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2018082164 Jafarov, Elchin E. (Los Alamos National Laboratory, Los Alamos, NM); Coon, Ethan T.; Harp, Dylan R.; Wilson, Cathy J.; Painter, Scott L.; Atchley, Adam L. and Romanovsky, Vladimir E. Modeling the role of preferential snow accumulation in through talik development and hillslope groundwater flow in a transitional permafrost landscape: Environmental Research Letters, 13(10), Paper no. 105006, illus. incl. 1 table, 56 ref., October 2018.
Through taliks-thawed zones extending through the entire permafrost layer-represent a critical type of heterogeneity that affects water redistribution and heat transport, especially in sloping landscapes. The formation of through taliks as part of the transition from continuous to discontinuous permafrost creates new hydrologic pathways connecting the active layer to sub-permafrost regions, with significant hydrological and biogeochemical consequences. At hilly field sites in the southern Seward Peninsula, AK, patches of deep snow in tall shrubs are associated with higher winter ground temperatures and an anomalously deep active layer. To better understand the thermal-hydrologic controls and consequences of through taliks, we used the coupled surface/subsurface permafrost hydrology model ATS (Advanced Terrestrial Simulator) to simulate through taliks associated with preferentially distributing snow. Scenarios were developed based on an intensively studied hillslope transect on the southern Seward Peninsula, which predominately has taller shrubs midslope and tundra in upslope and downslope areas. The model was forced with detrended meteorological data with snow preferentially distributed at the midslope of the domain to investigate the potential role of vegetation-induced snow trapping in controlling through talik development under conditions typical of the current-day Seward Peninsula. We simulated thermal hydrology and talik development for five permafrost conditions ranging in thickness from 17-45 m. For the three thinnest permafrost configurations, a through talik developed, which allowed water from the seasonally thawed layer into sub-permafrost waters, increasing sub-permafrost groundwater flow. These numerical experiments suggest that in the transition from continuous to discontinuous permafrost, through taliks may appear at locations that preferential trap snow and that the appearance of those through taliks may drive significant changes in permafrost hydrology. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aadd30
2018082162 Liu Futing (Chinese Academy of Sciences, Institute of Botany, Laboratory of Vegetation and Environmental Change, Beijing, China); Chen Leiyi; Abbott, Benjamin W.; Xu Yunping; Yang Guibiao; Kou Dan; Qin Shuqi; Strauss, Jens; Wang Yinghui; Zhang Beibei and Yang Yuanhe. Reduced quantity and quality of SOM along a thaw sequence on the Tibetan Plateau: Environmental Research Letters, 13(10), Paper no. 104017, illus. incl. 1 table, sketch map, 50 ref., October 2018.
Carbon (C) release from thawing permafrost is potentially the largest climate feedback from terrestrial ecosystems. However, the magnitude of this feedback remains highly uncertain, partly due to the limited understanding of how abrupt permafrost thaw (e.g. permafrost collapse) alters soil organic matter (SOM) quality. Here we employed elemental analysis, stable isotope analysis, biomarker and nuclear magnetic resonance techniques to explore changes in soil C concentration and stock as well as SOM quality following permafrost collapse on the Tibetan Plateau. Our results showed that permafrost collapse resulted in a 21% decrease in soil C concentration and a 32% reduction in C stock of the top 15 cm of soil over 16 years. Moreover, permafrost collapse led to a significant decline in SOM quality: the relative abundance of labile SOM fractions (e.g. carbohydrates) decreased, whereas recalcitrant SOM fractions (e.g. suberin-derived compounds) increased 16 years after collapse. By contrast, the relative abundances of labile and recalcitrant compounds showed no significant differences in the control plots along the thaw sequence. These results demonstrate that permafrost collapse and consequent changes in soil environmental conditions could trigger substantial C release on decadal timescales, implying that abrupt thaw may be a dominant mechanism exposing soil C to mineralization. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aae43b
2018082163 Schädel, Christina (Northern Arizona University, Center for Ecosystem Science and Society and Department of Biology, Flagstaff, AZ); Koven, Charles D.; Lawrence, David M.; Celis, Gerardo; Garnello, Anthony J.; Hutchings, Jack; Mauritz, Marguerite; Natali, Susan M.; Pegoraro, Elaine; Rodenhizer, Heidi; Salmon, Verity G.; Taylor, Meghan A.; Webb, Elizabeth E.; Wieder, William R. and Schuur, Edward A. G. Divergent patterns of experimental and model-derived permafrost ecosystem carbon dynamics in response to Arctic warming: Environmental Research Letters, 13(10), Paper no. 105002, illus. incl. 1 table, 48 ref., October 2018.
In the last few decades, temperatures in the Arctic have increased twice as much as the rest of the globe. As permafrost thaws in response to this warming, large amounts of soil organic matter may become vulnerable to decomposition. Microbial decomposition will release carbon (C) from permafrost soils, however, warmer conditions could also lead to enhanced plant growth and C uptake. Field and modeling studies show high uncertainty in soil and plant responses to climate change but there have been few studies that reconcile field and model data to understand differences and reduce uncertainty. Here, we evaluate gross primary productivity (GPP), ecosystem respiration (Reco), and net ecosystem C exchange (NEE) from eight years of experimental soil warming in moist acidic tundra against equivalent fluxes from the Community Land Model during simulations parameterized to reflect the field conditions associated with this manipulative field experiment. Over the eight-year experimental period, soil temperatures and thaw depths increased with warming in field observations and model simulations. However, the field and model results do not agree on warming effects on water table depth; warming created wetter soils in the field and drier soils in the models. In the field, initial increases in growing season GPP, Reco, and NEE to experimentally-induced permafrost thaw created a higher C sink capacity in the first years followed by a stronger C source in years six through eight. In contrast, both models predicted linear increases in GPP, Reco, and NEE with warming. The divergence of model results from field experiments reveals the role subsidence, hydrology, and nutrient cycling play in influencing the C flux responses to permafrost thaw, a complexity that the models are not structurally able to predict, and highlight challenges associated with projecting C cycle dynamics across the Arctic. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aae0ff
2018084255 Anthony, Katey Walter (University of Alaska-Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Schneider von Deimling, Thomas; Nitze, Ingmar; Frolking, Steve; Emond, Abraham; Daanen, Ronald; Anthony, Peter; Lindgren, Prajna; Jones, Benjamin and Grosse, Guido. 21st-century modeled permafrost carbon emissions accelerated by abrupt thaw beneath lakes: Nature Communications, 9(Article 3262), 11 p., illus., 88 ref., August 15, 2018.
Permafrost carbon feedback (PCF) modeling has focused on gradual thaw of near-surface permafrost leading to enhanced carbon dioxide and methane emissions that accelerate global climate warming. These state-of-the-art land models have yet to incorporate deeper, abrupt thaw in the PCF. Here we use model data, supported by field observations, radiocarbon dating, and remote sensing, to show that methane and carbon dioxide emissions from abrupt thaw beneath thermokarst lakes will more than double radiative forcing from circumpolar permafrost-soil carbon fluxes this century. Abrupt thaw lake emissions are similar under moderate and high representative concentration pathways (RCP4.5 and RCP8.5), but their relative contribution to the PCF is much larger under the moderate warming scenario. Abrupt thaw accelerates mobilization of deeply frozen, ancient carbon, increasing 14C depleted permafrost soil carbon emissions by ~125-190% compared to gradual thaw alone. These findings demonstrate the need to incorporate abrupt thaw processes in earth system models for more comprehensive projection of the PCF this century.
DOI: 10.1038/s41467-018-05738-9
2018082160 Carpino, Olivia A. (University of Guelph, Department of Geography, Guelph, ON, Canada); Berg, Aaron A.; Quinton, William L. and Adams, Justin R. Climate change and permafrost thaw-induced boreal forest loss in northwestern Canada: Environmental Research Letters, 13(8), Paper no. 084018, illus. incl. 1 table, 35 ref., August 2018.
Permafrost distribution throughout the western Canadian subarctic is not well understood due to the remoteness and size of the region, its spatial and temporal heterogeneity, limited data availability, and sparse monitoring networks. These factors severely challenge investigations of how climate warming might affect the distribution of permafrost and provide strong justification for new methods of evaluating permafrost extent using remote sensing platforms. This study quantifies forest loss at ten subarctic boreal sites in the southern Northwest Territories and northeastern British Columbia between 1970 and 2010. Historical air photos and optical remote sensing images were assessed using a change detection approach over the ten sites, each 10 km2 spanning a north/south transect of 200 km. This study is the first to apply change detection methods to a large-scale gradient and spans the southern margin of discontinuous permafrost where results demonstrate variable patterns of net forest loss at each site ranged from 6.9% to 11.6% over the 40 year study period. Here we show that these differential rates of landcover change can be explained in part through climatic and environmental factors that vary latitudinally across the selected sites. Change statistics-net change, forest gain and forest loss were significantly correlated with an assortment of factors that varied across the ten-site transect. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aad74e
2018082161 Estop-Aragonés, Cristian (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Czimczik, Claudia I.; Heffernan, Liam; Gibson, Carolyn; Walker, Jennifer C.; Xu, Xiaomei and Olefeldt, David. Respiration of aged soil carbon during fall in permafrost peatlands enhanced by active layer deepening following wildfire but limited following thermokarst: Environmental Research Letters, 13(8), Paper no. 085002, illus. incl. sketch map, 43 ref., August 2018.
Permafrost peatlands store globally significant amounts of soil organic carbon (SOC) that may be vulnerable to climate change. Permafrost thaw exposes deeper, older SOC to microbial activity, but SOC vulnerability to mineralization and release as carbon dioxide is likely influenced by the soil environmental conditions that follow thaw. Permafrost thaw in peat plateaus, the dominant type of permafrost peatlands in North America, occurs both through deepening of the active layer and through thermokarst. Active layer deepening exposes aged SOC to predominately oxic conditions, while thermokarst is associated with complete permafrost thaw which leads to ground subsidence, inundation and soil anoxic conditions. Thermokarst often follows active layer deepening, and wildfire is an important trigger of this sequence. We compared the mineralization rate of aged SOC at an intact peat plateau (~70 cm oxic active layer), a burned peat plateau (~120 cm oxic active layer), and a thermokarst bog (~550 cm anoxic peat profile) by measuring respired 14C-CO2. Measurements were done in fall when surface temperatures were near-freezing while deeper soil temperatures were still close to their seasonal maxima. Aged SOC (1600 yrs BP) contributed 22.1±11.3% and 3.5±3.1% to soil respiration in the burned and intact peat plateau, respectively, indicating a fivefold higher rate of aged SOC mineralization in the burned than intact peat plateau (0.15±0.07 versus 0.03±0.03 g CO2-C m2 d1). None or minimal contribution of aged SOC to soil respiration was detected within the thermokarst bog, regardless of whether thaw had occurred decades or centuries ago. While more data from other sites and seasons are required, our study provides strong evidence of substantially increased respiration of aged SOC from burned peat plateaus with deepened active layer, while also suggesting inhibition of aged SOC respiration under anoxic conditions in thermokarst bogs. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aad5f0
2018084254 Gibson, Carolyn M. (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Chasmer, Laura E.; Thompson, Dan K.; Quinton, William L.; Flannigan, Mike D. and Olefeldt, David. Wildfire as a major driver of recent permafrost thaw in boreal peatlands: Nature Communications, 9(Article 3041), 9 p., illus. incl. geol. sketch maps, 62 ref., August 2, 2018.
Permafrost vulnerability to climate change may be underestimated unless effects of wildfire are considered. Here we assess impacts of wildfire on soil thermal regime and rate of thermokarst bog expansion resulting from complete permafrost thaw in western Canadian permafrost peatlands. Effects of wildfire on permafrost peatlands last for 30 years and include a warmer and deeper active layer, and spatial expansion of continuously thawed soil layers (taliks). These impacts on the soil thermal regime are associated with a tripled rate of thermokarst bog expansion along permafrost edges. Our results suggest that wildfire is directly responsible for 2200±1500 km2 (95% CI) of thermokarst bog development in the study region over the last 30 years, representing ~25% of all thermokarst bog expansion during this period. With increasing fire frequency under a warming climate, this study emphasizes the need to consider wildfires when projecting future circumpolar permafrost thaw.
DOI: 10.1038/s41467-018-05457-1
2018084256 Kramshoj, Magnus (University of Copenhagen, Department of Biology, Copenhagen, Denmark); Albers, Christian N.; Holst, Thomas; Holzinger, Rupert; Elberling, Bo and Rinnan, Riikka. Biogenic volatile release from permafrost thaw is determined by the soil microbial sink: Nature Communications, 9(Article 3412), 9 p., illus. incl. 2 tables, 41 ref., August 24, 2018.
Warming in the Arctic accelerates thawing of permafrost-affected soils, which leads to a release of greenhouse gases to the atmosphere. We do not know whether permafrost thaw also releases non-methane volatile organic compounds that can contribute to both negative and positive radiative forcing on climate. Here we show using proton transfer reaction-time of flight-mass spectrometry that substantial amounts of ethanol and methanol and in total 316 organic ions were released from Greenlandic permafrost soils upon thaw in laboratory incubations. We demonstrate that the majority of this release is taken up in the active layer above. In an experiment using 14C-labeled ethanol and methanol, we demonstrate that these compounds are consumed by microorganisms. Our findings highlight that the thawing permafrost soils are not only a considerable source of volatile organic compounds but also that the active layer regulates their release into the atmosphere.
DOI: 10.1038/s41467-018-05824-y
2018082159 Lamontagne-Hallé, Pierrick (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada); McKenzie, Jeffrey M.; Kurylyk, Barret L. and Zipper, Samuel C. Changing groundwater discharge dynamics in permafrost regions: Environmental Research Letters, 13(8), Paper no. 084017, illus. incl. 1 table, 65 ref., August 2018.
Permafrost thaw due to climate warming modifies hydrological processes by increasing hydrological connectivity between aquifers and surface water bodies and increasing groundwater storage. While previous studies have documented arctic river baseflow increases and changing wetland and lake distributions, the hydrogeological processes leading to these changes remain poorly understood. This study uses a coupled heat and groundwater flow numerical model with dynamic freezing and thawing processes and an improved set of boundary conditions to simulate the impacts of climate warming on permafrost distribution and groundwater discharge to surface water bodies. We show a spatial shift in groundwater discharge from upslope to downslope and a temporal shift with increasing groundwater discharge during the winter season due to the formation of a lateral supra-permafrost talik underlying the active layer. These insights into changing patterns of groundwater discharge help explain observed changes in arctic baseflow and wetland patterns and are important for northern water resources and ecosystem management. Copyright (Copyright) 2018 IOP Publishing Ltd
DOI: 10.1088/1748-9326/aad404
2018084257 Lin Zhenzhou (China University of Geosciences-Wuhan, Institute of Geophysics and Geomatics, Wuhan, China); Pan Heping; Fang Hui; Gao Wenli and Liu Dongming. High-altitude well log evaluation of a permafrost gas hydrate reservoir in the Muli area of Qinghai, China: Scientific Reports, 8(Article 12596), 11 p., illus. incl. 6 tables, geol. sketch map, 33 ref., August 22, 2018.
The Muli area is the only permafrost region on the Chinese mainland wherein gas hydrates have been discovered. The gas hydrates are present in the fractures and pore spaces of the host rocks with a lamellar or micro-disseminated structure. By combining conventional and image logs, we describe the thickness of the permafrost layer and the well log responses of the gas hydrate reservoir, and calculate the porosity and gas hydrate saturation. We then analyze the advantages and disadvantages of different logging methods for evaluating gas hydrate reservoirs. Our results indicate that (1) gas hydrates are present below the permafrost in the Muli area, (2) gas hydrates predominantly occur in rock fractures, (3) the apparent resistivity is sensitive to gas hydrates present in pore spaces, and both apparent resistivity and acoustic logs are sensitive to gas hydrates present in fractures, (4) a density log is more appropriate for calculating porosity, and (5) gas hydrate saturation can be effectively calculated by the Archie equation, the modified Archie equation, and the Indonesian equation.
DOI: 10.1038/s41598-018-30795-x
2018084278 Zhang, Chao (Colorado School of Mines, Department of Civil and Environmental Engineering, Golden, CO); Liu, Zhen and Deng, Peng. Using molecular dynamics to unravel phase composition behavior of nano-size pores in frozen soils; does Young-Laplace equation apply in low temperature range?: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 55(8), p. 1144-1153, illus. incl. 1 table, 53 ref., August 2018.
The phase composition curve of frozen soils is a fundamental relationship in understanding permafrost and seasonally frozen soils. However, due to the complex interplay between adsorption and capillarity, a clear physically based understanding of the phase composition curve in the low temperature range, i.e., <265 K, is still absent. Especially, it is unclear whether the Young-Laplace equation corresponding to capillarity still holds in nano-size pores where adsorption could dominate. In this paper, a framework based on molecular dynamics was developed to investigate the phase transition behavior of water confined in nano-size pores. A series of simulations was conducted to unravel the effects of the pore size and wettability on the freezing and melting of pore water. This is the first time that the phase composition behavior of frozen soils is analyzed using molecular dynamics. It is found that the Young-Laplace equation may not apply in the low temperature range.
DOI: 10.1139/cgi-2016-0150
2018084059 Kuhn, McKenzie (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada); Lundin, Erik J.; Giesler, Reiner; Johansson, Margareta and Karlsson, Jan. Emissions from thaw ponds largely offset the carbon sink of northern permafrost wetlands: Scientific Reports, 8(9535), illus., 31 ref., June 22, 2018.
Northern regions have received considerable attention not only because the effects of climate change are amplified at high latitudes but also because this region holds vast amounts of carbon (C) stored in permafrost. These carbon stocks are vulnerable to warming temperatures and increased permafrost thaw and the breakdown and release of soil C in the form of carbon dioxide (CO2) and methane (CH4). The majority of research has focused on quantifying and upscaling the effects of thaw on CO2 and CH4 emissions from terrestrial systems. However, small ponds formed in permafrost wetlands following thawing have been recognized as hotspots for C emissions. Here, we examined the importance of small ponds for C fluxes in two permafrost wetland ecosystems in northern Sweden. Detailed flux estimates of thaw ponds during the growing season show that ponds emit, on average (±SD), 279 ± 415 and 7 ± 11 mmol C m-2 d-1 of CO2 and CH4, respectively. Importantly, addition of pond emissions to the total C budget of the wetland decreases the C sink by ~39%. Our results emphasize the need for integrated research linking C cycling on land and in water in order to make correct assessments of contemporary C balances.
DOI: 10.1038/s41598-018-27770-x
2018077356 Song Yanyu (Chinese Academy Sciences, Northeast Institute of Geography and Agroecology, Laboratory of Wetland Ecology and Environment, Changchun, China); Song Changchun; Hou Aixin; Ren Jiusheng; Wang Xianwei; Cui Qian and Wang Mingquan. Effects of temperature and root additions on soil carbon and nitrogen mineralization in a predominantly permafrost peatland: Catena (Giessen), 165, p. 381-389, illus. incl. 3 tables, sketch map, 60 ref., June 2018.
Approximately one-third of northern peatlands are within permafrost regions. Soil organic matter (SOM) and plant root biomass in permafrost peatlands are vulnerable to future global warming. However, previous studies have primarily focused on the response of SOM mineralization to increases in temperature without analysing the potential interaction effects of increased plant root biomass. This study investigated the influence of temperature and root additions on soil carbon and nitrogen mineralization as well as the mechanisms driving mineralization in a high latitude permafrost peatland in the Da Xing'an Mountains, Northeast China. We investigated changes in shallow soil (0-15 cm) and deep soil (15-30 cm) carbon mineralization, available N contents, microbial biomass carbon (MBC), dissolved organic carbon (DOC), and enzyme activities in response to increasing temperature and Eriophorum vaginatum root additions by using an incubation experiment. Our results indicate that elevated temperature significantly increased soil carbon mineralization. The Q10 values of the carbon mineralization rates in the shallow soil and deep soil were 3.95 and 2.91, respectively. In contrast, the soil MBC and DOC decreased significantly, confirming that labile carbon is the main driving force of microbial mineralization activities under warming conditions. Elevated temperature significantly increased the shallow soil net N mineralization rates and increased the net nitrification rates in both soil layers. At high temperatures, ammonification rates increased in the shallow soil but decreased in the deep soil. The increase in the incubation temperature resulted in significantly increased shallow soil b-glucosidase activity and decreased invertase activity. This suggests the increased production of complex substrate enzymes, and decreased production of simple substrate-acquiring enzymes. The root additions significantly increased the soil C mineralization and stimulated the secretion of invertase by soil microorganisms. These findings indicate that future climate warming in the northern high latitude will significantly stimulate soil carbon and nitrogen mineralization in permafrost peatlands. Furthermore, increases in plant roots will enhance C accumulation and may even enhance the response of soil C mineralization to temperature, significantly impact the soil C balance in high latitude permafrost peatlands.
DOI: 10.1016/j.catena.2018.02.026
2018084214 Wolfe, Stephen A. (Geological Survey of Canada, Ottawa, ON, Canada); Morse, Peter D.; Neudorf, Christina M.; Kokelj, Steven V.; Lian, Olav B. and O'Neill, H. Brendan. Contemporary sand wedge development in seasonally frozen ground and paleoenvironmental implications: Geomorphology, 308, p. 215-229, illus. incl. 4 tables, sketch map, 76 ref., May 2018. Includes appendices.
Contemporary sand wedges and sand veins are active in seasonally frozen ground within the extensive discontinuous permafrost zone in Northwest Territories, Canada. The region has a subarctic continental climate with 291 mm a-1 precipitation, -4.1°C mean annual air temperature, warm summers (July mean 17.0°C), and cold winters (January mean -26.6°C). Five years of continuous observations indicate that interannual variation of the ground thermal regime is dominantly controlled by winter air temperature and snow cover conditions. At sandy sites, thin snow cover and high thermal conductivity promote rapid freezing, high rates of ground cooling, and low near-surface ground temperatures (-15 to -25°C), resulting in thermal contraction cracking to depths of 1.2 m. Cracking potentials are high in sandy soils when air temperatures are <-30°C on successive days, mean freezing season air temperatures are ≤&eq;-17°C, and snow cover is <0.15 m thick. In contrast, surface conditions in peatlands maintain permafrost, but thermal contraction cracking does not occur because thicker snow cover and the thermal properties of peat prolong freezeback and maintain higher winter ground temperatures. A combination of radiocarbon dating, optical dating, and stratigraphic observations were used to differentiate sand wedge types and formation histories. Thermal contraction cracks that develop in the sandy terrain are filled by surface (allochthonous) and/or host (autochthonous) material during the thaw season. Epigenetic sand wedges infilled with allochthonous sand develop within former beach sediments beneath an active eolian sand sheet. Narrower and deeper syngenetic wedges developed within aggrading eolian sand sheets, whereas wider and shallower antisyngenetic wedges developed in areas of active erosion. Thermal contraction cracking beneath vegetation-stabilized surfaces leads to crack infilling by autochthonous host and overlying organic material, with resultant downturning and subsidence of adjacent strata. Sand wedge development in seasonally frozen ground with limited surface sediment supply can result in stratigraphy similar to ice-wedge and composite-wedge pseudomorphs. Therefore, caution must be exercised when interpreting this suite of forms and inferring paleoenvironments.
DOI: 10.1016/j.geomorph.2018.02.015
2018084222 Cable, Stefanie (University of Copenhagen, Center for Permafrost, Copenhagen, Denmark); Elberling, Bo and Kroon, Aart. Holocene permafrost history and cryostratigraphy in the High-Arctic Adventdalen Valley, central Svalbard: Boreas, 47(2), p. 423-442, illus. incl. strat. cols., 4 tables, sketch map, 98 ref., April 2018.
This paper presents the history and cryostratigraphy of the upper permafrost in the High-Arctic Adventdalen Valley, central Svalbard. Nineteen frozen sediment cores, up to 10.7 m long, obtained at five periglacial landforms, were analysed for cryostructures, ice, carbon and solute contents, and grain-size distribution, and were 14C- and OSL-dated. Spatial variability in ice and carbon contents is closely related to the sedimentary history and mode of permafrost aggradation. In the valley bottom, saline epigenetic permafrost with pore ice down to depths of 10.7 m depth formed in deltaic sediments since the mid-Holocene; cryopegs were encountered below 6 m. In the top 1 to 5 m, syngenetic and quasi-syngenetic permafrost with microlenticular, lenticular, suspended and organic-matrix cryostructures developed due to loess and alluvial sedimentation since the colder late Holocene, which resulted in the burial of organic material. At the transition between deltaic sediments and loess, massive ice bodies occurred. A pingo developed where the deltaic sediments reached the surface. On hillslopes, suspended cryostructure on solifluction sheets indicates quasi-syngenetic permafrost aggradation; lobes, in contrast, were ice-poor. Suspended cryostructure in eluvial deposits reflects epigenetic or quasi-syngenetic permafrost formation on a weathered bedrock plateau. Landform-scale spatial variations in ground ice and carbon relate to variations in slope, sedimentation rate, moisture conditions and stratigraphy. Although the study reveals close links between Holocene landscape evolution and permafrost history, our results emphasize a large uncertainty in using terrain surface indicators to infer ground-ice contents and upscale from core to landform scale in mountainous permafrost landscapes. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1111/bor.12286
2018084227 Liu Yeyi (Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China) and Jiang Dabang. Mid-Holocene frozen ground in China from PMIP3 simulations: Boreas, 47(2), p. 498-509, illus. incl. 4 tables, 49 ref., April 2018.
Extensive degradation of frozen ground in the mid-Holocene is widely assumed on the basis of sparse proxy data. Here, the simulated soil temperature from the Paleoclimate Modelling Intercomparison Project Phase 3 is used to address this issue over China. By comparing with the results of a preindustrial (0 ka, baseline) simulation, we show that frozen ground in the mid-Holocene (6 ka) simulation is degraded mainly in northeast China and on the northern Tibetan Plateau. The change follows closely orbitally induced variations in insolation. Quantitatively, permafrost area reduces by 0.02´106 km2 in northeast China in response to an orbitally induced increase in boreal summer insolation but increases by 0.08´106 km2 on the southern Tibetan Plateau due to local summer cooling. Changing values of active layer thickness vary greatly amongst different locations. On average, they are 3 and 4 cm thicker than the preindustrial values in northeast China and on the Tibetan Plateau, respectively. No degradation in seasonally frozen ground is detected over China as a whole. Regionally, its coverage increases by 0.21´106 km2 near the middle and lower reaches of the Yangtze River valley. In addition, the maximum depth of seasonal frost penetration is on average 8.5 cm deeper than preindustrial values due to widespread winter cooling. The changes in frozen ground are consistent amongst models. However, the models disagree with proxy data in terms of not only the changes in frozen ground but also climate. Further modelling improvements and adequate proxy data are both needed to fill in the gaps between models and the data in our knowledge of the mid-Holocene frozen ground. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1111/bor.12285
2018084224 Sannel, Anna Britta Kristina (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Hempel, Liljen; Kessler, Alexander and Preskienis, Vilmantas. Holocene development and permafrost history in sub-arctic peatlands in Tavvavuoma, northern Sweden: Boreas, 47(2), p. 454-468, illus. incl. 2 tables, sketch map, 72 ref., April 2018.
Under changing climatic conditions permafrost peatlands can play an important role in the global carbon budget through permafrost carbon feedbacks and shifts in carbon assimilation. To better predict future dynamics in these ecosystems an increased understanding of their Holocene carbon and permafrost history is needed. In Tavvavuoma, northern Sweden, we have performed detailed analyses of vegetation succession and geochemical properties at six permafrost peatland sites. Peatland initiation took place around 10 000 to 9600 cal. a BP, soon after retreat of the Fennoscandian Ice Sheet, and the peatlands have remained permafrost-free fens throughout most of the Holocene. At the four sites that showed a continuous accumulation record during the late Holocene radiocarbon dating of the shift from wet fen to dry bog vegetation, characteristic of the present permafrost peatland surface, suggests that permafrost developed at around 600-100 cal. a BP. At the other two sites peat accumulation was halted during the late Holocene, possibly due to abrasion, making it more difficult to imply the timing of permafrost aggradation. However also at these sites there are no indications of permafrost inception prior to the Little Ice Age. The mean long-term Holocene carbon accumulation rate at all six sites was 12.3±2.4 gC m-2 a-1 (±SD), and the mean soil organic carbon storage was 114±27 kg m-2. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1111/bor.12276
2018084058 Mu Cuicui (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Li Lili; Wu Xiaodong; Zhang Feng; Jia Lin; Zhao Qian and Zhang Tingjun. Greenhouse gas released from the deep permafrost in the northern Qinghai-Tibetan Plateau: Scientific Reports, 8(4205), illus. incl. sketch map, 52 ref., March 9, 2018.
Deep carbon pool in permafrost regions is an important component of the global terrestrial carbon cycle. However, the greenhouse gas production from deep permafrost soils is not well understood. Here, using soils collected from 5-m deep permafrost cores from meadow and wet meadow on the northern Qinghai-Tibetan Plateau (QTP), we investigated the effects of temperature on CO2 and N2O production under aerobic incubations and CH4 production under anaerobic incubations. After a 35-day incubation, the CO2, N2O and CH4 production at -2°C to 10°C were 0.44~2.12 mg C-CO2/g soil C, 0.0027~0.097 mg N-N2O/g soil N, and 0.14~5.88mg C-CH4/g soil C, respectively. Greenhouse gas production in deep permafrost is related to the C:N ratio and stable isotopes of soil organic carbon (SOC), whereas depth plays a less important role. The temperature sensitivity (Q10) values of the CO2, N2O and CH4 production were 1.67-4.15, 3.26-5.60 and 5.22-10.85, without significant differences among different depths. These results indicated that climate warming likely has similar effects on gas production in deep permafrost and surface soils. Our results suggest that greenhouse gas emissions from both the deep permafrost and surface soils to the air will increase under future climate change.
DOI: 10.1038/s41598-018-22530-3
2018084190 Zhang Shuhong (Shangqiu Normal University, College of Food and Science, Shangqiu, China); Yang Guangli; Hou Shugui; Zhang Tingjun; Li Zhiguo and Liang Feng. Distribution of ARGs and MGEs among glacial soil, permafrost, and sediment using metagenomic analysis: Environmental Pollution (1987), 234, p. 339-346, illus. incl. 3 tables, 61 ref., March 2018.
Antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) can be identified with metagenomic analyses comparing relatively pristine and human-impacted environments. We collected samples from 3 different environments: glacial soil little affected by anthropogenic activity, deep permafrost dated to 5821 BP (before human antibiotics), and sediment from the Pearl River. Sulfonamides, tetracyclines, and fluoroquinolones were common in the sediment samples. Sulfonamides and tetracycline were not found in permafrost; tetracycline was also not found in glacial soil. ARGs from the sediment were more abundant and diverse than those from glacial soil and permafrost. More types of resistance mechanisms were also present in the sediment. The diversity of MGEs was significantly correlated with the abundance and diversity of ARGs. The result will help future workers to better understand the distribution of ARGs among environments more or less impacted by anthropogenic activities.
DOI: 10.1016/j.envpol.2017.11.031
2018079439 Ravolainen, Virve (Norsk Polarinstitutt, Norway); Strom, Hallvard; Elvevold, Synnove; Fuglei, Eva; Pedersen, Ashild Onvik; Svenning, Martin; Routti, Heli; Gabrielsen, Geir Wing; Nordgard, Ida Kessel; Vongraven, Dag; Gerland, Sebastian; Kohler, Jack; Pavlova, Olga; Lydersen, Christian; Aars, Jon; Myhre, Per Inge; Nylund, Ingvild; Overrein, Oystein; von Quillfeldt, Cecilie; Hallanger, Ingeborg; Ask, Amalie; Itkin, Mikhail; Hansen, John Richard; Skoglund, Anders and Morgensen, Nina Mari. Kunnskapsgrunnlaget for Sentral-Spitsbergen [Basic knowlege for central Spitsbergen]: Rapportserie - Norsk Polarinstitutt, 150, 325 p., illus. incl. tables, sketch maps, 367 ref., 2018. ISBN: 978-82-7666-411-9; 978-82-7666-412-6. Includes appendices.
2018075995 Rudolph, Elizabeth M. (University of the Free State, Department of Geography, Bloemfontein, South Africa); Meiklejohn, K. Ian; Hansen, Christel D.; Hedding, David W. and Nel, Werner. Rock glaciers in the Jutulsessen, Dronning Maud Land, East Antarctica: Polish Polar Research, 39(1), p. 1-17, illus. incl. 3 tables, sketch map, 70 ref., 2018.
DOI: 10.24425/118736
2018082827 Bu, Q. T. (China University of Geosciences, School of Earth Sciences, State Key Laboratory of Biogeology and Environmental Geology, Wuhan, China); Hu, G. W.; Ye, Y. G.; Liu, C. L.; Li, C. F.; Best, A. I. and Wang, J. S. The elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems: Journal of Geophysics and Engineering, 14(3), p. 555-569, illus. incl. 2 tables, 45 ref., June 2017. Includes appendices.
Knowledge of the elastic wave velocities of hydrate-bearing sediments is important for geophysical exploration and resource evaluation. Methane gas migration processes play an important role in geological hydrate accumulation systems, whether on the seafloor or in terrestrial permafrost regions, and their impact on elastic wave velocities in sediments needs further study. Hence, a high-pressure laboratory apparatus was developed to simulate natural continuous vertical migration of methane gas through sediments. Hydrate saturation (Sh) and ultrasonic P- and S-wave velocities (Vp and Vs) were measured synchronously by time domain reflectometry (TDR) and by ultrasonic transmission methods respectively during gas hydrate formation in sediments. The results were compared to previously published laboratory data obtained in a static closed system. This indicated that the velocities of hydrate-bearing sediments in vertical gas migration systems are slightly lower than those in closed systems during hydrate formation. While velocities increase at a constant rate with hydrate saturation in the closed system, P-wave velocities show a fast-slow-fast variation with increasing hydrate saturation in the vertical gas migration system. The observed velocities are well described by an effective-medium velocity model, from which changing hydrate morphology was inferred to cause the fast-slow-fast velocity response in the gas migration system. Hydrate forms firstly at the grain contacts as cement, then grows within the pore space (floating), then finally grows into contact with the pore walls again. We conclude that hydrate morphology is the key factor that influences the elastic wave velocity response of methane gas hydrate formation in vertical gas migration systems. Copyright (Copyright) 2017 Sinopec Geophysical Research Institute
DOI: 10.1088/1742-2140/aa6493
2018082884 Monnier, Sébastien (Pontificia Universidad Católica de Valparaíso, Instituto de Geografía, Valparaiso, Chile) and Kinnard, Christophe. Pluri-decadal (1955-2014) evolution of glacier-rock glacier transitional landforms in the Central Andes of Chile (30-33° S): Earth Surface Dynamics, 5(3), p. 493-509, illus. incl. 5 tables, sketch map, 54 ref., 2017.
Three glacier-rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955-2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr-1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr-1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere against climate change.
DOI: 10.5194/esurf-5-493-2017
2018075908 Szewczyk, Jan (Polish Geological Institute-National Research Institute, Warsaw, Poland). The deep-seated lowland relict permafrost from the Suwalki region (NE Poland); analysis of conditions of its development and preservation: Geological Quarterly, 61(4), p. 845-858, illus., 37 ref., 2017.
The Udryn PIG 1 research borehole drilled in northeastern Poland (54°14'49"N, 23°03'29"E, 223 m a.s.l.) revealed a permafrost layer, at least 93 m thick, within the sedimentary succession below a depth of 357 m. The base of the permafrost has not been reached at 450 m depth, where the drilling stopped, so its total present thickness remains unknown. The relict permafrost, unexpected in this part of Central Europe, is in the ice-water transition phase at a temperature slightly below the 0°C. Analysis of geophysical and hydrogeological data indicates the possibility of preserving the permafrost in the central part of sedimentary cover of the Suwalki Anorthosite Massif over an area of probably 50 km2. Preliminary results of geothermal modelling indicate maximum palaeothickness of permafrost at the end of the Last Glacial Maximum of probably 600 m. The development of such a thick permafrost results both from a very low average annual temperature in the Weichselian Glaciation and a very low terrestrial heat flow density. It is very probable that similar zones of deep relict permafrost occurrences, undetected so far, may exist in other areas of the Precambrian Platform not only in Poland, but also in the neighbouring countries.
DOI: 10.7306/gq.1378
2018082630 Rangecroft, Sally (University of Exeter, Environment and Sustainability Institute, Penryn, United Kingdom); Suggitt, Andrew J.; Anderson, Karen and Harrison, Stephan. Future climate warming and changes to mountain permafrost in the Bolivian Andes: Climatic Change, 137(1-2), p. 231-243, illus. incl. 1 table, geol. sketch map, 47 ref., July 2016.
Water resources in many of the world's arid mountain ranges are threatened by climate change, and in parts of the South American Andes this is exacerbated by glacier recession and population growth. Alternative sources of water, such as more resilient permafrost features (e.g. rock glaciers), are expected to become increasingly important as current warming continues. Assessments of current and future permafrost extent under climate change are not available for the Southern Hemisphere, yet are required to inform decision making over future water supply and climate change adaptation strategies. Here, downscaled model outputs were used to calculate the projected changes in permafrost extent for a first-order assessment of an example region, the Bolivian Andes. Using the 0 °C mean annual air temperature as a proxy for permafrost extent, these projections show that permafrost areas will shrink from present day extent by up to 95 % under warming projected for the 2050s and by 99 % for the 2080s (under the IPCC A1B scenario, given equilibrium conditions). Using active rock glaciers as a proxy for the lower limit of permafrost extent, we also estimate that projected temperature changes would drive a near total loss of currently active rock glaciers in this region by the end of the century. In conjunction with glacier recession, a loss of permafrost extent of this magnitude represents a water security problem for the latter part of the 21st century, and it is likely that this will have negative effects on one of South America's fastest growing cities (La Paz), with similar implications for other arid mountain regions. Copyright 2016 Springer Science+Business Media Dordrecht and The Author(s)
DOI: 10.1007/s10584-016-1655-8
2018075198 Ulyantsev, A. S. (Russian Academy of Sciences, Shirshov Institute of Oceanology, Moscow, Russian Federation); Bratskaya, S. Yu.; Romankevich, E. A.; Semiletov, I. P. and Avramenko, V. A. Particle size composition of Holocene-Pleistocene deposits of the Laptev Sea (Buor-Khaya Bay): Doklady Earth Sciences, 467(1), p. 241-245, illus. incl. sketch map, 8 ref., March 2016.
New data on the particle size composition of the Laptev Sea shelf deposits were obtained on the basis of results of low-angle laser light-scattering of core samples from the columns studied. It was revealed that the sand fraction dominates. The results of comparative analysis of the particle size composition of deposits show that the Laptev Sea shelf zone was characterized by highly variable spatial-temporal conditions and settings of sedimentation in the Quaternary, a polygenic character of deposits, and a pulsating influence of fluvial and slope processes on the conditions of sedimentation. A tendency of coarsening in the vertical sequence that contributes to thawing of the permafrost was revealed in the Ivashkina lagoon. Copyright 2016 Pleiades Publishing, Ltd.
DOI: 10.1134/S1028334X16030168
2018075213 Ulyantsev, A. S. (Russian Academy of Sciences, Shirshov Institute of Oceanology, Moscow, Russian Federation); Polyakova, N. V.; Romankevich, E. A.; Semiletov, I. P. and Sergienko, V. I. Ionic composition of pore water in shallow shelf deposits of the Laptev Sea: Doklady Earth Sciences, 467(1), p. 308-313, illus. incl. sketch map, 11 ref., March 2016.
The cationic and anionic compositions of pore water in shallow deposits of Buor-Khaya Bay is studied. Significant concentration heterogeneity of the vertical ionic profile in the studied drill columns is shown. It is established that the vertical ionic profile of shelf deposits of the Laptev Sea is basically formed under the influence of thawing of underwater permafrost, hydrodynamic conditions, the water mass, and heat flows and depends on the lithological and granulometric types of the deposits. The highest concentrations of ions are registered in plant detritus represented by ground grass vegetation. A relationship between the ionic composition of pore water and cryogenic state of the sequence and its variability is demonstrated using the method of major components. Copyright 2016 Pleiades Publishing, Ltd.
DOI: 10.1134/S1028334X16030211
2018082897 Zielinski, Pawel (Maria Curie-Sklodowska University, Department of Geoecology and Palaeogeography, Lublin, Poland); Sokolowski, Robert J.; Fedorowicz, Stanislaw; Woronko, Barbara; Holub, Beata; Jankowski, Michal; Kuc, Michal and Tracz, Michal. Depositional conditions on an alluvial fan at the turn of the Weichselian to the Holocene; a case study in the Zmigrod Basin, southwest Poland: Geologos (Wroclaw), 22(2), p. 105-120, illus. incl. 2 tables, 92 ref., 2016.
Presented are the results of research into the fluvio-aeolian sedimentary succession at the site of Postolin in the Zmigrod Basin, southwest Poland. Based on lithofacies analysis, textural analysis, Thermoluminescence and Infrared-Optical Stimulated Luminescence dating and GIS analysis, three lithofacies units were recognised and their stratigraphic succession identified: 1) the lower unit was deposited during the Pleni-Weichselian within a sand-bed braided river functioning under permafrost conditions within the central part of the alluvial fan; 2) the middle unit is the result of aeolian deposition and fluvial redeposition on the surface of the fan during long-term permafrost and progressive decrease of humidity of the climate at the turn of the Pleni- to the Late Weichselian; 3) the upper unit accumulated following the development of longitudinal dunes at the turn of the Late Weichselian to the Holocene; the development of dunes was interrupted twice by the form being stabilised by vegetation and soil development.
DOI: 10.1515/logos-2016-0012
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2018079336 Nyland, Kelsey E. (Michigan State University, Department of Geography, East Lansing, MI); Schaetzl, Randall J.; Ignatov, Anthony and Miller, Bradley A. A new depositional model for sand-rich loess on the Buckley Flats outwash plain, northwestern Lower Michigan: in INQUA LoessFest 2016; western Wisconsin (Rawling, J. Elmo, III, editor; et al.), Aeolian Research, 31(Part B), p. 91-104, illus. incl. sketch maps, 38 ref., April 2018. Meeting: INQUA LoessFest 2016, Sept. 22-26, 2016, Eau Claire, WI.
Loess was first studied in Michigan on the Buckley Flats, where outwash, overlain by ~70 cm of loamy sediment, was originally interpreted as loess mixed with underlying sands. This paper re-evaluates this landscape through a spatial analysis of data from auger samples and soil pits. To better estimate the loamy sediment's initial textures, we utilized "filtered" laser diffraction data, which remove much of the coarser sand data. Textures of filtered silt data for the loamy sediment are similar to loess. The siltiest soils are found in the low-relief, central part of the Flats. Spatial analyses revealed that many silt fractions are nearly uniformly distributed, suggesting that the loess was not derived from a single source. The previous depositional model for the loamy mantle relied on loessfall followed by pedoturbation, but does not explain (1) the variation in sand contents across the Flats, or (2) the abrupt contact below the loamy mantle. This contact suggests that the outwash was frozen when the sediments above were deposited. Deep gullies at the western margins of the Flats were likely cut as permafrost facilitated runoff. Our new model for the origin of the loamy mantle suggests that the sands on the uplands were generated from eroding gullies and saltated onto the uplands along with loess that fell more widely. Sands saltating to the west of the Flats may have entrained some silts, facilitating loessfall downwind. At most sites, the loamy mantle gets increasingly silty near the surface, suggesting that saltation ended before loess deposition.
DOI: 10.1016/j.aeolia.2017.05.005
2018076138 Zoet, Lucas (University of Wisconsin at Madison, Department of Geoscience, Madison, WI); Barrette, Nolan and Rawling, J. Elmo, III. Green Bay Lobe drumlin morphology and spacing [abstr.]: in Geological Society of America, North-Central Section, 52nd annual meeting, Abstracts with Programs - Geological Society of America, 50(4), Abstract no. 19-6, April 2018. Meeting: Geological Society of America, North-Central Section, 52nd annual meeting, April 16-17, 2018, Ames, IA.
The Green Bay Lobe (GBL) formed thousands of drumlins during its late Wisconsin advance. GBL drumlin composition varies including disturbed and undisturbed outwash, till and bedrock, which has been interpreted to indicate that at least some subset of the drumlins is erosional while others may be depositional. In addition, a wide range of morphologies are found in the GBL drumlins. Questions remain about the formation process of drumlins and which glaciological controls have a significant impact on their final form and spacing. A better quantitative assessment of the forms and spacing of the drumlins of the GBL may provide insights into the glaciological processes of the Laurentide Ice Sheet. We have mapped over 13,000 drumlins in the footprint of the GBL using high resolution (2-m) LiDAR derived digital elevation models resulting in 3d morphologies for each drumlin. We determine best-fit ellipsoids for each drumlin to calculate height - length - width ratios that can be compared to spatial factors (e.g. ice advance phase, bedrock geology, depth to bedrock, and local slope). Then we focused on a subset of ca. 5000 drumlins located in Jefferson and Dodge counties where the variability in the geology and topography is minimal to determine the importance of various glaciological factors (i.e. time under the ice, total displacement, bed conditions, ice velocity) have on the final form and spacing of the drumlins. We determine that in this simplified region time under the ice correlates well with drumlin form. Drumlins that have spent the longest time under the ice were found to have the largest length to height ratios indicating that formation was a continual process. Furthermore, where postglacial fluvial erosion was not significant in the simplified region, drumlin spacing was determined to be random with greater than 95% confidence. Random drumlin spacing is in agreement with the heterogeneous pattern of bed strength that is expected if melting permafrost beneath the ice served as the impetus for drumlin initiation.
2018077042 Czerniawska, Jolanta (Adam Mickiewicz University, Institute of Geoecology and Geoinformation, Poznan, Poland) and Chlachula, Jiri. Present permafrost thaw in central Yakutia, north-east Siberia; surficial geology and hydrology evidence [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11606, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Current climate change in the high-latitudes of Eurasia is a generally accepted phenomenon characterized by increased annual temperature values and marked weather anomalies observed in the sub-polar and polar regions. In the northern and NE Siberia, this trend of the MAT rise, documented particularly over the last three decades, is believed to account for the territorial lowland as well as insular mountain frozen ground thaw that in turn has triggered ecosystem feedbacks on the local as well as regional scales. In the northern regions of Yakutia, this is principally witnessed by accelerated near-surface dynamics of seasonally activated de-freezing grounds and interlinked geomorphic and hydrological actions affecting large-scale tundra landscape settings. In the southern and central taiga-forest areas with perennial alpine and continuous permafrost conditions, respectively, an increased depth of the seasonally melted top-soil layers has become evident accompanied by thermokarst lake expansion and ground surface collapsing. Some cryogenic depressions generated from small gullies over the past decades eloquently demonstrate the intensity and scales of the current permafrost degradation in the Siberian North. The fluvial discharge is most dynamic in late spring to mid-summer because of the cumulative effect of snow-melting because of a high solar radiation and short intervals of torrential rains. Yet, the climate-change-dependent and most active geomorphic agent is the accelerated permafrost thaw seen in landslides and tundra-forest cover decay due to a higher water table. Numerous preserved biotic fossiliferous records Pleistocene and early Holocene in age are being exposed in this process providing unique palaeoecology evidence at particular sites. These climate-generated processes have mostly highly negative effects to the natural habitats (migratory animal routes and riverine biota due to an earlier ice-melting) as well as the local settlement communities (infrastructure destruction resulting from the top-ground melt-water saturation, road-base disintegration, slope slumping, drinking water supply, etc.). [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11606.pdf
2018077088 McKenzie, Jeffrey (McGill University, Montreal, QC, Canada); Lamontagne-Hallé, Pierrick; Zipper, Samuel and Kurylyk, Barret. Advances in the simulation of groundwater flow and permafrost thaw [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11726, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The presence of permafrost affects the movement and storage of groundwater in cold regions. There are three primary pathways by which groundwater flows in permafrost terrain: 1) above permafrost through the active zone (or supra-permafrost aquifers), 2) below permafrost (i.e. sub-permafrost aquifers), and 3) through taliks, perennially unfrozen vertical or horizontal 'holes' in permafrost. With thawing of permafrost, these pathways can become larger and more connected, increasing both the storage and flux of groundwater through the arctic waterscape. Already there is extensive evidence of this hydrologic change, such as increasing flow in arctic rivers, the disappearance or emergence of lakes, and increased carbon export. An important new tool for understanding and predicting these hydrologic changes are groundwater models that incorporate dynamic freezing and thawing processes (e.g., variable permeability as a function of ice content, latent heat effects, etc.). This presentation will provide an overview of the current status of these types of models. A particular challenge is that the parameterization and coupling of surface boundary conditions to the model domain is complex and often poorly implemented. We propose to use a parametric modeling approach with the US Geological Survey's SUTRA model to evaluate model outcomes as a result of different boundary configurations. The presented simulation results will improve our understanding of the model sensitivity to boundary condition design, and will improve our conceptualization of permafrost-groundwater models. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11726.pdf
2018079401 Telles-Langdon, M. (BGC Engineering, Vancouver, BC, Canada); Arenson, L. U.; Craig, J. and Festa, J. Assessing the vulnerability to climate change for three northern airports [abstr.]: in GAC-MAC 2016; abstracts--GAC-MAC 2016; résumés, Abstract Volume (Geological Association of Canada), 39, p. 96, 2016. Meeting: GAC-MAC 2016, June 1-3, 2016, Whitehorse, YT, Canada.
URL: http://www.mineralogicalassociation.ca/doc/GAC2016_AbstractVol.pdf
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