ALBERT

Description: ABSTRACT Climate warming has been observed for some time in the permafrost regions on the Qinghai-Tibet Plateau (QTP), China, resulting in active layer thickening, shrinkage or expansion of thermokarst lakes, and reduced permafrost extent. Little is known, however, about the hydrological processes near thermokarst lakes and their influences on lake development. We employed ground-penetrating radar (GPR) profiling, topographic mapping and drilling to explore the interaction between hydrological processes and thermokarst lake development at a site on the QTP. The GPR data and borehole water-level measurements revealed spatio-temporal variation of the frost table and soil water storage, and indicated the main direction of subsurface flow through soil on hillslopes near the lake. The measurements hinted at the self-organised formation of lateral flow channels at the thawing frost table near the lake. The ensuing recharge of the lake is balanced by drainage from the deepest end of the lake, down the topographic gradient, as ascertained by coring and lake bed mapping. Such a process-based qualitative understanding is crucial for assessing the impact of climate change, in conjunction with the local topography and hydrogeology, on the evolution of thermokarst lakes on the QTP. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT The Late Cenozoic alluvial deposits in the Tunka depression of the Baikal Rift Zone, Russia, contain wedge-shaped structures and involutions that provide valuable palaeogeographic information about the southern part of eastern Siberia. The structure of the unconsolidated host deposits, the shape and size of the deformation structures (wedge shaped, wave like or drop like) and the physical-mechanical properties of the sediments (particle size, density, porosity, water content and colour) point to a cryogenic origin of the deformation structures, as ice wedge pseudomorphs and cryoturbations, rather than an origin associated with seismic activity or sedimentation. The oldest pseudomorphs and cryoturbations developed during climate-warming periods of the subboreal climatic phase (3600–2600 years ago). Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Automated monitoring that combines time-lapse photography and sensor-based data logging can elucidate the environmental conditions, processes and rates of soil movement on remote periglacial hillslopes. This study presents the results from 5 years of time-lapse photography of soil movements, supported by time series data on frost heave, soil temperature, soil moisture and surface weather, on an alpine stone-banked lobe subject to frequent diurnal freeze-thaw cycles and deep seasonal frost on Mt Ainodake in the Japanese Alps. The lobe is dominated by biannual shallow soil movements, mostly originating from diurnal frost heave by needle ice or shallow ice lens formation and approximated by potential frost creep. The surface velocity shows a small interannual variation mainly reflecting snow conditions that control the spatio-temporal variability of freeze-thaw action, while it is independent of mean annual air temperature that influences the intensity of seasonal freezing. Occasional rill erosion occurs when the topmost frozen soil is rapidly thawed and super-saturated by intensive rainfall during seasonal thawing periods. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Non-invasive geophysical prospecting and a thermodynamic model were used to examine the structure, depth and lateral extent of the frozen core of a palsa near Lake Peerajärvi in northwest Finland. A simple thermodynamic model verified that the current climatic conditions in the study area allow sustainable palsa development. A ground penetrating radar (GPR) survey of the palsa under both winter and summer conditions revealed its internal structure and the size of its frozen core. GPR imaging in summer detected the upper peat/core boundary, and imaging in winter detected a deep reflector that probably represents the lower core boundary. This indicates that only a combined summer and winter GPR survey completely reveals the lateral and vertical extent of the frozen core of the palsa. The core underlies the active layer at a depth of ~ 0.6 m and extends to about 4 m depth. Its lateral extent is ~ 15 m x ~ 30 m. The presence of the frozen core could also be traced as minima in surface temperature and ground conductivity measurements. These field methods and thermodynamic models can be utilised in studies of climate impact on Arctic wetlands. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT The influence of permafrost growth and thaw on the evolution of ice-rich lowland terrain in the Koyukuk-Innoko region of interior Alaska is fundamental but poorly understood. To elucidate this influence, the cryostratigraphy and properties of perennially frozen sediments from three areas in this region are described and interpreted in terms of permafrost history. The upper part of the late Quaternary sediments at the Koyukuk and Innoko Flats comprise frozen organic soils up to 4.5 m thick underlain by ice-rich silt characterised by layered and reticulate cryostructures. The volume of visible segregated ice in silt locally reaches 50 per cent, with ice lenses up to 10 cm thick. A conceptual model of terrain evolution from the Late Pleistocene to the present day identifies four stages of yedoma degradation and five stages of subsequent permafrost aggradation-degradation: (1) partial thawing of the upper ice wedges and the formation of small shallow ponds in the troughs above the wedges; (2) formation of shallow thermokarst lakes above the polygons; (3) deepening of thermokarst lakes and yedoma degradation beneath the lakes; (4) complete thawing of yedoma beneath the lakes; (5) lake drainage; (6) peat accumulation; (7) permafrost aggradation in drained lake basins; (8) formation of permafrost plateaus; and (9) formation and expansion of a new generation of thermokarst features. These stages can occur in differing places and times, creating a highly complex mosaic of terrain conditions, complicating predictions of landscape response to future climatic changes or human impact. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Old Crow Flats is a 5600 km 2 glaciolacustrine plain that straddles the forest-tundra ecotone in northern Yukon. Continuous taiga corridors occur in the entrenched river valleys, where annual mean ground temperatures (T g ) at the depth of zero annual amplitude at two locations were −3.1 and −4.0ºC in 2013. On the Flats, the vegetation cover is patchy, and T g varied between −5.1 and −2.6ºC. Annual mean near-surface permafrost temperatures (T ps ) measured on the Flats between 2008 and 2011 in patches of taiga, tall shrubs and low shrubs were correlated with local snow depth. Snow depth was controlled by vegetation height if the snow supply was not limited, for example, where low shrubs and large lakes dominate the landscape. In this setting, snow depths and, hence, T ps in taiga patches were higher (−2.6 to −2.9ºC) than in the surrounding shrub vegetation (−3.5 to −5.5ºC). Where taiga patches were more extensive, redistributed snow was trapped at the patch edge and T ps in taiga was lower (−4.1 to −4.3ºC) than in the surrounding shrub patches (−3.2 to −3.6ºC). The permafrost temperature field is heterogeneous under patchy vegetation in the forest-tundra ecotone. Our data suggest that it is governed by both the snow-holding capacity of local vegetation patches and the spatial configuration of vegetation in the surrounding landscape, which controls snow supply. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Fluvial thermal erosion following ice breakups of the Lena River (Yakutia, Siberia) is a significant geomorphic process. During the initial stage of ice breakup, ice pushes up onto the river banks and produces large accumulations of ice and sediments that protect the islands’ heads against the mechanical and thermal effects of the river's flow. This initial stage is relatively short and terminates only a few days after breakup begins. In the second phase of flooding, after the river ice has melted, the island heads become free of ice. Hence, when water levels are high, the floodwaters are in sustained contact with the frozen banks of the islands, causing efficient thermal and mechanical erosion of their banks. Such erosion may also occur later in summer, if there is a second discharge peak. Between 2009 and 2012, the retreat of the banks of the river islands displayed high interannual variation that is attributed to the variability of the duration and timing of the flood season. For a given island, the annual rate varied from 2 m to 40 m and the duration of active thermal erosion of the frozen islands varied from 6 days to 39 days. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Arctic amplification of climate warming is intensifying the thaw and coastal erosion of the widespread and carbon-rich Siberian Ice Complex Deposits (ICD). Despite the potential for altering long-term carbon dynamics in the Arctic, the susceptibility of organic carbon (OC) to degradation as the ICD thaw is poorly characterised. This study identifies signs of OC degradation in three Siberian ICD regimes of coastal erosion through elemental, isotopic and molecular analyses. The degree of erosion appears to determine the extent of degradation. The moisture-limited and beach-protected ICD bluff near Buor-Khaya Cape, characterised by thermokarst mounds ( baydzherakhs ), represents a dormant regime with limited ongoing degradation. Conversely, the more exposed ICD scarps on eroding riverbanks (Olenek Channel, Lena Delta) and coastal slopes (Muostakh Island) showed more pronounced signs of ongoing OC decay. Different parameters suggest that degradation can partially explain the shift of the OC signature with 14 C age in the thawing ICD. Exposure time, degree of erosion, slope gradient and moisture conditions appear to be key factors determining the degradation propensity of OC in exposed ICD. These field results document the lability of OC in ICD upon thaw and illustrate the potential for transferring old OC into the rapidly cycling atmosphere-biosphere carbon pools. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Multi-method geophysical investigations, accompanied by microclimatic measurements and vegetation mapping, were performed at an undercooled scree slope near Schladming (Austria) in the eastern Alps in order to detect, map and monitor mountain permafrost. The study site, at an elevation of 990 m asl, is one of the lowest-lying examples of a cold, undercooled scree slope in the Alps. Geophysical measurements with electrical resistivity tomography, ground-penetrating radar and seismic refraction indicate the presence of several isolated areas of frozen ground over a full year, far below the regional lower limit of mountain permafrost. Frozen sediments identified at shallow depths (beneath 1–3 m) were 5–20 m thick and ice-rich. Near-surface temperatures at the foot of the scree slope were strongly influenced by pronounced cooling. Vegetation mapping showed a dominance of cryophilic plant species. The results suggest that the scree slope is strongly influenced by the interplay of vegetation cover, ground thermal regime and the distribution of frozen sediments. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Thawed soils in Antarctica represent organic carbon (C) reservoirs with great potential to increase the net losses of CO 2 to the atmosphere under climate change scenarios. This study spatially zones CO 2 emissions from soil and vegetation along a transect in front of the retreating margin of Ecology Glacier in Admiralty Bay, King George Island, South Shetlands, near the Polish Antarctic station Henryk Arctowski. Two experiments were carried out to determine soil respiration: (1) a transect of 150 measuring points spaced 1 m apart, statistically analysed with split moving windows, identified three regions with different patterns of CO 2 emissions; (2) a survey with three grids containing 60 sampling points, with a minimum distance between points of 0.30 m, totalling 2.7 × 1.5 m, in each of the identified locations. The survey showed that CO 2 emission rates decreased (from 2.38 to 0.00 µmol m -2 s -1 ) and soil temperature at 5 cm depth increased (from 1.9 to 7°C) near the glacier. The site farthest from the glacier provided an emission 3.5 times higher than the closest site. The spatial variability of CO 2 emissions decreased with distance from the glacier. Soil development and vegetation are identified as key drivers of CO 2 emissions. Soil formation and vegetation growth increased with longer exposure since deglaciation, leading to enhanced homogeneity of CO 2 emissions, independent of permafrost occurrence and stability. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Retrogressive thaw slumps are a dominant agent of geomorphic change in ice-rich permafrost landscapes and may remain active for decades. Previous studies of slump activity have used aerial photographs and/or high-resolution satellite images acquired at (multi)-decadal time intervals. This study investigates if the calculation of the three Tasselled Cap transformations (brightness, greenness and wetness) from a dense stack of Landsat Thematic Mapper and Enhanced Thematic Mapper+ images can be used to identify slump activity and map slump evolution at near-annual resolution. Results obtained from analysis of slumps in the Richardson Mountains-Peel Plateau region of the Northwest Territories, Canada, suggest that Tasselled Cap linear trend images effectively identify both active and stable thaw slumps. In addition, the analysis of single-date Tasselled Cap values at the pixel level can be used to map the initiation, growth and stabilisation of slumps at near-annual timescales. The Tasselled Cap trend analysis method therefore offers the possibility to: (1) map the distribution of thaw slumps by activity level (active, stable or relict); (2) derive headwall retreat rates at near-annual resolution; and (3) determine patterns of stabilisation and re-vegetation over the period of available Landsat images. The rich temporal information provided by Landsat analysis complements conventional, higher spatial resolution (but lower temporal resolution) methods that map slumps from pairs of aerial photographs and high-resolution satellite imagery. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Rock glaciers in the arid Bolivian Andes are potentially important water sources, but little is known about their spatial distribution and characteristics. We provide the first rock glacier inventory for the region (15–22°S), based on mapping using remote sensing data in Google Earth, supported by field validation. Of the 94 rock glaciers identified, 57 per cent were classified as active (containing ice) and the remaining as relict (not containing ice). The majority (87%) have a southerly aspect (SE, S and SW), and the rock glacier length and area averages were 500 m and 0.12 km 2 , respectively. We approximate the lower limit of permafrost to be at 4700 m in the Bolivian Andes, with the mean minimum altitude of rock glacier fronts estimated to be 4980 m for active rock glaciers, and about 100 m lower for relict rock glaciers. The inventory provides an important first step towards assessing the spatial distribution of regional permafrost as well as information to allow permafrost-based water resources in the Bolivian Andes to be understood against a backdrop of severe glacier recession. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Freeze/thaw simulations were performed for seven permafrost sites at the Kolyma Water Balance Station (KWBS), northeast Russia, using the hydrological model Hydrograph equipped with a heat transfer analytical solution that accounts for soil profile phase changes. The study sites include slopes and plateaus with thaw depths of 0.5 to 1.8 m. Landscape conditions are characterised as rocky talus, mountain tundra with dwarf tree brush, moss-lichen cover and sparse-growth forest or larch forest. Soil horizons are distinguished as moss-lichen cover, peat layer, clay with a high stone content and weathered clayey shale. Schematisation of soil-vegetation profiles and model parameters were developed for each landscape. Parameterised model output was verified using time series of observed active layer thickness for the period of 1950 to 1990. The simulated values agree well with the observed values at the study sites. The results suggest that the soil profile schematisation and model parameters, along with the proposed algorithm of heat transfer, effectively simulate active layer dynamics under various landscape conditions at the KWBS and are suitable for hydrological modelling in the permafrost zone. The modelling efforts and results are highly relevant because the natural conditions at the KWBS are representative of large areas of northeastern Russia. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Zonal alpine meadow is widespread in the source area of the Datong River, northeastern Qinghai-Tibet Plateau, China, and can be divided into typical meadow and swamp meadow, according to variations in the soil moisture content. A total of 56 measurements of the mean annual ground temperature (MAGT) revealed a significant difference in the MAGT of the two vegetation types. The measured MAGT varied from -2.8 to 0.46°C in the swamp meadow, and from -0.6 to 2.5°C in the typical meadow. Measurements of 0°C were found at approximately 3710 m asl and 3660 m asl in the typical meadow and swamp meadow, respectively. Using the measured MAGT and calculated topo-climatic parameters as dependent and independent variables, two statistical models of MAGT were constructed for each vegetation type. The calculated results were classified into different zones and types to determine the permafrost stability in different vegetated areas. Semi-stable permafrost (-3.0°C 〈MAGT ≤ -1.5°C) and transitory permafrost (-1.5°C 〈MAGT ≤ -0.5°C) were the two predominant permafrost types in the swamp meadow, whereas unstable permafrost (-0.5°C 〈MAGT ≤ +0.5°C) and seasonally frozen ground (MAGT 〉0.5°C) were the two main types in the typical meadow. The differences in permafrost temperatures and stability between the two vegetation types can be explained by the local environmental characteristics, including vegetation cover and soil water content. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Permafrost peatlands are both an important source of atmospheric CH 4 and a substantial sink for atmospheric CO 2 . Climate change can affect this balance, with higher temperatures resulting in the conversion of permafrost soils to wetlands and associated accelerated mineralisation and increased CH 4 emission. To better understand the impact of such processes on methanogen populations, we investigated the anaerobic decay of soil carbon in a low Arctic, discontinuous permafrost peatland. Cores were collected monthly from sedge and Sphagnum mires in north Sweden during the summer of 2006. We determined CH 4 concentrations and production potentials, together with variations in the size of the methanogenic community as indicated by concentrations of archaeal lipid biomarkers (phosphorylated archaeol, archaeol and hydroxyarchaeol). Concentrations of methanogen biomarkers generally were higher at the sedge site, increased with depth for all sites and months, and were usually below the detection limits in shallow (〈10 cm) Sphagnum peat. The distribution of biomarkers reflects the strong influence of water table depth on anaerobic conditions and methanogen populations, while differences in biomarker concentrations can be explained by differences in vegetation cover and pH. However, methanogen populations inferred from biomarker data show a decoupling from in-situ CH 4 production over the season and from CH 4 production potential, suggesting that other factors such as the availability of labile organic substrates can influence methanogen abundance. Archaeal lipid biomarkers appear to offer a potential new means to investigate permafrost biogeochemical processes but the interpretation of signals remains complex. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Large slope failures in steep alpine bedrock present significant geological hazards. Ice segregation is thought to be one of the mechanisms involved in high-mountain bedrock fracture but has not been reproduced experimentally in hard, intact rock. Here, we report results from a 3 month freezing experiment that aimed to reproduce ice-lens growth at the interface between the active layer and permafrost in a 15 cm cube of hard, intact rock (Arolla gneiss). Monitoring of acoustic emissions (AEs) recorded the propagation of microcracks horizontally through the block, resulting in a continuous and thick macrocrack near the base of the artificial active layer. Microcracking occurred within an approximate temperature range of −0.5 °C to −2.7 °C, consistent with ice segregation theory. Hypocentres of recorded AE events were concentrated in a 40 mm thick band between depths of 4.5 and 8 cm in the block. The band approximately coincides with the frozen fringe and indicates that ice segregation can induce micro- and macrocracking in gneiss. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Geophysical measurements were carried out in six boreholes at three periglacial talus slopes in the Swiss Alps in order to determine the talus structure and the geological and permafrost stratigraphy. These are important elements of interpretation of the palaeoclimatic significance of Alpine talus slopes. This study combined three nuclear well logging methods. Natural radioactivity of rocks and ice-rich permafrost were determined by using natural gamma-ray logs through the lack of radioactivity of massive ice. Quantification of the ice content in frozen layers and the air content in unfrozen layers by variations in bulk density was provided by the application of gamma-gamma logs. Neutron-thermal neutron logs were used to calculate the water content, linked with the porosity of the formation. Combination of the three logs allowed three-phase models (rock, ice and air/water) of the subsurface to be obtained. Results show that the air content decreases with depth because of the increasing in-situ stresses that cause compression of the rock debris and the existence of a fine matrix filling the voids. Calculation of the ice content variations shows that talus slopes are frequently partially saturated with ice or, at most, slightly supersaturated with ice. All three logs provide complementary information on the progressive infilling of the voids with depth and the occurrence of ice-rich layers. A similar trend in ice content and the apparent porosity was highlighted by the joint application of gamma-gamma and neutron-neutron logs, which provide a mirror image of these two parameters. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Northern Tien Shan is characterised by a distinct periglacial belt that contains many rock glaciers with an area of 1 km 2 or more. To investigate the reason for their large size and variable occurrence, we analysed a representative subsample of the rock glaciers with respect to topographic and climatic variables. A simple permafrost model indicates that the rock glaciers originate in the zone where permafrost occurrence is very likely and some large rock glaciers flow down to elevations where permafrost is unlikely to exist outside the rock glaciers themselves. Correlation and multiple regression analyses revealed that the occurrence and characteristics of the rock glaciers can only be partly explained by the characteristics of the contributing area (e.g. its area or the headwall height). The correlation is greater with talus-type rock glaciers than with moraine-type rock glaciers. The climate can explain the general occurrence of rock glaciers but not their specific characteristics. It is hypothesised that the main reason for the specific distribution and characteristics of these large rock glaciers relates to the interaction with polythermal glaciers, topographic characteristics, intensive weathering and rock avalanches triggered by seismic activity. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Rockglaciers often feature a prominent furrow-and-ridge topography. Previous studies suggest that this morphology develops due to longitudinal compressive flow during rockglacier creep; however, no satisfactory mechanical/physical model has been provided explaining both the observed characteristic wavelength and the growth rate necessary to amplify the structure to its final size. Our study identifies viscous buckle folding as the dominant process forming the furrow-and-ridge morphology on rockglaciers. Buckle folding is the mechanical response of layered viscous media to layer-parallel compression. The Murtèl rockglacier (Switzerland) exhibits a spectacular furrow-and-ridge morphology and is chosen as a case study. Its well-determined internal structure can be approximated by two layers: the upper 3–5 m thick active layer consisting mainly of rock boulders and fragments above a thick, almost pure, ice layer, both assumed to exhibit viscous rheology. We analysed a high-resolution digital elevation model of the Murtèl rockglacier using analytical buckle-folding expressions, which provide quantitative relationships between the observed wavelength, the layer thickness and the effective viscosity ratio between the folded layer and the underlying ice. Based on this geometrical and rheological information, we developed a finite-element model to simulate dynamical gravity-driven two-dimensional rockglacier flow. A buckling instability of the upper layer develops and amplifies self-consistently, reproducing several key features of the Murtèl rockglacier (wavelength, amplitude and distribution of the furrow-and-ridge morphology), as well as the quasi-parabolic deformation profile observed in boreholes. Comparing our model with published surface flow velocities constrains the time necessary to produce the furrow-and-ridge morphology to about 1000–1500 years. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Mountain permafrost is highly susceptible to the effects of climate warming, because its thermal regime is close to 0 °C. This can be evidenced by the acceleration of average annual creep rates of several rock glaciers in the Swiss Alps, whereby some exhibit even more extreme signs of degradation. Measurements obtained from a borehole drilled from a relatively flat area on a rock glacier, below the Furggwanghorn peak, Turtmanntal (Switzerland), showed positive mean annual values of ground temperatures in the active layer over two hydrological years, from 1 October 2010 to 30 September 2012. The thermal conditions in this borehole were much warmer than those measured at the same time in other boreholes in the same rock glacier. A test pit excavated in the active layer close to this borehole, and instrumented with thermistors, indicated similar thermal conditions. It was hypothesised that the thick snow cover that accumulated on the flat area during winter and an existing supra-permafrost talik were responsible for the warm thermal regime, given the relevant meteorological inputs over this period. The degradation of the rock glacier in this flat area was probably driven by a high summer heat flux into the rock glacier, which could not be reversed in winter due to a thick insulating snow layer that accumulated from October onwards. A coupled one-dimensional numerical model, based on SNOWPACK and HYDRUS, was developed to interpret the thermal behaviour in the active layer. The resulting numerical analysis was validated, showing that the simulated ground temperatures agreed well with measured values at various depths. The heat loss from the ground was found to be very small during the winter, due to insulation by autumnal snowfalls, whereas the heat flux to the ground had been relatively high in recent summers. The mean positive heat flux to the supra-permafrost talik was calculated to be 1.75 Wm -2 over the 2 year period, which is sufficient to cause considerable ice melt. Furthermore, water flow in the supra-permafrost talik appeared to limit temperature variations in the active layer to 0.12 °C in summer. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Although warming air temperatures are contributing to permafrost degradation across the circumpolar zone, understanding of permafrost and environmental feedbacks to climate change is limited. Palsas can be used as indicators of permafrost stability given their sensitivity to changes in temperature and precipitation. However, field observations on the effects of vegetation cover are needed to compare permafrost dynamics of wooded and non-wooded palsas. This study examined the influence of vegetation on the soil thermal regime of wooded palsas covered by black spruce trees and non-wooded palsas covered by shrubs in discontinuous permafrost of the Boniface River area of northern Quebec, Canada. It investigated the effects of organic layer thickness, vegetation and snow depth on soil temperature at 50 cm and 100 cm depths for over 2 years. The coldest summer soil temperatures were associated with thick organic layers. In summer, soil temperatures were colder under spruce stands than under shrub canopies and forest openings, whereas the thick snow cover in spruce stands and forest openings maintained warmer winter soil temperatures than under shrub canopies. Well-defined zero-curtain periods during fall and spring could be an early indicator of current changes in the soil thermal regime of palsas. At the northern edge of discontinuous permafrost, non-wooded palsas have the most favourable conditions for permafrost stability, because heterogeneous vegetation cover on wooded palsas promotes snow trapping and lateral heat transfer. Vegetation types should be considered in estimating future rates of permafrost degradation. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Wedge-ice volume (WIV) is a key factor in assessing the response of ice-rich permafrost landscapes to thaw and in quantifying deep permafrost soil carbon inventories. Here, we present a method for calculating WIV in late Pleistocene Yedoma deposits and Holocene thermokarst basin deposits at four study areas in Siberia and Alaska. Ice-wedge polygons and thermokarst mound (baydzherakh) patterns were mapped on different landscape units using very high-resolution (0.5 m/pixel) satellite imagery (WorldView-1 and GeoEye-1). In a geographic information system (GIS) environment, Thiessen polygons were automatically created to reconstruct relict ice-wedge polygonal networks, and field and published data on ice-wedge dimensions were used to generate three-dimensional subsurface models that distinguish between epi- and syngenetic ice-wedge geometry. The results reveal significant variations in WIV between the study sites and within certain terrain units. Calculated maximum WIV ranges from 31.4 to 63.2 vol% for Yedoma deposits and from 6.6 to 13.2 vol% for thermokarst basin deposits. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Application of novel hydrological methods for assessing runoff generation in remote northern landscapes is necessary to identify the consequences of climate variability and change. In Old Crow Flats, a lake-rich thermokarst landscape in northern Yukon Territory (Canada), local land users have concerns over the effects of recent lake drainage and fluctuating river discharge on their traditional way of life. In the absence of hydrometric stations, we evaluate the utility of isotopic monitoring of the lower Old Crow River, which is fed by several tributaries and drains the flats, for tracking runoff generation. Isotopic ‘snapshots’ obtained from 2007, 2008 and 2009 during the recession limb of the spring freshet hydrograph provided characteristic patterns of deuterium excess (d-excess) along the Old Crow River. River sampling in June 2007 captured a pulse of evaporatively enriched lake water originating from a rainfall-triggered catastrophic lake drainage event, identified by decreased d-excess values. June 2008 was marked by negligible variability in d-excess values along the same reach of the river, consistent with minimal export of lake waters after a winter of below-normal snow accumulation. In contrast, rising d-excess values along the study reach in June 2009 indicate enhanced rainfall-generated runoff. River isotope sampling could be used to monitor spatial and temporal variability in runoff generation processes in the Old Crow Flats and other northern lake-rich landscapes drained by rivers. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Environmental factors that affect the activity-inactivity variation of periglacial features may differ from those factors that control the distributional patterns of active features. To explore this potential difference, a statistically based modelling approach and comprehensive data on active and inactive cryoturbation and solifluction features from a subarctic area of Finnish Lapland are investigated at a landscape scale. In the cryoturbation modelling, vegetation abundance is the most important environmental variable explaining both the activity-inactivity variation and the distribution of active sites. The next most important variables are soil moisture and (micro)climatological conditions in the activity modelling, and slope angle and ground material in the distribution modelling. For solifluction, the key variables determining the activity-inactivity variation are mean annual air temperature and mean maximum snow depth, whereas vegetation abundance and slope angle control the distribution of active sites. Comparison between the environmental conditions of active and inactive periglacial features may provide new insights into activity-environment relationships, which in turn are valuable when the effects of climate change on periglacial processes are explored. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT The paucity of reports on relict thermal contraction crack polygons in the mid-Atlantic Coastal Plain and many other areas in eastern North America has hampered our understanding of the extent and nature of past permafrost south of the Late Wisconsinan glacial limit. Examination of Google Earth™ imagery revealed orthogonal to hexagonal polygons, mostly 10–30 m in diameter, at more than 160 sites in sand and gravel deposits in southern New Jersey and the Delmarva Peninsula. The polygons are interpreted to indicate that continuous permafrost extended to 38.5°N in a zone more than 250 km wide to the south of the glacial limit under a mean annual air temperature of ≤ −6°C probably during the Late Wisconsinan. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Thaw ponds on the Arctic Coastal Plain of Alaska are productive ecosystems, providing habitat and food resources for many fish and bird species. Permafrost in this region creates unique pond morphologies: deep troughs, shallow low-centred polygons (LCPs) and larger coalescent ponds. By monitoring seasonal trends in pond volume and chemistry, we evaluated whether pond morphology and size affect water temperature and desiccation, and nitrogen (N) and phosphorus (P) fluxes. Evaporation was the largest early-summer water flux in all pond types. LCPs dried quickly and displayed high early-summer nutrient concentrations and losses. Troughs consistently received solute-rich subsurface inflows, which accounted for 12 to 42 per cent of their volume and may explain higher P in the troughs. N to P ratios increased and ammonium concentrations decreased with pond volume, suggesting that P and inorganic N availability may limit ecosystem productivity in older, larger ponds. Arctic summer temperatures will likely increase in the future, which may accelerate mid-summer desiccation. Given their morphology, troughs may remain wet, become warmer and derive greater nutrient loads from their thawing banks. Overall, seasonal- to decadal-scale warming may increase ecosystem productivity in troughs relative to other Arctic Coastal Plain ponds. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Microbial permafrost communities play an important role in carbon cycling and greenhouse gas fluxes. Despite the importance of these processes, there is a lack of knowledge about how environmental and climatic changes affect the abundance and composition of microorganisms. Here, we investigated the changing distribution of permafrost microorganisms in response to climate and lake-level changes. The permafrost core was drilled at the near shore of Lake El'gygytgyn, Far East Russian Arctic, and a combined microbiological and lipid biomarker approach was applied. The lower part of the permafrost core, deposited under subaquatic conditions, contains only small amounts of microbial signals; total organic carbon (TOC) content is sparse. After exposure of the site to subaerial conditions during the Allerød, the abundance of Bacteria and Archaea started to increase and the lake-level change is especially evidenced by the relative proportion of archaeal biomarkers. This increase is supported by rising bacterial and archaeal 16S ribosomal ribonucleic acid (rRNA) gene copy numbers and significant amounts of TOC during the late Allerød. After a small decrease during the colder Younger Dryas, the TOC content and the microbial signals strongly increase during the Holocene, presumably stimulated by pedogenesis. The occurrence of intact phospholipids indicates the presence of living microorganisms in these deposits. Our data suggest that methane formation is mainly expected for the subaerial interval, especially the Holocene where methanogens were identified by fingerprinting. This study emphasises the role of the uppermost permafrost deposits as a hotspot of carbon cycling in arctic environments, especially in the light of expected future global warming. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Permafrost underlying forested north-facing slopes and seasonally frozen ground underlying mountain steppes on south-facing slopes co-exist within a small mountain basin that represents the most general landscape type in northern central Mongolia. A 5-year time series of hydro-meteorological parameters on these slopes is presented in order to identify the factors controlling ground temperature regimes. A thick organic layer (0.2–0.4 m) beneath the forest on a north-facing slope impedes the effects of summer air temperature on the ground, and the forest canopy strongly blocks downward shortwave radiation during summer. Active layer thickness was determined by summer warmth. The mountain steppe on a dry south-facing slope receives a large amount of downward shortwave radiation compared to an adjacent forested slope, and therefore the surface temperature exceeds air temperature during summer, leading to a warm soil profile. In winter, snow cover was the main factor controlling interannual variations in the thickness of seasonally frozen ground. The onset of soil thawing in the forested area was later than in the mountain steppe, even though soil freezing began simultaneously in both areas. Overall, the forest cover keeps the ground cool and allows permafrost to persist in this region. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT To improve hydrologic modelling in permafrost zones, we present a new hydrological modelling approach to simulate ground thaw/freeze processes and the consequent contribution to the hydrologic response. We apply several techniques to simplify the differential equations of heat transfer in soil profiles, from which we derive an analytical solution that accounts for phase changes in soil and includes specific approaches for heat transfer and phase-dependent soil and snow conductivity. Use of soil horizon physical properties as the model parameters allows robust assessment relative to landscape characteristics. Following integration of these methods within the Hydrograph hydrological model, verification was conducted against a time series of soil temperature observed at the Kolyma Water Balance Station in the continuous permafrost zone of northeast Russia. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT About 30 per cent of the mountain soils with permafrost have an active layer depth (ALD) of less than 1 or 2 m and, therefore, can be classified as Cryosols. Mountain Cryosols have a total area of approximately 1.26 million km 2 and account for approximately 12 per cent of the Cryosols worldwide. An ALD of less than 2 m appears to occur only where the mean annual air temperature is 〈 -6 °C. There is a negative correlation (R = 0.86; p 〈0.001) between latitude (°N) and elevation (m) at which the ALD occurs at less than 2 m. Mountain Cryosols are most abundant in the western Cordillera of the USA and Canada (360 000 km 2 ), the Qinghai-Tibet Plateau of China (280 000 km 2 ), Greenland (185 000 km 2 ), the Yablonoi-Sayan-Stanovoi Mountains of Russia (153 000 km 2 ) and the Ural Mountains of Russia (90 000 km 2 ). Despite that the Qinghai-Tibet Plateau contains 70 per cent of the world's mountain permafrost, only about 20 per cent of the soils are Cryosols, because they are limited to areas above 5100 m asl. Cryosols occur in the central Andes above 4900 m asl and in the southern Andes above 1000 m asl. Potential impacts of recent climate warming on mountain permafrost and Cryosols are discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Cryoturbation in high-latitude soils is crucial for the long-term cycling of elements, but the rates of soil motion are poorly constrained. Here, we test whether the rate of frost creep, soil erosion and vertical soil mixing in frost boils can be estimated using short-lived radionuclides ( 137 Cs and 210 Pb). We find a small-scale variation in 137 Cs and 210 Pb inventories in the lower levels of the eroding regions of frost boils in comparison to the expected depositional sites; hence, the distribution of the radionuclides appears to reflect a lateral transport of atmospheric fallout from the centre of the boil (inner domain) towards the surrounding soil (outer domain). 14 C dating of the soil indicates that fallout of 137 Cs was mobile in the soil and that 210 Pb moved with the soil matrix. A soil creep model and a surface soil erosion model are derived and applied to the lateral and vertical distributions of 210 Pb in the frost boil. Both models predict the expected trajectories of soil motion and provide rates of creep, erosion and mixing at a mm yr −1 to cm yr −1 scale. The distribution of 210 Pb provides new insights about the processes and rates of soil mass movement in frost boils, if sound mass-balance models are applied. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Rock glaciers near the Andean mountains of central and northwestern Argentina provide an important supply of water for agriculture, but data on their number, size, geographic distribution and altitudinal range are poorly known. Here, we provide the first detailed rock glacier inventory of the Valles Calchaquíes region of Salta, Argentina, based on 2.5 m x 2.5 m resolution Advanced Land Observing Satellite PRISM (Panchromatic Remote-sensing Instruments for Stereo Mapping) satellite images. Rock glacier outlines were manually digitised and a total of 488 were identified, which cover a total area of c . 59 km 2 . The lower limits of intact and fossil rock glaciers are at c . 4300 m asl and 4100 m asl, respectively. Because rock glaciers are protected by law in Argentina, the inventory provides an important basis for political decision-making about water resources and for further periglacial and environmental studies in this region. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT The warming and degradation of mountain permafrost within alpine areas is an important process influencing the stability of steep slopes and rock faces. In the mountains of southern Norway (Jotunheimen), an increase in ground temperatures has been recorded during the last 12 years, and modelling studies suggest the possible degradation of most mountain permafrost during the 21 st century. To better estimate the thermal state of permafrost in steep rock walls in Norway, five temperature loggers were installed in 2009 and 2010, measuring the near-surface rock wall temperatures in vertical rock faces. Surface temperatures in rock walls in Norway are on average higher than the ambient air temperature, by about 1 °C in shaded faces to more than 3 °C in faces with other aspects. An aspect dependency of rock wall temperatures is mainly visible during summer, with deviations of up to 4 °C between north- and south-facing walls. Based on a 1D transient heat flow model, the active-layer thickness at the study sites was estimated to be in the range of 3 m to 5 m at 2300 m asl and 1600 m asl, respectively. As a first-order approximation, a spatial regression model based on elevation and potential incoming short-wave radiation was used to estimate the lower limit and distribution of rock wall permafrost under present-day conditions and for a scenario with average air temperatures increased by 2 °C. Today, the lower limit ranges from 1200–1300 m asl to 1600–1700 m asl in north- and south-facing rock walls, respectively. With a warming of 2 °C, the lower limit would increase to about 1700 m and 2100 m, respectively, which corresponds to a loss of 70 per cent of the rock walls underlain by permafrost today in the study area, where more than half of the rock walls potentially containing permafrost are situated below 1800 m asl. Copyright © 2014 John Wiley & Sons, Ltd.

Description: ABSTRACT Permafrost maps are needed for infrastructure planning, climatic change adaptation strategies and northern development but often lack sufficient detail for these purposes. The high-resolution (30 x 30 m grid cells) probability model for the southern Yukon and northern British Columbia presented in this paper (regional model) is a combination of seven local empirical-statistical models, each developed from basal temperature of snow measurements in winter and ground-truthing of frozen-ground presence in summer. The models were blended using a distance-decay power approach to generate a map of permafrost probability over an area of almost 500 000 km 2 between 59°N and 65°N. The result is broadly similar to previous permafrost maps with an average permafrost probability of 58 per cent for the region as a whole. There are notable differences in detail, however, because the main predictive variable used in the local models is equivalent elevation, which incorporates the effects of gentle or inverted surface lapse rates in the forest zone. Most of the region shows permafrost distribution patterns that are non-linear, resembling those from continental areas such as Mongolia. Only the southwestern area shows a similar mountain permafrost distribution to that in the European Alps with a well-defined lower limit and a linear increase in probability with elevation. The results of the modelling can be presented on paper using traditional classifications into permafrost zones but given the level of detail, they will be more useful as an interactive online map. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Four retrogressive thaw slumps (RTS) located on Herschel Island and the Yukon coast (King Point) in the western Canadian Arctic were investigated to compare the environmental, sedimentological and geochemical setting and characteristics of zones in active and stabilised slumps and at undisturbed sites. In general, the slope, sedimentology and biogeochemistry of stabilised and undisturbed zones differ, independent of their age or location. Organic carbon contents were lower in slumps than in the surrounding tundra, and the density and compaction of slump sediments were much greater. Radiocarbon dating showed that RTS were likely to have been active around 300 a BP and are undergoing a similar period of increased activity now. This cycle is thought to be controlled more by local geometry, cryostratigraphy and the rate of coastal erosion than by variation in summer temperatures. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Rock instability is believed to be causally linked to permafrost degradation, but it is difficult to demonstrate this directly because of the short record of slope failures in high mountains. While abductive scientific reasoning of ‘increasing permafrost-related instability’ based on the short time frame of recorded rockfall events in high mountains is still difficult, our deductive systemic understanding points toward a strong process linkage between permafrost degradation and rock instability. Enhanced technical understanding of coupled thermo-hydro-mechanical processes and systemic geomorphic understanding of rock slope adjustment in space and over (reaction/relaxation) time are required to accurately predict hazards associated with the impact of climate change on permafrost in bedrock. We identify research needs in four major areas and at the interfaces between them: rock temperature measurement and modelling; remote sensing of rock walls; process understanding of rock mass instability; and flow propagation models of rock-ice avalanches. This short communication identifies key interfaces between research directions to gain a better understanding of trajectories of destabilisation in time and space. We propose coordinated systemic research with respect to scale dependent and transient thermal behaviour, coupled thermo-hydro-mechanical understanding, enhanced remote inventorying of rock wall instability and integrated approaches for a better understanding and modelling of mixed avalanches. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Russia's West Siberian Lowland (WSL) contains the most extensive peatlands on Earth with many underlain by permafrost. We present a new database of 12 705 measurements of vertical water content and bulk soil properties from 98 permafrost and non-permafrost cores collected in raised bogs and peat plateaus across the region, together with in-situ measurements of surface moisture and thaw depth, botanical descriptions of dominant surface vegetation species assemblage, and field notes. Data analyses reveal significant contrasts ( p  〈 0.01 to p  〈 0.0001) between permafrost and non-permafrost sites. On average, permafrost WSL peatlands exhibit drier surfaces, shallower depth, lower organic matter content and higher bulk density than do non-permafrost sites. Peat bulk density and ash-free density increase with depth for non-permafrost but not for permafrost sites. Gravimetric water content averages 92.0% near the surface and 89.3% at depth in non-permafrost, but 81.6% and 85.4%, respectively, in permafrost, suggesting that the disappearance of permafrost could produce moister surfaces across the WSL. GIS extrapolation of these results suggests that WSL peatlands may contain ~1200 km 3 of water and ice, a large storage equivalent to ~2-m average liquid water depth and approximately three times the total annual flow in the Ob' River. A global estimate of ~6900-km 3 subsurface water storage for all northern peatlands suggests a volume comparable to or greater than the total water storage in northern lakes. The database is freely available as supplementary material for scientific use. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Assessing possible permafrost degradation related to engineering projects, climate change and land use change is of critical importance for protecting the environment and in developing sustainable designs for vital infrastructure in cold regions. A major challenge in modelling the future degradation of permafrost is finding ways to constrain changes in the upper thermal boundary condition over time and space at appropriate scales. Here, we report on an approach designed to predict time series of air, ground surface and shallow ground temperatures at a spatial scale on the order of 10 2  m 2 for engineering design of a railway or highway project. The approach uses a regional-scale atmospheric model to downscale global climate model output, and then stepwise multiple regression to develop an equation that provides a best-fit prediction of site-specific observational data using bilinearly interpolated output from the atmospheric model. This approach bridges the scale difference between atmospheric climate models and permafrost thermal models, and allows for a wider range of factors to be used in predicting the thermal boundary condition. For a research site located in Beiluhe, China, close to the Qinghai-Tibet Railway, a comparison of model predictions with observational data not used in the construction of the model shows that this method can be used with a high degree of accuracy to determine the upper boundary condition for a permafrost thermal model. Once a model is constructed, it can be used to predict future changes in boundary condition parameters under different greenhouse emission scenarios for climate change. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Thermokarst lakes on the Qinghai-Tibet Plateau cause considerable thermal disturbance to the surrounding permafrost, giving rise to anomalous ground-temperature conditions and open-talik formation below some lakes. Using in situ data and information from monitoring of a representative thermokarst lake in the Beiluhe Basin, this study simulates the rate of talik development beneath the lake, the time taken for an open talik to form, and the rate of permafrost lateral thaw after open-talik formation. The simulation uses a simplified two-dimensional unsteady finite-element model for heat transfer with phase change under a cylindrical coordinate system. The results indicate that a bowl-shaped talik forms under the lake and that the talik thickness increases substantially over time. An open talik forms below the lake 733 years after the lake formed. The average maximum thaw rates at the top and bottom of permafrost beneath the lake before the open talik forms are 5.8 cm year -1 and 0.7 cm year -1 , respectively. By 1100 years after lake formation, permafrost beneath the central deep pool and shallow nearshore zone of the lake thaws completely and the heat-source effect caused by the lake becomes very limited. The volume of the open talik beneath the lake still increases gradually with time 1500 years after lake formation, but the increase is very limited. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Surface hydrology is an important aspect of northern environments on account of the thermal influence of water on permafrost. In this study, we demonstrate the ability of light detection and ranging (LiDAR) to map wet terrain within an area of discontinuous permafrost adjacent to the Northwest Territories Highway 3, located west of Yellowknife, Canada. Wet terrain was identified from LiDAR intensity measurements beneath forest canopies and across vegetated surfaces, including peatlands, fens, flooded black spruce and birch forests, and terrain adjacent to the highway embankment. Surface water pathways representing hydrological connections between water bodies and wet terrain were also identified at locations otherwise indiscernible from optical imagery. Statistical separability between terrain types, and thus the ability to map them, was improved by integrating LiDAR all-return and bare-earth intensity with colour orthophotos. The average classification accuracy for wet terrain was 93 per cent. These results indicate that LiDAR intensity can be used for local-scale mapping of wet terrain, as required by northern engineers and scientists. Future integration of LiDAR intensity and elevation measurements may be used to assess changes in surface hydrological conditions impacting permafrost. Copyright © Her Majesty the Queen in Right of Canada 2012.

Description: ABSTRACT To assess the role of thermal contraction-crack polygons (sublimation polygons) in modulating sublimation of buried glacier ice in Antarctica, we applied a 2D numerical model using COMSOL Multiphysics that calculates the rate and spatial variability of vapour diffusion through porous media. Specifically, we examined vapour transport through Granite drift, a dry supraglacial till marked with thermal contraction-crack polygons that rests on glacier ice reportedly ≥8-million years in age. The model results show that sublimation varies with drift texture and surface topography. Initially, the rates are highest beneath relatively coarse-grained sand-wedge deposits at polygon margins, creating deep, surface troughs. As troughs approach ~1-m depth, the cooler atmospheric and soil temperatures that arise from solar shielding reduce the rates of ice sublimation to levels below that at polygon centres, preventing runaway ice loss at polygon margins. Including the effects of a salt-cemented horizon at 10 − 15-cm depth (porosity 20%) and a rocky surface pavement (75% ground coverage), our modelled ice loss at polygon centres, for example, is 0.022 mm a −1 , an order of magnitude lower than previous estimates (0.14 mm a −1 ). This finding highlights the importance of including field-based data for drift texture, topography and microclimate variation in modelling ice sublimation. The results also suggest that stable conditions (no ice loss) at polygon centres are possible with either a 1.9°C decrease in mean annual atmospheric temperature or a 12 per cent increase in mean annual relative humidity. These results indicate that the preservation of buried, multi-million-year-old ice is plausible in the coldest and driest regions of Antarctica. Copyright © 2011 John Wiley & Sons, Ltd.

Description: ABSTRACT Four retrogressive thaw slumps (RTS) located on Herschel Island and the Yukon coast (King Point) in the western Canadian Arctic were investigated to compare the environmental, sedimentological and geochemical setting and characteristics of zones in active and stabilised slumps and at undisturbed sites. In general, the slope, sedimentology and biogeochemistry of stabilised and undisturbed zones differ, independent of their age or location. Organic carbon contents were lower in slumps than in the surrounding tundra, and the density and compaction of slump sediments were much greater. Radiocarbon dating showed that RTS were likely to have been active around 300 a BP and are undergoing a similar period of increased activity now. This cycle is thought to be controlled more by local geometry, cryostratigraphy and the rate of coastal erosion than by variation in summer temperatures. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Rock instability is believed to be causally linked to permafrost degradation, but it is difficult to demonstrate this directly because of the short record of slope failures in high mountains. While abductive scientific reasoning of ‘increasing permafrost-related instability’ based on the short time frame of recorded rockfall events in high mountains is still difficult, our deductive systemic understanding points toward a strong process linkage between permafrost degradation and rock instability. Enhanced technical understanding of coupled thermo-hydro-mechanical processes and systemic geomorphic understanding of rock slope adjustment in space and over (reaction/relaxation) time are required to accurately predict hazards associated with the impact of climate change on permafrost in bedrock. We identify research needs in four major areas and at the interfaces between them: rock temperature measurement and modelling; remote sensing of rock walls; process understanding of rock mass instability; and flow propagation models of rock-ice avalanches. This short communication identifies key interfaces between research directions to gain a better understanding of trajectories of destabilisation in time and space. We propose coordinated systemic research with respect to scale dependent and transient thermal behaviour, coupled thermo-hydro-mechanical understanding, enhanced remote inventorying of rock wall instability and integrated approaches for a better understanding and modelling of mixed avalanches. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Russia's West Siberian Lowland (WSL) contains the most extensive peatlands on Earth with many underlain by permafrost. We present a new database of 12 705 measurements of vertical water content and bulk soil properties from 98 permafrost and non-permafrost cores collected in raised bogs and peat plateaus across the region, together with in-situ measurements of surface moisture and thaw depth, botanical descriptions of dominant surface vegetation species assemblage, and field notes. Data analyses reveal significant contrasts ( p  〈 0.01 to p  〈 0.0001) between permafrost and non-permafrost sites. On average, permafrost WSL peatlands exhibit drier surfaces, shallower depth, lower organic matter content and higher bulk density than do non-permafrost sites. Peat bulk density and ash-free density increase with depth for non-permafrost but not for permafrost sites. Gravimetric water content averages 92.0% near the surface and 89.3% at depth in non-permafrost, but 81.6% and 85.4%, respectively, in permafrost, suggesting that the disappearance of permafrost could produce moister surfaces across the WSL. GIS extrapolation of these results suggests that WSL peatlands may contain ~1200 km 3 of water and ice, a large storage equivalent to ~2-m average liquid water depth and approximately three times the total annual flow in the Ob' River. A global estimate of ~6900-km 3 subsurface water storage for all northern peatlands suggests a volume comparable to or greater than the total water storage in northern lakes. The database is freely available as supplementary material for scientific use at http://onlinelibrary.wiley.com/doi/10.1002/ppp.735/suppinfo . Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT A series of systematic shear tests were performed using an inclinable shear box containing a coarse-grained active layer overlying a fine-grained permafrost layer, a stratigraphy observed in the field. The angle of mobilised interface friction Φ mob was determined as depending on the grain size of the active layer and the permafrost, the water content of the active layer and the ice content of the permafrost. Φ mob was found to be 8° lower for ice-free permafrost compared to permafrost containing ice. This result implies a possible long-term decrease of active-layer slope stability on scree slopes in Alpine permafrost terrain under warming conditions. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Thermal conditions in seven rock glaciers (RGs) in the Retezat Mountains were examined using ground surface temperature, the bottom temperature of snow (BTS) and late-summer water temperature at springs. Direct current resistivity profiles were used to detect ice-rich layers and to estimate RG volume. These parameters were supplemented by measurements of RG surface movement and morphological characteristics in order to develop a RG typology. RG activity is suggested based on BTS values and the mean annual surface temperature. The lower altitudinal limits for permafrost occurrence and the activity of RGs were found to be at 2000 m and 2100 m asl, respectively. The two highest and most active RGs are younger than 8 ka and developed following a cold climate event at 8.2 ka when a last isolated glacial episode occurred in their hosting cirques, while the remaining RGs date from 11.5–8.7 ka. Calculated rockwall denudation rates to produce these forms range from 0.8–1.1 mm/yr. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Extensive fields of vegetated, dome-shaped earth hummocks 5–35 cm high and typically 80–200 cm in diameter occur on slopes of up to 15° at elevations of 320–440 m asl on Dartmoor, SW England, but are limited to terrain underlain by metasedimentary rocks and dolerite, and absent from granite areas. Hummocks occur within archaeological sites, implying formation within the last ~ 3000 years and ruling out development over permafrost. The hummocks are composed of frost-susceptible silty soil (modal grain size 10–100 µm) with occasional clasts, but exhibit no evidence for cryoturbation or diapirism. Hummock size and spacing are fairly consistent at particular sites but vary between sites. Hummock age, distribution and characteristics are incompatible with non-frost action origins and most proposed frost action origins (cryostatic pressure, soil circulation, permafrost aggradation, soil injection), but regular spacing and granulometry favour initiation by differential frost heave under conditions of periodic shallow (0.2–0.4 m) seasonal ground freezing. We suggest that hummock growth may reflect migration of silt in advance of inclined freezing planes until equilibrium is achieved with soil loss down hummock sides. Our results confirm that hummock formation by frost action occurs on silty soils in humid cool temperate climates with only limited seasonal frost penetration. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Thermal conditions in seven rock glaciers (RGs) in the Retezat Mountains were examined using ground surface temperature, the bottom temperature of snow (BTS) and late-summer water temperature at springs. Direct current resistivity profiles were used to detect ice-rich layers and to estimate RG volume. These parameters were supplemented by measurements of RG surface movement and morphological characteristics in order to develop a RG typology. RG activity is suggested based on BTS values and the mean annual surface temperature. The lower altitudinal limits for permafrost occurrence and the activity of RGs were found to be at 2000 m and 2100 m asl, respectively. The two highest and most active RGs are younger than 8 ka and developed following a cold climate event at 8.2 ka when a last isolated glacial episode occurred in their hosting cirques, while the remaining RGs date from 11.5–8.7 ka. Calculated rockwall denudation rates to produce these forms range from 0.8–1.1 mm/yr. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Perennial frost mounds are present near the edges of ponds located on the terrace between the mountain flank and a valley-bottom lake in the Akkol valley of the Russian Altai Mountains. These mounds are 10–50 m in diameter and 3–6 m in height. We describe one mound, identified as a lithalsa, which had been eroded so as to expose almost its entire vertical cross-section, revealing its internal structure. The frozen core consisted mainly of soil segments suspended in reticulate ice lenses with a mean thickness of 11–48 mm and a maximum thickness of about 160 mm. The shapes of the soil segments matched their neighbours. Other features included soil segments suspended in the ice veins shaped like ‘En echelon gash veins’, and the presence of a radial structure of ice-rich and sediment-rich frozen bands. These features all suggest the greater importance of a differential stress field during heaving of the mound and after ice segregation, compared to the thermal gradient and water supply. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT The physical and chemical characteristics of two High Arctic lakes were investigated at the Cape Bounty Arctic Watershed Observatory on Melville Island, in response to large active-layer detachments generated by extreme summer temperatures in 2007. In the two years following the permafrost disturbances, there was an elevated loading of total dissolved solids into both lakes, but no concomitant increase in suspended sediment levels. The physical dynamics of one lake were significantly altered by an internal sediment input, which was not directly related to watershed processes. The results indicate that localised permafrost disturbance in the watersheds resulted in changes to chemical conditions in these relatively deep, large lakes, while increased sediment transport from disturbances did not have a sustained impact. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Mid-winter wet avalanche cycles in High Arctic Svalbard occurred during January 2010 and March 2011, allowing studies of slush and wet slab avalanche deposits. Both cycles represented extreme events in magnitude and frequency and were caused by the passage of low-pressure atmospheric systems with positive air temperatures, high wind speeds and 100-year record monthly rainfall. Slush avalanches were confined to river-cut gorges, with low starting-zone inclinations, and deposits consisting of flow lobes and levées. Wet slab avalanches were not confined topographically, started anywhere on open mountain slopes and displayed tongue-shaped debris deposits. During both of the two wet avalanche periods analysed, snowpack conditions favoured the release of slush avalanches, as the snowpack consisted of a coarse-grained middle section above a water-impermeable ice layer. Such snowpack conditions are typical for central Svalbard. The resulting slush and wet slab avalanches were extreme in their size and runout distances, crossing frequently used snowmobile tracks at 20 locations and posing a threat to traffic and infrastructure. Four additional potential large-scale slush avalanche periods were identified from analysis of the meteorological record from Longyearbyen (1912–2011). They cluster in the mid to early 1990s, with comparable meteorological conditions to the January 2010 and March 2011 wet avalanche cycles. It is concluded that the frequency and duration of low-pressure weather systems are the dominant controls on wet snow avalanches, and that mean snow season air temperature (October–May) is of little importance. Copyright © 2011 John Wiley & Sons, Ltd.

Description: ABSTRACT Perennially flowing groundwater discharges along a 15-km section of the Fishing Branch River, Yukon causing open water during winter and numerous discrete springs near Bear Cave Mountain. Groundwater flow occurs in karstified marine carbonate rocks as well as in alluvial river talik(s). The P CO2 and δ 13 C indicate groundwater dissolves CO 2 during recharge in organic soils and weathers limestone in the aquifer. These analyses show three groundwater chemistry groups and variability in surface water chemistry. The variations in water chemistry are related to differences in the rocks exposed in the recharge area. The δ 18 O and δ 2 H results show that groundwater represents approximately the annual average of precipitation based on samples collected in the region. Noble gases were used to determine that the recharge temperature lies between 0 and 5 °C which suggests that recharge happens during the summer. Groundwater ages, calculated using 3 H- 3 He dating, were found to be between 0 and 17.7 years. River discharge was measured during spring and summer under different water-level conditions. Winter baseflow was calculated based on summer discharge measurements and the width of the river channel in winter. Although river flow decreases in winter, groundwater discharge maintains open water. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Permafrost maps are needed for infrastructure planning, climatic change adaptation strategies and northern development but often lack sufficient detail for these purposes. The high-resolution (30 x 30 m grid cells) probability model for the southern Yukon and northern British Columbia presented in this paper (regional model) is a combination of seven local empirical-statistical models, each developed from basal temperature of snow measurements in winter and ground-truthing of frozen-ground presence in summer. The models were blended using a distance-decay power approach to generate a map of permafrost probability over an area of almost 500 000 km 2 between 59°N and 65°N. The result is broadly similar to previous permafrost maps with an average permafrost probability of 58 per cent for the region as a whole. There are notable differences in detail, however, because the main predictive variable used in the local models is equivalent elevation, which incorporates the effects of gentle or inverted surface lapse rates in the forest zone. Most of the region shows permafrost distribution patterns that are non-linear, resembling those from continental areas such as Mongolia. Only the southwestern area shows a similar mountain permafrost distribution to that in the European Alps with a well-defined lower limit and a linear increase in probability with elevation. The results of the modelling can be presented on paper using traditional classifications into permafrost zones but given the level of detail, they will be more useful as an interactive online map. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Extensive fields of vegetated, dome-shaped earth hummocks 5–35 cm high and typically 80–200 cm in diameter occur on slopes of up to 15° at elevations of 320–440 m asl on Dartmoor, SW England, but are limited to terrain underlain by metasedimentary rocks and dolerite, and absent from granite areas. Hummocks occur within archaeological sites, implying formation within the last ~ 3000 years and ruling out development over permafrost. The hummocks are composed of frost-susceptible silty soil (modal grain size 10–100 µm) with occasional clasts, but exhibit no evidence for cryoturbation or diapirism. Hummock size and spacing are fairly consistent at particular sites but vary between sites. Hummock age, distribution and characteristics are incompatible with non-frost action origins and most proposed frost action origins (cryostatic pressure, soil circulation, permafrost aggradation, soil injection), but regular spacing and granulometry favour initiation by differential frost heave under conditions of periodic shallow (0.2–0.4 m) seasonal ground freezing. We suggest that hummock growth may reflect migration of silt in advance of inclined freezing planes until equilibrium is achieved with soil loss down hummock sides. Our results confirm that hummock formation by frost action occurs on silty soils in humid cool temperate climates with only limited seasonal frost penetration. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Pocket forms several decimetres in diameter, 0.5–1.5 m deep and infilled mainly with glaciogenic sands, silts and clays of Saalian age are commonly developed on the top of the karstified chalk massif of the Lublin Upland, eastern Poland. Analysis of lithofacies, particle-size distribution and micromorphology of three pocket infills in the Chełm chalk quarry reveals a prominent clay cortex between the host chalk and the glaciogenic infill and suggests that periglacial processes have played a considerable role in the formation of the pockets and in the redistribution of their primary glaciogenic infill. A conceptual model for epikarst morphogenesis for the chalk karst of Lublin Upland is proposed, involving three stages. Stage I: In the absence of permafrost, precipitation water infiltrates unconsolidated glaciogenic deposits. Stage II: Periglacial transformation with underlying permafrost. Primary cryoturbation structures became protokarst forms, and then epikarst forms. Stage III: Degradation of the permafrost, with increased carbonate dissolution and development of a clay karst cortex. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Small patterned-ground features (PGFs) in the Arctic have unique soil properties that vary with latitude and may greatly affect tundra biogeochemistry. Because nitrogen availability can strongly limit arctic vegetation growth, we examined how soil nitrogen transformations differ between PGFs and the surrounding inter-PGF tundra along an arctic latitudinal gradient. We collected soils at eight sites from the Alaskan Low Arctic to the Canadian High Arctic. The soils were incubated for 21 days at 9 °C and 15 °C and analysed for changes in total inorganic nitrogen, nitrate and extractable organic nitrogen (EON). We found greater nitrogen immobilisation in the surrounding inter-PGF soils than in the PGF soils. Along the latitudinal gradient, differences in net nitrogen mineralisation and EON cycling between PGF and inter-PGF soils were strongly influenced by the presence of a pH boundary within the Low Arctic and the transition between the High and Low Arctic, with greater immobilisation in the nonacidic and Low Arctic sites, respectively. Incubation temperature affected EON flux but did not affect net nitrogen mineralisation or nitrification. These results show that spatial heterogeneity at several scales can influence soil nitrogen dynamics, and is therefore an important influence on arctic ecosystem function. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT The debris cones known as Amorphous Glacier and Boulder Clay are located in an ice-free region in Northern Victoria Land, Antarctica, and differ in their isotopic composition, mechanisms of ice distribution, geological formation and age. However, to date it is not known if bacterial community profiles within ice and permafrost can be established for these environments, and then whether glaciological differences between the two areas would be reflected in the bacterial community composition. In order to gather first evidence for the bacterial communities in these glacial zones, we carried out terminal-restriction fragment length polymorphism (T-RFLP) analysis on the 16S rRNA gene using a universal bacterial amplification protocol on two permafrost cores. The DNA yields from ice-core samples ranged from 0.29 ng μL -1 in Amorphous Glacier to 88 ng μL -1 in Boulder Clay. Bray-Curtis cluster analysis suggested Boulder Clay bacterial profiles were similar to each other, but cluster separately from the Amorphous Glacier bacterial profile. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Phase-contrast synchrotron micro-computed tomography (μCT) is well suited to studying the microstructure of frozen soil. To take advantage of the high-resolution three-dimensional images that can be generated using μCT, a specialised in-situ rig was designed and commissioned. This miniature temperature-controlled oedometer is capable of controlling soil sample thermal gradients and applying uniaxial deformation while measuring stress. This system was used to apply repeated freeze-thaw cycles to water-saturated samples of Leighton Buzzard sand, Reigate sand and spherical glass ballotini (an idealised soil). High-resolution images were obtained using a monochromatic, parallel beam of x-rays generated on Beamline I12 of the Diamond synchrotron. Cracking in the ice was directly measured utilising the phase-contrast fringes generated by ice-air interfaces. Examination of these images revealed two modes of crack formation in the ice phase of frozen soil: micro-cracks between soil particles, and longer, well-developed cracks that follow along ice-soil particle boundaries and span across the ice between particles. Both crack types were orientated parallel to the freezing front (normal to the heat flow), affecting both the frozen soils' mechanical behaviour, and we hypothesise that these cracks are potential initiation sites for ice lens development. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT This study investigates and compares active layer characteristics determined from ground temperature measurements at ten borehole sites in various types of Alpine permafrost terrain. Active layer thickness ( ALT ) remained fairly constant at the individual boreholes over the past five to 14 years, but was highly variable among the sites due to local terrain characteristics. To allow intra-site comparisons, a characteristic depth within the active layer was determined for each site. The temperature series either measured or interpolated for that depth were used to investigate different thermal stages during the annual thawing and refreezing cycle. The relation between air temperature thawing-degree days and ALT was investigated on an annual, seasonal and daily basis. The results show that at least daily data are required to establish the relevant characteristics of active layer development. Periods of slow advance of the thaw plane, interpreted as being due to the presence of ice-bearing layers within the active layer, are particularly important to the final ALT . Rapid active layer deepening, however, can occur due to the formation of taliks caused by lateral thermal disturbances below the active layer. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Soil organic carbon (SOC) contents were examined beneath two grassland vegetation communities and cold desert sites in permafrost areas of the central western part of the Qinghai-Tibet Plateau. Mean SOC stocks in the top 150 cm were 7.73 kg m -2 for Stipa roborowskyi communities and 3.72 kg m -2 for Carex moorcroftii communities, but only 1.84 kg m -2 for cold alpine desert. More than 80 per cent of SOC stocks beneath the grasslands were in the top 100 cm. Correlation analyses showed that SOC stocks in the top 150 cm are linked to soil moisture content, and the vertical distribution of SOC is mainly affected by depth and soil moisture content. Moisture content and vegetation communities are therefore important factors associated with SOC content in this cold, arid area, while active-layer thickness, vegetation cover and topographical factors play non-significant roles in SOC distribution. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Perennial frost mounds are present near the edges of ponds located on the terrace between the mountain flank and a valley-bottom lake in the Akkol valley of the Russian Altai Mountains. These mounds are 10–50 m in diameter and 3–6 m in height. We describe one mound, identified as a lithalsa, which had been eroded so as to expose almost its entire vertical cross-section, revealing its internal structure. The frozen core consisted mainly of soil segments suspended in reticulate ice lenses with a mean thickness of 11–48 mm and a maximum thickness of about 160 mm. The shapes of the soil segments matched their neighbours. Other features included soil segments suspended in the ice veins shaped like ‘En echelon gash veins’, and the presence of a radial structure of ice-rich and sediment-rich frozen bands. These features all suggest the greater importance of a differential stress field during heaving of the mound and after ice segregation, compared to the thermal gradient and water supply. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT The physical and chemical characteristics of two High Arctic lakes were investigated at the Cape Bounty Arctic Watershed Observatory on Melville Island, in response to large active-layer detachments generated by extreme summer temperatures in 2007. In the two years following the permafrost disturbances, there was an elevated loading of total dissolved solids into both lakes, but no concomitant increase in suspended sediment levels. The physical dynamics of one lake were significantly altered by an internal sediment input, which was not directly related to watershed processes. The results indicate that localised permafrost disturbance in the watersheds resulted in changes to chemical conditions in these relatively deep, large lakes, while increased sediment transport from disturbances did not have a sustained impact. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT Perennially flowing groundwater discharges along a 15-km section of the Fishing Branch River, Yukon causing open water during winter and numerous discrete springs near Bear Cave Mountain. Groundwater flow occurs in karstified marine carbonate rocks as well as in alluvial river talik(s). The P CO2 and δ 13 C indicate groundwater dissolves CO 2 during recharge in organic soils and weathers limestone in the aquifer. These analyses show three groundwater chemistry groups and variability in surface water chemistry. The variations in water chemistry are related to differences in the rocks exposed in the recharge area. The δ 18 O and δ 2 H results show that groundwater represents approximately the annual average of precipitation based on samples collected in the region. Noble gases were used to determine that the recharge temperature lies between 0 and 5 °C which suggests that recharge happens during the summer. Groundwater ages, calculated using 3 H- 3 He dating, were found to be between 0 and 17.7 years. River discharge was measured during spring and summer under different water-level conditions. Winter baseflow was calculated based on summer discharge measurements and the width of the river channel in winter. Although river flow decreases in winter, groundwater discharge maintains open water. Copyright © 2012 John Wiley & Sons, Ltd.

Description: ABSTRACT A series of systematic shear tests were performed using an inclinable shear box containing a coarse-grained active layer overlying a fine-grained permafrost layer, a stratigraphy observed in the field. The angle of mobilised interface friction Φ mob was determined as depending on the grain size of the active layer and the permafrost, the water content of the active layer and the ice content of the permafrost. Φ mob was found to be 8° lower for ice-free permafrost compared to permafrost containing ice. This result implies a possible long-term decrease of active-layer slope stability on scree slopes in Alpine permafrost terrain under warming conditions. Copyright © 2012 John Wiley & Sons, Ltd.