October 2017 Permafrost Alert

The U.S. Permafrost Association is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute, with support from the National Science Foundation, has “migrated” the previous Cold Regions Bibliography to a new platform. Included are the US Permafrost Association supported Monthly Permafrost Alerts dating back to 2011. The Bibliography is searchable at : www.coldregions.org.

Have a look for your favorite topic, location and/or author. For example, a search using “permafrost” and “Barrow” found 146 references dating back to at least 1952 and up to the more recent September 2015 Seventh Canadian Permafrost Conference.

The individual Monthly Permafrost Alerts are found on the US Permafrost Association website : http://www.uspermafrost.org/monthly-alerts.shtml.

Browse by Reference Type:

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2017090206 Giles, David (University of Portsmouth, School of Earth and Environmental Sciences, Portsmouth, United Kingdom); Martin, Chris and Williams, Ron. Engineering geology of the Quaternary: Quarterly Journal of Engineering Geology and Hydrogeology, Pre-Issue Publication, unpaginated, illus. incl. 2 tables, geol. sketch maps, 86 ref., October 19, 2017.

Throughout the 50 years of the Quarterly Journal of Engineering Geology and Hydrogeology papers have been published on case studies, site characterization and material geotechnical properties that have been influenced by the climatic and geomorphological environments experienced during the Quaternary. This period of geological time has left a significant legacy for ground engineering and construction projects with a complexity of ground conditions whose interpretation and understanding are crucial for the success of any such schemes. This review presents key papers that mainly focus on the effects of cold climates, both glacial and periglacial, developed during this time. Advances in landsystem description and ground model development published in the journal for these terrains are discussed.

DOI: 10.1144/qjegh2017-104

2017091991 Wolicki, Jenny (Colorado School of Mines, Department of Geology and Geological Engineering, Golden, CO); Santi, Paul; Haugen, Benjamin D.; Hagbery, Jacquelyn N.; Faber, Ethan J.; Semmens, Stephen N. and Brown, Hayden E. Development of a rapid system to diagnose ground settlement: Environmental & Engineering Geoscience, Pre-Issue Publication, illus. incl. 2 tables, 18 ref., October 20, 2017.

Ground settlement causes extensive damage worldwide and has a significant impact on engineering design and mitigation. Identification of settlement origins can be challenging and expensive. The ability to identify the likely cause(s) of settlement using a rapid forensic analysis can reduce field time and constrain site investigation strategies, thereby reducing costs. The Rapid Settlement Diagnostic System (RSDS) has been developed as a preliminary tool for efficiently identifying likely sources of geology-related settlement. The four-step questionnaire in Microsoft Excel format enables personnel to quickly isolate potential causes of settlement using initial site observations and basic site knowledge. The first step distinguishes whether or not the observations involve geology-related settlement or another issue, such as structural instability. The second and third steps narrow down the list of likely settlement causes for the area of concern through a series of questions regarding the site conditions with answer options of "yes", "no", or "unknown". The fourth step provides a final calculation and rank indicating the most likely cause(s) of settlement that should be investigated further through a detailed site investigation. The RSDS has been tested using historic cases of settlement with known causes to evaluate the effectiveness and ease of use of the tool. The results from the validation process have been used to revise the questions and scoring system in the RSDS in order to improve the usefulness and clarity of the tool.

DOI: 10.2113/EEG-1979

2017087465 Eichel, Jana (University of Bonn, Department of Geography, Bonn, Germany); Draebing, Daniel; Klingbeil, Lasse; Wieland, Markus; Eling, Christian; Schmidtlein, Sebastian; Kuhlmann, Heiner and Dikau, Richard. Solifluction meets vegetation; the role of biogeomorphic feedbacks for turf-banked solifluction lobe development: Earth Surface Processes and Landforms, 42(11), p. 1623-1635, illus. incl. 1 table, 108 ref., September 15, 2017.

Vegetation is an important factor influencing solifluction processes, while at the same time, solifluction processes and landforms influence species composition, fine-scale distribution and corresponding ecosystem functioning. However, how feedbacks between plants and solifluction processes influence the development of turf-banked solifluction lobes (TBLs) and their geomorphic and vegetation patterns is still poorly understood. We addressed this knowledge gap in a detailed biogeomorphic investigation in the Turtmann glacier foreland (Switzerland). Methods employed include geomorphic and vegetation mapping, terrain assessment with unmanned aerial vehicle (UAV) and temperature logging. Results were subsequently integrated with knowledge from previous geomorphic and ecologic studies into a conceptual model. Our results show that geomorphic and vegetation patterns at TBLs are closely linked through the lobe elements tread, risers and ridge. A conceptual four-stage biogeomorphic model of TBL development with ecosystem engineering by the dwarf shrub Dryas octopetala as the dominant process can explain these interlinked patterns. Based on this model, we demonstrate that TBLs are biogeomorphic structures and follow a cyclic development, during which the role of their components for engineer and non-engineer species changes. Our study presents the first biogeomorphic model of TBL development and highlights the applicability and necessity of biogeomorphic approaches and research in periglacial environments. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/esp.4102

2017087972 Ramage, Justine L. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Irrgang, Anna M.; Herzschuh, Ulrike; Morgenstern, Anne; Couture, Nicole and Lantuit, Hugues. Terrain controls on the occurrence of coastal retrogressive thaw slumps along the Yukon coast, Canada: Journal of Geophysical Research: Earth Surface, 122(9), p. 1619-1634, illus. incl. 4 tables, sketch maps, 59 ref., September 2017.

Retrogressive thaw slumps (RTSs) are among the most active landforms in the Arctic; their number has increased significantly over the past decades. While processes initiating discrete RTSs are well identified, the major terrain controls on the development of coastal RTSs at a regional scale are not yet defined. Our research reveals the main geomorphic factors that determine the development of RTSs along a 238 km segment of the Yukon Coast, Canada. We (1) show the current extent of RTSs, (2) ascertain the factors controlling their activity and initiation, and (3) explain the spatial differences in the density and areal coverage of RTSs. We mapped and classified 287 RTSs using high-resolution satellite images acquired in 2011. We highlighted the main terrain controls over their development using univariate regression trees model. Coastal geomorphology influenced both the activity and initiation of RTSs: active RTSs and RTSs initiated after 1972 occurred primarily on terrains with slope angles greater than 3.9° and 5.9°, respectively. The density and areal coverage of RTSs were constrained by the volume and thickness of massive ice bodies. Differences in rates of coastal change along the coast did not affect the model. We infer that rates of coastal change averaged over a 39 year period are unable to reflect the complex relationship between RTSs and coastline dynamics. We emphasize the need for large-scale studies of RTSs to evaluate their impact on the ecosystem and to measure their contribution to the global carbon budget. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017JF004231

2017087600 Wang Qingfeng (Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Jin Huijun; Zhang Tingjun; Cao Bin; Peng Xiaoqing; Wang, Kang; Xiao Xiongxin; Guo Hong; Mu Cuicui and Li Lili. Hydrothermal processes and thermal offsets of peat soils in the active layer in an alpine permafrost region, NE Qinghai-Tibet Plateau: Global and Planetary Change, 156, p. 1-12, illus. incl. 1 table, sketch map, 77 ref., September 2017.

Observation data of the hydrothermal processes in the active layer are vital for the verification of permafrost formation and evolution, eco-hydrology, ground-atmosphere interactions, and climate models at various time and spatial scales. Based on measurements of ground temperatures in boreholes, of temperatures and moisture contents of soils in the active layer, and of the mean annual air temperatures at the Qilian, Yeniugou and Tuole meteorological stations in the upper Heihe River Basin (UHRB) and the adjacent areas, a series of observations were made concerning changes in the lower limit of permafrost (LLP) and the related hydrothermal dynamics of soils in the active layer. Because of the thermal diode effect of peat soils, the LLP (at 3600 m) was lower on the northern slope of the Eboling Mountains at the eastern branch of the UHRB than that (at 3650-3700 m) on the alluvial plain at the western branch of the UHRB. The mean temperature of soils at depths of 5 to 77 cm in the active layer on peatlands was higher during periods with subzero temperatures and lower during periods with above-zero temperatures in the vicinity of the LLP on the northern slope of the Eboling Mountains than those at the LLP at the western branch of the UHRB. The thawing and downward freezing rates of soils in the active layer near the LLP on the northern slope of the Eboling Mountains were 0.2 and 1.6 times those found at the LLP at the western branch of the UHRB. From early May to late August, the soil water contents at the depths of 20 to 60 cm in the active layer near the LLP on the northern slope of the Eboling Mountains were significantly lower than those found at the LLP at the western branch of the UHRB. The annual ranges of soil temperatures (ARSTs), mean annual soil temperatures (MASTs) in the active layer on peatlands, and the mean annual ground temperature (MAGT) at a depth of 14 m of the underlying permafrost were all significantly lower near the LLP on the northern slope of the Eboling Mountains. Moreover, the thermophysical properties of peat soils and high moisture contents in the active layer on peatlands resulted in the lower soil temperatures in the active layer close to the LLP on the northern slope of the Eboling Mountains than those found at the LLP at the western branch of the UHRB in the warm season, especially at the deeper depths (20-77 cm). They also resulted in the smaller freezing index (FI) and thawing index (TI) and larger FI/TI ratios of soils at the depths of 5 to 77 cm in the active layer near the LLP on the northern slope of the Eboling Mountains. In short, peatlands have unique thermophysical properties for reducing heat absorption in the warm season and for limiting heat release in the cold season as well. However, the permafrost zone has shrunk by 10-20 km along the major highways at the western branch of the UHRB since 1985, and a medium-scale retrogressive slump has occurred on the peatlands on the northern slope of the Eboling Mountains in recent decades. The results can provide basic data for further studies of the hydrological functions of different landscapes in alpine permafrost regions. Such studies can also enable evaluations and forecasts the hydrological impacts of changing frozen ground in the UHRB and of other alpine mountain regions in West China.

DOI: 10.1016/j.gloplacha.2017.07.011

2017091666 Byun, Eunji (Seoul National University, School of Earth and Environmental Science, Seoul, South Korea); Yang, Ji-Woong; Kim, Yongwon and Ahn, Jinho. Trapped greenhouse gases in the permafrost active layer; preliminary results for methane peaks in vertical profiles of frozen Alaskan soil cores: Permafrost and Periglacial Processes, 28(2), p. 477-484, illus. incl. sketch map, 24 ref., June 2017.

Degradation of organic carbon stored in permafrost may represent an additional source of atmospheric greenhouse gases (GHGs) in a warming climate. However, there is no clear understanding of how seasonal freeze-thaw affects gas permeability and emission of methane in permafrost soils, in part due to the lack of chemical and physical characterisation of the soils. Here, we report vertical profiles of CO2, CH4 and other soil properties with resolutions of 0.05-0.1 m depth from five soil cores, drilled to 0.9 m depth, in Alaskan permafrost during the early spring of 2013, when the ground was frozen under snow cover. Two cores from tundra and black spruce bog showed sudden increases in methane concentration (up to 416 mmol litre-1soil), indicating excess CH4 trapped in gas-impermeable soil layers during the freezing period. Active-layer cooling in late autumn, producing a frozen surface and relatively warm sub-surface, may have allowed underground microbial activity and facilitated CH4 production, while the upward transport of CH4 was hampered by the frost. Our preliminary results show that estimating annual GHG efflux from permafrost regions can be complicated because of heterogeneous distributions of trapped methane within soil columns. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1935

2017091663 Draebing, Daniel (Technische Universität München, Chair of Landslide Research, Munich, Germany) and Eichel, Jana. Spatial controls of turf-banked solifluction lobes and their role for paraglacial adjustment in glacier forelands: Permafrost and Periglacial Processes, 28(2), p. 446-459, illus. incl. sketch map, 35 ref., June 2017.

In glacier forelands, solifluction is a major and fast-responding paraglacial process in the adjustment of low- or moderately-inclined moraine slopes. However, the spatial pattern of the factors that control solifluction and their interactions are poorly understood. In this study, we combine geomorphic and vegetation mapping, analysis of borehole material and time domain reflectometry with two-dimensional (2D) and three-dimensional (3D) electrical resistivity tomography (ERT) to quantify the controlling factors and evaluate their influence on sediment transport. The investigated turf-banked solifluction lobe is located on the distal slope of a 1920s lateral moraine in the foreland of the Turtmann glacier in the southern Swiss Alps. Our data demonstrate the interaction between material, soil moisture and vegetation, which results in geomorphometric features such as (i) frontal and lateral risers, (ii) a lobe tread and (iii) a ridge. Lobe size indicates intense solifluction movement in the last 100 years. The interaction of controlling factors results in a negative feedback which stabilises the lobe and, thus, limits paraglacial sediment transport to frost heave processes on the ridge. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1930

2017091657 Gisnas, Kjersti (University of Oslo, Oslo, Norway); Etzelmuller, Bernd; Lussana, Cristian; Hjort, Jan; Sannel, A. Britta K.; Isaksen, Ketil; Westermann, Sebastian; Kuhry, Peter; Christiansen, Hanne H.; Frampton, Andrew and Akerman, Jonas. Permafrost map for Norway, Sweden and Finland: Permafrost and Periglacial Processes, 28(2), p. 359-378, illus. incl. 2 tables, sketch maps, 69 ref., June 2017.

A research-based understanding of permafrost distribution at a sufficient spatial resolution is important to meet the demands of science, education and society. We present a new permafrost map for Norway, Sweden and Finland that provides a more detailed and updated description of permafrost distribution in this area than previously available. We implemented the CryoGRID1 model at 1 km2 resolution, forced by a new operationally gridded data-set of daily air temperature and snow cover for Finland, Norway and Sweden. Hundred model realisations were run for each grid cell, based on statistical snow distributions, allowing for the representation of sub-grid variability of ground temperature. The new map indicates a total permafrost area (excluding palsas) of 23 400 km2 in equilibrium with the average 1981-2010 climate, corresponding to 2.2 per cent of the total land area. About 56 per cent of the area is in Norway, 35 per cent in Sweden and 9 per cent in Finland. The model results are thoroughly evaluated, both quantitatively and qualitatively, as a collaboration project including permafrost experts in the three countries. Observed ground temperatures from 25 boreholes are within ±2°C of the average modelled grid cell ground temperature, and all are within the range of the modelled ground temperature for the corresponding grid cell. Qualitative model evaluation by field investigators within the three countries shows that the map reproduces the observed lower altitudinal limits of mountain permafrost and the distribution of lowland permafrost. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1922

2017091667 Krüger, Jan Paul (University of Basel, Environmental Geosciences, Basel, Switzerland); Conen, Franz; Leifeld, Jens and Alewell, Christine. Palsa uplift identified by stable isotope depth profiles and relation of d15N to C/N ratio: Permafrost and Periglacial Processes, 28(2), p. 485-492, illus. incl. 1 table, 43 ref., June 2017.

Palsas develop as permafrost aggradation uplifts peat out of the zone influenced by groundwater. Here we relate d15N values to C/N ratios along depth profiles through palsas in two peatlands near Abisko, northern Sweden, to identify perturbation of the peat. The perturbation by uplift as well as the potential nutrient input from the adjacent hollows can be detected in soil d15N values when related to the C/N ratio at the same depth. Nine out of ten profiles show a perturbation at the depth where peat was uplifted by permafrost. Palsa uplift could be detected by the d15N depth pattern, with the highest d15N values at the so-called turning point. The d15N values increase above and decrease below the turning point, when permafrost initiated uplift. Onset of permafrost aggradation calculated from peat accumulation rates was between 80 and 545 years ago, with a mean of 242 (±66) years for Stordalen and 365 (±53) years for Storflaket peatland. The mean ages of permafrost aggradation are within the Little Ice Age. Depth profiles of d15N, when related to C/N ratio, seem to be a suitable tool to detect perturbation and uplift of palsas. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1936

2017087884 Kuznetsova, Elena (Norwegian University of Science and Technology, Trondheim, Norway). Thermal conductivity and the unfrozen water contents of volcanic ash deposits in cold climate conditions; a review: Clays and Clay Minerals, 65(3), p. 168-183, illus. incl. 3 tables, 129 ref., June 2017.

Layers of volcanic ash and Andosol soils derived from the ash may play an important role in preserving snow and ice as well as in the development of permafrost conditions in (a) the immediate vicinity of volcanoes at high elevations or at high latitudes and (b) land areas that are often distant from volcanic activity and are either prone to permafrost or covered by snow and ice, but have been affected by subaerial ash deposition. The special properties of volcanic ash are critically reviewed, particularly in relation to recent research in Kamchatka in the Far East of Russia. Of special importance are the thermal properties, the unfrozen water contents of ash layers, and the rate of volcanic glass weathering. Weathering of volcanic glass results in the development of amorphous clay minerals (e.g allophane, opal, palagonite), but occurs at a much slower rate under cold compared to warm climate conditions. Existing data reveal (1) a strong correlation between the thermal conductivity, the water/ice content, and the mineralogy of the weathered part of the volcanic ash, (2) that an increase in the amounts of amorphous clay minerals (allophane, palagonite) increases the proportion of unfrozen water and decreases the thermal conductivity, and (3) that amorphous silica does not alter to halloysite or other clay minerals, even in the Early Pleistocene age (Kamchatka) volcanic ashes or in the Miocene and Pliocene deposits of Antarctica due to the cold temperatures. The significance of these findings are discussed in relation to past climate reconstruction and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers.

DOI: 10.1346/CCMN.2017.064057

2017091664 Roux, Nicolas (Université Paris-Sud, Orsay, France); Costard, François and Grenier, Christophe. Laboratory and numerical simulation of the evolution of a river's talik: Permafrost and Periglacial Processes, 28(2), p. 460-469, illus. incl. 3 tables, 40 ref., June 2017.

Experiments simulating the evolution of a river talik were performed in a cold room where a small channel carried flowing water through frozen saturated porous soil in a hydraulic flume. The sensitivity of thaw propagation to water temperature and velocity was determined to indicate the relative importance of these controlling parameters. Two types of soils were investigated (sand and silty clay), corresponding to contrasting hydrological, thermal and mechanical behaviours. The experimental results show that the sensitivity to water temperature was much higher than that to water velocity for the ranges considered. The experiments were compared with results from one-dimensional numerical simulations to identify the thermal boundary conditions of the riverbed and to evaluate the capacity of the numerical code to represent the propagation of heat at depth. The results showed that the proper boundary conditions are of the Neumann type, where flux is expressed as a coefficient multiplied by the temperature difference between water and the soil surface. The value of this coefficient is evaluated as a function of flow velocity based on these experiments. As a first-order approximation, this coefficient is assumed to be constant when considering seasonal flow variations. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1929

2017091658 Shmelev, Denis (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems in Soil Science, Pushchino, Russian Federation); Veremeeva, Alexandra; Kraev, Gleb; Kholodov, Alexander; Spencer, Robert G. M.; Walker, Wayne S. and Rivkina, Elizaveta. Estimation and sensitivity of carbon storage in permafrost of north-eastern Yakutia: Permafrost and Periglacial Processes, 28(2), p. 379-390, illus. incl. 5 tables, sketch map, 52 ref., June 2017.

Organic carbon derived from permafrost can provide a substrate for greenhouse gas production where the buried carbon pool thaws and mobilizes into biogeochemical cycles. Much attention has focused on the permafrost carbon of the Yedoma region of Siberia due to the wide distribution of organic and ice-rich deposits. Here, we present a new estimation of carbon storage in the upper 25 m of permafrost in north-eastern Yakutia based on a novel database of total carbon (TC) content, bulk density and ice content of permafrost, and a new map of Quaternary deposits derived from drilling data. The stratigraphic units contain 0.6-2.1% TC, with the highest concentrations in the Holocene cover layer and Late Pleistocene Yedoma superhorizon. The largest carbon pool is found in the Pliocene/Middle Pleistocene Olyor superhorizon. The TC pool of Yedoma is estimated to be 1.5-2 times less than that calculated previously. The TC pool of the study area is 31.2±15.2 Pg C spread across 88 000 km2, with a mean specific carbon content of approximately 14.3 kg C m-3. Carbon storage is estimated excluding the ice-wedge volume and, due to the limited data for Yedoma and Alas deposits, we present a maximal assessment of the carbon pool for the Yedoma region. Refinement of the size of the Yedoma TC pool is critical for quantifying the scale of permafrost feedback to the carbon cycle. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1933

2017091668 Uxa, Tomas (Charles University in Prague, Department of Physical Geography and Geoecology, Prague, Czech Republic). Active layer thickness prediction on the western Antarctic Peninsula; discussion: Permafrost and Periglacial Processes, 28(2), p. 493-498, illus. incl. 2 tables, 32 ref., June 2017. For reference to original see Wilhelm, K. R., Bockheim, J. G., and Kung, S., Permafrost and Periglacial Processes, Vol. 26, p. 188-199, DOI: 10.1022/ppp.1845, 2015.

Wilhelm et al. (2015) employed the widely used Stefan and Kudryavtsev equations to predict the maximum active-layer thickness (ALT) on Amsler Island, Western Antarctic Peninsula. Their predictions far exceed the observations of ALT reported from other parts of the region. Here, I demonstrate that the values of ALT are significantly overestimated by the predictive equations because the authors incorrectly assumed that little or no latent heat of phase change is absorbed during thawing. Although the area is the warmest in the Antarctic Peninsula region, with a rapid increase in air temperature and permafrost temperatures close to 0°C, the active layer is likely to be substantially thinner than values predicted by Wilhelm et al. (2015). Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1888

2017091662 Watanabe, Tatsuya (Kitami Institute of Technology, Department of Civil and Environmental Engineering, Kitami, Japan); Matsuoka, Norikazu; Christiansen, Hanne H. and Cable, Stefanie. Soil physical and environmental conditions controlling patterned-ground variability at a continuous permafrost site, Svalbard: Permafrost and Periglacial Processes, 28(2), p. 433-445, illus. incl. 5 tables, sketch map, 43 ref., June 2017.

This study examines soil physical and environmental conditions controlling patterned-ground variability on an alluvial fan in a continuous permafrost landscape, at Adventdalen, Svalbard. On-site monitoring of ground temperature, soil moisture and snow depth, laboratory analyses of soil physical properties and principal component analysis indicate that the distribution of patterned ground depends primarily on soil texture, soil moisture and the winter ground thermal regime associated with snow cover. Mudboils and composite patterns (mudboils surrounded by small polygons) occupy well-drained areas composed of clay-rich aeolian sediments. Compared to mudboils, composite patterns show a sharper contrast in soil texture between barren centres and vegetated rims. Hummocks filled with organic materials develop on poorly drained lowlands associated with a shallow water table. Ice-wedge polygons are dominant on sandy loess-covered areas where the local wind regime minimises snow cover, enhancing ground cooling that promotes thermal contraction cracking. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1924

2017091669 Wilhelm, Kelly (University of Wisconsin, Department of Soil Science, Madison, WI) and Bockheim, James. Active layer thickness prediction on the western Antarctic Peninsula; reply: Permafrost and Periglacial Processes, 28(2), p. 499-503, illus. incl. 1 table, June 2017. For reference to discussion see Uxa, T., Permafrost and Periglacial Processes, Vol. 28, p. 493-498, DOI: 10.1002/ppp.1888, 2017; for reference to original see Wilhelm, K. R., Bockheim, J. G., and Kung, S., Permafrost and Periglacial Processes, Vol. 26, p. 188-199, DOI: 10.1022/ppp.1845, 2015.

Uxa (2016) used alternative assumptions to calculate active-layer thicknesses (ALTs) on Amsler Island, Western Antarctic Peninsula, and concluded that assumptions in Wilhelm et al. (2015) overestimate ALTs in the region. Here, we accept that the core of his argument is correct, but we contend that observations using multiple devices, along with the HYDRUS model, indicate that in some cases assumptions used by Uxa (2016) overcompensate and predict an unrealistically thin active layer for the study area. Observed and predicted ALTs are much greater than would be expected, relative to measurements farther to the north. Such a thick active layer could be due to glacial proximity and topographically controlled hydraulic features that promote wetter-than-expected soils. Copyright (Copyright) 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1923

2017091665 You Yanhui (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Frozen Soils Engineering, Lanzhou, China); Yu Qihao; Pan Xicai; Wang Xinbin and Guo Lei. Geophysical imaging of permafrost and talik configuration beneath a thermokarst lake: Permafrost and Periglacial Processes, 28(2), p. 470-476, illus. incl. sketch map, 22 ref., June 2017.

The development of thermokarst lakes in permafrost regions can relate to climate change and significantly impact the hydrological regime. We investigated the configuration of permafrost and a talik under a thermokarst lake on the Qinghai-Tibet Plateau (QTP), China, using GPR, electrical resistivity tomography, drilling and ground temperature measurements. The boundaries and ice content of permafrost and the talik were identified adjacent to and under the lake. The thickness of permafrost differed by about 4 m on opposite sides of the lake. The thickness and extent of ice-rich permafrost under the northwest shore was greater than under the southeast shore. A talik penetrated the permafrost base beneath both the shallower and deeper parts of the lake, where water depths were all less than the maximum thickness of winter ice. The talik was wider beneath shallower parts of the lake than in deeper areas. This investigation demonstrates that a through-talik developed although the water depth was less than the maximum thickness of winter ice, indicating that the general relation between water depth and ice thickness is not reliable for identifying the nature of taliks on the QTP. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1938

2017091660 Young, Kathy L. (York University, Geography Department, Toronto, ON, Canada); Scheffel, Harold-Alexis; Abnizova, Anna and Siferd, John R. Spatial and temporal dynamics of groundwater flow across a wet meadow, Polar Bear Pass, Bathurst Island, Nunavut: Permafrost and Periglacial Processes, 28(2), p. 405-419, illus. incl. 2 tables, sketch map, 65 ref., June 2017.

Interest is growing about how groundwater supplies will shift in warming northern terrains. We evaluated the seasonal and spatial pattern of groundwater flow in a wet meadow bordered by a late-lying snowbed and tundra ponds at Polar Bear Pass, Bathurst Island (75.7°N, 98.7°W). A water budget approach signalled the relative importance of groundwater inflow to tundra ponds. Groundwater flow across the wet meadow was estimated using a modified Darcy's equation, which requires information on both water and frost tables, and hydraulic conductivity. These data were obtained from 2007 to 2009 along a series of water wells extending from a late-lying snowbed across the wet meadow to a nearby study pond. Groundwater fluxes across the wet meadow were limited in magnitude and duration in a warm/dry year (2007), when the late-lying snowbed was the main external water source, a response differing from rainy/cool years (2008 and 2009). Overall, seasonal water budgets indicate that groundwater fluxes were minimal in the wet meadow and an adjacent tundra pond. Late-lying snowbeds play a limited role in sustaining wet meadows and ponds here. Summer precipitation and evaporation continue to drive wet meadow and tundra pond hydrological response in low-gradient wetlands, especially in the post-snowmelt season. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1931

2017091661 Zhang Yanlin (Hunan University of Science and Technology, National-Local Joint Engineering Laboratory of Geo-Spatial Information Technology, Xiangtan, China); Cheng Guodong; Li Xin; Jin Huijun; Yang Dawen; Flerchinger, Gerald N.; Chang Xiaoli; Bense, Victor F.; Han Xujun and Liang Ji. Influences of frozen ground and climate change on hydrological processes in an alpine watershed; a case study in the upstream area of the Hei'he River, northwest China: Permafrost and Periglacial Processes, 28(2), p. 420-432, illus. incl. 2 tables, sketch map, 70 ref., June 2017.

In cold regions, the occurrence of frozen ground has a fundamental control over the character of the water cycle. To investigate the impact of changing ground temperature conditions on hydrological processes in the context of climate change, a distributed hydrological model with an explicit frozen ground module was applied to an alpine watershed in the upstream area of the Hei'he River in the Qilian Mountains, northwest China. After evaluating the base model, we considered scenarios of frost-free ground and climate change. Results showed that the base model with a frozen ground module successfully captured the water balance and thermal regimes in the basin. When the frozen ground module was turned off, the simulated groundwater recharge and base flow increased by a factor of two to three because surface runoff caused by exceeding infiltration capacities at high elevations, which occurred in the base model, was eliminated. Consequently, the river hydrograph became smoother and flatter, with summer flood peaks delayed and reduced in volume. The annual mean depth where subsurface runoff was generated, was about 2.4 m compared to 1.1 m in the base model. For a warming climate, a combination of increasing evapotranspiration and reducing permafrost area results in smoother and flatter hydrographs, and a reduction in total river discharge. Although our analysis using numerical models has its limitations, it still provides new quantitative understanding of the influences of frozen ground and climate change on hydrological processes in an alpine watershed. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1928

2017091659 Zhao Shuping (Nanjing Normal University, Laboratory of Virtual Geographic Environment, Nanjing, China); Nan Zhuotong; Huang Yingbing and Zhao Lin. The application and evaluation of simple permafrost distribution models on the Qinghai-Tibet Plateau: Permafrost and Periglacial Processes, 28(2), p. 391-404, illus. incl. 7 tables, sketch map, 50 ref., June 2017.

The performance of simple permafrost distribution models widely used on the Qinghai-Tibet Plateau (QTP) has not been fully evaluated. In this study, two empirical models (the elevation model and mean annual ground temperature model) and three semi-physical models (the surface frost number model, the temperature at the top of permafrost model and the Kudryavtsev model) were investigated. The simulation results from the models were compared to each other and validated against existing permafrost maps of the entire QTP and in three representative areas investigated in the field. The models generally overestimated permafrost distribution in the investigated areas, but they captured the broad characteristics of permafrost distribution on the entire QTP, and performed best in areas with colder, continuous permafrost. Large variations in performance occurred at elevations of 3800-4500 m asl and in areas with thermally unstable permafrost. The two empirical models performed best in areas where permafrost is strongly controlled by elevation, such as eastern QTP. In contrast, the three semi-physical models were better in southern island permafrost areas with relatively flat terrain, where local factors considerably impact the distribution of permafrost. Model performance could be enhanced by explicitly considering the effects of elevation zones and regional conditions. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1939

2017091508 Abolt, Charles J. (University of Texas at Austin, Bureau of Economic Geology, Jackson School of Geosciences, Austin, TX); Young, Michael H. and Caldwell, Todd G. Numerical modelling of ice-wedge polygon geomorphic transition: Permafrost and Periglacial Processes, 28(1), p. 347-355, illus. incl. 2 tables, sketch map, 34 ref., March 2017.

A numerical model is presented to test whether a hillslope diffusion approach can simulate the topographic evolution of some recently developed high-centred ice-wedge polygons south of Prudhoe Bay, Alaska. The polygons are adjacent to a highway whose construction appears to have triggered their geomorphic transition. The model is calibrated using a light detection and ranging data-set that captures both the high-centred polygons and some neighbouring low-centred polygons that appear to be unaffected by thermokarst. The latter are used to represent initial conditions. Model simulations are analysed to estimate potential fluxes of soil from polygon edges into troughs and the loss of depressional water storage during development of the high-centred polygons. Overall, a match between the topography of simulated and observed high-centred polygons suggests that diffusive hillslope processes represent a feasible mechanism driving polygon transition. Rates of soil displacement inferred from optimised simulations, moreover, are within the range previously observed in permafrost terrain with a similar climate. Direct observations of the soil velocity profile in actively transitioning polygons would help resolve whether and to what extent hillslope processes, as opposed to pure thaw-related subsidence at the polygon edges, drive the development of high-centred forms in natural systems. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1909

2017091495 Bodin, Xavier (Université Savoie Mont-Blanc, Laboratoire Environnements Dynamiques et Territoires de la Montagne, Le Bourget-du-Lac, France); Krysiecki, Jean-Michel; Schoeneich, Philippe; Le Roux, Olivier; Lorier, Lionel; Echelard, Thomas; Peyron, Michel and Walpersdorf, Andrea. The 2006 collapse of the Bérard rock glacier (southern French Alps): Permafrost and Periglacial Processes, 28(1), p. 209-223, illus. incl. sketch map, 52 ref., March 2017.

In the Mediterranean French Alps, the Berard rock glacier suddenly collapsed during the summer of 2006; this was a rarely documented event in the world, exceptional for the amount of disturbed material (estimated at 250 000-500 000 m3). Located near the lower limit of permafrost, the Berard rock glacier collapse might exemplify the possible consequences of the degradation of ice-rich mountain permafrost. The causes of the collapse may include long-term atmospheric warming, recent air temperature anomalies, niveo-meteorological conditions prior to the collapse, geological settings and topographical context. Geomorphological interpretations and analysis of climatic data-sets allow us to specify the different stages of the collapse and discuss the respective roles of the geological and hydro-climatic factors and unfrozen water in the ground which could have led to the collapse. Geophysical measurements and ice observations in the scarp reveal that the internal structure of the intact part of the rock glacier is composed of both ice-cemented and massive-ice layers. The rock glacier also contains a high proportion of fine material (essentially silt and clay), which could have played an important role in the collapse. Geodetic measurements repeated since 2007 show that, with the exception of the upper part, the whole rock glacier was still experiencing destabilisation in 2010, with very high deformation rates exceeding 30 m in 3 years. The continuous monitoring of surface displacement carried out during the summer of 2007 has not shown any clear meteorological control on the post-collapse rock glacier dynamics. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1887

2017091507 Bonnaventure, Philip P. (University of Lethbridge, Department of Geography, Lethbridge, AB, Canada); Lamoureux, Scott F. and Favaro, Elena A. Over-winter channel bed temperature regimes generated by contrasting snow accumulation in a High Arctic river: Permafrost and Periglacial Processes, 28(1), p. 339-346, illus. incl. 2 tables, sketch map, 42 ref., March 2017.

We report experimental results of near-surface winter temperatures along and adjacent to the channel bed of a High Arctic river on Melville Island, Canada. Temperature loggers 5 cm below the ground surface in areas where the terrain suggests varying snow accumulation patterns revealed that the maximum winter difference between air and near-surface temperatures ranged from 0 to +30°C during the winter of 2012-13, and that shallow near-surface freezing conditions were delayed for up to 21 days in some locations. Cooling to -10°C was delayed for up to 117 days. Modelled temperature at the top of permafrost indicates that permafrost at locations with thick snow can be up to 8°C warmer than those with thin snow. This thermal evidence for an ameliorated surface environment indicates the potential for substantial extended microbial and biogeochemical cycling during early winter. Rapid thaw of the bed during initiation of snowmelt in spring also indicates a high degree of hydrological connectivity. Therefore, snow-filled channels may contribute to biogeochemical and aquatic cycling in High Arctic rivers. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1902

2017091481 Boucher-Brossard, Geneviève (Université du Québec à Rimouski, Geography Department, Rimouski, QC, Canada); Bernatchez, Pascal; Corriveau, Maude and Jolivet, Yvon. Calculating lateral frost front penetration in a rapidly retreating cliff of fine sediments: Permafrost and Periglacial Processes, 28(1), p. 32-41, illus. incl. 1 table, sketch map, 60 ref., March 2017.

An adapted version of the Stefan equation (CLIFFSE) was tested to predict lateral progression of the frost front into cohesive sediments that form coastal cliffs along the north shore of the maritime estuary and gulf of the St Lawrence River (Quebec, Canada). The equation was adapted to accommodate the influence of cliff erosion on lateral penetration of freezing and thawing into vertical cliff faces. As the cliff erodes, freezing and thawing are initiated from the newly revealed surface. Frost progression and erosion were measured with an automated thermal erosion pin system. Measured observations agreed with predictions from the adapted equation (78 to 99% of the variability explained). Erosion associated with thawing front progression during winter warm spells led to a relative reduction in the frost front depth. Subsequently, progression of the frost front into the cliff contributed to an additional 50 cm of sediment freezing and erosion by the end of the cold season, which was not predicted by the original Stefan equation. Our findings support the hypothesis that multiple warm spells influence the amount of lateral penetration of the frost front in vertical cliffs. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1883

2017091483 Briggs, Martin A. (U. S. Geological Survey, Office of Groundwater, Storrs, CT); Campbell, Seth; Nolan, Jay; Walvoord, Michelle A.; Ntarlagiannis, Dimitrios; Day-Lewis, Frederick D. and Lane, John W. Surface geophysical methods for characterising frozen ground in transitional permafrost landscapes: Permafrost and Periglacial Processes, 28(1), p. 52-65, illus. incl. 1 table, sketch map, 44 ref., March 2017.

The distribution of shallow frozen ground is paramount to research in cold regions, and is subject to temporal and spatial changes influenced by climate, landscape disturbance and ecosystem succession. Remote sensing from airborne and satellite platforms is increasing our understanding of landscape-scale permafrost distribution, but typically lacks the resolution to characterise finer-scale processes and phenomena, which are better captured by integrated surface geophysical methods. Here, we demonstrate the use of electrical resistivity imaging (ERI), electromagnetic induction (EMI), ground penetrating radar (GPR) and infrared imaging over multiple summer field seasons around the highly dynamic Twelvemile Lake, Yukon Flats, central Alaska, USA. Twelvemile Lake has generally receded in the past 30 yr, allowing permafrost aggradation in the receded margins, resulting in a mosaic of transient frozen ground adjacent to thick, older permafrost outside the original lakebed. ERI and EMI best evaluated the thickness of shallow, thin permafrost aggradation, which was not clear from frost probing or GPR surveys. GPR most precisely estimated the depth of the active layer, which forward electrical resistivity modelling indicated to be a difficult target for electrical methods, but could be more tractable in time-lapse mode. Infrared imaging of freshly dug soil pit walls captured active-layer thermal gradients at unprecedented resolution, which may be useful in calibrating emerging numerical models. GPR and EMI were able to cover landscape scales (several kilometres) efficiently, and new analysis software showcased here yields calibrated EMI data that reveal the complicated distribution of shallow permafrost in a transitional landscape. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1893

2017091490 Draebing, Daniel (Technische Universität München, Faculty of Civil, Geo and Environmental Engineering, Munich, Germany); Haberkorn, Anna; Krautblatter, Michael; Kenner, Robert and Phillips, Marcia. Thermal and mechanical responses resulting from spatial and temporal snow cover variability in permafrost rock slopes, Steintaelli, Swiss Alps: Permafrost and Periglacial Processes, 28(1), p. 140-157, illus. incl. 2 tables, sketch maps, 40 ref., March 2017.

The aim of this study is to investigate the influence of snow on permafrost and rock stability at the Steintaelli (Swiss Alps). Snow depth distribution was observed using terrestrial laser scanning and time-lapse photography. The influence of snow on the rock thermal regime was investigated using near-surface rock temperature measurements, seismic refraction tomography and one-dimensional thermal modelling. Rock kinematics were recorded with crackmeters. The distribution of snow depth was strongly determined by rock slope micro-topography. Snow accumulated to thicknesses of up to 3.8 m on less steep rock slopes (<50°) and ledges, gradually covering steeper (up to 75°) slopes above. A perennial snow cornice at the flat ridge, as well as the long-lasting snow cover in shaded, gently inclined areas, prevented deep active-layer thaw, while patchy snow cover resulted in a deeper active-layer beneath steep rock slopes. The rock mechanical regime was also snow-controlled. During snow-free periods, high-frequency thermal expansion and contraction occurred. Rock temperature locally dropped to -10°C, resulting in thermal contraction of the rock slopes. Snow cover insulation maintained temperatures in the frost-cracking window and favoured ice segregation. Daily thermal-induced and seasonal ice-induced fracture kinematics were dominant, and their repetitive occurrence destabilises the rock slope and can potentially lead to failure. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1921

2017091482 Fagan, John D. (6 Westminster Place, Morristown, NJ) and Nelson, Frederick E. Spatial sampling design in the circumpolar active layer monitoring programme: Permafrost and Periglacial Processes, 28(1), p. 42-51, illus. incl. 1 table, sketch map, 22 ref., March 2017.

Prior to development of the Circumpolar Active Layer Monitoring (CALM) programme, little attention was paid to formal spatial sampling designs for measuring active-layer thickness (ALT). This omission made the accuracy of many data-sets questionable, in part because spatial periodicities caused by landscape features such as ice-wedge polygons and thaw lakes can significantly influence the depth of thaw. Early in the development of CALM's protocols, ALT was sampled in the continuous permafrost zone in northern Alaska and simulated by computer, to determine how ALT could be measured accurately. The simulated and field data-sets were analysed by comparing the means, variances and frequency distributions obtained using four spatial sampling designs (random, systematic, systematic random and systematic stratified unaligned). By a small margin, systematic stratified unaligned sampling provided the most accurate results. Systematic designs can, however, provide adequate estimates of the statistical moments of ALT with significant savings in cost, time and ease of implementation. Based on these results, the CALM programme recommended use of 10´10, 100´100 or 1000´1000 m grids, with sampling intervals of 1, 10 and 100 m, respectively. Most probed CALM sites now employ this strategy, except in terrain with unusual landscape elements or other special constraints. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1904

2017091506 Fedorov, Alexander N. (Russian Academy of Sciences, Melnikov Permafrost Institute, Yakutskk, Russian Federation); Iwahana, Go; Konstantinov, Pavel Y.; Machimura, Takashi; Argunov, Radomir N.; Efremov, Peter V.; Lopez, Larry M. C. and Takakai, Fumiaki. Variability of permafrost and landscape conditions following clear cutting of larch forest in central Yakutia: Permafrost and Periglacial Processes, 28(1), p. 331-338, illus. incl. 1 table, sketch map, 32 ref., March 2017.

Permafrost landscape dynamics were investigated between 1998 and 2012 at Neleger, near Yakutsk, in central Yakutia, to determine the effects on permafrost of clear cutting of larch forest. Changes in ground temperature, soil moisture, seasonal thaw depth and surface subsidence at a control (forest) site and a site cleared of forest were associated with vegetation recovery and climate change. Before clear cutting (1998-2000), permafrost temperatures were similar to the 1998-2012 average. After cutting (2001-04), permafrost temperatures decreased in the undisturbed forest site, but increased in the cleared site. The thermal disturbance of clear cutting caused increases in thaw depth and led to 4.8 cm of ground surface subsidence. Significant warming of permafrost in 2005-08, coincident with maximum snow depth and precipitation, caused up to 14.6 cm of additional ground subsidence, which represented the maximum changes observed in the landscape. Between 2009 and 2012, permafrost began to stabilise and subsidence was restricted to 1.8 cm. The reduced thaw depth and the growth of young birch shoots during this period indicated stabilisation of permafrost conditions and the beginning of landscape restoration. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1897

2017091499 Gray, James (Université de Montréal, Department of Geography, Cold Regions Geomorphology and Geotechnical Laboratory, Montreal, QC, Canada); Davesne, Gautier; Fortier, Daniel and Godin, Etienne. The thermal regime of mountain permafrost at the summit of Mont Jacques-Cartier in the Gaspé Peninsula, Québec, Canada; a 37 year record of fluctuations showing an overall warming trend: Permafrost and Periglacial Processes, 28(1), p. 266-274, illus. incl. 1 table, sketch map, 28 ref., March 2017.

The geothermal record for 1977-2014 from a 29 m deep borehole in permafrost on Mont Jacques-Cartier, in southeastern Canada, shows substantial decadal fluctuations and an overall warming trend. An extremely thin winter snow cover on the wind-blown summit favours the presence of permafrost. As a consequence, the instability of the thermal regime was found to be a direct response to air temperature variations modelled from data produced by the National Center for Environmental Prediction and National Center for Atmospheric Research. At a depth of 14 m, an increase of 0.4°C from 1979 to 1984 was followed by a decrease of 0.7°C over the next decade, and then by a marked, but irregular increase of 1°C up to 2013. Since 2008, diurnal data, refined by a one-dimensional, transient heat transfer model, indicate an active layer averaging 8.6 m in depth, but whose thickness is sensitive to fluctuations in annual mean ground surface temperatures. For a permafrost body already close to the thawing point, the continuation of the overall warming trend of the last 37 years would lead to its rapid degradation, and the permafrost would then become relict, thinning progressively both from the base and the surface. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1903

2017091503 Iijima, Yoshihiro (Mie University, Graduate School of Bioresources, Tsu, Japan); Park, Hotaek; Konstantinov, Pavel Y.; Pudov, Grigory G. and Fedorov, Alexander N. Active-layer thickness measurements using a handheld penetrometer at boreal and tundra sites in eastern Siberia: Permafrost and Periglacial Processes, 28(1), p. 306-313, illus., 37 ref., March 2017.

Active-layer thickness (ALT) is one of the most robust measures used to assess the impact of climate change on terrestrial permafrost. Testing of a handheld dynamic cone penetrometer showed that it was capable of measuring ALT with the same level of accuracy as conventional methods in boreal and tundra sites in eastern Siberia. The penetrometer also characterised the vertical structure of ground hardness within the active layer. The vertical profile of penetrometer measurements corresponded closely with soil plasticity and the liquid limit in high-centred polygons produced by thermokarst subsidence in dry grassland areas at a boreal site at Churapcha. The ALT was markedly deeper (>70 cm) at gravelly slope points adjacent to a wet tundra plain (<50 cm) in a CALM grid (R8) at Tiksi. Overall, the penetrometer is considered to provide an accurate and informative proxy for rapidly assessing the spatial heterogeneity and interannual changes in ALT. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1908

2017091494 Kenner, R. (Swiss Institute for Snow and Avalanche Research, Davos Dorf, Switzerland) and Magnusson, J. Estimating the effect of different influencing factors on rock glacier development in two regions in the Swiss Alps: Permafrost and Periglacial Processes, 28(1), p. 195-208, illus. incl. 3 tables, sketch map, 37 ref., March 2017.

To elucidate the factors that influence rock glacier distribution, we created a rock glacier inventory for two regions in the Swiss Alps (the Albula Alps and the Glarner Alps) and identified their spatial characteristics by adding topographical and meteorological data to a GIS. We evaluated the influence of mean annual precipitation (MAP), mean annual air temperature, head wall erosion, glacier coverage, lithology, slope, aspect, elevation and snow cover on rock glacier occurrence and characteristics, taking into account the interactions between these factors. MAP, lithology and head wall erosion significantly influenced rock glacier distribution, and the interaction of precipitation and lithology seemed to play a key role. Wind-driven snow redistribution influenced rock glacier frequency on hillslopes with different aspects. Rock glaciers interact with all of the factors analysed and exhibit complex relations with their regional environments. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1910

2017091491 Keuschnig, Markus (GEORESEARCH Forschungsgesellschaft, Wals, Austria); Krautblatter, Michael; Hartmeyer, I.; Fuss, C. and Schrott, L. Automated electrical resistivity tomography testing for early warning in unstable permafrost rock walls around alpine infrastructure: Permafrost and Periglacial Processes, 28(1), p. 158-171, illus. incl. 1 table, sketch map, 36 ref., March 2017.

Subsurface monitoring of permafrost conditions at depths up to 20-30 m is crucial to assess the safety and reliability of mountain infrastructure, because permafrost degradation critically affects rock slope stability in high mountains. Electrical resistivity tomography (ERT) provides a straightforward tool for monitoring near-surface bedrock permafrost at monthly or longer intervals. But as rockfalls are often prepared over periods of hours or days, ERT for early warning purposes should also detect short-term triggering events such as pressurised water flow. Here, we present the first approach to monitor steep permafrost rock walls quasi-continuously with ERT. We measured ERT every 4 h at the up to 67° steep rock wall below the Kitzsteinhorn cable car, Austria. Wenner datasets (n=996) were analysed from February 2013 to February 2014 in terms of data stability, raw data characteristics and measurement errors coinciding with potential disturbing factors. Strong resistivity changes coincided with rapid freezing or water inundating rock fractures. Automatically detected periods with large resistivity changes produce ERT time series with low resistivities extending from the bottom upwards during times of snowmelt. We infer that flow of pressurised water in fractures warms the surrounding rock in an upward direction, based on fracture inventories, visual observations of cleftwater and near-surface temperature measurements. We develop a strategy for ERT monitoring suitable for potential early warning systems, where high apparent resistivity changes in 4 h intervals may precede critical hydrostatic events confined by permafrost rocks. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1916

2017091498 Klug, Christophe (University of Innsbruck, Institute of Geography, Innsbruck, Austria); Rieg, L.; Ott, P.; Mössinger, M.; Sailer, R. and Stötter, J. A multi-methodological approach to determine permafrost occurrence and ground surface subsidence in mountain terrain, Tyrol, Austria: Permafrost and Periglacial Processes, 28(1), p. 249-265, illus. incl. 2 tables, sketch map, 72 ref., March 2017.

This study evaluates the potential of using high-resolution remote sensing data to detect permafrost patterns in a recently deglaciated alpine area on the mountain ridge of 'Rofenberg', Tyrol, Austria. Here, small but continuous settling of the surface was detected in differential digital terrain models throughout an annual airborne laser scanning (ALS) data series (2001-11). The settling is hypothesised to result from thawing of perennially frozen ground. To test this hypothesis, we applied a combination of established methods -- geomorphological observations, permafrost modelling, near-surface ground temperature measurements (bottom of the winter snowpack and temperature logging) and geophysical surveys (electrical resistivity tomography, ground penetrating radar, seismic refraction) -- that revealed the occurrence of permafrost in recently deglaciated terrain (above 3100 m asl). Consequently, the surface changes detected in the ALS data series are attributed to permafrost thaw and serve as a possible indicator of permafrost occurrence. The applied geophysical measurements also elucidate the recent development of permafrost after glacier recession since the Little Ice Age. However, to prove the existence of permafrost and its possible degradation, ALS data alone are insufficient and a combination of methods is recommended. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1896

2017091489 Liu Guangyue (Chinese Academy of Sciences, Cryosphere Research Station on the Qinghai-Tibetan Plateau, Lanzhou, China); Zhao Lin; Li Ren; Wu Tonghua; Jiao Keqin and Ping, Chienlu. Permafrost warming in the context of step-wise climate change in the Tien Shan Mountains, China: Permafrost and Periglacial Processes, 28(1), p. 130-139, illus. incl. 3 tables, sketch map, 45 ref., March 2017.

The Tien Shan Mountains, the largest mountain range in the Xinjiang Autonomous Region of north-western China, significantly influence the climate of central Asia. Recent permafrost changes in the region of the headwaters of the Urumqi River, as well as its relationship to climatic factors, were studied based on ground temperatures measured in a 60 m deep borehole, air temperatures and precipitation over a period from 1992 to 2011. The results showed that the maximum active-layer thickness (ALT; 1.70 m) occurred in 2009 and 2011, with an increase of 0.45 m compared with 1992. The change in ALT was related to the variation in the climatic conditions, and the increase in the deep-seated permafrost temperature. The permafrost temperature increased from -1.7°C in 1992 to -1.1°C in 2011, and the permafrost base moved upwards by approximately 14 m from 1992 to 2011. The long-term step-wise change in the air temperature may be the main cause of the permafrost warming in the headwaters of the Urumqi River. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1885

2017091493 Luethi, Rachel (Swiss Institute for Snow and Avalanche Research, Davos Dorf, Switzerland); Phillips, Marcia and Lehning, Michael. Estimating non-conductive heat flow leading to intra-permafrost talik formation at the Ritigraben rock glacier (western Swiss Alps): Permafrost and Periglacial Processes, 28(1), p. 183-194, illus. incl. 3 tables, sketch map, 34 ref., March 2017.

Although non-conductive heat flow plays an important role in the evolution of rock glacier temperature and dynamics, few studies have quantified it. At the Ritigraben rock glacier (Switzerland), intra-permafrost talik formation was observed at around 12 m depth and related to snowmelt and rainfall infiltration. Our aim is to attribute the talik formation to physical processes by quantifying the heat required to explain the observed dynamics of the temperature profile. We combined measured borehole temperatures, meteorological data and borehole logs with physics-based modelling experiments using the one-dimensional SNOWPACK model. The simulations were run with a simulated heat sink/source controlled by modelled snow cover, measured meteorological data and borehole temperature measurements. This allowed us to estimate non-conductive heat flow for different synthetic ground profiles with varying physical properties based on borehole logs. Our model results corroborate the assumption that purely conductive heat exchange is incompatible with the observed talik formation. We attribute the talik to advective and conductive heating by infiltrating water (which causes local heating rates to the order of 1 W m-3) and circulating air (which causes cooling to the order of 0.1 W m-3). Copyright Copyright 2016 John Wiley & Sons, Ltd. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1911

2017091487 Matyshak, G. V. (Lomonosov Moscow State University, Soil Science Department, Moscow, Russian Federation); Goncharova, O. Yu.; Moskalenko, N. G.; Walker, D. A.; Epstein, H. E. and Shur, Y. Contrasting soil thermal regimes in the forest-tundra transition near Nadym, West Siberia, Russia: Permafrost and Periglacial Processes, 28(1), p. 108-118, illus. incl. 4 tables, sketch map, 36 ref., March 2017.

Permafrost and varying land surface properties greatly complicate modelling of the thermal response of Arctic soils to climate change. The forest-tundra transition near Nadym in west Siberia provides an excellent study area in which to examine the contrasting thermal properties of soils in a forested ecosystem without permafrost and peatlands with permafrost. We investigated the effects of forest shading, snow cover and variable organic soil horizons in three common ecosystems of the forest-tundra transition zone. Based on the year-round temperature profile data, the most informative annual parameters were: (1) the sum of positive average daily temperatures at depths of 10 and 20 cm; (2) the maximum penetration depth of temperatures above 10°C; and (3) the number of days with temperatures below 0°C at a depth of 20 cm. The insulative effect of snow cover in winter was at least twice that of the shading and cooling effect of vegetation in summer. In areas with shallow permafrost, the presence of a thick organic horizon, with an extremely low thermal diffusivity, creates a very steep temperature gradient that limits heat penetration to the top of the permafrost in summer. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1882

2017091492 Myhra, K. S. (University of Oslo, Department of Geosciences, Oslo, Norway); Westermann, Sebastian and Etzelmüller, Bernd. Modelled distribution and temporal evolution of permafrost in steep rock walls along a latitudinal transect in Norway by CryoGrid 2D: Permafrost and Periglacial Processes, 28(1), p. 172-182, illus. incl. 2 tables, 24 ref., March 2017.

Steep permafrost rock walls marking the transition from high-lying plains to low-altitude fjord and valley systems are common in Norway. We have investigated the climate sensitivity of rock wall permafrost along a latitudinal transect from southern to northern Norway (60°N to 70°N) using topographic profiles from both natural sites and idealised sites with simplified geometries with steep rock walls bordering a flat plateau. We applied a two-dimensional (2D) transient thermal model (CryoGrid 2D) that includes both space- and time-dependent thermal parameters and the latent heat of ice-water phase transitions. The model has been forced using temperature data interpolated from meteorological observations between the end of the Little Ice Age and present warmer climatic conditions. We varied our model runs by changing the assumption of snow covers and applying glaciers at the plateaus. Our results show that the existence, geometry and thermal regime of the permafrost varies strongly depending on the snow and glacier cover on the plateau. Snow-free rock walls substantially govern the heat flow out of the rock wall, cooling the mountain interior below the plateau and favouring the development of permafrost beneath the margins of some plateaus. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1884

2017091486 Obu, J. (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Lantuit, H.; Myers-Smith, I.; Heim, B.; Wolter, J. and Fritz, M. Effect of terrain characteristics on soil organic carbon and total nitrogen stocks in soils of Herschel Island, western Canadian Arctic: Permafrost and Periglacial Processes, 28(1), p. 92-107, illus. incl. 5 tables, sketch map, 72 ref., March 2017.

Permafrost landscapes experience different disturbances and store large amounts of organic matter, which may become a source of greenhouse gases upon permafrost degradation. We analysed the influence of terrain and geomorphic disturbances (e.g. soil creep, active-layer detachment, gullying, thaw slumping, accumulation of fluvial deposits) on soil organic carbon (SOC) and total nitrogen (TN) storage using 11 permafrost cores from Herschel Island, western Canadian Arctic. Our results indicate a strong correlation between SOC storage and the topographic wetness index. Undisturbed sites stored the majority of SOC and TN in the upper 70 cm of soil. Sites characterised by mass wasting showed significant SOC depletion and soil compaction, whereas sites characterised by the accumulation of peat and fluvial deposits store SOC and TN along the whole core. We upscaled SOC and TN to estimate total stocks using the ecological units determined from vegetation composition, slope angle and the geomorphic disturbance regime. The ecological units were delineated with a supervised classification based on RapidEye multispectral satellite imagery and slope angle. Mean SOC and TN storage for the uppermost 1 m of soil on Herschel Island are 34.8 kg C m-2 and 3.4 kg N m-2, respectively. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1881

2017091485 Rudy, Ashley C. A. (Queen's University, Department of Geography, Kingston, ON, Canada); Lamoureux, Scott F.; Treitz, Paul; Van Ewijk, Karin; Bonnaventure, Philip P. and Budkewitsch, Paul. Terrain controls and landscape-scale susceptibility modelling of active-layer detachments, Sabine Peninsula, Melville Island, Nunavut: Permafrost and Periglacial Processes, 28(1), p. 79-91, illus. incl. 3 tables, sketch map, 45 ref., March 2017.

Modelling the susceptibility of permafrost slopes to disturbance can identify areas at risk to future disturbance and result in safer infrastructure and resource development in the Arctic. In this study, we use terrain attributes derived from a digital elevation model, an inventory of permafrost slope disturbances known as active-layer detachments (ALDs) and generalised additive modelling to produce a map of permafrost slope disturbance susceptibility for an area on northern Melville Island, in the Canadian High Arctic. By examining terrain variables and their relative importance, we identified factors important for initiating slope disturbance. The model was calibrated and validated using 70 and 30 per cent of a data-set of 760 mapped ALDs, including disturbed and randomised undisturbed samples. The generalised additive model calibrated and validated very well, with areas under the receiver operating characteristic curve of 0.89 and 0.81, respectively, demonstrating its effectiveness at predicting disturbed and undisturbed samples. ALDs were most likely to occur below the marine limit on slope angles between 3 and 10° and in areas with low values of potential incoming solar radiation (north-facing slopes). Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1900

2017091496 Scotti, Riccardo (Universita di Milano-Bicocca, Earth and Environmental Sciences, Milan, Italy); Crosta, Giovanni Battista and Villa, Alberto. Destabilisation of creeping permafrost; the Plator rock glacier case study (central Italian Alps): Permafrost and Periglacial Processes, 28(1), p. 224-236, illus. incl. 2 tables, sketch maps, 60 ref., March 2017.

The Plator rock glacier is the first such landform identified in the Italian Alps that shows destabilised behaviour. Analysis of six sets of sequential orthophotographs from 1981 to 2012 reveals an exceptional advance of the rock glacier front (92.1 m) and a horizontal velocity up to 4 m a-1 in different zones. The spatial variability of kinematics was evaluated by tracking sets of 'tracer' boulders on the rock glacier through time. Its velocity has progressively increased from the rooting zone to the tongue, with complex trends associated with distinct morphological features. Destabilisation likely occurred between 1954 and 1981, probably due to the relatively low elevation of the tongue, which resulted in warm permafrost conditions. Field observations reveal the presence of a large rock fall deposit, which occurred before 1981, and suggest that the debris overload could have triggered destabilisation. Since June 2015, an intensive monitoring programme has been implemented on the rock glacier, as the tongue is expected to travel over a steeper slope segment within the next 3 to 5 years, which could evolve in a catastrophic movement. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1917

2017091497 Staub, Benno (University of Fribourg, Department of Geosciences and Geography, Fribourg, Switzerland) and Delaloye, Reynald. Using near-surface ground temperature data to derive snow insulation and melt indices for mountain permafrost applications: Permafrost and Periglacial Processes, 28(1), p. 237-248, illus. incl. sketch map, 46 ref., March 2017.

The timing and duration of snow cover in areas of mountain permafrost affect the ground thermal regime by thermally insulating the ground from the atmosphere and modifying the radiation balance at the surface. Snow depth records, however, are sparse in high-mountain terrains. Here, we present data processing techniques to approximate the thermal insulation effect of snow cover. We propose some simple 'snow thermal insulation indices' using daily and weekly variations in ground surface temperatures (GSTs), as well as a 'snow melt index' that approximates the snow melt rate using a degree-day approach with air temperature during the zero curtain period. The indices consider point-specific characteristics and allow the reconstruction of past snow thermal conditions and snow melt rates using long GST time series. The application of these indices to GST monitoring data from the Swiss Alps revealed large spatial and temporal variability in the start and duration of the high-insulation period by snow and in the snow melt rate. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1890

2017091500 Staub, Benno (University of Fribourg, Department of Geosciences and Geography, Fribourg, Switzerland); Hasler, Andreas; Noetzli, Jeannette and Delaloye, Reynald. Gap-filling algorithm for ground surface temperature data measured in permafrost and periglacial environments: Permafrost and Periglacial Processes, 28(1), p. 275-285, illus., 36 ref., March 2017.

Ground surface temperatures (GST) are widely measured in mountain permafrost areas, but their time series data can be interrupted by gaps. Gaps complicate the calculation of aggregates and indices required for analysing temporal and spatial variability between loggers and sites. We present an algorithm to estimate daily mean GST and the resulting uncertainty. The algorithm is designed to automatically fill data gaps in a database of several tens to hundreds of time series, for example, the Swiss Permafrost Monitoring Network (PERMOS). Using numerous randomly generated artificial gaps, we validated the performance of the gap-filling routine in terms of (1) the bias resulting on annual means, (2) thawing and freezing degree-days, and (3) the accuracy of the uncertainty estimation. Although quantile mapping provided the most reliable gap-filling approach overall, linear interpolation between neighbouring values performed equally well for gap durations of up to 3-5 days. Finding the most similar regressors is crucial and also the main source of errors, particularly because of the large spatial and temporal variability of ground and snow properties in high-mountain terrains. Applying the gap-filling technique to the PERMOS GST data increased the total number of complete hydrological years available for analysis by 70 per cent (>450-filled gaps), likely without exceeding a maximal uncertainty of ±0.25°C in calculated annual mean values. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1913

2017091484 Steedman, Audrey E. (University of Victoria, School of Environmental Studies, Victoria, BC, Canada); Lantz, Trevor C. and Kokelj, Steven V. Spatio-temporal variation in high-centre polygons and ice-wedge melt ponds, Tuktoyaktuk coastlands, Northwest Territories: Permafrost and Periglacial Processes, 28(1), p. 66-78, illus. incl. 3 tables, sketch maps, 32 ref., March 2017.

High-centred polygonal terrain is a widespread feature of Arctic landscapes that is sensitive to increasing ground temperatures because of its high ground-ice content. Understanding spatial variation in the distribution and sensitivity of high-centred polygonal terrain is important for predicting landscape change. In the Tuktoyaktuk Coastlands, Northwest Territories, Canada, mean annual ground temperatures in permafrost have increased between 1 and 2°C over the last 40 years and high-centred polygonal terrain comprises about 10 per cent of the terrestrial landscape. To investigate factors affecting the distribution and potential degradation of ice wedges, we mapped high-centred polygonal terrain and ice-wedge melt ponds, and documented ice wedge related thermokarst at anthropogenic disturbances using 2004 aerial photographs. Historical melt pond distribution was assessed using 1972 aerial photographs. The density of polygonal terrain (up to 37%) was significantly higher in the northern than the southern part of the study area, where more abundant lacustrine sediments and lower ground temperatures have favoured ice-wedge development. Larger proportional melt pond area (0.68%), increases in pond area (up to 3.74%) and a higher frequency of major thermokarst activity following anthropogenic surface disturbance (54%) suggest that high-centred polygonal terrain in the northern part of the study area is more susceptible to degradation than in the southern part. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1880

2017091479 Strzelecki, Mateusz C. (University of Wroclaw, Institute of Geography and Regional Development, Wroclaw, Poland); Long, Antony J. and Lloyd, Jerry M. Post-Little Ice Age development of a High Arctic paraglacial beach complex: Permafrost and Periglacial Processes, 28(1), p. 4-17, illus. incl. 3 tables, sketch maps, 60 ref., March 2017.

We reconstruct the behaviour of a High Arctic gravel-dominated beach complex that has developed in central Spitsbergen, Svalbard, since the end of the Little Ice Age (LIA). The studied coastal environment in northern Billefjorden (Petuniabukta) is characterised by limited wave action and ephemeral sediment delivery from non-glaciated, mainly snow-fed fans and talus slopes. Aerial photographic evidence and morpho-sedimentological observations of a beach-ridge plain and spit complex in northern Billefjorden reveal a dynamic coastal system. During the post-LIA period, a prominent coastal barrier at the mouth of the Ebbaelva migrated seawards several tens of metres and prograded northwards to form new spit systems, each >150 m in length. The post-LIA coastal evolution occurred in two main phases. In the first half of the 20th century, increased paraglacial sediment released by retreating land-based glaciers led to the development of a subaqueous spit platform and the progradation of an ebb-tide delta into the mouth of the Ebbaelva, diverting its mouth to the northwest. In the second half of the 20th century, the barrier prograded onto this platform, promoting the development of three massive spits. Sedimentological data suggest that changes in beach-ridge composition that occurred during the 20th century are linked to episodic sediment delivery from an adjacent permafrost and snow-fed alluvial fan and delta system. Our work provides a basis for a new model of paraglacial barrier development that recognises the fundamental role of climate and sediment supply as two intimately connected processes that control coastal development in the High Arctic over decadal to centennial timescales. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1879

2017091504 Sun Benhua (Northwest A & F University, College of Natural Resources and Environment, Yangling, China); Dennis, Paul G.; Newsham, Kevin K.; Hopkins, David W. and Hallett, Paul D. Gelifluction and thixotropy of maritime Antarctic soils; small-scale measurements with a rotational rheometer: Permafrost and Periglacial Processes, 28(1), p. 314-321, illus. incl. 2 tables, sketch map, 65 ref., March 2017.

Gelifluction, thixotropy and yield stress were measured from <5 g soil samples taken from Signy, Alectoria, Greenwich, Wiencke and Livingston islands in the maritime Antarctic using a temperature-controlled rotational rheometer. The small sample size that this method permitted is compatible with sampling from sensitive sample locations. An oscillating 10 Pa shear stress was applied to samples at -0.5 kPa water potential. Two freeze-thaw cycles had temperature ramps from 5°C to -10°C over 2 h, followed by -10°C to 5°C over 2 h and finally at 5°C for 1 h. At freezing onset, the shear modulus, G, dropped to 4-50 per cent of thawed G, with no differences between locations. At thawing onset, G dropped to 8-32 per cent of thawed G, with significant differences between locations (P<0.001). Thixotropy was then measured by applying a 2 kPa oscillating shear stress for 10 min, followed by relaxation at 10 Pa for 2 h. The increased shear stress caused G to drop to less than 8 per cent of the pre-stressed value, with no difference between locations. After 0.1 and 2 h, G was 18-65 per cent and 31-82 per cent of the pre-stressed value, respectively. A shear ramp determined yield stresses ranging from 494-2217 Pa. These findings demonstrate the potential risk of more frequent freeze-thaw cycles or the occurrence of thawed soil to the stability of polar soils. Gelifluction through more frequent freeze-thaw cycles could result in increased slope movement, whereas thixotropy caused by trampling of thawed soils could exacerbate mechanical damage of surface soils. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1886

2017091501 Wilson, Peter (Ulster University, School of Geography and Environmental Sciences, Coleraine, United Kingdom); Matthews, John A. and Mourne, Richard W. Relict blockstreams at Insteheia, Valldalen-Tafjorden, Southern Norway; their nature and Schmidt hammer exposure age: Permafrost and Periglacial Processes, 28(1), p. 286-297, illus. incl. 4 tables, 85 ref., March 2017.

Two small relict blockstreams occur at Insteheia, a col at 910 m asl on the watershed between Valldalen and Tafjorden (More og Romsdal), southern Norway. Both blockstreams display morphological and sedimentological characteristics indicative of boulder accumulations that have moved downslope by solifluction, probably under a permafrost climatic regime. These comprise preferred orientation and dip patterns of boulders; inverse grading, with surface boulders overlying successively finer, well-sorted cobble, pebble and fine-grained (sand/silt dominated) sediment layers; imbrication, with the packing of small boulders behind larger boulders; and proximity to boulder-strewn hillslopes whose constituent boulders (organised into lobes and terraces) feed downslope into the blockstreams. Schmidt hammer exposure ages indicate that the blockstreams were last active during the Younger Dryas Stadial-Holocene transition. Blockstream development probably began at ~15 ka, following the Last Glacial Maximum, and lasted for ~5 ka. Since then any fine-grained material within the near-surface parts may have been progressively removed. The relatively rapid development of the blockstreams suggests that larger-scale forms of considerably greater age in the southern hemisphere may also have formed rapidly and have been inactive for long periods. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1915

2017091488 Yang Yuzhong (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Laboratory of Frozen Soil Engineering, Lanzhou, China); Wu Qingbai; Jiang Guanli and Zhang Peng. Stable isotopic stratification and growth patterns of ground ice in permafrost on the Qinghai-Tibet Plateau, China: Permafrost and Periglacial Processes, 28(1), p. 119-129, illus. incl. 3 tables, sketch map, 65 ref., March 2017.

Stable isotope analysis of ground ice from a deep borehole in permafrost in the Kunlun Mountain Pass on the Qinghai-Tibet Plateau, China, was carried out to assess the water source and origin of the ground ice. Five sections were isotopically distinguished in the borehole. The ground-ice samples had d18O values ranging from -20.2 to -8.5 ppm (mean: -11.0 ppm), dD values from -151.9 to -73.1 ppm (mean: -84.9 ppm) and D-excess values from -16.7 to 9.8 ppm (mean: 2.7 ppm). The isotopic contents and the freezing line (Sd18O-dD=6.86) of ground-ice samples in the five sections showed significant deviations from modern isotopic values of regional precipitation and surface water, indicating discrepancies in the replenishment of source water and different climatic conditions during periods of ice formation. Near-surface ground ice (0-3 m depth) (D-excess: 9.8 ppm) formed mainly from modern precipitation, whereas deep ground ice was related to the source water and freezing conditions during ice formation. Ground ice from 3.8 to 9.6 m and from 9.6 to 16 m is segregated in origin and a stable freezing front at 9.6 m was identified. Ground ice from 16 to 50 m was replenished by precipitation in the period during ground-ice formation. Between 50 and 91.3 m, ground ice formed in an unstable climate and a palaeo-permafrost table at 91.3m was distinguished. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1892

2017091505 Zhan, Shengan (University of Cincinnati, Department of Geography, Cincinnati, OH); Wang, Shujie; Beck, Richard A.; Hinkel, Kenneth M. and Liu, Hongxing. Post-storm water circulation patterns in Teshekpuk Lake (Alaska) derived from sequential optical satellite images: Permafrost and Periglacial Processes, 28(1), p. 322-330, illus. incl. 1 table, sketch map, 32 ref., March 2017.

Water flow speeds and directions in Teshekpuk Lake on the Arctic Coastal Plain of northern Alaska were derived from remotely sensed optical images captured after a major storm event. A Landsat 7 Enhanced Thematic Mapper Plus image and a Terra Advanced Spaceborne Thermal Emission and Reflection Radiometer image, acquired about 41 min apart on 15 August 2000, were analysed with an image matching technique based on cross-correlation to find corresponding features in both images. Flow speed and direction were calculated by measuring the horizontal displacement of such features in the two images. The derived water current speed ranged from 0.6 to 9.6 cm/s (mean 3.0 cm/s), during a wind blowing from the SE at an average speed of 4.9 m/s. The fastest currents (>2 standard deviations) fringed the shorelines and flowed in the direction of the wind (toward the NW), likely reflecting the direct influence of the wind conditions at the time of image acquisition. In contrast, a 10 km-wide gyre rotating clockwise developed towards the centre of the lake, likely reflecting the influence of a storm-driven wind veering over a 7 day period prior to the time of image acquisition. This study demonstrates that extensive water velocity fields in a lake can be derived from remotely sensed images using an image matching technique. The different flow patterns would not be readily observable without the synoptic view provided by satellite images, although the accuracy of flow speeds and directions needs further validation. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1889

2017091502 Zhang Shujuan (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Du Haimin and Harbor, Jon. The effect of confining pressure and water content on compressive strength and deformation of ice-rich silty sand: Permafrost and Periglacial Processes, 28(1), p. 298-305, illus. incl. 1 table, 22 ref., March 2017.

The characteristics of ice-rich frozen soils are important to engineering design in cold-climate regions. Previous work has concentrated on uniaxial strength properties, and limited data exist on triaxial strength and deformation as a function of volumetric ice content and confining pressure. Triaxial compressive tests carried out on ice-rich frozen silty sand indicated that the strength decreases to a minimum and then increases up to that of pure ice for a range of volumetric ice contents. However, the effect of confining pressure on the strength depends on the volumetric ice content itself. The strength was at a nearly constant minimum level when the volumetric ice content was between 48.2 and 65.1 per cent, dominated by the cohesion of the ice matrix. In contrast, at volumetric ice contents of > 27.2 to <50.2 per cent and >80.9 per cent, the strength increased with increasing confining pressure. The volumetric ice contents corresponding to maximum failure strain and minimum strength were 50.2 and 61.9 per cent, respectively. Thus, in this range an increase of about 10 per cent in volumetric ice content causes the failure strain to drop to the value for pure ice. The results indicate that there is a transition zone when the volumetric ice content is between 50.2 and 61.9 per cent that separates sample behaviour from that of frozen soil to that of pure ice. Copyright Copyright 2016 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1906

2017088854 Chang, Liao (Purdue University, Department of Earth, Atmospheric and Planetary Sciences, West Lafayette, IN) and Zhuang, Qianlai. Quantifying the role of permafrost distribution in groundwater and surface water interactions using a three-dimensional hydrological model: Arctic, Antarctic, and Alpine Research, 49(1), p. 81-100, illus. incl. 3 tables, sketch map, 96 ref., February 2017. Includes appendix.

This study uses a three-dimensional groundwater flow model to investigate groundwater dynamics and groundwater-surface water (GW-SW) interactions considering the effects of permafrost distribution for the Tanana Flats Basin in interior Alaska. The Parameter ESTimation (PEST) code is used to calibrate the model with observed stream discharge data. A 36-year MODLFOW-USG regional simulation shows the following. (1) Permafrost impedes groundwater movement in all directions and through taliks provides a major pathway to connect the groundwater and surface water systems. More than 80% of the vertical groundwater flow occurs within the permafrost-free zones. (2) Permafrost holds a significant amount of water that cannot be easily released through groundwater movements; however, water above the permafrost table has much higher renewal rates than deep groundwater. (3) Groundwater upwelling supports the base flow for the Tanana River and its tributaries throughout the year and feeds water to the wetland ecosystems at the Tanana Flats through unfrozen zones. Stream leakage is also highly correlated with stream discharge. Our study suggests that cold regional hydrological cycle studies should consider the effects of permafrost distribution under future warming conditions. This study provides a robust three-dimensional hydrological modeling tool that can be applied for the regions underlain with either continuous or discontinuous permafrost.

DOI: 10.1657/AAAR0016-022

2017089559 Vasil'chuk, Yu. K. (Moscow State University, Moscow, Russian Federation); Budantseva, N. A.; Vasil'chuk, A. C.; Rogov, V. V.; Podborny, Ye. Ye. and Chizhova, Ju. N. New data on variations of stable isotopes in the pingo ice core in the southern part of the Tazovsky Peninsula: Doklady Earth Sciences, 472(2), p. 200-204, illus. incl. 2 tables, 11 ref., February 2017.

The aim of this work is to obtain the vertical isotopic profile of the thick Pestsovoe pingo ice core in the southern part of the Tazovsky Peninsula, to determine the oxygen and hydrogen isotopic composition of the ice, and to reveal its formation conditions. Two trends were identified for the isotopic profile of the pingo ice: an insignificant increase of the d18O (»1.5 ppm) and dD (»9 ppm) values at depths of 12-15 m and a gradual decrease of isotopic values by 3.8 and 23 ppm for d18O and dD, respectively, at a depth of 15-26 m. The formation of the pingo ice core in the semiclosed system resulted in fractionation of the isotopic composition of oxygen and hydrogen by more than 4 and 20 ppm, respectively. Copyright 2017 Pleiades Publishing, Ltd.

DOI: 10.1134/S1028334X17020064

2017088940 Azócar, Guillermo F. (University of Waterloo, Department of Geography and Environmental Management, Waterloo, ON, Canada); Brenning, Alexander and Bodin, Xavier. Permafrost distribution modelling in the semi-arid Chilean Andes: The Cryosphere (Online), 11(2), p. 877-890, illus. incl. 3 tables, sketch maps, 71 ref., 2017.

Mountain permafrost and rock glaciers in the dry Andes are of growing interest due to the increase in mining industry and infrastructure development in this remote area. Empirical models of mountain permafrost distribution based on rock glacier activity status and temperature data have been established as a tool for regional-scale assessments of its distribution; this kind of model approach has never been applied for a large portion of the Andes. In the present study, this methodology is applied to map permafrost favourability throughout the semi-arid Andes of central Chile (29-32° S), excluding areas of exposed bedrock. After spatially modelling of the mean annual air temperature distribution from scarce temperature records (116 station years) using a linear mixed-effects model, a generalized additive model was built to model the activity status of 3524 rock glaciers. A permafrost favourability index (PFI) was obtained by adjusting model predictions for conceptual differences between permafrost and rock glacier distribution. The results indicate that the model has an acceptable performance (median AUROC: 0.76). Conditions highly favourable to permafrost presence (PFI >&eq; 0.75) are predicted for 1051 km2 of mountain terrain, or 2.7% of the total area of the watersheds studied. Favourable conditions are expected to occur in 2636 km2, or 6.8% of the area. Substantial portions of the Elqui and Huasco watersheds are considered to be favourable for permafrost presence (11.8% each), while in the Limarí and Choapa watersheds permafrost is expected to be mostly limited to specific sub-watersheds. In the future, local ground-truth observations will be required to confirm permafrost presence in favourable areas and to monitor permafrost evolution under the influence of climate change.

DOI: 10.5194/tc-11-877-2017

2017088939 Emmert, Adrian (University of Würzburg, Institute of Geography and Geology, Wurzburg, Germany) and Kneisel, Christof. Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging: The Cryosphere (Online), 11(2), p. 841-855, illus. incl. 1 table, 72 ref., 2017.

Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.

DOI: 10.5194/tc-11-841-2017

2017088938 Girod, Luc (University of Oslo, Department of Geosciences, Oslo, Norway); Nuth, Christopher; Kaab, Andreas; Etzelmuller, Bernd and Kohler, Jack. Terrain changes from images acquired on opportunistic flights by SfM photogrammetry: The Cryosphere (Online), 11(2), p. 827-840, illus. incl. 2 tables, 29 ref., 2017.

Acquiring data to analyse change in topography is often a costly endeavour requiring either extensive, potentially risky, fieldwork and/or expensive equipment or commercial data. Bringing the cost down while keeping the precision and accuracy has been a focus in geoscience in recent years. Structure from motion (SfM) photogrammetric techniques are emerging as powerful tools for surveying, with modern algorithm and large computing power allowing for the production of accurate and detailed data from low-cost, informal surveys. The high spatial and temporal resolution permits the monitoring of geomorphological features undergoing relatively rapid change, such as glaciers, moraines, or landslides. We present a method that takes advantage of light-transport flights conducting other missions to opportunistically collect imagery for geomorphological analysis. We test and validate an approach in which we attach a consumer-grade camera and a simple code-based Global Navigation Satellite System (GNSS) receiver to a helicopter to collect data when the flight path covers an area of interest. Our method is based and builds upon Welty et al. (2013), showing the ability to link GNSS data to images without a complex physical or electronic link, even with imprecise camera clocks and irregular time lapses. As a proof of concept, we conducted two test surveys, in September 2014 and 2015, over the glacier Midtre Lovénbreen and its forefield, in northwestern Svalbard. We were able to derive elevation change estimates comparable to in situ mass balance stake measurements. The accuracy and precision of our DEMs allow detection and analysis of a number of processes in the proglacial area, including the presence of thermokarst and the evolution of water channels.

DOI: 10.5194/tc-11-827-2017

2017091741 Matsuoka, Norikazu (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan); Waragai, Tetsuya and Wakasa, Sachi A. Rock physical weathering; linking laboratory experiments,field observations, and natural features: in Rock weathering from nanoscale to global scale; 1, Microscopic weathering and basic studies (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 126(3), p. 369-405, (Japanese) (English sum.), illus. incl. 3 tables, 197 ref., 2017.

Physical rock weathering has been studied through laboratory experiments, field observations, and numerical modeling, but linking these approaches and applying the results to weathering features in the field are often problematic. We review recent progress in three weathering processes--frost shattering, thermal fracturing, and lightning strikes--and explore better approaches to linking weathering processes and products. New visual and sensor technologies have led to great advances in field monitoring of weathering of fractured bedrock and resulting rockfalls in cold mountains. Laboratory simulations successfully produce fractures resulting from segregational freezing in various intact rocks. Modelling approaches illustrate the long-term evolution of periglacial slopes well, but improvements are required to apply laboratory derived criteria to frost weathering. The efficacy of thermal weathering, which has long been under debate, is now partly supported by laboratory and field evidence that cracking takes place when wild fires or artificial explosions lead to thermal shock. Rock fracturing due to strong radiation is also reevaluated from the presence of large cooling/warming rates and meridian cracks in rocks exposed to arid environments. Linking laboratory simulations and natural features, however, needs further field-based observations of thermal fracturing. Irregular fractures formed in boulders are often attributed to lightning strikes, despite rarely being witnessed. Artificial lightning in the laboratory produces radial cracks, marking the first step toward interpreting irregular fractures in the bedrock that are unlikely to originate from other weathering processes. Identifying the origins of fractured rocks in the field requires distinguishing between fracture patterns derived from these processes.

DOI: 10.5026/jgeography.126.369

2017088943 Wang Xiaowen (Chinese University of Hong Kong, Earth System Science Programme, Hong Kong, China); Liu Lin; Zhao Lin; Wu Tonghua; Li Zhongqin and Liu Guoxiang. Mapping and inventorying active rock glaciers in the northern Tien Shan of China using satellite SAR interferometry: The Cryosphere (Online), 11(2), p. 997-1014, illus. incl. 3 tables, sketch map, 71 ref., 2017. Includes appendices.

Rock glaciers are widespread in the Tien Shan. However, rock glaciers in the Chinese part of the Tien Shan have not been systematically investigated for more than 2 decades. In this study, we propose a new method that combines SAR interferometry and optical images from Google Earth to map active rock glaciers (ARGs) in the northern Tien Shan (NTS) of China. We compiled an inventory that includes 261 ARGs and quantitative information about their locations, geomorphic parameters, and downslope velocities. Our inventory shows that most of the ARGs are moraine-derived (69%) and facing northeast (56%). The altitude distribution of ARGs in the western NTS is significantly different from those located in the eastern part. The downslope velocities of the ARGs vary significantly in space, with a maximum of about 114 cm yr-1 and a mean of about 37 cm yr-1. Using the ARG locations as a proxy for the extent of alpine permafrost, our inventory suggests that the lowest altitudinal limit for the presence of permafrost in the NTS is about 2500-2800 m, a range determined by the lowest ARG in the entire inventory and by a statistics-based estimation. The successful application of the proposed method would facilitate effective and robust efforts to map rock glaciers over mountain ranges globally. This study provides an important dataset to improve mapping and modeling permafrost occurrence in vast western China.

DOI: 10.5194/tc-11-997-2017

2017091205 Espinoza-Ojeda, O. M. (Universidad Michoacana de San Nicolás de Hidalgo, Instituto de Investigaciones en Ciencias de la Tierra, Morelia, Mexico) and Santoyo, E. A new empirical method based on log-transformation regressions for the estimation of static formation temperatures of geothermal, petroleum and permafrost boreholes: Journal of Geophysics and Engineering, 13(4), p. 559-596, illus. incl. 24 tables, 67 ref., August 2016.

A new practical method based on logarithmic transformation regressions was developed for the determination of static formation temperatures (SFTs) in geothermal, petroleum and permafrost bottomhole temperature (BHT) data sets. The new method involves the application of multiple linear and polynomial (from quadratic to eight-order) regression models to BHT and log-transformation (Tln) shut-in times. Selection of the best regression models was carried out by using four statistical criteria: (i) the coefficient of determination as a fitting quality parameter; (ii) the sum of the normalized squared residuals; (iii) the absolute extrapolation, as a dimensionless statistical parameter that enables the accuracy of each regression model to be evaluated through the extrapolation of the last temperature measured of the data set; and (iv) the deviation percentage between the measured and predicted BHT data. The best regression model was used for reproducing the thermal recovery process of the boreholes, and for the determination of the SFT. The original thermal recovery data (BHT and shut-in time) were used to demonstrate the new method's prediction efficiency. The prediction capability of the new method was additionally evaluated by using synthetic data sets where the true formation temperature (TFT) was known with accuracy. With these purposes, a comprehensive statistical analysis was carried out through the application of the well-known F-test and Student's t-test and the error percentage or statistical differences computed between the SFT estimates and the reported TFT data. After applying the new log-transformation regression method to a wide variety of geothermal, petroleum, and permafrost boreholes, it was found that the polynomial models were generally the best regression models that describe their thermal recovery processes. These fitting results suggested the use of this new method for the reliable estimation of SFT. Finally, the practical use of the new method was highlighted because it only requires the use of BHT and shut-in time measurements as the main input data, which represents an enormous advantage over most of the analytical methods reported in the literature that require a large number of measurements (e.g. circulation time, the thermophysical and transport properties of the formation or drilling fluid, among others). Copyright (Copyright) 2016 Sinopec Geophysical Research Institute

DOI: 10.1088/1742-2132/13/4/559

2017088728 Jin Huijun (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Gansu, China); Chang Xiaoli; Luo Dongliang; He Ruixia; Lu Lanzhi; Yang Sizhong; Guo Dongxin; Chen Xuemei and Harris, Stuart A. Evolutiuon of permafrost in northeast China since the late Pleistocene: Sciences in Cold and Arid Regions, 8(4), p. 269-296, illus. incl. 1 table, sketch maps, 123 ref., August 2016.

In Northeast China, permafrost advanced and retreated several times under the influences of fluctuating paleo-climates and paleo-environments since the Late Pleistocene. During the last 60 years, many new data were obtained and studies were conducted on the evolution of permafrost in Northeast China, but so far no systematic summary and review have been made. Based on sedimentary sequences, remains of past permafrost, paleo-flora and -fauna records, and dating data, permafrost evolution since the Late Pleistocene has been analyzed and reconstructed in this paper. Paleo-temperatures reconstructed from the remains of past permafrost and those from paleo-flora and -fauna are compared, and thus the southern limit of permafrost (SLP) in each climate period is inferred by the relationship of the permafrost distribution and the mean annual air/ground temperatures (MAAT/MAGT). Thus, the evolutionary history of permafrost is here divided into five stages: (1) the Late Pleistocene (Last Glaciation, or LG) (65 to 10-8.5 ka), the Last Glaciation Maximum (LGM, 21-13 ka) in particular, the coldest period in the latest history with a cooling of about 6-10°C, characterized by extensive occurrences of glaciation, flourishing Mammathas-Coelodonta Faunal Complex (MCFC), widespread aeolian deposits, and significant sea level lowering, and permafrost greatly expanded southwards almost to the coastal plains (37°N-41°N); (2) the Holocene Megathermal Period (HMP, 8.5-7.0 to 4.0-3.0 ka), 3-5°C warmer than today, permafrost retreated to about 52°N; (3) the Late Holocene Cold Period (Neoglaciation) (4.0-3.0 to 1.0-0.5 ka), a cooling of 1-3°C, some earlier thawed permafrost was refrozen or attached, and the SLP invaded southwards to 46°N; (4) the Little Ice Age (LIA, 500 to 100-150 a), the latest cold period with significant permafrost expansion; and (5) climate warming since the last century, during which Northeast China has undergone extensive permafrost degradation. The frequent and substantial expansions and retreats of permafrost have greatly impacted cold-region environments in Northeast China. North of the SLP during the HMP, or in the present continuous permafrost zone, the existing permafrost was largely formed during the LG and was later overlapped by the permafrost formed in the Neoglaciation. To the south, it was formed in the Neoglaciation. However, many aspects of permafrost evolution still await further investigations, such as data integration, numerical reconstruction, and merging of Chinese permafrost history with those of bordering regions as well as collaboration with related disciplines. Of these, studies on the evolution and degradation of permafrost during the past 150 years and its hydrological, ecological, and environmental impacts should be prioritized.

DOI: 10.3724/SP.J.1226.2016.00269

2017091190 Holloway, Jean E. (Queen's University, Department of Geography, Kingston, ON, Canada); Lamoureux, Scott F.; Montross, Scott N. and Lafrenière, Melissa J. Climate and terrain characteristics linked to mud ejection occurrence in the Canadian High Arctic: Permafrost and Periglacial Processes, 27(2), p. 204-218, illus. incl. 3 tables, sketch map, 48 ref., June 2016.

Pressurised slurries of fine-grained sediment expelled from the base of the active layer have been observed in recent years in the High Arctic. Such mud ejections, however, are poorly understood in terms of how exactly climate and landscape factors determine when and where they occur. Mud ejections at the Cape Bounty Arctic Watershed Observatory, Melville Island, Nunavut, were systematically mapped in 2012 and 2013, and this was combined with observations of mud ejection activity and climatic measurements carried out since 2003. The mud ejections occur late in the melt season during warm years and closely following major rainfall events. High-resolution satellite imagery demonstrates that mud ejections are associated with polar semi-desert vegetative settings, flat or low-sloping terrain and south-facing slopes. The localised occurrence of mud ejections appears to be related to differential soil moisture retention. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1870

2017091189 Kurylyk, Barret L. (University of Calgary, Department of Geoscience, Calgary, AB, Canada) and Hayashi, Masaki. Improved Stefan equation correction factors to accommodate sensible heat storage during soil freezing or thawing: Permafrost and Periglacial Processes, 27(2), p. 189-203, illus. incl. 5 tables, 53 ref., June 2016.

In permafrost regions, the thaw depth strongly controls shallow subsurface hydrologic processes that in turn dominate catchment runoff. In seasonally freezing soils, the maximum expected frost depth is an important geotechnical engineering design parameter. Thus, accurately calculating the depth of soil freezing or thawing is an important challenge in cold regions engineering and hydrology. The Stefan equation is a common approach for predicting the frost or thaw depth, but this equation assumes negligible soil heat capacity and thus exaggerates the rate of freezing or thawing. The Neumann equation, which accommodates sensible heat, is an alternative implicit equation for calculating freeze-thaw penetration. This study details the development of correction factors to improve the Stefan equation by accounting for the influence of the soil heat capacity and non-zero initial temperatures. The correction factors are first derived analytically via comparison to the Neumann solution, but the resultant equations are complex and implicit. Explicit equations are obtained by fitting polynomial functions to the analytical results. These simple correction factors are shown to significantly improve the performance of the Stefan equation for several hypothetical soil freezing and thawing scenarios. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1865

2017091187 Lacelle, Denis (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Lapalme, Caitlin; Davila, Alfonso F.; Pollard, Wayne; Marinova, Margarita; Heldmann, Jennifer and McKay, Christopher P. Solar radiation and air and ground temperature relations in the cold and hyper-arid Quartermain Mountains, McMurdo dry valleys of Antarctica: Permafrost and Periglacial Processes, 27(2), p. 163-176, illus. incl. 2 tables, sketch maps, 68 ref., June 2016.

This study compares the relations between solar radiation and air and ground temperatures in the Quartermain Mountains of the McMurdo Dry Valleys of Antarctica with those in ice-free Victoria Land and Arctic Canada. The surface offset is near 0°C at all sites in the Quartermain Mountains and other sites in coastal Victoria Land, whereas the thermal offset is near 0°C at shallow ice table depths (<20 cm) and near 1°C for ice tables deeper than the depth of diurnal temperature variation. The surface and thermal offsets in Victoria Land differ markedly from those in Arctic Canada, which are generally characterised by a positive surface offset and a negative thermal offset. These important differences highlight the effects of a lack of vegetation, surface organic layer, snow cover and moisture content in near-surface soils on the direction and magnitude of surface and thermal offsets. Summer ground surface temperatures in the Quartermain Mountains correlate strongly with incoming solar radiation. Based on measured ground surface temperatures and modelled potential incoming solar radiation, two zones with distinct ground surface temperatures are defined in the Quartermain Mountains: (i) perennially cryotic zones (PCZs) characterised by ground surface temperatures always below 0°C; and (ii) seasonally non-cryotic zones (NCZs) characterised by ground surface temperatures >0°C for at least a few hours. Soils in the PCZs experience water exchange through vapour diffusion, whereas soils in the NCZs contain features associated with liquid water activity, such as increased soil moisture and frozen ponds recharged by snow/glacier meltwater. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1859

2017091186 Morse, Peter D. (Natural Resources Canada, Geological Survey of Canada, Ottawa, ON, Canada); Wolfe, S. A.; Kokelj, S. V. and Gaanderse, A. J. R. The occurrence and thermal disequilibrium state of permafrost in forest ecotopes of the Great Slave region, Northwest Territories, Canada: Permafrost and Periglacial Processes, 27(2), p. 145-162, illus. incl. 3 tables, sketch map, 45 ref., June 2016.

Permafrost underlies peatlands of the Great Slave region, Northwest Territories, Canada, but permafrost relations beneath other ecotopes of black spruce (Picea mariana), white birch (Betula papyrifera) and mixed forests remain unknown. Permafrost-ecotope relations examined over a 3 year period (2010-13) establish the occurrence and thermal state of permafrost under these different types of forest. Air temperatures and snow depths are regionally consistent. Ground temperature variation primarily reflects latent heat effects during the freezing season, with the duration of season-normalised active-layer freezeback explaining 76% of 1 m ground temperature variation among all sites except xeric peatland. Low apparent thermal diffusivities from substantial latent heat effects strongly attenuate ground temperature variation with depth, and yield zero annual amplitude depths of 7 m or less where annual mean ground temperatures range among sites from -1.4°C to 0.0°C. Extensive discontinuous permafrost conditions, related to the extent of forested ecotopes, are commonly in thermal disequilibrium. Whereas permafrost in peatlands may be ecosystem-protected, this represents only about 2% of the area of the region. Permafrost in other forested ecotopes, occurring in ice-rich unconsolidated sediments, is climate-driven and ecosystem-protected because of latent heat effects. Though the rate of permafrost degradation may be reduced, an eventual transition to isolated permafrost retained primarily within ecosystem-driven peatlands implies substantial reductions of permafrost extent in this region. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1858

2017091192 Pawelec, Halina (University of Silesia, Faculty of Earth Sciences, Sosnowiec, Poland) and Ludwikowska-Kedzia, Malgorzata. Macro- and micromorphologic interpretation of relict periglacial slope deposits from the Holy Cross Mountains, Poland: Permafrost and Periglacial Processes, 27(2), p. 229-247, illus. incl. 2 tables, sketch maps, 76 ref., June 2016.

Relict periglacial slope cover deposits in the Holy Cross Mountains of Poland are composed of material derived from bedrock, loess and sand of polygenic origin. The aim of this study was to interpret the processes that deposited three massive coarse-grained diamictons near the base of gentle hillslopes. Based on macroscopic and microscopic sedimentological analyses, the diamictons are attributed to deposition by three processes--active-layer detachment, solifluction and high-energy overland flow--due to climatic and geomorphologic factors. The use of microscopic analysis revealed the detailed texture and structure of these deposits, and was particularly important in interpreting fine-grained sediments produced by low-energy overland flow. This technique served as the basis for the differentiation of solifluction deposits and high-density flow deposits. The active-layer detachment deposit (adjacent to the slip plane) was characterised by a heterogenous texture and breccia-type structure with domains and clasts oriented parallel to the slope. The deposit included erosional surfaces and individual slip planes. The solifluction deposit was a clayey diamicton with a banded structure oriented parallel to the slope. The low-energy overland flow deposit was laminated and sorted with laminae oriented parallel to the slope. The high-energy overland flow deposit was a homogeneous and massive diamicton with a silty/sandy matrix and randomly oriented clasts and grains. The following characteristics helped identify the sediment type: the degree of homogenisation, texture, sedimentary structure and fabric. Features including plasmic fabric, deformation structures and microporosity played an additional role in identifying the studied deposits. In relict slope deposits, these features may be formed as a result of depositional or postdepositional processes. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1864

2017091188 Sannel, A. Britta K. (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Hugelius, Gustaf; Jansson, Peter and Kuhry, Peter. Permafrost warming in a subarctic peatland; which meteorological controls are most important?: Permafrost and Periglacial Processes, 27(2), p. 177-188, illus. incl. 1 table, sketch map, 87 ref., June 2016.

Because climate change can affect the carbon balance and hydrology in permafrost peatlands, a better understanding of their sensitivity to changes in temperature and precipitation is needed. In Tavvavuoma, northernmost Sweden, meteorological parameters and ground thermal properties have been monitored in a peat plateau from 2006 to 2013. During this time period, the air temperature record shows no warming trend, and the late-season thaw depth has been relatively stable at around 55-60 cm. Meanwhile, the mean annual ground temperature at 1 m depth has increased by 0.06°C/yr and at 2-5 m depth the permafrost is currently warmer than -0.3°C. Statistical analyses suggest that interannual changes in thaw depth and ground temperatures are affected by different meteorological factors. Summer air temperatures and annual thawing degree-days control thaw depth (p≤&eq;0.05), whereas winter precipitation/snow depth affects ground temperatures (p≤&eq;0.1). The permafrost in this peat plateau is likely relict and not in equilibrium with current climatic conditions. Since the early 20th century, there has been a regional increase in air temperature and snow depth. If the ongoing permafrost warming in Tavvavuoma is a result of these long-term trends, short-term variability in meteorological parameters can still have an impact on the rate of permafrost degradation, but unless pronounced climate cooling occurs, thawing of the peat plateau is inevitable. Copyright Copyright 2015 John Wiley & Sons, Ltd.

DOI: 10.1002/ppp.1862

2017088634 Chen Ji (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Zhao Lin; Sheng Yu; Li Jing; Wu Xiaodong; Du Erji; Liu Guangyue and Pang Qiangqiang. Some characteristics of permafrost and its distribution in the Gaize area on the Qinghai-Tibet Plateau, China: Arctic, Antarctic, and Alpine Research, 48(2), p. 395-409, illus. incl. 1 table, sketch map, 68 ref., May 2016.

An investigation of permafrost in the Gaize area in the west Qinghai-Tibet Plateau in China was conducted in October and November of 2010 and 2011. It was found that mean annual ground temperature was >-1°C with a permafrost thickness of <60 m in the widespread alpine steppe below an altitude of 5400 m a.s.l. The active layer thickness was usually deeper than 3 m with a maximum of about 5.7 m. Overall, the ice/water content of the top 15 m of frozen soil was usually <10%. The altitudinal limit of permafrost in the alpine steppe was about 5100, 5000, and 4950 m a.s.l. on south-, east-west-, and north-facing slopes, respectively. A permafrost map was constructed using the ARCGIS platform and topographic information from the TOPO 30 digital elevation model. Statistical analysis of the map revealed that permafrost is primarily distributed in the hilly/mountainous areas of Gaize, covering 51% of the study area. The area of permafrost in this map is considerably less than in the Permafrost Map of the Qinghai-Tibet Plateau drawn in 1996. Further analysis revealed that the large difference between the two maps could be attributed to both errors in the earlier mapping method and permafrost degradation.

DOI: 10.1657/AAAR0014-023

2017086527 Liu Lin (Chinese University of Hong Kong, Earth System Science Programme, Hong Kong, China); Schaefer, K. M.; Chen, A. C.; Gusmeroli, A.; Zebker, H. A. and Zhang, T. Remote sensing measurements of thermokarst subsidence using InSAR: Journal of Geophysical Research: Earth Surface, 120(9), p. 1935-1948, illus. incl. 1 table, sketch maps, 35 ref., September 2015.

Thawing of ice-rich permafrost followed by surface subsidence results in irregular, depressed landforms known as thermokarst. Many remote sensing studies have identified thermokarst landforms and mapped their changes. However, the intrinsic dynamic thermokarst process of surface subsidence remains a challenge to quantify and is seldom examined using remote sensing methods. In this study we used spaceborne interferometric synthetic aperture radar (InSAR) data to map surface subsidence trends at a thermokarst landform located near Deadhorse on the North Slope of Alaska. A pipeline access road constructed in the 1970s triggered the thawing of the permafrost, causing subsequent expansion of the thermokarst landform. Using Phased Array type L band Synthetic Aperture Radar images acquired by the Advanced Land Observing Satellite-1, our InSAR analysis reveals localized thermokarst subsidence of 2-8 cm/yr between 2006 and 2010, equivalent to an ice volume loss of about 1.2 ´ 107 m3/yr. Comparisons between InSAR subsidence trends and lidar microtopography suggest a characteristic time of 8 years of thermokarst development. We also quantitatively explain the difficulty, uncertainties, and possible biases in separating thermokarst-induced, irreversible subsidence from cyclic seasonal deformation. Our study illustrates that InSAR is an effective tool for mapping and studying active thermokarst processes and quantifying ice loss. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015JF003599

2017086513 Morse, Peter D. (Canadian Geological Survey, Ottawa, ON, Canada) and Wolfe, S. A. Geological and meteorological controls on icing (aufeis) dynamics (1985 to 2014) in subarctic Canada: Journal of Geophysical Research: Earth Surface, 120(9), p. 1670-1686, illus. incl. 2 tables, sketch maps, 23 ref., September 2015.

Icings are widespread yet poorly understood winter hydrological phenomena that develop over the winter by freezing successive overflows of groundwater to the surface. Groundwater hydrology in arctic regions is constrained by geological setting and permafrost extent, and overflows are possibly driven by cold winters, winter warming intervals, high antecedent autumn rainfall, and low early winter snowfall. Consequently, icings are spatially recurrent but not necessarily annually nor to the same extent. We test the significance of identified meteorological forcing variables against a long-term data set of icing dynamics and distribution we developed for the Great Slave region around Yellowknife, Northwest Territories. Climate is regionally consistent, but variable geology and permafrost create hydrological conditions representative of much of the subarctic. We mapped 5500 icings in the study area (21,887 km2) with a semiautomated approach utilizing late spring Landsat archival images (1985 to 2014). Individual icing size, ranging 3 orders of magnitude (1.8 ´ 10-3 km2 to 4.1 km2), is related to return frequency. Infrequent ice (25% return frequency) accounts for 94% of the total icing area (86 km2). Winter warming intervals (>&eq;5°C; typically over 1-3 days) and autumn rainfall (September and October) explain 28% of icing density interannual variation overall. Interannual icing variation and significant meteorological forcing variables differ among ecoregions where varied geological settings and permafrost conditions influence the hydrological regime. Future icings may develop less frequently due to decreasing winter warming intervals, but increasing autumn rainfall may increase icing density where Canadian Shield leads to strong threshold-mediated runoff generation processes. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2015JF003534

2017086514 Nelson, Peter A. (Colorado State University, Department of Civil and Environmental Engineering, Fort Collins, CO); McDonald, Richard R.; Nelson, Jonathan M. and Dietrich, William E. Coevolution of bed surface patchiness and channel morphology; 1, Mechanisms of forced patch formation: Journal of Geophysical Research: Earth Surface, 120(9), p. 1687-1707, illus., 32 ref., September 2015.

Riverbeds frequently display a spatial structure where the sediment mixture composing the channel bed has been sorted into discrete patches of similar grain size. Even though patches are a fundamental feature in gravel bed rivers, we have little understanding of how patches form, evolve, and interact. Here we present a two-dimensional morphodynamic model that is used to examine in greater detail the mechanisms responsible for the development of forced bed surface patches and the coevolution of bed morphology and bed surface patchiness. The model computes the depth-averaged channel hydrodynamics, mixed-grain-size sediment transport, and bed evolution by coupling the river morphodynamic model Flow and Sediment Transport with Morphological Evolution of Channels (FaSTMECH) with a transport relation for gravel mixtures and the mixed-grain-size Exner equation using the active layer assumption. To test the model, we use it to simulate a flume experiment in which the bed developed a sequence of alternate bars and temporally and spatially persistent forced patches with a general pattern of coarse bar tops and fine pools. Cross-stream sediment flux causes sediment to be exported off of bars and imported into pools at a rate that balances downstream gradients in the streamwise sediment transport rate, allowing quasi-steady bar-pool topography to persist. The relative importance of lateral gravitational forces on the cross-stream component of sediment transport is a primary control on the amplitude of the bars. Because boundary shear stress declines as flow shoals over the bars, the lateral sediment transport is increasingly size selective and leads to the development of coarse bar tops and fine pools. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2014JF003428

2017085109 Gogin, Ivan Ya. (Russian Geological Research Institute, St. Petersburg, Russian Federation) and Vdovets, Marina S. Geosites of international significance in the UNESCO WHS Lena Pillars Nature Park (Sakha Republic, Russia): Geoheritage, 6(3), p. 173-184, 15 ref., September 2014.

The Lena Pillars Nature Park belonging to the Sakha Republic (Yakutiya) is situated in the southeastern Siberian Platform on the right bank of the middle Lena River. The park is mainly known for the almost continuous chain of fancy pillar-like carbonate weathering outliers spreading along the right bank of the Lena River and banks of its tributaries Botoma and Sinyaya. However, the main reason of the ultimate importance of the park is that it represents a pivotal evidence of relatively rapid evolutionary development and growth of the skeleton and soft-bodied fauna and algae diversity, which took place about 541-509 Ma ago. This event is well known in the scientific world as the "Cambrian Explosion". The International Union of Nature Conservation included it into the list of key evolutionary events in the Earth's history. Numerous geosites of different types and significance levels are located in the park, and six of them are of international importance. They are highly representative in terms of stratigraphy, paleontology, paleoecology, and geomorphology. Stratigraphic geosites demonstrate nearly a continuous record of the Upper Ediacaran-Middle Cambrian deposits. Before the 1990s, stratotypes of the Lower Cambrian stages were used for standardization of the Lower Cambrian in the International Stratigraphic Chart. Paleontological geosites are mainly represented by fossil localities of the Early Cambrian, characterized by high level of preservation and diversity. Sinsk localities of the Early Cambrian biota are listed among the Cambrian Lagerstättens. Many geosites are objects of paleoecological investigations because their deposits were formed in synchronously existing parts of a former single paleobasin (inner lagoon, transitional reef, and outer abyssal) with different physical and chemical parameters. Geomorphologic sites represent different types of permafrost karst, as well as weathering outliers of columnar shape, the so-called Lena Pillars. The scientific and aesthetic value of the Lena Pillars Nature Park is globally recognized, and in 2012 it was inscribed into UNESCO WHL based on the criteria vii and viii.

DOI: 10.1007/s12371-013-0089-1

2017086122 Ravanel, L. (University of Savoie, EDYTEM Laboratory, Le Bourget du Lac, France); Bodin, X. and Deline, P. Using terrestrial laser scanning for the recognition and promotion of high-alpine geomorphosites: in New digital technologies applied to the management of geoheritage (Cayla, Nathalie, editor; et al.), Geoheritage, 6(2), p. 129-140, 55 ref., June 2014.

High-alpine geomorphosites are poorly understood and developed, mostly because of the heavy constraints of high mountain areas. Meanwhile, they are geoheritage areas that are often extremely vulnerable to global warming: glaciers and permafrost areas are currently affected by major changes due to increasing air temperature. To deal with the high spatial variability of landforms and processes, research on alpine geomorphosites often needs the use of advanced methods of high-resolution topography, among which terrestrial laser scanning plays an increasingly crucial role. Carried out on some tenth of high-elevation sites across the Alps since the beginning of the 2000s, this method is particularly interesting for the recognition and development of high-alpine geomorphosites. Indeed, it can be implemented for identifying and characterizing the geomorphic objects (survey, monitoring and mapping), helping planning and protection policies and serving geotouristic development (communication about the processes involved, basis for documents).

DOI: 10.1007/s12371-014-0104-1

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2017090087 Harris, Stuart A.; Brouchkov, Anatoli and Cheng Guodong. Geocryology; characteristics and use of frozen ground and permafrost landforms: CRC Press, Boca Raton, FL, illus., September 28, 2017. ISBN: 978-1-138054-165. Based on Publisher-supplied data.

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2017090014 Schorghofer, Norbert (University of Hawaii, Institute for Astronomy, Honolulu, HI); Leopold, Matthias; Martin, Jake; Morelli, Amanda and Yoshikawa, Kenji. High-altitude permafrost and microclimates in cinder cone craters on Maunakea, Hawaii [abstr.]: in Proceedings of the Pacific Division of the American Association for the Advancement of Science; 98th annual meeting (Christianson, Roger G., chairperson), Proceedings of the Pacific Division, American Association for the Advancement of Science, 36, Part 1, p. 67-68, June 19, 2017. Meeting: Pacific Division of the American Association for the Advancement of Science; 98th annual meeting, June 19-23, 2017, Waimea, HI.

2017085622 Antonova, Sofia (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany); Duguay, Claude R.; Kaeaeb, Andreas; Heim, Birgit; Langer, Moritz; Westermann, Sebastian and Boike, Julia. Monitoring bedfast ice in lakes of the Lena River delta using TerraSAR-X backscatter and coherence time series [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C33B-0818, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Thermokarst lakes and ponds are major elements of permafrost landscapes, occupying up to 40% of the land area in some Arctic regions. Deeper lakes (> 2 m) remain unfrozen beneath floating ice during winter, leading to the formation of talik, facilitating microbial activity and greenhouse gases production throughout the year. Shallower lakes (< 2 m) experience complete freezing down to the bottom which prevents talik formation and limits the length of the greenhouse gases production period. Thus, distinguishing floating from grounded lake ice is crucial for evaluating the thermal and geobiochemical state of tundra landscapes. A remote sensing method based on differences between radar backscatter intensity signatures is most frequently used to distinguish floating from bedfast ice. Although the method has been known since the 1970s, the potential of new generation satellite radar imagery has yet to be evaluated. Our study is based on a unique TerraSAR-X (TSX) data set that spans three winter seasons (2012-2013, 2013-2014 and 2014-2015). We investigate the viability of TSX backscatter intensity time series with high spatial (10 m) and temporal (11 days) resolution for monitoring bedfast lake ice in the zone of continuous permafrost in the Lena River Delta, Siberia. In situ ice thickness measurements from a number of lakes were used for validation. Additionally, an 11-day sequential interferometric coherence time series was analysed as a supplementary approach for the bedfast ice monitoring and as an explorative step for a possible derivation of shallow lakes bathymetry based on InSAR. Results demonstrate that TSX backscatter intensity time series is an excellent tool for the monitoring floating/grounded lake ice regime. Particularly, due to a better temporal resolution of TSX data, retrieval of the timing of ice grounding is improved compared to previous studies which used RADARSAT or ERS data. The coherence time series is shown to detect most ice grounding and to have the potential to monitor freezing of sediments.

2017085621 Baughman, C. A. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Jones, B. M.; Babcock, Esther; Bodony, Karin L.; Mann, Daniel H.; Larson, Chris F. and Smith, Jeremy. Remotely sensing a cold region dune field using airborne LiDAR and high resolution aerial photography [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C33B-0817, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Sand dunes and sheets respond to global and regional climatic changes, ecological succession, and disturbance events. Approximately 100,000 km2 of active and stable sand sheets occur in the Arctic and Subarctic today. These cold regions dunes are also subject to changes in permafrost conditions. Permafrost can influence soil moisture and vegetation, which then influences sand availability and transport. This study describes the morphometry and dynamics of the Nogahabara Dunes of interior Alaska's discontinuous permafrost zone and local permafrost conditions using 2015 airborne LiDAR, historic aerial photography, ground penetrating radar, and historical climate data. Average active dune height is 10 meters, with a maximum dune height of 28 meters. Dune spacing is approximately 130 meters. Where dunes are irregularly shaped and have variable orientation, dune spacing ranges from 40 to 200+ meters. Average dune migration between 1952 and 2015 is 63cm yr-1. Dune migration direction was variable; however, the predominant direction of movement was to the southeast. This agrees with historical wind records. Despite substantial within-field movement, the overall extent of the active dune field has not changed in 60 years. Small blow-out features were observed in the aftermath of fires that occurred in the vegetated portion of the dune field in 2015. Inferred reflectors in GPR data show that permafrost is present within the active dune field 2-4 meters below ground surface, but there does not appear to be any morphometric features directly related to permafrost. Depth-to-permafrost is shallower within the inactive dunes adjacent to the active dune field due to surface stability and cover by vegetation and insulating soil organics. Recent fire on the inactive dunes has the potential to reactivate dormant dunes through the degradation of underlying permafrost however long term monitoring will be required to validate this scenario. Acquisition of contemporary airborne LiDAR data provides a baseline from which to quantify potential activation of currently stable dune landforms as permafrost warms and thaws in Alaska.

2017089188 Eckhardt, Bridget A. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Barnes, David L.; Daanen, Ronald P. and Walter Anthony, Katey M. Transport of CH4 through open-talik lakes in discontinuous permafrost aquifers [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H43E-1490, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

As northern regions of the world experience warming climate, scientists look to permafrost, a crucial component of arctic and subarctic ecosystems, as a source and sink of atmospheric carbon. It is well-known that the thawing of permafrost from above as a result of warming climate is a considerable source of greenhouse gases. However, few studies have considered the production of methane, a potent greenhouse gas, beneath the permafrost. A rugged permafrost bottom is proposed to favor the storage of gas in "pockets" that have been formed through permafrost thaw and degradation from below. Sub-permafrost methane can migrate to reach the atmosphere when connections between the sub-permafrost and supra- permafrost (open taliks) form or when changing permafrost morphology opens pathways from the pocket to the bottom of an open-talik lake. We hypothesize that the migration of methane into open-talik lakes from the sub-permafrost can occur through advection and diffusion as a dissolved gas and by movement as an immiscible fluid. Two lakes with varying degrees of talik formation within Goldstream Cr. Basin, Fairbanks, Alaska, serve as the major study sites. To distinguish advection and diffusion of dissolved-phase methane we analyze dissolved methane concentrations, stable isotopes and major ions as tracers and through hydraulic gradient analysis. Monthly collection and analysis of water samples from surface, subsurface, and benthic sources allow for observation of seasonal changes in composition and flow dynamics. Observations and data collected to date indicate the occurrence of multiphase flow. We test the occurrence of immiscible-phase flow through measurement of displacement pressures and aging methane captured in desaturated pore channels beneath the lake bottom. Results to date also bring attention to the complexity of open-talik systems that has previously not been observed. Data obtained in this study will aid in the understanding of greenhouse gas fluxes, and thereby improve research in climate change predictions.

2017085580 Gergel, Diana R. (University of Washington, Seattle, WA); Hamman, Joseph and Nijssen, Bart. Modeling the evolution of seasonally frozen soils and permafrost in the Arctic [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C22B-03, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Seasonally frozen soil and permafrost cover a significant portion of the land surface in the Arctic. Warming temperatures and the additional effects of Arctic amplification are already altering the seasonal cycle of frozen soils, decreasing the areal extent of permafrost and increasing the active-layer depth (ALD), the layer of soil that freezes and thaws annually. These changes are projected to have broad effects on "greening the Arctic" in terms of carbon availability and land-atmosphere interactions. Land surface models vary in their treatment of frozen soils. The Variable Infiltration Capacity (VIC) model uses either an approximate soil temperature profile or a finite difference solution that takes soil ice content into account. In this study, we use VIC 5.0, a new version of VIC that can be part of fully-coupled earth system models such as the Regional Arctic System Model (RASM), and perform uncoupled VIC simulations at a 10km resolution over the pan-Arctic domain to characterize changes in the ALD and the areal extent of permafrost. These uncoupled simulations will be used to improve the modeling of frozen soils over the Arctic for later application in fully-coupled RASM simulations. We compare simulated distribution of permafrost and soil temperatures to observations from the Circumpolar Active Layer Monitoring (CALM) program, an observation network that was established in the 1990s and monitors the long-term response of the active layer and near-surface permafrost at over 200 sites in the Arctic and Subarctic lowlands, including measurements of both ALD and soil temperature. Our comparison focuses on VIC's ability to capture seasonal trends.

2017089010 Jia, Yuanyuan (Ohio State University, Columbus, OH); Shum, C. K.; Kim, Jinwoo; Lu Zhong; Kuo Chungyen; Zhang Lei and Ding Xiaoli. Study of the Qinghai-Tibetan Plateau permafrost active layer thickening rate using ALOS-1/-2 interferometric SAR data [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract G43A-1047, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The Qinghai-Tibetan Plateau (QTP) is the world's largest and the highest plateau with distinct and competing surface and subsurface processes. It is the Third Pole and the World Water Tower, owing to its vast ice reservoir with the largest number of glaciers in the world. The QTP is covered by a large (1.3 to 1.6 million km2) layer of discontinuous and sporadic alpine permafrost, and is the origin of the largest rivers across Asia, feeding water to billions of people downstream. One such origin is the Three-River Headwater System, comprising of the mighty Yangtze, Yellow, and Lancang/Mekong Rivers, a subject of this study. The thawing over QTP permafrost regions is thought to be more severe compared with other high latitude permafrost regions by the fact that most of the permafrost is warm. During the past few decades, 10% permafrost has degraded. The overall mean active layer (AL) thickening rates over the QTP from model studies were 1.4 cm yr-1 during 1980-2001 and approximately 6.3 cm yr-1 during 2006-2010, based on soil temperature profiles for 27 monitoring sites along Qinghai-Tibetan railway (QTR). Here we report on a study on quantifying AL thickening rate in the northern QTP along the QTR, using ALOS-1/-2 InSAR observed land subsidence and AL thickness modeling. We have characterized high spatial resolution (30 m) and spatially varying ALT thickening rates, 2007-2010, along the QTR's large permafrost areas (> 10,000 km2). InSAR measured subsidence rates over various thermokarst surfaces in the study region are then converted to AL thickening rates using models with estimates ranging from 2.0 cm yr-1 to 10.7 cm yr-1. Comparisons with five borehole in situ sites showed excellent agreements with r2 >0.9. Using the ALOS-1/-2 InSAR data, we have further studied the plausible contribution of permafrost in NE QTP to the Yangtze headwater runoff near the Tuotuo river.

2017087184 Kemna, A. (University of Bonn, Bonn, Germany); Weigand, M.; Wagner, F.; Hilbich, C. and Hauck, C. Monitoring the dynamics of water flow at a high-mountain permafrost site using electrical self-potential measurements [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H34A-06, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Flow of (liquid) water plays a crucial role in the dynamics of coupled thermo-hydro-mechanical processes in terrestrial permafrost systems. To better understand these processes in the active layer of permafrost regions, with the ultimate goal of adequately incorporating them in numerical models for improved scenario prediction, monitoring approaches offering high spatial and temporal resolution, areal coverage, and especially sensitivity to subsurface water flow, are highly desired. This particularly holds for high-mountain slopes, where strong variability in topography, precipitation, and snow cover, along with significant subsurface soil/rock heterogeneity, gives rise to complex spatio-temporal patterns of water flow during seasonal thawing and freezing periods. The electrical self-potential (SP) method is well known to, in theory, meeting the above monitoring demands by measuring the electrical streaming potential which is generated at the microscopic scale when water flows along electrically non-neutral interfaces. Despite its inherent sensitivity to subsurface water flow, the SP method has not yet been used for the monitoring of high-mountain permafrost sites. We here present first results from an SP monitoring survey conducted at the Schilthorn (2970 m asl) in the Bernese Alps, Switzerland, where SP data have been collected since September 2013 at a sampling rate of 10 min on a permanently installed array of 12 non-polarizing electrodes covering an area of 35 m by 15 m. While the SP time series exhibit systematic daily variations, with part of the signal clearly correlated with temperature, in particular in the snow-free periods, the largest temporal changes in the SP signal occur in spring, when the snow cover melts and thawing sets on in the active layer. The period of higher temporal SP variations continues until autumn, when the signal gradually returns to relatively low variations, coinciding with the freezing of the ground. Our results suggest that the SP method is a suitable tool for the monitoring of seasonal water flow dynamics at high-mountain permafrost sites. Current work is directed towards an improved field setup, as well as the quantitative analysis of the SP data based on laboratory calibration measurements.

2017089128 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Carey, Michael; O'Donnell, Jonathan; Sjoberg, Ylva and Zimmerman, Christian E. Changing groundwater-surface water interactions impact stream chemistry and ecology at the Arctic-Boreal transition in western Alaska [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H42C-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The arctic-boreal transition zone of Alaska is experiencing rapid change related to unprecedented warming and subsequent loss of permafrost. These changes in turn may affect groundwater-surface water (GW-SW) interactions, biogeochemical cycling, and ecosystem processes. While recent field and modeling studies have improved our understanding of hydrology in watersheds underlain by thawing permafrost, little is known about how these hydrologic shifts will impact bottom-up controls on stream food webs. To address this uncertainty, we are using an integrative experimental design to link GW-SW interactions to stream biogeochemistry and biota in 10 first-order streams in northwest Alaska. These study streams drain watersheds that span several gradients, including elevation, aspect, and vegetation (tundra vs. forest). We have developed a robust, multi-disciplinary data set to characterize GW-SW interactions and to mechanistically link GW-SW dynamics to water quality and the stream ecosystem. Data includes soil hydrology and chemistry; stream discharge, temperature, and inflow rates; water chemistry (including water isotopes, major ions, carbon concentration and isotopes, nutrients and chlorophyll-a), and invertebrate and fish communities. Stream recession curves indicate a decreasing rate later in the summer in some streams, consistent with seasonal thaw in lower elevation and south-facing catchments. Base cation and water isotope chemistry display similar impacts of seasonal thaw and also suggest the dominance of groundwater in many streams. Coupled with estimates of GW-SW exchange at point, reach, and catchment scales, these results will be used to predict how hydrology and water quality are likely to impact fish habitat and growth given continued warming at the arctic-boreal transition.

2017085578 Koven, Charles D. (Lawrence Berkeley National Laboratory, Berkeley, CA); Lawrence, David M.; McGuire, Anthony David; Slater, Andrew G.; Hugelius, Gustaf and Parazoo, Nick. Permafrost in Earth system models; recent progress and future challenges [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C22B-01, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Permafrost is a crucial component of the Earth system, representing a key intersection point of soil physical and carbon cycle dynamics, yet has been poorly represented in Earth system models. None of the ESMs of the CMIP5 generation included permafrost carbon dynamics, and many had poor representation of soil thermal dynamics. Subsequent to CMIP5, a number of key improvements have been made to address these shortcomings, including strategies for including permafrost carbon dynamics in models, as well as methods and datasets for benchmarking both the physical and biogeochemical components of the models. I will discuss recent progress and outstanding challenges that remain in understanding and quantifying the role that permafrost soils may play as feedback agents in the Earth system.

2017085590 Liao, Chang (Purdue University, West Lafayette, IN) and Zhuang, Qianlai. Quantifying the role of permafrost distribution in groundwater dynamics and surface water interactions using a three-dimensional hydrological model [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C23A-0730, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

This study uses a three-dimensional groundwater flow numerical model to investigate the groundwater dynamics and groundwater-surface water interactions considering the effects of the permafrost distribution for the Tanana Flats basin in interior Alaska. The Parameter ESTimation (PEST) package is used to calibrate the model with stream discharge data. Results showed that: (1) permafrost impedes groundwater movement in all directions and through talik provides the major pathway connecting the groundwater systems and the surface water systems, and more than 78% of the vertical groundwater flow occurs within the permafrost-free zone; (2) permafrost holds a significant amount of water which cannot be easily released through groundwater movements. However, water above the permafrost table has much higher refresh rates than deep groundwater; (3) the average groundwater upwelling rate (8.0´102 m3d-1) under streams is much higher in permafrost-free zones than that (3.8´102 m3d-1) in permafrost zones; and (4) groundwater upwelling supports the base flow for the Tanana River and its tributaries, and feeds water to the wetland ecosystem at the Tanana Flats through unfrozen zone at a rate of 5.0´102 m3d-1. However, stream leakage beneath the Tanana River dominates the groundwater upwelling over 10 times in summer and is highly correlated with the discharge rate. These estimates are consistent with field measurements in this region. Our study suggests that hydrologic cycle studies should consider the effects of permafrost distribution under future warming conditions.

2017087180 Liljedahl, Anna K. (University of Alaska Fairbanks, Fairbanks, AK); Gaedeke, A.; Baraer, M.; Chesnokova, A.; Lebedeva, L.; Makarieva, O. and O'Neel, S. Decrease in glacier coverage contributes to increased winter baseflow of Arctic rivers [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H33R-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Rising minimum daily flows in northern Eurasian and North American rivers suggest a growing influence of groundwater in the Arctic hydrological cycle, while the impact of a warmer high-latitude climate system is evident in decreased glacier coverage and increasing permafrost temperatures. Multiple mechanisms have been proposed to explain the increased discharge, which is well documented but relatively poorly understood. Here we assess the long-term (up to 88 yrs) linkages between climate, glaciers and hydrology in Alaska, Canadian and Russian glacierized (from 0.3 to 60% glacier cover) and non-glacierized watersheds (31 to 186,000 km2). We are specifically interested in analyzing trends in late winter discharge from larger watersheds to refine our understanding of the regional aquifer status and annual discharge from smaller headwater basins. Field measurements of differential runoff in Interior Alaska show that glaciated headwater streams can lose significant amounts of water in summer to the underlying aquifer. The aquifer is in turn feeding the larger lowland river system throughout the year. Groundwater storage status in Arctic regions is especially prominent through winter river discharge as it is typically the only source of water to the river system for at least 6 months of the year. Our analyses aim to explore the hypothesis that the documented increase in later winter river discharge of larger watersheds can be explained at least partly, by increased glacier melt in summer as observed by long-term decreases in glacier coverage. If true, a decrease in winter freshwater exports to the Arctic Ocean could potentially follow as glaciers retreat to higher (cooler) elevations. Increased Arctic river baseflow can favor sea ice growth and fish habitats, while negatively impacting local communities in their river ice travel.

2017089009 Michaelides, Roger J. (Stanford University, Stanford, CA); Zebker, Howard A.; Schaefer, Kevin M.; Chen, Jingyi; Parsekian, Andy; Jafarov, Elchin E. and Liu Lin. Active-layer thickness estimation in the Yukon-Kuskokwim Delta, Alaska, via inversion of InSAR data and field measurements [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract G43A-1046, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The active layer in permafrost environments plays a critical role in land surface processes, surface hydrology, vegetation succession, and thermokarst processes. We define the active layer as the uppermost portion of the ground subject to annual freeze/thaw cycles. Measuring the active layer thickness provides valuable insight into the above-mentioned processes, but due to the heterogenous nature of active layer thickness and the sparsity of traditional measurement methods, accurately characterizing the active layer thickness across broad permafrost regions can be very challenging. We apply interferometric synthetic aperture radar (InSAR) to measure the active layer thickness to study permafrost processes in the Yukon-Kuskokwim (YK) delta in southwest Alaska. This area is a lowland marsh characterized by low-gradient meandering rivers and numerous lakes, several of which are thermokarst thaw lakes. Using ALOS PALSAR data acquired between 2007-2011, we generate a time-series of cm-scale surface deformation, from which we determine both seasonal subsidence and long-term (secular) thermokarst subsidence. We use a previously-developed algorithm to infer active-layer thickness across the study region from the InSAR-derived surface deformation maps. In addition, we compare in-situ field measurements of active layer thickness, organic layer thickness, and soil saturation acquired by ground-penetrating radar and mechanical probing measurements during a field campaign to the YK delta in August 2016. Finally, we discuss the uncertainty in our inversion results, and several coherence-based and phase variance-based data masking techniques for optimal active-layer thickness reconstruction.

2017085617 Miles, Charles (University of Missouri Columbia, Department of Geological Sciences, Columbia, MO); Savage, Austin and Gomez, Francisco G. Remote sensing of rock glacier activity in the Spanish Peaks region of southern Colorado [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C33B-0795, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Owing to the significance of rock glaciers for water resources and indicators of climate change, there is a need to improve the capability to monitor changes in rock glacier activity (and, hence, the state of the ground ice) for alpine settings. Remote sensing tools potentially provide means of conducting regional studies. This study focuses on the Spanish Peaks region of southern Colorado where glacial- and talus-derived rock glaciers are found predominantly on slopes of late Cenozoic felsic intrusions. Mapping of rock glaciers and other rock-debris landforms is based on high resolution optical imagery. Talus-derived rock glaciers are typically found at lower altitudes than those derived from rock-buried glaciers and moraines. We utilize Interferometric Synthetic Aperture Radar (InSAR) to identify active rock glaciers (and their temporal kinematic variations). InSAR analyses includes recent data from the Sentinel-1 mission (2015 - present), as well as older archived data spanning through the 1990s. For selected rock glaciers, field verification is also provided by repeat GPS surveys and ground-based radar interferometry spanning 2014 - 2016. Seasonal changes in flow rate are observed, as well as annual variations that may correspond with differing amounts of winter precipitation. This study also explores the utility of thermal remote sensing as a possible tool to identify landforms with significant ground ice. Analysis of thermal emittance data from Landsat and ASTER imagery suggests that active rock glaciers and relatively ice-free landforms (as determined from InSAR) might be distinguishable. This is further tested using 1-dimensional thermal modeling. Compared with InSAR data archives, the potential utility of thermal remote sensing data may allow analysis of longer data archives for a better view of changes periglacial environmental state.

2017085625 Muskett, Reginald R. (University of Alaska Fairbanks, Fairbanks, AK). ICESat GLAS elevation changes and ALOS PALSAR InSAR line-of-sight changes on the continuous permafrost zone of the North Slope, Alaska [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C33B-0828, 1 ref., December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Measuring centimeter-scale and smaller surface changes by satellite-based systems on the periglacial terrains and permafrost zones of the northern hemisphere is an ongoing challenge. We are investigating this challenge by using data from the NASA Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (ICESat GLAS) and the JAXA Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) on the continuous permafrost zone of the North Slope, Alaska. Using the ICESat GLAS exact-repeat profiles in the analysis of ALOS PALSAR InSAR Line-Of-Sight (LOS) changes we find evidence of volume scattering over much of the tundra vegetation covered active-layer and surface scattering from river channel/banks (deposition and erosion), from rock outcropping bluffs and ridges. Pingos, ice-cored mounds common to permafrost terrains can be used as benchmarks for assessment of LOS changes. For successful InSAR processing, topographic and tropospheric phase cannot be assumed negligible and must be removed. The presence of significant troposphere phase in short-period repeat interferograms renders stacking ill suited for the task of deriving verifiable centimeter-scale surface deformation phase and reliable LOS changes. Ref.: Muskett, R.R. (2015), Int. Journal of Geosciences, 6 (10), 1101-1115. doi:10.4236/ijg.2015.610086 URL: http://www.scirp.org/Journal/PaperDownload.aspx?paperID=60406

2017085624 Obu, Jaroslav (University of Oslo, Geosciences, Oslo, Norway); Westermann, Sebastian; Kaab, Andreas and Bartsch, Annett. Mapping the thermal state of permafrost through modelling and remote sensing in ESA GlobPermafrost project [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C33B-0824, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Permafrost cannot be directly detected from space, but many permafrost surface properties and features are observable with a variety of earth observation sensors. ESA's GlobPermafrost project develops, validates and implements different permafrost information products to support the research communities and related international organisations. Within GlobPermafrost, we aim to produce a circum-polar map of permafrost extent and thermal state. The thermal state of the ground cannot be directly inferred from spaceborne platforms with current remote sensing technologies. We overcome these limitations by combining the information content of several remote sensing products, namely time series of remotely sensed land surface temperature, snow cover and snow water equivalent. These products are employed to force ground thermal models at 1 km resolution which deliver ground temperatures and probability of permafrost occurrence within a grid cell. This semi-empirical approach has been tested in non-glaciated, land area in the North Atlantic region. Mean annual ground temperatures were estimated at a spatial resolution of 1 km at using MODIS land surface temperatures and ERA reanalysis products. The results are compared to in-situ temperature measurements and show accuracy of approximately 2.5 °C. This procedure was improved with land surface temperature gap filling, snow water equivalent information and ground surface properties. We present first results and discuss the challenges in application of the scheme on the circumpolar scale.

2017089195 Parhizkar, Masoumeh (Laval University, Department of Geology and Geological Engineering, Quebec City, QC, Canada); Therrien, Rene; Molson, John W. H.; Lemieux, Jean-Michel; Fortier, Richard; Talbot Poulin, Marie-Catherine; Therrien, Pierre and Ouellet, Michel. Application of a 3D model to assess the thermo-hydrological effects of climate warming in a discontinuous permafrost zone, Umiujaq, northern Quebec, Canada [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H43E-1503, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The rate of permafrost degradation in northern Quebec, Canada, has increased over the last two decades due to climate warming, which is expected to significantly modify the hydrogeologic and thermal regimes. Groundwater accessibility is also expected to increase and could become a significant source of drinking water for northern communities. In this project, an integrated surface water / groundwater flow model, HydroGeoSphere, is being applied to a 2 km2 catchment in northern Quebec to assess the effect of future climate change on thermo-hydrological conditions as well as on changes in groundwater availability for northern communities. The catchment is located in a discontinuous but widespread permafrost zone near Umiujaq (northern Quebec, Canada) where the subsurface consists of a 10-30 m-thick coarse-grained glaciofluvial layer forming a good aquifer beneath a permafrost-rich silty marine unit. A conceptual thermo-hydrological model of the catchment has been built from field data collected over 5 years, including hydraulic heads, stream flow rates, subsurface geology, as well as ground temperatures and thermal fluxes around two 10-20 m-thick permafrost mounds. The integrated 3D numerical model includes variably-saturated groundwater flow with transient recharge, as well as advective-conductive heat transport driven by transient air temperatures (varying from about -40 to +30 °C) and a geothermal heat flux of 60 mW/m2. The model is calibrated to observed heads and temperatures by coupling PEST with HydroGeoSphere, allowing changes in hydraulic and thermal conductivities. Preliminary results are consistent with the available observed data, however non-uniqueness remains an important issue. The simulations are providing useful predictions of the permafrost thaw rate and associated changes to the hydrogeological flow system, including increased aquifer recharge following permafrost thaw.

2017085579 Tao, Jing (University of Maryland, College Park, MD); Reichle, Rolf H.; Koster, Randal D.; Forman, Barton A. and Xue, Yuan. Improving thermodynamic representation in permafrost modeling within the NASA Catchment Land Surface Model [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C22B-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Understanding the impact of permafrost on the terrestrial water, energy and carbon cycles is crucial to sustaining ecosystems in cold regions. Obstacles to a better understanding of permafrost dynamics include our limited understanding of heat transfer mechanisms, sparse observations of soil thermal properties, and the lack of a systematic evaluation platform. Here we aim to enhance the thermodynamic process representation in NASA's Catchment Land Surface Model (CLSM). First, a baseline CLSM simulation for Alaska was generated at 9km resolution from 1980 to 2014, with simulated soil temperature from the surface down to 13m below the surface. The baseline results were evaluated using in-situ observations from permafrost sites across Alaska, demonstrating skill at adequately capturing the inter- and intra-annual variability of soil temperature. Next, moisture dynamics were coupled to the soil temperature processes in CLSM to address the dependency of soil thermal conductivity on the degree of saturation. An investigation into sub-grid variability revealed that: 1) the representativeness of local meteorological forcing limits the model's capability of producing accurate simulation at the top layer; and 2) vegetation and soil heterogeneity has a profound influence on subsurface thermodynamics through affecting snow physics and energy exchange at surface. Furthermore, a more physically realistic parameterization that accounts for the influence of soil organic content on soil thermal properties was introduced into CLSM. Sensitivity analysis demonstrates that the soil carbon fraction plays a significant role in determining soil thermal properties and thus substantially altering soil freezing and thawing states. Overall, improving the thermodynamic representation enhances CLSM's capability of simulating permafrost dynamics. Ultimately, this could provide a more realistic assessment of permafrost resilience in Alaska under the context of climate change.

2017085591 Tyler, Scott (University of Nevada Reno, Department of Geological Sciences and Engineering, Reno, NV). Can you hear me now? Recent advances distributed fiber-optic sensing in the cryosphere [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract C23C-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The last decade has seen an explosion in the development and deployment of optical fiber-based measurement of temperature and strain. Essentially "Lidar in a fiber", it is now possible to measure temperatures every 10-50 cm over fiber lengths of kilometers at frequencies as fast as 1 Hz, and with temperature resolution as low as 10 mK. Microstrain can also be measured over similar spatial scales, and recent developments in Rayleigh backscatter approaches can now resolve acoustic emissions at from tenths of hertz to the kilohertz range. While first developed for oil and gas development, distributed fiber sensing is now used many environmental and earth science research. In the cryosphere, where environmental conditions are often very challenging for conventional sensors, distributed fiber sensing is well suited, as only changes in the optical properties of the fiber are needed and no additional sensors are needed. In this talk, I will highlight recent developments in fiber sensing to measure both ice shelf and sub-ice shelf conditions in Antarctica, strain measurements in permafrost and advances in refraction seismology sensing that may have broad applications to glaciers.

2017089123 Wlostowski, Adam N. (Institute of Arctic and Alpine Research, Boulder, CO); Gooseff, Michael N.; McKnight, Diane M.; Lyons, William B. and Saelens, Elsa. Unsteady flows control hydrologic turnover rates in Antarctic hyporheic zones [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract H41H-08, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Hydrologic turnover of the hyporheic zone (HZ) is the process of HZ flowpaths receiving water and solutes from the stream channel while simultaneously contributing water and solutes from the HZ back to the stream channel. The influence of hydrologic turnover on HZ solute storage depends on the relative magnitude of hyporheic exchange rates (i.e. physical transport) and biogeochemical reaction rates. Because both exchange rates and reaction rates are unsteady in natural systems, the availability of solutes in the HZ is controlled by the legacy of hydraulic and biological conditions. In this study, we quantify the influence of unsteady flows on hydrologic turnover of the HZ. We study a glacial melt stream in the McMurdo Dry Valleys of Antarctica (MDVs). The MDVs provide an ideal setting for investigating hydrologic and chemical storage characteristics of HZs, because nearly all streamflow is generated from glacier melt and the HZ is vertically bounded by continuous permafrost. A dense network of shallow groundwater wells and piezometers was installed along a 60-meter reach of Von Guerard Stream. 12 days of continuous water level data in each well was used to compute the magnitude and direction of 2D hydraulic gradients between the stream channel and lateral hyporheic aquifer. Piezometers were sampled daily for stable isotope abundances. The direction and magnitude of the cross-valley (CV), perpendicular to the thalweg, component of hydraulic gradients is sensitive to daily flood events and exhibits significant spatial heterogeneity. CV gradients are consistently oriented from the hyporheic aquifer towards the stream channel on 2 sections of the study reach, whereas CV gradients are consistently oriented from the stream channel towards the hyporheic aquifer on 1 section. Three sections show diel changes in orientation of CV gradients, coincident with the passage of daily flood events. During a 4-day period of low flows, the HZ is isotopically distinct from the stream channel. However, after only 2 days of high flows, the HZ becomes isotopically similar to the open channel. These results indicate that daily flood events control rates of hydrologic turnover and that complete flushing of the HZ can occur in less than 48 hours.

2017087044 Leblon, Brigitte (University of New Brunswick, Faculty of Forestry and Environmental Management, Fredericton, NB, Canada); Larocque, Armand; Ou, Chunping; Zhang, Yu; Webster, Kara and McLaughlin, Jim. Use of RADARSAT-2 SAR and LANDSAT-5 TM images; for permafrost feature distribution mapping [abstr.]: in 35th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 35, Abstract 2463, 2016. Meeting: 35th international geological congress, Aug. 27-Sept. 4, 2016, Cape Town, South Africa.

Over a discontinuous permafrost region located in the Hudson Bay Lowland (northern Ontario, Canada), we applied the Northern Ecosystem Soil Temperature (NEST) to map the distribution of permafrost conditions and their changes from the 1960s to the 2000s at high spatial resolution. Some of the model inputs were estimated based on land cover and surficial material maps derived from Landsat-5 TM and RADARSAT-2 SAR C-HH and C-HV images. By comparison to field observations, we were able to achieve an average accuracy of more than 90% for both the land cover and surficial material maps when both Landsat-5 TM and RADARSAT-2 SAR were used. The distribution maps of permafrost features (palsas and peat plateaux), the active layer thickness, and the depth of permafrost base show that the increases in mean annual air temperature (1.9°C) and precipitation (2.4%) since the 1960s has deepened the active layer by 20.5%, reduced the depth of permafrost base by 3.1%, but only reduced permafrost extent by 0.4% on average. Both last studies were funded by the Canadian Space Agency and a NSERC-NBIF Post-graduate Scholarship. Support to the field work has been provided by OMNR and De Beers Canada.

URL: http://www.americangeosciences.org/sites/default/files/igc/2463.pdf

2017085247 Pharr, J. D. (University of Texas at Austin, Department of Aerospace Engineering and Engineering Mechanics, Center for Space Research, Austin, TX); Holt, J. W.; Levy, J. S.; Nerozzi, S.; Peterson, E. I. and Stuurman, C. M. Internal structure and composition of the upper Galena Creek Rock Glacier, Wyoming, inferred from electromagnetic methods: in 47th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 47, Abstract no. 2809, illus., 4 ref., 2016. Meeting: 47th lunar and planetary science conference, March 21-25, 2016, Woodlands, TX.


2017085464 Belmonte, Louise Josefine (Danish Technical University, Civil Engineering, Arctic Technology Centre, Lyngby, Denmark); Foged, Niels and Ingeman-Nielsen, Thomas. Weathering of glaciogene marine clays from West Greenland [abstr.]: in Euroclay 2015; the quadrennial meeting of the European Clay Groups Association (ECGA) jointly with the annual meeting of the Clay Minerals Society (CMS) and in association with the International Natural Zeolite Association (INZA) and the Geological Society (Hillier, Stephen, prefacer), James Hutton Institute, Aberdeen, United Kingdom, p. 253, 9 ref., 2015. Meeting: Euroclay Edinburgh 2015, July 5-10, 2015, Edinburgh, United Kingdom.

2017086820 Kuznetsova, Elena (Norwegian University of Science and Technology, Trondheim, Norway) and Danielsen, Svein Willy. Fines from aggregate quarrying and its influence on frost protection in roads [abstr.]: in Euroclay 2015; the quadrennial meeting of the European Clay Groups Association (ECGA) jointly with the annual meeting of the Clay Minerals Society (CMS) and in association with the International Natural Zeolite Association (INZA) and the Geological Society (Hillier, Stephen, prefacer), James Hutton Institute, Aberdeen, United Kingdom, p. 398, 2015. Meeting: Euroclay Edinburgh 2015, July 5-10, 2015, Edinburgh, United Kingdom.

2017085557 Kuznetsova, Elena (Norwegian University of Science and Technology, Trondheim, Norway) and Rimma, Motenko. Opaline silica in cold climate [abstr.]: in Euroclay 2015; the quadrennial meeting of the European Clay Groups Association (ECGA) jointly with the annual meeting of the Clay Minerals Society (CMS) and in association with the International Natural Zeolite Association (INZA) and the Geological Society (Hillier, Stephen, prefacer), James Hutton Institute, Aberdeen, United Kingdom, p. 359, illus., 1 ref., 2015. Meeting: Euroclay Edinburgh 2015, July 5-10, 2015, Edinburgh, United Kingdom.

2017085558 Lessovaia, Sofia (Saint Petersburg State University, Institute of Earth Sciences, St. Petersburg, Russian Federation); Plötze, Michael and Polekhovsky, Yury. Weathering and soil formation on ultramafic rock (Polar Ural, Russia) [abstr.]: in Euroclay 2015; the quadrennial meeting of the European Clay Groups Association (ECGA) jointly with the annual meeting of the Clay Minerals Society (CMS) and in association with the International Natural Zeolite Association (INZA) and the Geological Society (Hillier, Stephen, prefacer), James Hutton Institute, Aberdeen, United Kingdom, p. 360, 2015. Meeting: Euroclay Edinburgh 2015, July 5-10, 2015, Edinburgh, United Kingdom.

2017090889 Cermak, Vladimir (Czech Academy of Sciences, Geophysical Institute, Prague, Czech Republic). Borehole climatology; principles, applications and results [abstr.]: in Proceedings; First assembly of the Latin-American and Caribbean Seismological Commission; Second Latin-American and Caribbean symposium of Geophysics; Third Latin-American congress of Seismology; Fourth Colombian congress of Seismology, Earth Sciences Research Journal, 18, Special Issue, p. 91, July 2014. WWW. Meeting: First assembly of the Latin-American and Caribbean Seismological Commission; Second Latin-American and Caribbean symposium of Geophysics; Third Latin-American congress of Seismology; Fourth Colombian congress of Seismology, July 23-25, 2014, Bogota, Colombia.

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