 10.1016/j.gloplacha.2015.12.002

2016088616 Makusa, Gregory P. (Lulea University of Technology, Department of Civil, Environmental, and Natural Resources Engineering, Lulea, Sweden); Bradshaw, Sabrina L.; Berns, Erin; Benson, Craig H. and Knutsson, Sven. Freeze-thaw cycling concurrent with cation exchange and the hydraulic conductivity of geosynthetic clay liners: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 51(6), p. 591-598, illus. incl. 3 tables, 39 ref., June 2014.

A study was conducted to assess the effect of cation exchange concurrent with freeze-thaw cycling on the hydraulic conductivity of a geosynthetic clay liner (GCL). GCLs were prehydrated by contact with silica flour moistened with synthetic subgrade pore water and subsequently permeated with a solution representing the pore water in the cover soil over a tailings facility. Control tests were conducted using the same procedure, except deionized (DI) water was used as the permeant liquid to preclude cation exchange from the permeant liquid. The GCLs were subjected to 1, 3, 5, 15, and 20 freeze-thaw cycles, and the hydraulic conductivity and exchange complex were determined before and after freeze-thaw cycling to assess chemical changes that occurred during freezing, thawing, and permeation. GCLs undergoing freeze-thaw cycling experienced little to no cation exchange through 5 freeze-thaw cycles. After 20 freeze-thaw cycles, 50% of the sodium (Na⁺) initially in the exchange complex was replaced by calcium (Ca²⁺). Dissolution of calcite within the bentonite is a likely source of the Ca²⁺. Hydraulic conductivity of the GCLs exposed to freeze-thaw cycling was lower than the hydraulic conductivity of a new GCL permeated with DI water (<2.2 ´ 10^-11 m/s). A small increase in hydraulic conductivity (~2.3 times), which may have been caused by cation exchange, occurred between 15 and 20 freeze-thaw cycles, but the hydraulic conductivity remained below the hydraulic conductivity of a new GCL unexposed to freeze-thaw cycling and permeated with DI water.

DOI: 10.1139/cgj-2013-0127

2016088653 Li Yueming (Jilin University, College of Environment and Resource, Changchun, China); Kang Chunli; Zhang Yingxin; Ming Lian; Zhang Sai and Guo Ping. Dissolved organic matter effect on Pb leaching and release in Pb contaminated soil dealt with freeze-thaw action: Jilin Daxue Xuebao (Diqiu Kexue Ban) = Journal of Jilin University (Earth Science Edition), 43(3), p. 945-953, (Chinese) (English sum.), illus. incl. 4 tables, 17 ref., May 26, 2013.

The effect of dissolved organic matter (DOM) on Pb leaching in Pb-contaminated soil treated by freeze-thaw action was investigated with laboratory simulation experiments. The results showed that physiochemical properties of soil and chemical speciation of Pb were significantly changed by freeze-thaw action; DOM could significantly facilitate Pb leaching in freeze-thaw soil compared with non-freeze-thaw soil. The leaching influences of DOM on Pb in Pb-contaminated soil were closely related to the soil type, soil contamination time and contamination degree. The leaching influence of DOM on Pb in brown soil was greater than that of in black soil, and increased with the time and degree of soil contaminated by Pb increase. The leaching influences of DOM on Pb in Pb-contaminated soil were also closely related to mass concentration, properties and component of DOM. The leaching amount of Pb was improved by the increase of DOM mass concentration; the lower pH of DOM and the low-molecular-weight hydrophilic fraction of DOM facilitated the leaching of Pb from in soil.

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2016092414 Korosi, Jennifer (University of Ottawa, Department of Biology, Ottawa, ON, Canada); McDonald, Jamylynn; Coleman, Kristen; Palmer, Michael; Smol, John P.; Simpson, Myrna and Blais, Jules. Tracking peat subsidence and aquatic ecosystem change in the discontinuous sporadic permafrost zone (Northwest Territories, Canada) using organic biomarkers preserved in lake sediment cores [abstr.]: in Geological Society of America, Northeastern Section, 51st annual meeting, Abstracts with Programs - Geological Society of America, 48(2), Abstract no. 32-7, 2016. Meeting: Geological Society of America, Northeastern Section, 51st annual meeting, March 21-23, 2016, Albany, NY.

Northern boreal ecoregions globally are experiencing a rapid loss of permafrost in response to climate warming, with many implications for aquatic ecosystems. In particular, permafrost thaw in these organic-rich landscapes is expected to increase the transport of allochthonous carbon and catchment-derived contaminants such as mercury to lakes. In the Great Slave lowlands region of the southern Northwest Territories, the subsidence of permafrost-supported peat plateaus can cause pronounced hydrological changes that alter run-off of terrestrial organic matter from the catchment to aquatic ecosystems. Aquatic ecosystems are greatly influenced by terrestrial organic matter inputs, which influences many lake processes, such as the depth of light penetration, thermal stratification, and the bioavailability of contaminants. Consequently, understanding the long-term trajectory of changes in terrestrial organic matter inputs to boreal lake ecosystems has been highlighted as an important avenue for future research. In this study, we analyzed plant biomarkers and other geochemical proxies in sediment cores from two lakes in the southern Northwest Territories that have documented extensive peat subsidence in the catchment in recent years, to provide a long-term perspective on permafrost thaw and allochthonous carbon inputs. We observed changes in the quantity and source of terrestrial organic matter entering lakes, and documented relationships between allochthonous carbon inputs and mercury accumulation in the sediments. In one lake, an increase in terrestrial organic matter inputs was associated with ecological changes in aquatic biota indicative of decreased water clarity. This research demonstrates how the use of organic biomarkers can advance our understanding of the transformative changes occurring in watersheds in permafrost-supported northern boreal forests as a result of climate warming.

DOI: 10.1130/abs/2016NE-272112

2016093679 Endalamaw, Abraham Melesse (International Arctic Research Center, Fairbanks, AK); Bolton, William R.; Hinzman, Larry D.; Morton, Don and Cable, Jessica. Sensitivity of residual soil moisture content in VIC model soil property parameterizations for sub-arctic discontinuous permafrost watersheds [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H23B-1581, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Most soil property representations in large scale hydrological and atmospheric models are derived from empirical relationships of soil texture, wherein the average hydraulic, thermal and thermodynamic processes are described for each layer of the soil column. Of all the soil hydraulic properties, hydraulic conductivity is one of the most difficult to estimate, particularly in permafrost environments. This is because, for large-scale models, it is estimated from soil properties that are originally estimated from other empirical relationships of soil texture, such as residual soil moisture content. Residual soil moisture content determines the amount of available moisture for evapotranspiration and drainage in unsaturated flow. In cold regions, it is also important to estimate the depth of the freezing front by estimating the antecedent soil moisture status before the soils freeze for the winter. This will have direct and indirect effects on the freeze-thaw depth and runoff generation the following spring. Therefore, inaccurate data on residual soil moisture will impact on hydrological modeling of the discontinuous permafrost watersheds in Interior Alaska, where soil water content is highly variable even within a given soil texture. The main objective of this study is to test the sensitivity of models to variation in residual soil moisture for runoff, evaporation, evapotranspiration and soil moisture simulations in discontinuous permafrost watersheds of Interior Alaska. We use the Variable Infiltration Capacity model, a meso-scale hydrological model, and HYDRUS 1D, a software package for simulating water, heat and solute movement, to estimate the soil hydraulics properties at the two contrasting sub-basins of the Caribou Poker Creek Research Watershed. . Preliminary modeling results show that small variations in the residual soil moisture content results in significant differences in the timing and amount of runoff, evapotranspiration and soil moisture storage. Our analysis reveals that, although residual soil moisture is sensitive for both sub-basins, the low permafrost sub-basin is more sensitive than the high permafrost dominated sub-basin. This may be due to the dry mineral soil layer and higher transpiration by the deciduous plants in the low-permafrost ecosystem.

2016096194 Paull, Charles K. (Monterey Bay Aquarium Research Institute, Watsonville, CA); Dallimore, Scott; Caress, David W.; Gwiazda, Roberto; Lundsten, Eve M.; Anderson, Krystle; Riedel, Michael and Melling, Humfrey. Slope edge deformation and permafrost dynamics along the Arctic Shelf edge, Beaufort Sea, Canada [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract OS22B-07, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

The shelf of the Canadian Beaufort Sea is underlain by relict offshore permafrost that formed in the long intervals of terrestrial exposure during glacial periods. At the shelf edge the permafrost thins rapidly and also warms. This area has a very distinct morphology that we attribute to both the formation and degradation of ice bearing permafrost. Positive relief features include circular to oval shaped topographic mounds, up to 10 m high and ~50 m in diameter which occur at a density of ~6 per km2. Intermixed are circular topographic depressions up to 20 m deep. This topography was investigated using an autonomous underwater vehicle that provides 1 m horizontal resolution bathymetry and chirp profiles, a remotely operated vehicle to document seafloor textures, and sediment cores to sample pore waters. A consistent down-core freshening at rates of 14 to 96 mM Cl^- per meter was found in these pore waters near the shelf edge. Downward extrapolation of these trends indicates water with ≤&eq;335 mM Cl^- should occur at 2.3 to 22.4 m sub-seafloor depths within this shelf edge deformation band. Pore water with 335 mM Cl^- or less freezes at -1.4°C. As bottom water temperatures in this area are persistently (<-1.4°C) cold and ground ice was observed in some core samples, we interpret the volume changes associated with mound formation are in part due to pore water freezing. Thermal models (Taylor et al., 2014) predict brackish water along the shelf edge may be sourced in relict permafrost melting under the adjacent continental shelf. Buoyant brackish water is hypothesized to migrate along the base of the relict permafrost, to emerge at the shelf edge and then refreeze when it encounters the colder seafloor. Expansion generated by the formation of ice-bearing permafrost generates the positive relief mounds and ridges. The associated negative relief features may be related to permafrost dynamics also. Permafrost dynamics may have geohazard implications that are unique to the Arctic shelf edge.

2016088874 Mollenhauer, Gesine (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany); Dummann, Wolf; Winterfeld, Maria; Hefter, Jens; Lembke-Jene, Lester and Tiedemann, Ralf. Release of pre-aged terrestrial organic matter from the Amur Watershed during deglacial permafrost thaw revealed by compound-specific ¹⁴C analysis [abstr.]: in Goldschmidt abstracts 2015, V.M. Goldschmidt Conference - Program and Abstracts, 25, p. 2168, 2015. Meeting: Goldschmidt 2015, Aug. 16-21, 2015, Prague, Czech Republic.

URL: http://goldschmidt.info/2015/uploads/abstracts/finalPDFs/2168.pdf

2016088723 Parshin, A. V. (Irkutskiy Gosudarstvennyy Tekhnicheskiy Universitet, Irkutsk, Russian Federation); Budyak, A. Ye.; Blinov, A. V. and Kosterev, A. N. Kompleks metodov poiskov zoloto-uranovykh rudoproyavleniy v usloviyakh kriolitozonyy rayona Baykalo-Amurskoy magistrali [Complex of mineral exploration methods for gold and uranium ore deposits under permafrost conditions in the Baikal-Amur regions]: in Metallogeniya drevnikh i sovremennykh okeanov, 2015; mestorozhdeniya okeanicheskikh struktur; geologiya, mineralogiya, geokhimiya i usloviya obrazovaniya; materialy Dvadtsat' pervoy nauchnoy molodezhnoy shkoly (Maslennikov, V. V., editor; et al.), Metallogeniya Drevnikh i Sovremennykh Okeanov ... Materialy ... Nauchnoy Studencheskoy Shkoly, 21, p. 177-181, illus., 6 ref., 2015. Meeting: Metallogeniya drevnikh i sovremennykh okeanov, 2015; mestorozhdeniya okeanicheskikh struktur; geologiya, mineralogiya, geokhimiya i usloviya obrazovaniya; dvadtsat' pervaya nauchnaya molodezhnaya shkola, April 20-24, 2015, Chelyabinsk, Russian Federation.

2016091865 Constable, Steven (Scripps Institution of Oceanography, La Jolla, CA). Water and electricity do mix; studying plates, petroleum, and permafrost using marine electromagnetism [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract GP24B-01, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Marine magnetotelluric (MT) and controlled-source electromagnetic (CSEM) sounding methods were developed in the early 1980's as deep-water academic tools to study the oceanic lithosphere and mantle. Electrical conductivity is a strong function of porosity, temperature, melting, and volatile content, and so marine MT and CSEM data can be used to address a variety of geological questions related to plate tectonics. These include the distribution of melt at mid-ocean ridges, the fate of fluids in subduction zones, and the nature of the lithosphere-asthenosphere boundary. With the advent of deepwater oil and gas drilling in the late 1990's, marine EM methods were embraced by the exploration community, and are now routinely used to assist in exploration and make drilling decisions for wells costing $100M or more. For countries without conventional hydrocarbon resources, gas hydrate offers the potential for energy production, and marine CSEM methods may be the only effective way to explore for and characterize this resource. The use of EM methods to map geothermal, groundwater, and mineral resources also has application in the marine environment. Water and electricity has proved to be a very successful mix!

2016089314 Carey, Sean K. (McMaster University, Hamilton, ON, Canada). From hills to holes; how climate change and mining are altering runoff processes in Canada [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H42F-08, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Canadian environments are under considerable pressure from both climate and land-use change. While warming temperatures are widespread and amplified in the north, surface mining has resulted in large-scale landscape disturbance. How these changes affect catchment response is profound, fundamentally altering the cycling and delivery of water and geochemicals to the drainage network. In permafrost-underlain environments, coupled mass and energy processes control runoff response, and as ground thaw increases, new subsurface pathways become accessible while changing overall catchment storage. With surface mining, watersheds are altered such that they bare little resemblance to what existed prior to mining. In this presentation, data will be presented from long-term experiments exploring the impact of climate and mining on runoff processes in cold catchments using stable isotopes of water and associated hydrometric measurements. In southern Yukon, results from the Wolf Creek Research Basin highlights the influence of surface energy balances on controlling the timing and magnitude of flow response, with inter-annual variability largely driven by how atmospheric forcing interacts with permafrost-underlain areas of the catchment. In mountainous areas of southern British Columbia, surface mining reconfigures landscapes as valleys are filled with waste-rock. Mine-influenced catchments exhibit attenuated flows with delays in spring freshet and a more muted to precipitation. Stable isotopes in stream water suggests that both waste-rock and reference catchments are well mixed, however reference catchments are more responsive to enrichment and depletion events and that mine-influenced catchments had a heavier isotope signature than reference watersheds, suggesting enhanced influence of rainfall on recharge. In both cases, snow storage and release exerts considerable control on streamflow responses, and future changes in streamflow regimes will reflect both a changes in the snow regime and inherent catchment storage properties that are dynamic with time.

2016096209 Frederick, Jennifer Mary (University of California Berkeley, Berkeley, CA) and Buffett, Bruce A. Is submarine groundwater discharge a gas hydrate formation mechanism on the circum-Arctic shelf? [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract OS23B-1995, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Methane hydrate is an ice-like solid that can sequester large quantities of methane gas in marine sediments along most continental margins where thermodynamic conditions permit its formation. Along the circum-Arctic shelf, relict permafrost-associated methane hydrate deposits formed when non-glaciated portions of the shelf experienced subaerial exposure during ocean transgressions. Gas hydrate stability and the permeability of circum-Arctic shelf sediments to gas migration is closely linked with relict submarine permafrost. Heat flow observations on the Alaskan North Slope and Canadian Beaufort Shelf suggest the movement of groundwater offshore, but direct observations of groundwater flow do not exist. Submarine discharge, an offshore flow of fresh, terrestrial groundwater, can affect the temperature and salinity field in shelf sediments, and may be an important factor in submarine permafrost and gas hydrate evolution on the Arctic continental shelf. Submarine groundwater discharge may also enhance the transport of organic matter for methanogenesis within marine sediments. Because it is buoyancy-driven, the velocity field contains regions with a vertical (upward) component as groundwater flows offshore. This combination of factors makes submarine groundwater discharge a potential mechanism controlling permafrost-associated gas hydrate evolution on the Arctic continental shelf. In this study, we quantitatively investigate the feasibility of submarine groundwater discharge as a control on permafrost-associated gas hydrate formation on the Arctic continental shelf, using the Canadian Beaufort Shelf as an example. We have developed a shelf-scale, two-dimensional numerical model based on the finite volume method for two-phase flow of pore fluid and methane gas within Arctic shelf sediments. The model tracks the evolution of the pressure, temperature, salinity, methane gas, methane hydrate, and permafrost fields given imposed boundary conditions, with latent heat of water ice and hydrate formation included. The permeability structure of the sediments is coupled to changes in the permafrost and gas hydrate deposits, and the model can be run over several glacial cycles. Model development and preliminary results will be presented.

2016089247 King, T. (Utah State University, Logan, UT); Neilson, B. T.; Jensen, A.; Torres-Rua, A. F.; Winkelaar, Mark and Rasmussen, Mitchell T. High resolution channel geometry from repeat aerial imagery [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H41E-1370, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

River channel cross sectional geometry is a key attribute for controlling the river energy balances where surface heat fluxes dominate and discharge varies significantly over short time periods throughout the open water season. These dynamics are seen in higher gradient portions of Arctic rivers where surface heat fluxes can dominates river energy balances and low hillslope storage produce rapidly varying hydrographs. Additionally, arctic river geometry can be highly dynamic in the face of thermal erosion of permafrost landscape. While direct in-situ measurements of channel cross sectional geometry are accurate, they are limited in spatial resolution and coverage, and can be access limited in remote areas. Remote sensing can help gather data at high spatial resolutions and large areas, however techniques for extracting channel geometry is often limited to the banks and flood plains adjacent to river, as the water column inhibits sensing of the river bed itself. Green light LiDAR can be used to map bathymetry, however this is expensive, difficult to obtain at large spatial scales, and dependent on water quality. Alternatively, 3D photogrammetry from aerial imagery can be used to analyze the non-wetted portion of the river channel, but extracting full cross sections requires extrapolation into the wetted portion of the river. To bridge these gaps, an approach for using repeat aerial imagery surveys with visual (RGB) and near infrared (NIR) to extract high resolution channel geometry for the Kuparuk River in the Alaskan Arctic was developed. Aerial imagery surveys were conducted under multiple flow conditions and water surface geometry (elevation and width) were extracted through photogrammetry. Channel geometry was extracted by combining water surface widths and elevations from multiple flights. The accuracy of these results were compared against field surveyed cross sections at many locations throughout the study reach and a digital elevation model created under extremely low flow conditions. These extrapolation methods have shown to be promising for estimating detailed channel geometry at large scales.

2016089300 Lettenmaier, D. P. (University of California Los Angeles, Department of Geography, Los Angeles, CA). Improving the understanding and diagnosis of Earth system changes in cold regions [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H42D-05, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

I review key hydrological state variables and fluxes relevant to cold regions, specifically snow, permafrost and seasonally frozen soils, lakes, and wetlands, and comment on the ability of current models to represent the associated processes, and the quality of the data sets upon which model development and diagnosis efforts rest. Although snow processes are relatively well represented in current generation land surface models, at least at large scales for deep mountain snowpacks, the representation of high latitude snow processes remain complicated by the role of snow redistribution, and of sublimation during the shoulder (especially spring) season. Most credible land surface models now include representations of permafrost, some of which perform well when forced with local climate data; however their performance over large areas is limited by spatial variability of key processes, including soil thermal characteristics. Likewise, many land surface models now represent the hydrology and energetics of lakes, which cover a substantial portion of the landscape in many high latitude environs. However, accurate representation of lakes requires knowledge of certain characteristics of their bathymetry and hydrological connectivity, information which is not always available. Likewise, the representation of wetlands in models, although improved in many cases, is limited by topography (and the role of microtopography, even at large scales). Nonetheless, increased attention to high latitude hydrological processes has demonstrably improved the fidelity of land surface representations over the last decade or so.

2016089322 Mendbayar, U. (University of Alaska Fairbanks, Fairbanks, AK); Misra, D.; Gupta, T. and Ghosh, T. Investigation and quantification of water track networks in boreal regions using remote sensing and geophysical data [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H43C-1503, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Water tracks are the most prominent drainage pathways that route water through the soil over permafrost in the polar environment and thus play a major role in hydrology, geomorphology, and geochemistry of the polar ecosystem. Existing literature on water tracks is limited and is largely confined to tundra areas devoid of vegetation. The objective of this study is to initiate the investigation of water tracks in thickly vegetated boreal regions, many of which contain predominant engineered infrastructures. The ancillary objectives include the development of methods for mapping the distribution of water tracks in boreal regions and a preliminary analysis of the geotechnical impacts of water track interception on infrastructures. The study area is Goldstream Road in Fairbanks, Alaska. This road experiences high amounts of damage, possibly due to interception of prominent water tracks. To investigate the road damage, the Alaska Department of Transportation has collected geophysical data in 2012. We plan to create a water track distribution map around the Goldstream Road using high-spatial-and-spectral-resolution remote sensing imagery and correlate it with the geophysical data from 2012. We have collected ground data from two water tracks: one in a residence in Fairbanks and the other besides the Goldstream Road. The two tracks vary greatly in size and features. Both water tracks revealed different yet quite promising characteristics. These findings will be used to extract other water tracks from remotely sensed images of the Goldstream Road area. So far, a 2010 SPOT 5 image (2.5 m x 2.5 m), an aerial orthophoto (14 cm x 14 cm) and a DEM (57 cm x 57 cm) from September 2014 have been acquired. Normalized Difference Vegetation Index (NDVI) processing was performed on the 2010 SPOT 5 image. A detailed water track database was created and water tracks are being manually digitized from the available imagery and Web Mapping Services (WMS). As a test, using FLIR, handheld thermal infrared camera, we have successfully characterized water track on the residential property. Our research will provide essential insight into water tracks in boreal regions, engineering solutions and mitigation of damages from water track interception as vital considerations for future engineering designs.

2016095890 Micheletti, Natan (University of Lausanne, Lausanne, Switzerland); Lane, Stuart N. and Lambiel, Christophe. The sediment yield of high mountain environment watersheds; strong evidence of transport capacity limitation [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract EP53B-1014, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Alpine landscapes are likely to be particularly sensitive to climate change, because of: (1) the vulnerability of permafrost and glacial and nival processes to changes in atmospheric temperature and precipitation; (2) their history, which may have led to high rates of sediment production, and hence high rates of sediment supply; and (3) the steep slopes that may sustain sediment transport. Assessing the effects of climate change upon these processes over the timescale of recent rapid warming (i.e. decades) is difficult because of the lack of available data. Here, we use two unique data sources to assess the relative importance of these three processes for two high mountain basins (altitude range 2,000 to 3,500 m asl): (1) histories of surface change from the late 1950s, based upon construction of digital elevation models from archival imagery; and (2) a long term record, beginning in the early 1960s, of sediment export based upon the flushing of sediment from hydropower intakes. The two basins contain glaciers, rock glaciers, permafrost and the legacy of past glacial activity. These data show that the level of geomorphic activity within both basins is orders of magnitude higher than the volume of sediment exported from the basins. Decadal scale changes in elevation and surface displacement velocities suggest an acceleration of landscape dynamics from the 1980s. Changes in atmospheric temperature remain a key control of this process, but precipitation and snow cover prove critical in controlling rock glacier behaviour and can induce acceleration of surface displacements even under cold atmospheric conditions. However, the analysis of the sediment export data show that despite generally greater within basin dynamics, the rate of export of sediment remains orders of magnitude lower than rates of sediment production. Calculations of sediment transport capacity suggest that this is because the fundamental limit upon sediment yield is the capacity of the stream to evacuate sediment that, in turn, is highly dependent upon annual winter snow cover. There is no clear trend in the latter suggesting that warming enhanced sediment production does not translate into sediment export from the basins studied.

2016096059 Parsekian, Andy (University of Wyoming, Laramie, WY); Jones, Benjamin M.; Arp, Christopher D.; Creighton, Andrea; Daanen, Ronald P.; Gaedeke, Anne and Bondurant, Allen. Bedfast and floating ice lake talik properties measured using surface nuclear magnetic resonance on the North Slope, Alaska [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract NS21A-1913, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Lakes within permafrost regions have been identified as a source of carbon gas emissions, however the geometry of the thawed sediments and water content below these lakes that hold the carbon-rich source sediment remains difficult to measure. Surface nuclear magnetic resonance (NMR) is a geophysical measurement that is unambiguously sensitive to liquid water and therefore is well suited to discriminating between the sub-lake talik (thaw bulb) and surrounding permafrost. Here we report on talik thickness, water content, and pore scale properties observed using surface NMR in lakes located on the Arctic Coastal Plain of northern Alaska. The study lakes range in size from 0.5 km-2 km in diameter. They have formed within a Pleistocene sand sheet deposit where permafrost extends 200 to 300 m below the surface. Lake depth ranges from less than 1 m (bedfast ice) to 5 m (floating ice); drained lake basins with no water or water ice were also measured for comparison. Floating ice lakes are interpreted to have a talik between 20-25 m below the surface. Bedfast ice lakes had either no measureable talik, a talik to <20 m, or an isolated talik. Drained lake basins had either no measureable talik or an isolated talik. The presence of isolated taliks below some bedfast ice lakes and drained lake basins was a surprising result, suggesting that zones of unfrozen sediment may be present in the region even when the surface conditions suggest otherwise. These results of talik presence/absence and geometry bring new insight into permafrost-influenced lake subsurface hydrology and provide value data for validating hydrological modeling outputs. Our application of using surface NMR on Arctic Lakes will be extended to the region with numerous thermokarst lakes and drained lake basins north of Teshekpuk Lake next April.

2016089515 Roberti, Gioachino Luigi (Simon Fraser University, Burnaby, BC, Canada); Ward, Brent C.; van Wyk de Vries, Benjamin; Falorni, Giacomo; Perotti, Luigi and Clague, John J. Mount Meager volcano, Canada; a case study for landslides on glaciated volcanoes [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract NH41C-1836, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Mount Meager is a strato-volcano massif in the Northern Cascade Volcanic Arc (Canada) that erupted in 2350 BP, the most recent in Canada. To study the stability of the Massif an international research project between France (Blaise Pascal University), Italy (University of Turin) and Canada (Simon Fraser University) and private companies (TRE-sensing the planet) has been created. A complex history of glacial loading and unloading, combined with weak, hydrothermally altered rocks has resulted in a long record of catastrophic landslides. The most recent, in 2010 is the third largest (50´10⁶ m³) historical landslide in Canada. Mount Meager is a perfect natural laboratory for gravity and topographic processes such as landslide activity, permafrost and glacial dynamics, erosion, alteration and uplift on volcanoes. Research is aided by a rich archive of aerial photos of the Massif (1940s up to 2006): complete coverage approximately every 10 years. This data set has been processed and multi-temporal, high resolution Orthophoto and DSMs (Digital Surface Models) have been produced. On these digital products, with the support on field work, glacial retreat and landslide activity have been tracked and mapped. This has allowed for the inventory of unstable areas, the identification of lava flows and domes, and the general improvement on the geologic knowledge of the massif. InSAR data have been used to monitor the deformation of the pre-2010 failure slope. It will also be used to monitor other unstable slopes that potentially can evolve to catastrophic collapses of up to 1 km3 in volume, endangering local communities downstream the volcano. Mount Meager is definitively an exceptional site for studying the dynamics of a glaciated, uplifted volcano. The methodologies proposed can be applied to other volcanic areas with high erosion rates such as Alaska, Cascades, and the Andes.

2016095878 Schwans, Emily (Colorado School of Mines, Golden, CO); Meng, Tyler M.; Prudhomme, Kristen and Morgan, Matthew L. On the origin of the Crestone Crater; low-latitude periglacial features in San Luis Valley, Colorado [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract EP53A-1002, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Located within the northern boundary of the Great Sand Dunes National Park is the Crestone Crater, a elliptical bowl-shaped feature consisting of a raised rim surrounding a central depression. The elongate crater has an approximate diameter of 100 m and reaches a depth of 10 m at its center relative to its rim, which rises 10 m above the elevation of the surrounding surface. Its precise origin is largely unknown and has perplexed regional geologists and residents of Crestone, Colorado for more than 80 years. This project used on-site and remote geophysical methods to characterize the processes that led to the geomorphologic surface expression observed today. Formation hypotheses examined encompass extraterrestrial, eolian, and periglacial processes. Field methods included a new gravity survey and reanalysis of gravity data collected in a previous student investigation of the feature. Additionally, a recent LiDAR dataset spanning San Luis Valley was examined to analyze the main structure, similar features in the area, and surrounding eolian and alluvial surfaces. An extraterrestrial origin, as suggested by numerous previous investigators, was deemed unlikely due to the non-unique gravity signature of the crater, its topographic similarity to many other like features identified in San Luis Valley, as well as its failure to excavate below the elevation of the surrounding surface. Furthermore, the expression of confirmed eolian landforms in San Luis Valley indicates that eolian processes alone would not produce such a prominent form in the level of vegetation observed. Proximal glacial deposits in the Sangre de Cristo Mountains show that the windblown sand in which all these features are clustered is adjacent to areas of past glaciations, and thus would have been affected by freeze-thaw cycles and thin, localized permafrost. Ice extent maps provided by the Colorado Geological Survey, as well as research on the timing of the formation of the Great Sand Dunes reinforce this claim. Results indicate that the Crestone Crater and nearby similar structures are relic collapsed hydraulic pingos, formed during Pleistocene periglacial activity. This conclusion provides further insight into periglacial landforms at low latitudes while demonstrating the value of LiDAR analysis of small geologic features on a regional scale.

2016091855 Sherman, Joanna (University of California at San Diego); Constable, Steven and Kannberg, Peter K. Surface towed CSEM systems for shallow water mapping [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract GP23C-02, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

We have developed a low-power, surface towed electric dipole-dipole system suitable for mapping seafloor geology in shallow water and deployable from small boats. The transmitter is capable of up to 50 amps output using 12 VDC from a 110/240 VAC power supply, and can generate an arbitrary GPS stabilized ternary waveform. Transmitter antennas are typically 50 to 100 m long. Receivers are built around the standard Scripps seafloor electrode, amplifier, and logging systems but housed in floating PVC cases and equipped with GPS timing and positioning, pitch/roll/heading sensors, and accelerometers. Receiver dipoles are 1.5 m long rigid booms held 1 m below the surface. As with the Scripps deep-towed Vulcan system, rigid antennas are used to avoid noise associated with flexible antennas moving across Earth's magnetic field. The tow cable is a simple floating rope up to 1000 m long. Water depth and conductivity are sampled continuously in order to provide constraints for apparent resistivity calculations and inversion, and moored seafloor recorders can be used to extend transmitter/receiver offsets. The entire system can be air freighted and transported in one utility vehicle. We will present results from a study to map permafrost in shallow water off Prudhoe Bay, Alaska.

2016096063 Tyler, Scott W. (University of Nevada, Geological Sciences and Engineering, Reno, NV). Updates on time-space continuous measurement of thermal profiles in frozen media [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract NS21A-1917, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Measurement of temperature, and perhaps more importantly, thermal gradient measurement represents a critical observation in permafrost and glaciated regions. In the past 5 years, application of Raman-backscatter temperature sensing along optical fibers to glaciers, ice and permafrost regions has now become both possible and practical. Distributed temperature sensing (DTS) provides spatially resolved temperatures at scales less than 50 cm, and over distances of kilometers. Temperature resolution is now commonly achievable down to 20-30 mK, with sampling frequencies of 30-60 seconds. While individual point measurements of temperature are valuable, DTS systems provide far more exciting high-resolution measurement of thermal gradients. In this work, the resolution of DTS-derived thermal gradients in ice and frozen ground are presented, along with examples of the use of DTS-derived thermal gradients to derive geothermal heat fluxes, glacial basal melt rates and time-variability in thermal gradients to infer surface boundary condition changes.

2016096060 Voytek, Emily (Colorado School of Mines, Golden, CO); Rushlow, Caitlin R.; Godsey, Sarah and Singha, Kamini. Identifying hydrologic flowpaths on Arctic hillslopes using electrical resistivity and self potential [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract NS21A-1914, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of flowpaths are difficult to determine. In arctic environments, shallow subsurface flowpaths are limited to a thin zone of seasonal thaw above continuous permafrost, which is traditionally assumed to mimic to surface topography. Here we use a combined approach of electrical resistivity imaging (ERI) and self-potential measurements (SP) to map shallow subsurface flowpaths in and around water tracks, drainage features common to arctic hillslopes. ERI measurements delineate thawed zones in the subsurface that control flowpaths, while SP is sensitive to groundwater flow. We find that areas of low electrical resistivity in the water tracks are deeper than manual thaw depth estimates and variations from surface topography. This finding suggests that traditional techniques significantly underestimate active layer thaw and the extent of the flowpath network on arctic hillslopes. SP measurements identify complex 3-D flowpaths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flowpath networks on arctic hillslopes.

2016093684 You, Kehua (University of Texas at Austin, Austin, TX); Flemings, Peter B. and DiCarlo, David A. Quantifying hydrate formation in gas-rich environments using the method of characteristics [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract OS23B-2005, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Methane hydrates hold a vast amount of methane globally, and have huge energy potential. Methane hydrates in gas-rich environments are the most promising production targets. We develop a one-dimensional analytical solution based on the method of characteristics to explore hydrate formation in such environments. Our solution shows that hydrate saturation is constant with time and space in a homogeneous system. Hydrate saturation is controlled by the initial thermodynamic condition of the system, and changed by the gas fractional flow. Hydrate saturation increases with the initial distance from the hydrate phase boundary. Different gas fractional flows behind the hydrate solidification front lead to different gas saturations at the hydrate solidification front. The higher the gas saturation at the front, the less the volume available to be filled by hydrate, and hence the lower the hydrate saturation. The gas fractional flow depends on the relative permeability curves, and the forces that drive the flow. Viscous forces (the drive for flow induced from liquid pressure gradient) dominate the flow, and hydrate saturation is independent on the gas supply rates and the flow directions at high gas supply rates. Hydrate saturation can be estimated as one minus the ratio of the initial to equilibrium salinity. Gravity forces (the drive for flow induced from the gravity) dominate the flow, and hydrate saturation depends on the flow rates and the flow directions at low gas supply rates. Hydrate saturation is highest for upward flow, and lowest for downward flow. Hydrate saturation decreases with the flow rate for upward flow, and increases with the flow rate for downward flow. This analytical solution illuminates how hydrate is formed by gas (methane, CO₂, ethane, propane) flowing into brine-saturated sediments at both the laboratory and geological scales. It provides an approach to generalize the understanding of hydrate solidification in gas-rich environments, although complicated numerical models have been developed previously. Examples of gas expulsion into hydrate stability zones and the associated hydrate formation in both laboratory and geological scales, and CO₂ sequestration into CO₂-hydrates near the seafloor and under the permafrost will be presented.

2016092358 Dunkel, Caroline A. (Clarion University, Clarion, PA); Warner, Nathaniel W.; Hughes, Christopher G. and Graettinger, Alison. Exploration of maars on Mars [abstr.]: in Geological Society of America, Northeastern Section, 51st annual meeting, Abstracts with Programs - Geological Society of America, 48(2), Abstract no. 24-1, 2016. Meeting: Geological Society of America, Northeastern Section, 51st annual meeting, March 21-23, 2016, Albany, NY.

Any evidence of possible water on Mars gives us a better understanding of what happened on the planet and the possibility of life on Mars. In our research, we are actively looking at processes that happen on Earth and applying them to what we see in the northern polar region of Mars, between 69°N-81°N and 197°E-330°E. Using Context Camera (CTX) data to examine the morphology of the planet in a program called JMars, we are searching for evidence of maars craters. A maar is a type of volcano that forms when hot magma meets groundwater. This interaction leads to a series of explosions, cutting a crater into the surface. Finding one of these craters would be an indication that there was liquid or frozen ground water on Mars. As we can see on Earth, maars are craters that are not perfectly round and are sometimes elongated. This is because multiple explosions or eruptions can happen in any given area. There are many craters on the surface of Mars; however, they are usually very round in shape, implying that they are impact craters. What we are looking for is anything that is irregular in shape, elongated, and between the size of 3km-10km in diameter. If we find anything that meets these criteria then we will further investigate it, using CTX and other data, to find out if it is a maar. If after all of our searching, we still do not find a maar then we will still learn something about the conditions below the Martian surface.

DOI: 10.1130/abs/2016NE-272213

2016089395 Cummings, M. L. (Portland State University, Department of Geology, Portland, OR); Weatherford, J. M. and Eibert, D. Recharge of an unconfined pumice aquifer; winter rainfall versus snow pack, south-central Oregon [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H43I-1658, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Walker Rim study area, an uplifted fault block east of the Cascade Range, south-central Oregon, exceeds 1580 m elevation and includes Round Meadow-Sellers Marsh closed basin, and headwaters of Upper Klamath Basin, Deschutes Basin, and Christmas Lake Valley in the Great Basin. The water-bearing unit is 2.8 to 3.0 m thick Plinian pumice fall from the Holocene eruption of Mount Mazama, Cascade Range. The perched pumice aquifer is underlain by low permeability regolith and bedrock. Disruption of the internal continuity of the Plinian pumice fall by fluvial and lacustrine processes resulted in hydrogeologic environments that include fens, wet meadows, and areas of shallow water table. Slopes are low and surface and groundwater pathways follow patterns inherited from the pre-eruption landscape. Discharge for streams and springs and depth to water table measured in open-ended piezometers slotted in the pumice aquifer have been measured between March and October, WY 2011 through WY2015. Yearly occupation on same date has been conducted for middle April, June 1st, and end of October. WY2011 and WY2012 received more precipitation than the 30 year average while WY2014 was the third driest year in 30 years of record. WY2014 and WY2015 provide an interesting contrast. Drought conditions dominated WY2014 while WY2015 was distinct in that the normal cold-season snow pack was replaced by rainfall. Cumulative precipitation exceeded the 30-year average between October and March. The pumice aquifer of wet meadows and areas of shallow water table experienced little recharge in WY2015. Persistence of widespread diffuse discharge from fens declined by middle summer as potentiometric surfaces lowered into confining peat layers or in some settings into the pumice aquifer. Recharge of the perched pumice aquifer in rain-dominated WY2015 was similar to or less than in the snow-dominated drought of WY2014. Rain falling on frozen ground drove runoff rather than aquifer recharge.

2016098397 Nielsen, Lars (University of Copenhagen, Department for Geosciences and Natural Resource Management, Copenhagen, Denmark); Bendixen, Mette; Kroon, Aart; Hede, Mikkel; Clemmensen, Lars Bjorn and Elberling, Bo. Sea-level markers in West and South Greenland detected in fossil beach deposits using ground-penetrating radar [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract NS41A-1919, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Melting of the Greenland ice sheet contributes to global sea-level change and results in uplift of the Greenland lithosphere due to unloading. The result of these processes has left fossil raised beach ridge systems several tens of meters above present sea-level. These beach ridge systems were formed during the Holocene, and they represent a proxy for the establishment of relative sea-level curves for this important time period. Here, we present ground-penetrating radar images of fossil raised beach ridge systems from western and southern Greenland. The radar images show the overall beach ridge system development and show traces of processes, as for example solifluction, which have disturbed the original beach deposits. Moreover, we interpret the transition from beach face deposits to upper shoreface deposits based on the radar images. The markers obtained in this way probably represent a level close to sea-level at the time of formation of the beach ridge deposits, and thus we suggest to use these markers to form the basis for construction of relative sea-level curves over time. We discuss our interpretation in the light of previous findings from other (micro-tidal) environments in southwest Scandinavia, where the tidal range is much smaller. Finally, advantages of using ground-penetrating radar images collected across beach ridge systems for estimation of relative sea-level fluctuations during the Holocene are discussed and the methodology is compared to other methods, for example isolation basin or beach ridge surface morphology studies, which have traditionally been widely used in Greenland.

2016095927 Viparelli, Enrica (University of South Carolina, Columbia, SC); Hernandez Moreira, Ricardo R. and Blom, Astrid. Modeling the transition between upper plane bed regime and sheet flow without an active layer formulation; preliminary results [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract EP54A-05, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

A perusal of the literature on bedload transport revealed that, notwithstanding the large number of studies on bedform morphology performed in the past decades, the upper plane bed regime has not been thoroughly investigated and the distinction between the upper plane bed and sheet flow transport regimes is still poorly defined. Previous experimental work demonstrated that the upper plane bed regime is characterized by long wavelength and small amplitude bedforms that migrate downstream. These bedforms, however, were not observed in experiments on sheet flow transport suggesting that the upper plane bed and the sheet flow are two different regimes. We thus designed and performed experiments in a sediment feed flume in the hydraulic laboratory of the Department of Civil and Environmental Engineering at the University of South Carolina at Columbia to study the transition from upper plane bed to sheet flow regime. Periodic measurements of water surface and bed elevation, bedform geometry and thicknesses of the bedload layer were performed by eyes, and with cameras, movies and a system of six ultrasonic probes that record the variations of bed elevation at a point over time. We used the time series of bed elevations to determine the probability functions of bed elevation. These probability functions are implemented in a continuous model of river morphodynamics, i.e. a model that does not use the active layer approximation to describe the sediment fluxes between the bedload and the deposit and that should thus be able to capture the details of the vertical and streamwise variation of the deposit grain size distribution. This model is validated against the experimental results for the case of uniform material. We then use the validated model in the attempt to study if and how the spatial distribution of grain sizes in the deposit changes from upper plane bed regime to sheet flow and if these results are influenced by the imposed rates of base level rise.

2016088667 Rusakov, Alexey (Saint-Petersburg State University, Institute of Earth Sciences, St. Petersburg, Russian Federation); Nikonov, Andrei; Savelieva, Larisa; Simakova, Alexandra; Sedov, Sergey; Maksimov, Fedor; Kuznetsov, Vladislav; Savenko, Viktor; Starikova, Anna; Korkka, Maria and Titova, Darya. Landscape evolution in the periglacial zone of Eastern Europe since MIS5; proxies from paleosols and sediments of the Cheremoshnik key site (upper Volga, Russia): in Paleosols, pedosediments and landscape morphology as environmental archives (Terhorst, Birgit, editor; et al.), Quaternary International, 365, p. 26-41, illus. incl. sects., 1 table, sketch map, 82 ref., April 16, 2015. Meeting: XII international symposium and field workshop on Paleopedology; paleosols, pedosediments and landscape morphology as environmental archives, Aug. 10-15, 2013, Kursk, Russian Federation.

A variety of studies of the re-examined (new exposure) Late Pleistocene key section Cheremoshnik (East European plain, middle of the Volga Basin of Yaroslavl) was conducted on a new methodological level using modern methods. For the first time, a series of paleosols (MIS5-MIS1) from the section offering significant information in regard to chronostratigraphy and landscape evolution have been studied in detail and dated. An excavation ~7 m deep reveals a soil-sediment stratum which formed over the course of ~115 ka in an accumulative beam-like terrace and consists of five lithological layers and six pedostratigraphical units. The base of the section was determined to be an Early Mikulino peat-dark humus paleosol which marked incipient subaerial pedogenesis on the Moscow (Riss II) moraine and was covered with a thickness of gyttja with a peat horizon (Histosol) which had formed 114-115 ka and was reliably dated using uranium-thorium dating. The following paleosols were successfully identified within the series of weak stone gullied-channel sediments within the Valdai (Wurm) thickness (from bottom to top): (1) Bryansk paleosol (MIS3) - Gleysol - with three pedogenesis rhythms; (2) Trubchevskaya paleosol - Gleyic Turbic Cryosol (MIS2) and (3) pedosediment formed at the end of the Bolling interstadial (MIS2). Terminal Pleistocene formations are marked with a gravelly stratum on the section's surface formed during the Preboreal period. Recent Regosol formed on loess-like loam deposits was identified at the top of the whole soil-sediment stratum. The ¹⁴C age of the paleosol humus varied between 27,500 and 11,400 cal. BP. The paleosols represent the northernmost occurrence of MIS5-MIS2 fossil soil in Europe, dominated by features of gleyzation, cryogenic aggregation, cracking, and humus and peat formation. Pollen analysis results allowed estimation of changes in vegetation cover, climatic conditions and the age of deposit sedimentation for the period from the Moskow Late Glacial to the Valdai Late Glacial and early Holocene times. Successive stages in the development of vegetation, high contents of alder and hazel pollen and the climax and distinct appearance of broadleaf trees relate the formation of biogenic sediments (LPAZ 2-6) in the Cheremoshnik section to the Mikulino Interglacial. Valdai (MIS4-MIS2) glacial sediment is absent within the investigated area. Abstract Copyright (2015) Elsevier, B.V.

DOI: 10.1016/j.quaint.2014.09.029

2016091552 Hughson, Kynan H. G. (University of California at Los Angeles, Department of Earth, Planetary, and Space Sciences, Houston, TX); Russell, Christopher T.; Schmidt, Britney Elyce; Chilton, Heather; Scully, Jennifer E. C.; Byrne, Shane; Platz, Thomas; Ammannito, Eleonora; Schenk, Paul M. and Williams, David A. Scalloped and degraded craters as geomorphological evidence for pervasive ground ice on Ceres as seen by the Dawn Spacecraft [abstr.]: in Geological Society of America, 2015 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 47(7), p. 709, 2015. Meeting: Geological Society of America, 2015 annual meeting & exposition, Nov. 1-4, 2015, Baltimore, MD.

Five decades of observations of Ceres' albedo, surface composition, shape and density by Earth and space based telescopes suggest that Ceres is comprised of both silicates and several tens of percent water ice (McCord et al., 2010). Ceres' bulk density of ~2100 kg/m3 (McCord and Sortin, 2005), the detection of OH and water emissions from the Herschel Space Observatory (Kuppers et al., 2014), and recent Dawn observations of young craters containing high albedo spots all support this conclusion. We report initial geomorphological evidence for sublimative, evaporative, and flow like processes within a wide range of craters on Ceres. We interpret these features as indications of a significant water ice component in Ceres' surface or near subsurface. The craters we describe display a number of features indicative of the aforementioned processes, which include: asymmetrically scalloped rims that are morphologically reminiscent of scalloped terrain on Mars (Zanetti et al., 2010), degraded and recessed rims characterized by a high degree of mass wasting, and partial or completely circumferential pits located near the crater rims, which are followed by higher elevation material lobes towards the crater centers. These lobes appear similar to talus lobe and rampart features found in terrestrial glaciated terrains (Humlum, 1982). In some high latitude craters (~60°N and S), we observe lobate flows that emanate both inwardly and outwardly from "breached" rims that bear a striking similarity to terrestrial rock glaciers (Haeberli et al., 2006). Many of these high latitude craters also display symmetrical conical domes that frequently occur in clusters both on the crater floors and inward facing rims, and in some cases show evidence for high albedo or activity. These features could be due to local melt and extrusion via hydrologic gradients, forming domes similar to pingos (MacKay, 1998). The global distribution, along with the latitudinal/regional variation in the diversity and prevalence of these craters suggest that ground ice is a key parameter of the geology on Ceres. It also suggests that ice content within the surface and near subsurface is either spatially varied and/or activated by energetic events.

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