14002303 Brown, Jerry, 50th anniversary of the First international conference on Permafrost: Permafrost and Periglacial Processes, 24(4), p. 263-267, illus. incl. 2 tables, December 2013.
14002310 Christiansen, Hanne H. (International Permafrost Association, International). Report from the International Permafrost Association; high level of permafrost interdisciplinary research activity: Permafrost and Periglacial Processes, 24(4), p. 347-349, illus., December 2013.
14002304 Galushkin, Yu. I. (Lomonosow Moscow State University, Earth Science Museum, Moscow, Russian Federation); Sitar, K. A. and Frolov, S. V. Basin modelling of temperature and heat flow distributions and permafrost evolution, Urengoy and Kuyumbinskaya areas, Siberia: Permafrost and Periglacial Processes, 24(4), p. 268-285, illus. incl. 4 tables, sketch maps, 45 ref., December 2013.
The thermal history and permafrost evolution in the Urengoy area of the West Siberian basin and in the Kuyumbinskaya area of the Siberian platform during the Pliocene-Quaternary were reconstructed numerically in a forward model from 3.4 Ma using the software package FROST, part of the basin modelling system GALO. Calculations suggest that variations in rock composition with depth strongly influenced permafrost evolution. Rock temperatures decreased by 15-20°C within the upper 1500 m of the sedimentary sequence because of climate cooling in the Pliocene-Holocene. The effect of cooling is greater in the Kuyumbinskaya area, which has a thinner sedimentary cover, than in the more northern Urengoy area. The model estimates permafrost depth and the stability zone of methane gas hydrate. An increase in salt content in porewater from 1 to 30 g/l lowers the melting temperature of ice by 2°C and decreases permafrost thickness by almost 100 m. The change in shape of the unfrozen water curve W(T), dependent upon the lithological composition of sedimentary rocks, strongly influences the numerical estimations of permafrost depth. The modelling demonstrates that permafrost thickness and temperature and heat flow distributions with depth in the basins calculated with climate variations of the last 50 ka differ significantly from the more accurate values obtained with climate variations during the last 200 ka, 1 Ma or 3.4 Ma. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002305 Kitover, D. C. (Vrije Universiteit Amsterdam, Amsterdam, Netherlands); Balen, R. T.; Roche, D. M.; Vandenberghe, J. and Renssen, H. New estimates of permafrost evolution during the last 21 k years in Eurasia using numerical modelling: Permafrost and Periglacial Processes, 24(4), p. 286-303, illus. incl. 3 tables, sketch map, 110 ref., December 2013.
The evolution of past permafrost since the Last Glacial Maximum (LGM) is simulated using the Vrije Universiteit Amsterdam Permafrost (VAMPER) model. This method is different from a proxy-based approach which translates reconstructed air temperatures to estimate past permafrost extent and thickness. First, a sensitivity analysis was performed to assess the behaviour of the model. Then five case studies within Eurasia were performed using mean annual ground surface temperatures derived from an Earth system model as the surface forcing. In Central and West Siberia, the simulated LGM permafrost thicknesses of 730-940 m and 365-445 m, respectively, agree well with previous estimates. The LGM and present-day estimates for South Russia (9-15 m) are underestimated, which is likely due to a highly simplified land-atmosphere coupling. In West and Central Europe, however, the VAMPER model was not able to produce permafrost during LGM conditions, which is due to previously recognised biases of the Earth system model. A supplementary simulation was then performed, resulting in an LGM permafrost thickness estimate of 260-320 m. Average thawing rates are on the order of 1 to 3 cm/yr except for Central Siberia, where permafrost thawed at rates of 0.3 to 0.4 cm/yr. Overall results of these simulations provide a basis for future improvement in modelling the permafrost-climate relationship over millennia. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002308 Lilleoren, Karianne S. (University of Oslo, Department of Geosciences, Oslo, Norway); Etzelmuller, Bernd; Gartner-Roer, Isabelle; Kaab, Andreas; Westermann, Sebastian and Guethmundsson, Agust. The distribution, thermal characteristics and dynamics of permafrost in Trollaskagi, northern Iceland, as inferred from the distribution of rock glaciers and ice-cored moraines: Permafrost and Periglacial Processes, 24(4), p. 322-335, illus. incl. 3 tables, sketch maps, 82 ref., December 2013.
Knowledge of the characteristics and spatial distribution of permafrost in Iceland is important to understanding slope stability, climate change impacts and palaeo-glaciology. The permafrost distribution there, however, is poorly constrained. The presence of rock glaciers and stable ice-cored moraines in mountain settings relates to permafrost, making such landforms indicators of present or past permafrost. This study combines recently published aerial photographs (2002-07), radar interferometry based on Advanced Land Observing Satellite phased array type L-band synthetic aperture radar (ALOS PALSAR) data (2007), land surface temperatures estimated from moderate-resolution imaging spectroradiometer satellite data (MODIS; 2003-10) and field mapping to re-examine the permafrost distribution, thermal characteristics and dynamics on the Trollaskagi peninsula. An inventory of 265 landforms, mostly active or inactive (intact), categorised them by genesis and activity, the latter independently investigated by PALSAR interferometry. Intact landforms are mainly glacigenic, occurring as moraine-derived rock glaciers or ice-cored moraines. Their dominant orientation is between north and northeast, suggesting that topography and exposure influence their present-day formation. Permafrost landforms exist at all elevations on the Trollaskagi peninsula, with intact landforms at high elevations and relict landforms reaching down to sea level. Rock glaciers at sea level may imply early deglaciation of northern Iceland. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002246 Dafflon, Baptiste (Lawrence Berkeley National Laboratory, Berkeley, CA); Hubbard, Susan S.; Ulrich, Craig and Peterson, John E. Electrical conductivity imaging of active layer and permafrost in an arctic ecosystem, through advanced inversion of electromagnetic induction data: Vadose Zone Journal, 12(4), 19 p., illus. incl. charts, 56 ref., November 2013.
A novel approach has been developed to estimate the subsurface electrical conductivity distribution from electromagnetic induction data and evaluate influence of prior constraints, data information content, and solution non-uniqueness. Its application to an Arctic ecosystem enabled imaging of the variability of active layer and permafrost properties. Characterizing the spatial variability of active layer and permafrost properties is critical for parameterizing process-rich models that simulate feedbacks from Arctic ecosystem to a changing climate. Because of the sensitivity of electrical conductivity (EC) measurements to moisture content, salinity, and freeze state and the ease of collecting electromagnetic induction (EMI) data with portable tools (e.g., EM38, GEM2, or DUALEM) over large regions, EMI surveys hold great potential for Arctic ecosystem characterization. However, estimation of subsurface EC distribution from such data is challenging because of the insufficient amount of information such data provide towards finding a unique solution. The non-uniqueness problem is often approached by fixing inversion constraints and initial models without a clear understanding of their possible effects on the obtained results. Here we developed a direct search method, which involves a grid-based evaluation of one-dimensional layered model parameters, to estimate EC distribution from EMI data and evaluate the influence of prior constraints, data information content, and solution non-uniqueness. We applied the new method to EMI data acquired in Barrow, AK, as part of the Department of Energy Next-Generation Ecosystem Experiments (DOE NGEE-Arctic). Results demonstrate the success of the developed approach for estimating models that reproduce recorded data within a specified range of uncertainty at each measurement location, as well as the value of different types of constraints. Importantly, the method can be used to quickly investigate the need for and effects of different priors at numerous measurement locations, since the time-consuming simulation of the EMI signals from the multidimensional search grid is performed only once.
14005861 Gao, Xiang (Massachusetts Institute of Technology, Joint Program on the Science and Policy of Global Change, Cambridge, MA); Shlosser, C. Adam; Sokolov, Andrei; Anthony, Katey Walter; Zhuang, Qianlai and Kicklighter, David. Permafrost degradation and methane; low risk of biogeochemical climate-warming feedback: Environmental Research Letters, 8(3), Paper No. 035014, illus. incl. 1 table, 31 ref., September 2013.
Climate change and permafrost thaw have been suggested to increase high latitude methane emissions that could potentially represent a strong feedback to the climate system. Using an integrated earth-system model framework, we examine the degradation of near-surface permafrost, temporal dynamics of inundation (lakes and wetlands) induced by hydro-climatic change, subsequent methane emission, and potential climate feedback. We find that increases in atmospheric CH4 and its radiative forcing, which result from the thawed, inundated emission sources, are small, particularly when weighed against human emissions. The additional warming, across the range of climate policy and uncertainties in the climate-system response, would be no greater than 0.1°C by 2100. Further, for this temperature feedback to be doubled (to approximately 0.2°C) by 2100, at least a 25-fold increase in the methane emission that results from the estimated permafrost degradation would be required. Overall, this biogeochemical global climate-warming feedback is relatively small whether or not humans choose to constrain global emissions. Copyright 2013 IOP Publishing Ltd
14005872 Hiyama, Tetsuya (Research Institute for Humanity and Nature, Kyoto, Japan); Asai, Kazuyoshi; Kolesnikov, Alexander B.; Gagarin, Leonid A. and Shepelev, Victor V. Estimation of the residence time of permafrost groundwater in the middle of the Lena River basin, eastern Siberia: Environmental Research Letters, 8(3), Paper No. 035040, illus. incl. 3 tables, sketch map, 17 ref., September 2013.
Detection of changes in the hydrological cycles of permafrost regions is a critical issue in hydrology. Better understanding of groundwater dynamics in permafrost regions is needed to assess the vulnerability of the cryolithic water environment to changing climate. However, little is known about the age of groundwater in the Siberian Arctic region. In order to determine the residence time of permafrost groundwater in eastern Siberia, transient tracers including tritium (3H), chlorofluorocarbons (CFCs), and sulfur hexafluoride (SF6) were used to analyze a mixture of supra-permafrost and intra-permafrost groundwater in the middle of the Lena River basin. Tritium analyses showed that the concentration ranges from 1.0 to 16.8 TU, and the apparent age of groundwater ranged from around 1 to 55 years. One of the spring waters appeared to contain more than 90% water recharged by precipitation before the 1960s nuclear testing era, and the water could be partly sourced from thawing permafrost. Comparisons of apparent groundwater ages estimated from different tracers imply that 3H and CFC-12 are the most applicable to groundwater vulnerability assessments in this region. Because the apparent age is a mixture of those from supra-permafrost and intra-permafrost groundwater, further analysis would be required to assess the contribution ratio of the two types of groundwater. Copyright 2013 IOP Publishing Ltd
14005870 Jafarov, E. E. (University of Colorado at Boulder, National Snow and Ice Data Center, Boulder, CO); Romanovsky, V. E.; Genet, H.; McGuire, A. D. and Marchenko, S. S. The effects of fire on the thermal stability of permafrost in lowland and upland black spruce forests of interior Alaska in a changing climate: Environmental Research Letters, 8(3), Paper No. 035030, illus. incl. 1 table, 61 ref., September 2013.
Fire is an important factor controlling the composition and thickness of the organic layer in the black spruce forest ecosystems of interior Alaska. Fire that burns the organic layer can trigger dramatic changes in the underlying permafrost, leading to accelerated ground thawing within a relatively short time. In this study, we addressed the following questions. (1) Which factors determine post-fire ground temperature dynamics in lowland and upland black spruce forests? (2) What levels of burn severity will cause irreversible permafrost degradation in these ecosystems? We evaluated these questions in a transient modeling-sensitivity analysis framework to assess the sensitivity of permafrost to climate, burn severity, soil organic layer thickness, and soil moisture content in lowland (with thick organic layers, ~80 cm) and upland (with thin organic layers, ~30 cm) black spruce ecosystems. The results indicate that climate warming accompanied by fire disturbance could significantly accelerate permafrost degradation. In upland black spruce forest, permafrost could completely degrade in an 18 m soil column within 120 years of a severe fire in an unchanging climate. In contrast, in a lowland black spruce forest, permafrost is more resilient to disturbance and can persist under a combination of moderate burn severity and climate warming. Copyright 2013 IOP Publishing Ltd
14005867 Johansson, Margareta (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Callaghan, Terry V.; Bosio, Julia; Akerman, H. Jonas; Jackowicz-Korczynski, Marcin and Christensen, Torben R. Rapid responses of permafrost and vegetation to experimentally increased snow cover in sub-arctic Sweden: Environmental Research Letters, 8(3), Paper No. 035025, illus. incl. 1 table, 58 ref., September 2013.
Increased snow depth already observed, and that predicted for the future are of critical importance to many geophysical and biological processes as well as human activities. The future characteristics of sub-arctic landscapes where permafrost is particularly vulnerable will depend on complex interactions between snow cover, vegetation and permafrost. An experimental manipulation was, therefore, set up on a lowland peat plateau with permafrost, in northernmost Sweden, to simulate projected future increases in winter precipitation and to study their effects on permafrost and vegetation. After seven years of treatment, statistically significant differences between manipulated and control plots were found in mean winter ground temperatures, which were 1.5°C higher in manipulated plots. During the winter, a difference in minimum temperatures of up to 9°C higher could be found in individual manipulated plots compared with control plots. Active layer thicknesses increased at the manipulated plots by almost 20% compared with the control plots and a mean surface subsidence of 24 cm was recorded in the manipulated plots compared to 5 cm in the control plots. The graminoid Eriophorum vaginatum has expanded in the manipulated plots and the vegetation remained green longer in the season. Copyright 2013 IOP Publishing Ltd
14005869 Johnson, Kristofer D. (University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Harden, Jennifer W.; McGuire, A. David; Clark, Mark; Yuan, Fengming and Finley, Andrew O. Permafrost and organic layer interactions over a climate gradient in a discontinuous permafrost zone: Environmental Research Letters, 8(3), Paper No. 035028, illus. incl. 1 table, sketch map, 49 ref., September 2013.
Permafrost is tightly coupled to the organic soil layer, an interaction that mediates permafrost degradation in response to regional warming. We analyzed changes in permafrost occurrence and organic layer thickness (OLT) using more than 3000 soil pedons across a mean annual temperature (MAT) gradient. Cause and effect relationships between permafrost probability (PF), OLT, and other topographic factors were investigated using structural equation modeling in a multi-group analysis. Groups were defined by slope, soil texture type, and shallow (<28 cm) versus deep organic (>&eq;28 cm) layers. The probability of observing permafrost sharply increased by 0.32 for every 10-cm OLT increase in shallow OLT soils (OLTs) due to an insulation effect, but PF decreased in deep OLT soils (OLTd) by 0.06 for every 10-cm increase. Across the MAT gradient, PF in sandy soils varied little, but PF in loamy and silty soils decreased substantially from cooler to warmer temperatures. The change in OLT was more heterogeneous across soil texture types-in some there was no change while in others OLTs soils thinned and/or OLTd soils thickened at warmer locations. Furthermore, when soil organic carbon was estimated using a relationship with thickness, the average increase in carbon in OLTd soils was almost four times greater compared to the average decrease in carbon in OLTs soils across all soil types. If soils follow a trajectory of warming that mimics the spatial gradients found today, then heterogeneities of permafrost degradation and organic layer thinning and thickening should be considered in the regional carbon balance. Copyright 2013 IOP Publishing Ltd
14005863 Jorgenson, M. Torre (Alaska Ecoscience, Fairbanks, AK); Harden, Jennifer; Kanevskiy, Mikhail; O'Donnell, Jonathan; Wickland, Kim; Ewing, Stephanie; Manies, Kristen; Zhuang, Qianlai; Shur, Yuri; Striegl, Robert and Koch, Josh. Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes: Environmental Research Letters, 8(3), Paper No. 035017, illus. incl. sketch map, 63 ref., September 2013.
The diversity of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost histories, present enormous challenges for assessing how vegetation, water and soil carbon may respond to climate change in boreal regions. To address this complexity, we used a chronosequence approach to assess changes in vegetation composition, water storage and soil organic carbon (SOC) stocks along successional gradients within four landscapes: (1) rocky uplands on ice-poor hillside colluvium, (2) silty uplands on extremely ice-rich loess, (3) gravelly-sandy lowlands on ice-poor eolian sand and (4) peaty-silty lowlands on thick ice-rich peat deposits over reworked lowland loess. In rocky uplands, after fire permafrost thawed rapidly due to low ice contents, soils became well drained and SOC stocks decreased slightly. In silty uplands, after fire permafrost persisted, soils remained saturated and SOC decreased slightly. In gravelly-sandy lowlands where permafrost persisted in drier forest soils, loss of deeper permafrost around lakes has allowed recent widespread drainage of lakes that has exposed limnic material with high SOC to aerobic decomposition. In peaty-silty lowlands, 2-4 m of thaw settlement led to fragmented drainage patterns in isolated thermokarst bogs and flooding of soils, and surface soils accumulated new bog peat. We were not able to detect SOC changes in deeper soils, however, due to high variability. Complicated soil stratigraphy revealed that permafrost has repeatedly aggraded and degraded in all landscapes during the Holocene, although in silty uplands only the upper permafrost was affected. Overall, permafrost thaw has led to the reorganization of vegetation, water storage and flow paths, and patterns of SOC accumulation. However, changes have occurred over different timescales among landscapes: over decades in rocky uplands and gravelly-sandy lowlands in response to fire and lake drainage, over decades to centuries in peaty-silty lowlands with a legacy of complicated Holocene changes, and over centuries in silty uplands where ice-rich soil and ecological recovery protect permafrost. Copyright 2013 IOP Publishing Ltd
14005864 Mishra, U. (Argonne National Laboratory, Environmental Science Division, Argonne, IL); Jastrow, J. D.; Matamala, R.; Hugelius, G.; Koven, C. D.; Harden, J. W.; Ping, C. L.; Michaelson, G. J.; Fan, Z.; Miller, R. M.; McGuire, A. D.; Tarnocai, C.; Kuhry, P.; Riley, W. J.; Schaefer, K.; Schuur, E. A. G.; Jorgenson, M. T. and Hinzman, L. D. Empirical estimates to reduce modeling uncertainties of soil organic carbon in permafrost regions; a review of recent progress and remaining challenges: Environmental Research Letters, 8(3), Paper No. 035020, illus. incl. sketch maps, 70 ref., September 2013.
The vast amount of organic carbon (OC) stored in soils of the northern circumpolar permafrost region is a potentially vulnerable component of the global carbon cycle. However, estimates of the quantity, decomposability, and combustibility of OC contained in permafrost-region soils remain highly uncertain, thereby limiting our ability to predict the release of greenhouse gases due to permafrost thawing. Substantial differences exist between empirical and modeling estimates of the quantity and distribution of permafrost-region soil OC, which contribute to large uncertainties in predictions of carbon-climate feedbacks under future warming. Here, we identify research challenges that constrain current assessments of the distribution and potential decomposability of soil OC stocks in the northern permafrost region and suggest priorities for future empirical and modeling studies to address these challenges. Copyright 2013 IOP Publishing Ltd
14005860 Nossov, Dana R. (University of Alaska Fairbanks, Department of Biology and Wildlife, Fairbanks, AK); Jorgenson, M. Torre; Kielland, Knut and Kanevskiy, Mikhail Z. Edaphic and microclimatic controls over permafrost response to fire in interior Alaska: Environmental Research Letters, 8(3), Paper No. 035013, illus. incl. 1 table, sketch map, 44 ref., September 2013.
Discontinuous permafrost in the North American boreal forest is strongly influenced by the effects of ecological succession on the accumulation of surface organic matter, making permafrost vulnerable to degradation resulting from fire disturbance. To assess factors affecting permafrost degradation after wildfire, we compared vegetation composition and soil properties between recently burned and unburned sites across three soil landscapes (rocky uplands, silty uplands, and sandy lowlands) situated within the Yukon Flats and Yukon-Tanana Uplands in interior Alaska. Mean annual air temperatures at our study sites from 2011 to 2012 were relatively cold (-5.5°C) and favorable to permafrost formation. Burning of mature evergreen forests with thick moss covers caused replacement by colonizing species in severely burned areas and recovery of pre-fire understory vegetation in moderately burned areas. Surface organic layer thickness strongly affected thermal regimes and thaw depths. On average, fire caused a five-fold decrease in mean surface organic layer thickness, a doubling of water storage in the active layer, a doubling of thaw depth, an increase in soil temperature at the surface (-0.6 to +2.1°C) and at 1 m depth (-1.7 to +0.4°C), and a two-fold increase in net soil heat input. Degradation of the upper permafrost occurred at all burned sites, but differences in soil texture and moisture among soil landscapes allowed permafrost to persist beneath the active layer in the silty uplands, whereas a talik of unknown depth developed in the rocky uplands and a thin talik developed in the sandy lowlands. A changing climate and fire regime would undoubtedly influence permafrost in the boreal forest, but the patterns of degradation or stabilization would vary considerably across the discontinuous permafrost zone due to differences in microclimate, successional patterns, and soil characteristics. Copyright 2013 IOP Publishing Ltd
14005866 Vonk, J. E. (Utrecht University, Department of Earth Sciences, Utrecht, Netherlands); Mann, P. J.; Dowdy, K. L.; Davydova, A.; Davydov, S. P.; Zimov, N.; Spencer, R. G. M.; Bulygina, E. B.; Eglinton, T. I. and Holmes, R. M. Dissolved organic carbon loss from Yedoma permafrost amplified by ice wedge thaw: Environmental Research Letters, 8(3), Paper No. 035023, illus. incl. 2 tables, sketch map, 52 ref., September 2013.
Pleistocene Yedoma permafrost contains nearly a third of all organic matter (OM) stored in circum-arctic permafrost and is characterized by the presence of massive ice wedges. Due to its rapid formation by sediment accumulation and subsequent frozen storage, Yedoma OM is relatively well preserved and highly biologically available (biolabile) upon thaw. A better understanding of the processes regulating Yedoma degradation is important to improve estimates of the response and magnitude of permafrost carbon feedbacks to climate warming. In this study, we examine the composition of ice wedges and the influence of ice wedge thaw on the biolability of Yedoma OM. Incubation assays were used to assess OM biolability, fluorescence spectroscopy to characterize the OM composition, and potential enzyme activity rates to examine the controls and regulation of OM degradation. We show that increasing amounts of ice wedge melt water in Yedoma-leached incubations enhanced the loss of dissolved OM over time. This may be attributed to the presence of low-molecular weight compounds and low initial phenolic content in the OM of ice wedges, providing a readily available substrate that promotes the degradation of Yedoma OC. The physical vulnerability of ice wedges upon thaw (causing irreversible collapse), combined with the composition of ice wedge-engrained OM (co-metabolizing old OM), underlines the particularly strong potential of Yedoma to generate a positive feedback to climate warming relative to other forms of non-ice wedge permafrost. Copyright 2013 IOP Publishing Ltd
14005893 Chen, Min (Los Alamos National Laboratory, Los Alamos, NM); Rowland, Joel C.; Wilson, Cathy J.; Altmann, Garrett L. and Brumby, Steven P. The importance of natural variability in lake areas on the detection of permafrost degradation; a case study in the Yukon Flats, Alaska: Permafrost and Periglacial Processes, 24(3), p. 224-240, illus. incl. 6 tables, sketch map, 36 ref., July 2013.
Long-term lake area change has previously been measured to detect the temporal rate and spatial extent of permafrost degradation. However, the natural intra- and interannual variability of lake areas has not been considered explicitly and quantitatively, which can substantially interfere with the detection of long-term lake area change associated with permafrost degradation. In order to better understand the natural background variability of lake areas, we used Landsat 7 images obtained on 11 dates from 1999 to 2002 to quantify the intra- and interannual lake area variability for a 4224 km2 study area within the Yukon Flats, Alaska. Total lake areas ranged from 179 km2 (22 August 1999) to 326 km2 (6 June 2000). Even within a single year (year 2000), the total lake area decreased by 42 per cent from 6 June to 16 August, well exceeding the previously reported trends for long-term decrease (14% and 18%) for the Yukon Flats. Both intra- and interannual area variability in August and September were smaller than in June and July, suggesting that images from later in summer are more reliable for detecting long-term change in lake area. Variability of no-closure lakes was twice that of closed-basin lakes. Intra-annual area changes in closed-basin lakes can be explained by the intra-annual water balance, defined as cumulative precipitation minus evaporation between two consecutive dates within the same year. For a given period, the total lake area was correlated more strongly with the water balance since the preceding October than with the water balance in the preceding 12 months. Spatial heterogeneity in the intra-annual area change of individual lakes was observed, which might be caused by different topographical, geological and permafrost characteristics around and beneath the lakes. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14005890 Pastick, Neal J. (Stinger Ghaffarian Technologies, Sioux Falls, SD); Jorgenson, M. Torre; Wylie, Bruce K.; Minsley, Burke J.; Ji, Lei; Walvoord, Michelle A.; Smith, Bruce D.; Abraham, Jared D. and Rose, Joshua R. Extending airborne electromagnetic surveys for regional active layer and permafrost mapping with remote sensing and ancillary data, Yukon Flats ecoregion, central Alaska: Permafrost and Periglacial Processes, 24(3), p. 184-199, illus. incl. 4 tables, 30 ref., July 2013.
Machine-learning regression tree models were used to extrapolate airborne electromagnetic resistivity data collected along flight lines in the Yukon Flats Ecoregion, central Alaska, for regional mapping of permafrost. This method of extrapolation (r = 0.86) used subsurface resistivity, Landsat Thematic Mapper (TM) at-sensor reflectance, thermal, TM-derived spectral indices, digital elevation models and other relevant spatial data to estimate near-surface (0-2.6-m depth) resistivity at 30-m resolution. A piecewise regression model (r = 0.82) and a presence/absence decision tree classification (accuracy of 87%) were used to estimate active-layer thickness (ALT) (< 101 cm) and the probability of near-surface (up to 123-cm depth) permafrost occurrence from field data, modelled near-surface (0-2.6 m) resistivity, and other relevant remote sensing and map data. At site scale, the predicted ALTs were similar to those previously observed for different vegetation types. At the landscape scale, the predicted ALTs tended to be thinner on higher-elevation loess deposits than on low-lying alluvial and sand sheet deposits of the Yukon Flats. The ALT and permafrost maps provide a baseline for future permafrost monitoring, serve as inputs for modelling hydrological and carbon cycles at local to regional scales, and offer insight into the ALT response to fire and thaw processes. Abstract Copyright Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
14005891 Xie Changwei (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Cryospheric Sciences, Lanzhou, China); Gough, William A.; Tam, Andrew; Zhao Lin and Wu Tonghua. Characteristics and persistence of relict high-altitude permafrost on Mahan Mountain, Loess Plateau, China: Permafrost and Periglacial Processes, 24(3), p. 200-209, illus. incl. strat. cols., 2 tables, sketch map, 38 ref., July 2013.
Mahan Mountain is the only region in the Loess Plateau (China) where permafrost persists. The permafrost is typical warm permafrost and remains in a very fragile and sensitive state. Remnants of permafrost (approximately 0.134 km2 in area) remain in a low-lying swamp where the top 70 cm of soil contains abundant organic material (peat). The lowest temperature of the permafrost was -0.2°C between depths of 10 and 16 m, with temperature increasing upwards and downwards along a gradient of ± 0.01°C/m, and the permafrost thickness exceeded 30 m in this region. The distribution and thermal state of permafrost on Mahan Mountain closely relate to the surface conditions and soil type. In this study, the important protective effects of the peat layer and ground ice are illustrated using a one-dimensional finite difference model of heat flow. The simulation results indicate that active-layer thickness of permafrost on Mahan Mountain would increase by approximately 83 per cent under current climate conditions without the protection of the peat layer and ground ice. Based on the temperature projections of general circulation models, this study projects that permafrost will likely remain on Mahan Mountain for the next 40 to 50 years. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002309 Matthews, John A. (Swansea University, Department of Geography, Swansea, United Kingdom); Nesje, Atle and Linge, Henriette. Relict talus-foot rock glaciers at Oyberget, upper Ottadalen, Southern Norway; Schmidt hammer exposure ages and palaeoenvironmental implications: Permafrost and Periglacial Processes, 24(4), p. 336-346, illus. incl. 3 tables, sketch map, 66 ref., December 2013.
Three relict talus-foot rock glaciers at Oyberget, upper Ottadalen, were dated using high-precision Schmidt hammer exposure-age dating (SHD). A SHD calibration curve was constructed for the local banded gneiss using two control points: (1) fresh bedrock in a road cutting; and (2) glacially scoured bedrock surfaces deglaciated c. 9.7 ka. Two alternative hypotheses are suggested to explain SHD ages (± 95% confidence intervals) of 10 340 ± 1280, 9920 ± 1385 and 8965 ± 1700 years obtained for the three rock glaciers located ~ 1000 m below the present lower limit of mountain permafrost, at a site covered by glacier ice throughout the Late Weichselian. First, the rock glaciers may be paraglacial features, which formed rapidly during deglaciation when enhanced debris supply may have buried residual ice bodies. If this was the case, the SHD ages are a true reflection of rock glacier age. Second, the rock glaciers may have formed during several thousand years of permafrost conditions in the Mid-Weichselian (possibly during the Alesund Interstadial, c. 34.5-38.2 ka) and then been preserved beneath a cold-based ice sheet until renewed exposure during Holocene deglaciation. If the second hypothesis is true, then the true age of the rock glaciers is much older than their SHD ages, the latter failing to record the interval of burial when rock weathering would have been zero. Although evidence is currently insufficient to distinguish between these two interpretations, the paper demonstrates both the potential and limitations of high-precision SHD in the context of rock glaciers. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002241 Hayashi, Masaki (University of Calgary, Department of Geoscience, Calgary, AB, Canada). The cold vadose zone; hydrological and ecological significance of frozen-soil processes: Vadose Zone Journal, 12(4), 8 p., illus., 76 ref., November 2013.
Approximately 50% of soils in the Northern Hemisphere experience seasonal freezing and thawing, which influences physical, chemical, and biological processes in the vadose zone. Soil freeze-thaw drives mechanical processes, including frost heave and soil aggregate formation and breakdown, and controls snowmelt infiltration and runoff. These hydrologic processes determine the soil moisture conditions, which affect plant mortality and growth, soil microbial activities, and nutrient (e.g., C and N) cycles. Nutrients leached from the thawed soil, often with rapid infiltration of snowmelt water, may affect the quality of the groundwater and surface water, in combination with enhanced erosion and sediment load due to freeze-thaw. Nutrients released as greenhouse gases may contribute to climate feedback. With recent climate warming and changes in the extent and depth of frozen soil and permafrost, it is important to understand frozen-soil processes and their interaction with the environment. The objective of this review is to highlight important aspects of soil freeze-thaw and related processes and to point out research challenges and opportunities in the cold vadose zone.
14005862 Belshe, E. F. (University of Florida, Department of Biology, Gainesville, FL); Schuur, E. A. G. and Grosse, G. Quantification of upland thermokarst features with high resolution remote sensing: Environmental Research Letters, 8(3), Paper No. 035016 (10pp), illus. incl. 2 tables, sketch maps, 68 ref., September 2013.
Climate-induced changes to permafrost are altering high latitude landscapes in ways that could increase the vulnerability of the vast soil carbon pools of the region. Permafrost thaw is temporally dynamic and spatially heterogeneous because, in addition to the thickening of the active layer, localized thermokarst features form when ice-rich permafrost thaws and the ground subsides. Thermokarst produces a diversity of landforms and alters the physical environment in dynamic ways. To estimate potential changes to the carbon cycle it is imperative to quantify the size and distribution of thermokarst landforms. By performing a supervised classification on a high resolution IKONOS image, we detected and mapped small, irregular thermokarst features occurring within an upland watershed in discontinuous permafrost of Interior Alaska. We found that 12% of the Eight Mile Lake (EML) watershed has undergone thermokarst, predominantly in valleys where tussock tundra resides. About 35% of the 3.7 km2 tussock tundra class has likely transitioned to thermokarst. These landscape level changes created by permafrost thaw at EML have important implications for ecosystem carbon cycling because thermokarst features are forming in carbon-rich areas and are altering the hydrology in ways that increase seasonal thawing of the soil. Copyright 2013 IOP Publishing Ltd
14005868 Laurion, Isabelle (Université Laval, Centre d'Études Nordiques, Quebec City, QC, Canada) and Mladenov, Natalie. Dissolved organic matter photolysis in Canadian arctic thaw ponds: Environmental Research Letters, 8(3), Paper No. 035026, illus. incl. 5 tables, sketch map, 62 ref., September 2013.
The abundant thaw lakes and ponds in the circumarctic receive a new pool of organic carbon as permafrost peat soils degrade, which can be exposed to significant irradiance that potentially increases as climate warms and ice cover shortens. Exposure to sunlight is known to accelerate the transformation of dissolved organic matter (DOM) into molecules that can be more readily used by microbes. We sampled the water from two common classes of ponds found in the ice-wedge system of continuous permafrost regions of Canada, polygonal and runnel ponds, and followed the transformation of DOM over 12 days by looking at dissolved organic carbon (DOC) concentration and DOM absorption and fluorescence properties. The results indicate a relatively fast decay of color (3.4 and 1.6% loss d-1 of absorption at 320 nm for the polygonal and runnel pond, respectively) and fluorescence (6.1 and 8.3% loss d-1 of total fluorescent components, respectively) at the pond surface, faster in the case of humic-like components, but insignificant losses of DOC over the observed period. This result indicates that direct DOM mineralization (photochemical production of CO2) is apparently minor in thaw ponds compared to the photochemical transformation of DOM into less chromophoric and likely more labile molecules with a greater potential for microbial mineralization. Therefore, DOM photolysis in arctic thaw ponds can be considered as a catalytic mechanism, accelerating the microbial turnover of mobilized organic matter from thawing permafrost and the production of greenhouse gases, especially in the most shallow ponds. Under a warming climate, this mechanism will intensify as summers lengthen. Copyright 2013 IOP Publishing Ltd
14005888 Biskaborn, Boris K. (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Potsdam, Germany); Herzschuh, Ulrike; Bolshiyanov, Dmitry Y.; Schwamborn, Georg and Diekmann, Bernhard. Thermokarst processes and depositional events in a tundra lake, northeastern Siberia: Permafrost and Periglacial Processes, 24(3), p. 160-174, illus. incl. 2 tables, sketch maps, 34 ref., July 2013.
The relationships between thermokarst activity, limnogeological processes and climate change in the Siberian Arctic are not well understood. The objective of this paper is to identify the factors controlling the patterns of deposition, using grain size distribution, organic content, elemental composition and mineralogical composition of a 137-cm long sediment core with a maximum age of ~ 10.9 cal. kyr BP from Lake El'gene-Kyuele in the tundra of northeastern Siberia. Eight fine sand layers are attributed to depositional events associated with thaw slump activity acting upon orthogonally oriented patterns of ice-wedge networks in the ice-rich permafrost on the NW margin of the lake catchment. Sr/Rb ratios, which correspond to the total feldspar and illite content, serve as high-resolution grain size proxies. The Br content relates to the total organic carbon content, and the Fe/Mn ratio reflects the degree of oxidisation. Our results indicate a relationship between repeated phases of fine sand input and retrogressive thaw slumping dependent on hydroclimate variability and orthogonally oriented ice-wedge networks within the catchment. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14005894 Lafrenière, Melissa J. (Queen's University, Department of Geography, Kingston, ON, Canada) and Lamoureux, Scott F. Thermal perturbation and rainfall runoff have greater impact on seasonal solute loads than physical disturbance of the active layer: Permafrost and Periglacial Processes, 24(3), p. 241-251, illus. incl. 3 tables, sketch map, 22 ref., July 2013.
Climate warming in the Arctic will alter hydrological processes and biogeochemical exports from the landscape. Studies have reported that thermokarst disturbances and active-layer deepening increase solute concentrations in surface waters, but neither the spatial extent nor duration of the impacts of these changes is well understood. We measured total dissolved solute (TDS) concentrations and normalised seasonal TDS fluxes (kg mm-1) in a series of small headwater catchments in the Canadian High Arctic over three consecutive summers (2007-09) to examine the impact of thermal perturbation (increased soil temperatures) and physical disturbance (active-layer detachment slides) on solute dynamics in permafrost catchments. We find that usually high July soil temperatures (thermal perturbation) in 2007 resulted in a near-doubling of solute fluxes during the two subsequent summers, including in a catchment where there was no physical disturbance despite significantly cooler conditions. Solute concentrations increased with the spatial extent of physical disturbances, especially towards the end of the melt season. However, total seasonal solute fluxes did not always increase with the spatial extent of physical disturbances. The results show that the impact of the disturbance area on seasonal solute flux is limited by discharge and hydrological connectivity of the disturbed areas, and that summer rainfall allows for enhanced export of solutes from catchments subject to physical disturbance. Hence, seasonal solute export in these permafrost catchments was more sensitive to thermal perturbations and rainfall runoff than to physical disturbance of the active layer. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14005895 Xie, Changwei (University of Toronto, Department of Physical and Environmental Sciences, Toronto, ON, Canada) and Gough, William A. A simple thaw-freeze algorithm for a multi-layered soil using the Stefan equation: Permafrost and Periglacial Processes, 24(3), p. 252-260, illus. incl. 3 tables, 36 ref., July 2013.
The Stefan equation is one of the simplest approximate analytical solutions for the thaw-freeze problem. It provides a useful method for predicting the depth of thawing/freezing in soils when little site-specific information is available. The limited number of parameters in the Stefan equation makes possible its application in a multi-layered system. We demonstrate that a widely used algorithm (JL-algorithm), which has been frequently used in permafrost regions, was derived by an incorrect mathematical method. It will inevitably result in systematic errors in the simulation if this algorithm is used in a multi-layered soil. We present another simple thaw-freeze algorithm (XG-algorithm) for multi-layered soils. The new algorithm can be used to determine the freeze/thaw front in multi-layered soils no matter how thick each layer is and how many layers the soil profile contains. Simulation results of the JL-algorithm and the XG-algorithm are compared using hypothetical soil profiles, and the XG-algorithm is also used to simulate the thaw depth at three permafrost monitoring sites on the Qinghai-Tibet Plateau and one on the Loess Plateau, China. These applications show that the XG-algorithm could be readily used to analyse the factors that affect active-layer thickness. It can also be coupled with hydrological or land surface models to simulate the freeze-thaw cycles in permafrost regions and for related engineering applications. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14005889 Yoshikawa, Kenji (University of Alaska at Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Sharkhuu, Natsagdorj and Sharkhuu, Anarmaa. Groundwater hydrology and stable isotope analysis of an open-system pingo in northwestern Mongolia: Permafrost and Periglacial Processes, 24(3), p. 175-183, illus. incl. 2 tables, 44 ref., July 2013.
The first record of stable isotopes through a complete sequence of ice within an open-system pingo in northwestern Mongolia indicates a complex history of ice formation and pingo growth. A continuous section of ice 32 m long was cored through the centre of Mongot Pingo, and ice cores were analysed for stable isotopes and chemical composition. Two different stable isotope patterns in separate ice sections are identified: 1 open-system freezing and 2 semi-closed system (or closed system) freezing. Discharge measurements were observed in 2009 after drilling through pingo ice to artesian sub-pingo water and compared with data collected from the same pingo in 1968. Approximately 850-950 m3 of sub-pingo water discharged within 120 h during drilling in both 1968 and 2009, a volume equivalent to about 10 per cent of the current pingo ice volume. Between 1968 and 2009, permafrost (pingo ice) thickened by about 60 cm (1.46 cm per year), from 32.0 to 32.6 m, due to the decrease in sub-pingo artesian water pressure after water release from the 1968 drilling. The major mechanism for ice formation at this pingo is groundwater artesian pressure, though not continuously. Four major stages of pingo growth after 8790 yr BP are inferred. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002307 Krizek, Marek (Charles University, Department of Physical Geography and Geoecology, Prague, Czech Republic) and Uxa, Tomas. Morphology, sorting and microclimates of relict sorted polygons, Krkonose Mountains, Czech Republic: Permafrost and Periglacial Processes, 24(4), p. 313-321, illus. incl. 3 tables, sketch maps, 60 ref., December 2013.
The influence of past microclimates on the morphology and distribution of clasts is considered for relict large-scale sorted polygons in the Krkonose Mountains (Czech Republic). Sixty-two sorted polygons with an average length of 194 cm and an average height of 21.5 cm were measured at four sites on Mt Lucni hora, at elevations of 1455 to 1555 m asl. The polygons consist of tabular clasts with a mean length of 11 cm at the borders and 5 cm in the interiors. Smaller polygons are better sorted because of the shorter distances for the clasts to reach their borders. Polygons with greater relative height are better sorted due to more intensive slope processes associated with differential frost heaving. Better sorted and more domed polygons at higher altitudes suggest more severe and longer-lasting microclimates suitable for the development of sorted polygons. The altitudinal gradient in polygon morphology and sorting suggests the dominant role of microclimate in the periglacial environment of the summit area of the Krkonose Mountains during the Last Glacial/Holocene period. Polygon development probably involves positive feedback between morphology and frost susceptibility, driven by microclimate. The proposed method for evaluating frost sorting allows for rapid non-invasive assessment of sorting using modern methods including high-resolution remote sensing (especially terrestrial photogrammetry). Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002306 Marsz, Andrzej A. (Gdynia Maritime University, Department of Meteorology and Nautical Oceanography, Gdynia, Poland); Styszynska, Anna; Pekala, Kazimierz and Repelewska-Pekalowa, Janina. Influence of meteorological elements on changes in active-layer thickness in the Bellsund region, Svalbard: Permafrost and Periglacial Processes, 24(4), p. 304-312, illus. incl. 5 tables, sketch map, 53 ref., December 2013.
Measurements of active-layer thickness (ALT) at seven locations on Calypsostranda, Svalbard (CALM Site P1), over 1986-2009, are used to estimate the influence of cloudiness, precipitation, air temperature, the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO). Between 1986 and 2002, ALT amounted to 118 ± 14 cm and did not show any significant trend. During 2002-06, ALT increased rapidly (12.6 cm/yr) to a maximum of ~ 174 cm in 2006 and 2007. In 2008 and 2009, ALT decreased. No statistically significant correlations were determined between ALT and monthly precipitation and cloudiness at Barentsburg, Hornsund and Svalbard Airport stations. There were, however, very strong and highly significant (p < 0.001) relationships with air temperatures in May and June (the strongest association being with Svalbard Airport). The influence of air temperature in May and June on ALT is indirect; it regulates the time of the melt of snow cover, which determines the duration of the ground-warming period. Using statistical relationships between ALT and air temperature at Svalbard Airport, the time series of ALT at Calypsostranda is reconstructed from 1911 to 2010. It was also found that the AO and the NAO did not significantly affect ALT and air temperature on western Spitsbergen. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14005892 Klaus, Marcus (Umea University, Department of Ecology and Environmental Science, Umea, Sweden); Becher, Marina and Klaminder, Jonatan. Cryogenic soil activity along bioclimatic gradients in northern Sweden; insights from eight different proxies: Permafrost and Periglacial Processes, 24(3), p. 210-223, illus. incl. 3 tables, sketch map, 25 ref., July 2013.
Cryogenic soil activity caused by differential soil movements during freeze-thaw cycles is of fundamental importance for Arctic ecosystem functioning, but its response to climate warming is uncertain. Eight proxies of cryogenic soil activity (including measurements of soil surface motion, vegetation and grey values of aerial photographs) were examined at eight study sites where non-sorted patterned ground spans an elevation gradient (400-1150 m asl) and a precipitation gradient (300-1000 mm yr-1) near Abisko, northern Sweden. Six proxies were significantly correlated with each other (mean |r| = 0.5). Soil surface motion increased by three to five times along the precipitation gradient and was two to four times greater at intermediate elevations than at low and high elevations, a pattern reflected by vegetation assemblages. The results suggest that inferences about how cryogenic soil activity changes with climate are independent of the choice of the proxy, although some proxies should be applied carefully. Four preferred proxies indicate that cryogenic soil activity may respond differently to climate warming along the elevation gradient and could be greatly modified by precipitation. This underlines the strong but spatially complex response of cryogenic processes to climate change in the Arctic. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14002233 Kelleners, T. J. (University of Wyoming, Department of Ecosystem Science and Management, Laramie, WY). Coupled water flow and heat transport in seasonally frozen soils with snow accumulation: Vadose Zone Journal, 12(4), 11 p., illus. incl. 1 table, 42 ref., November 2013. Includes appendix.
A new numerical model was developed to calculate coupled water flow and heat transport in seasonally frozen soil and snow. Separate equations were presented to describe both unsaturated and saturated soil water flow. The effect of dissolved ions on soil water freezing point depression was included by combining an expression for osmotic head with the Clapeyron equation and the van Genuchten soil water retention function. The coupled water flow and heat transport equations were solved using the Thomas algorithm and Picard iteration. Ice pressure was always assumed zero, and frost heave was neglected. The new model was tested using data from an existing laboratory soil column freezing experiment and an ongoing field experiment in a high-elevation rangeland soil. A dimensionless impedance factor describing the effect of ice pore blocking on soil hydraulic conductivity was treated as a calibration parameter for both cases. Calculated values of total water content for the laboratory soil column freezing experiment compared well with measured values, especially during the early stages of the experiment, as was also found by others. Modeling statistics for the rangeland field experiment showed varied performance for soil water content (RMSE = 0.02-0.06 m3 m-3; modeling efficiency [ME] = -4.06 to +0.72) and excellent performance for soil temperature (RMSE = 1.0-2.1°C; ME = 0.93-0.98), in accordance with earlier results with an older version of the model.
14001876 Davies, Bethan J. (Aberystwyth University, Institute of Geography and Earth Sciences, Aberystwyth, United Kingdom); Glasser, Neil F.; Carrivick, Jonathan L.; Hambrey, Michael J.; Smellie, John L. and Nyvlt, Daniel. Landscape evolution and ice-sheet behaviour in a semi-arid polar environment; James Ross Island, NE Antarctic Peninsula: in Antarctic palaeoenvironments and Earth-surface processes (Hambrey, M. J., editor; et al.), Special Publication - Geological Society of London, 381, p. 353-395, illus. incl. 7 tables, geol. sketch maps, 60 ref., April 19, 2013. (Online First).
This study of landscape evolution presents both new modern and palaeo process-landform data, and analyses the behaviour of the Antarctic Peninsula Ice Sheet through the Last Glacial Maximum (LGM), the Holocene and to the present day. Six sediment-landform assemblages are described and interpreted for Ulu Peninsula, James Ross Island, NE Antarctic Peninsula: (1) the Glacier Ice and Snow Assemblage; (2) the Glacigenic Assemblage, which relates to LGM sediments and comprises both erratic-poor and erratic-rich drift, deposited by cold-based and wet-based ice and ice streams respectively; (3) the Boulder Train Assemblage, deposited during a Mid-Holocene glacier readvance; (4) the Ice-cored Moraine Assemblage, found in front of small cirque glaciers; (5) the Paraglacial Assemblage including scree, pebble-boulder lags, and littoral and fluvial processes; and (6) the Periglacial Assemblage including rock glaciers, protalus ramparts, blockfields, solifluction lobes and extensive patterned ground. The interplay between glacial, paraglacial and periglacial processes in this semi-arid polar environment is important in understanding polygenetic landforms. Crucially, cold-based ice was capable of sediment and landform genesis and modification. This land system model can aid the interpretation of past environments, but also provides new data to aid the reconstruction of the last ice sheet to overrun James Ross Island.
14000171 de Lafontaine, Guillaume (Université Bordeaux, National Institute for Agricultural Research, Talence, France) and Asselin, Hugo. Soil charcoal stability over the Holocene across boreal northeastern North America; reply: Quaternary Research, 78(1), p. 155-156, 11 ref., July 2012. For reference to original see de Lafontaine, G. and Asselin, H., Quaternary Research, Vol. 76, p. 196-200, 2011; for reference to discussion see Ohlson, M., Quaternary Research, Vol. 78, p. 154, 2012.
14003577 Veress, Marton; Pentek, Kalman; Unger, Zoltan and Almasi, Istvan. Development of covered karstic dolines in ground ice environment (Eastern Alps, Austria); interests of experimental and mathematical modelling: in Geomorphological environments; research methods on biotic and abiotic environments (Toth, Gabor, editor), Zeitschrift für Geomorphologie, 56, Suppl. 2, p. 79-104, 21 ref., 2012.
We studied the evolution of dolines in ground ice environment, in a paleouvala of the Hochschwab Mts. (Northern Calcareous Alps, Austria) as well as in laboratory conditions. We measured the ground ice thickness of the exploration area by geophysical methods. We estimated the melting (thinning) speed and the pertinent parameters for ground ice samples at different temperatures in laboratory conditions. After simulating the process we were able to determine the physical conditions generating the ground ice melting phenomena, and based on this we calculated its melting speed. Due to the air circulation in the karst, the lower level of the ground ice starts to melt and the covering sediment particles fall down. Thus the thinned covering sediments will fall-in and dropout dolines will mould the ground, or the surface may sink by the progress of the melting, entailing suffosion dolines to be generated.
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14000384 Bagard, M. L. (Université de Strasbourg, Laboratory of Hydrology and Geochemistry, Strasbourg, France); Schmitt, A. D.; Chabaux, François; Pokrovsky, Oleg S.; Viers, J.; Stille, Peter; Labolle, F. and Prokushkin, A. S. Ca isotope fractionation in a permafrost-dominated boreal ecosystem (Kulingdakan watershed, central Siberia) [abstr.]: in Goldschmidt abstracts 2013, Mineralogical Magazine, 77(5), p. 641, 2013. Meeting: Goldschmidt 2013, Aug. 25-30, 2013, Florence, Italy.
Ca isotope compositions were measured in different compartments (stream water, soil solutions, rocks, soils and soil leachates and vegetation) of a small permafrost-dominated forested watershed in the Central Siberian Plateau. Our results show that only the processes related to vegetation activity significantly fractionate Ca isotopes within the watershed. These fractionations occur during Ca uptake by roots and along the transpiration stream within the larch trees. Biomass degradation then significantly influences the Ca isotopic compositions of soil solutions and soil leachates via the release of light Ca. Furthermore, organic and organo-mineral colloids originated from organic matter degradation are thought to affect the Ca isotopic composition of soil solutions by preferential scavenging of 40Ca. This imprint of organic matter degradation on the d44/40Ca of soil solutions is much more significant for the warmer south-facing slope of the watershed than for the shallow and cold soil active layer of the north-facing slope, indicating that the available stock of biomass and the decomposition rates are critical parameters that regulate the impact of vegetation on the soil-water system. Moreover, the obtained d44/40Ca patterns contrast with those described for permafrost-free environments with a much lower d44/40Ca fractionation factor between soils and plants, suggesting particular processes related either to the presence of permafrost or to the specific features of organic matter degradation in permafrost environments. Finally, biologically induced Ca fractionation observed at the soil profile scale is not visible in stream and river waters, whose isotopic variability in the course of the year is likely controlled by the lithological heterogeneity of the sources. As such, we suggest a negligible influence of biologically related fractionation on the long-term Ca isotopic signatures of riverine fluxes carried to the ocean.
14005764 Lafrenière, M. J. (Queen's University, Department of Geography, Kingston, ON, Canada); Montross, S.; Holloway, J. and Lamoureux, S. F. Subsurface mineral weathering in transient layers of permafrost in the Canadian High Arctic [abstr.]: in Goldschmidt abstracts 2013, Mineralogical Magazine, 77(5), p. 1538, 2013. Meeting: Goldschmidt 2013, Aug. 25-30, 2013, Florence, Italy.
Chemical weathering in high latitude regions has largely been dismissed as insignificant, as frozen soils limit weathering reaction rates for more than 8 months a year, and also the movement of weathered products within the soil profile. We present evidence that subsurface mineral weathering in the transient layers of permafrost soils results in the formation and subsequent ejection of authigenic clay, onto the surface. Hundreds of active and dormant mud ejection features were witnessed and mapped during the summers of 2011 and 2012, on Melville Island, Nunavut, in the Canadian High Arctic. We measured the chemical composition of aqueous and mineral solid phases in material ejected from active features in order to determine the source of material and processess responsible for their formation. Fluids from these mud ejections are enriched in nutrients (dissolved nitrogen and organic carbon) and trace metals. Stable isotope ratios of water extracted from the mud indicates that water is not from precipitation or surface runoff and is likely from thawed permafrost, or water stored in the transient layer over several melt seasons. Bulk mineralogy, and trace metal and major ion ratios of fluids and mineral solids indicate subsurface chemical weathering reactions are occurring at near freezing temperatures in the permafrost transient layer. The results show that the material and solutions delivered to the ground surface are the products of extensive subsurface weathering of siliciclastic minerals to authigenic clays. These mud ejection features represent a mechanism that delivers fine grained material rich in dissolved metals and nutrients to the surface, where they are subject to mobilization and delivery to terrestrial and aquatic ecosystems.
14005373 Henkemans, Emily (University of Waterloo, Department of Earth Science, Waterloo, ON, Canada); Frape, Shaun; Ruskeeniemi, Timo; Liljedahl, Lillemor Claesson; Lehtinen, Anne and Engstrom, Jon. Groundwater evolution under permafrost conditions, south-west Greenland [abstr.]: in Goldschmidt 2012 abstract volume, Mineralogical Magazine, 76(6), p. 1835, illus., 2 ref., 2012. Meeting: Goldschmidt 2012, June 24-29, 2012, Montreal, QC, Canada.
The Greenland Analogue Project (GAP) aims to further the understanding of groundwater evolution due to the influence of a continental ice sheet and continuous permafrost. Geochemical and hydrogeological processes are being studied in the area around Kangerlussuaq, Greenland. Geochemical and isotopic (18O, 2H, 3H, 37Cl, 87Sr and 34S and 18O of SO4) tracers are used to interpret the flow and geochemical evolution of groundwater in this crystalline environment. Three boreholes have been drilled since 2009. Two boreholes are equipped with groundwater sampling devices: DH-GAP01 intersects a talik beneath a large lake and DH-GAP04 provides 3 sampling sections beneath and adjacent to the ice. Talik waters from DH-GAP01 and the first groundwaters sampled at DH-GAP04 appear to be geochemically similar in many ways, such as high concentrations of sulphate. High sulphate groundwaters are also found in other permafrost impacted crystalline environments in Northern Canada [1, 2]. GAP borehole waters are depleted in d18O and d2H compared to modern precipitation when a simple linear mixing model is used to calculate final compositions of DH-GAP04 based on the concentration of tracer in the samples (Fig. 1). Further sampling of DH-GAP04 is planned for 2012. A spring located directly in front of Leverett Glacier, about 10 km south of DH-GAP01, yields groundwaters that are geochemically distinct from the waters sampled from the boreholes with elevated iron concentrations up to 14.8 mg/L.
14005162 Rödder, T. (University of Würzburg, Institute of Geography and Geology, Wurzburg, Germany) and Kneisel, C. Ground thermal conditions and active layer processes within two glacier forefields with heterogeneous permafrost occurrence [abstr.]: in European Geosciences Union general assembly 2012, Geophysical Research Abstracts, 14, Abstract EGU2012-625, 2012. Meeting: European Geosciences Union general assembly 2012, April 22-27, 2012, Vienna, Austria.
14005200 Szuman, I. (Adam Mickiewicz University, Institute of Geoecology and Geoinformation, Poznan, Poland); Ewertowski, M.; Kasprzak, L. and Piotrowski, J. A. Ice sheet-permafrost interactions inferred from the sedimentary record of Weichselian glaciation in Poland [abstr.]: in European Geosciences Union general assembly 2012, Geophysical Research Abstracts, 14, Abstract EGU2012-712, 2012. Meeting: European Geosciences Union general assembly 2012, April 22-27, 2012, Vienna, Austria.
14005402 Lansard, Bruno (Université Paul Sabatier, Toulouse, France); Mucci, Alfonso; Brown, Kristina and Babin, Marcel. A multi-proxy study of the Mackenzie Shelf waters [abstr.]: in Goldschmidt 2012 abstract volume, Mineralogical Magazine, 76(6), p. 1973, 3 ref., 2012. Meeting: Goldschmidt 2012, June 24-29, 2012, Montreal, QC, Canada.
The Arctic Ocean is one of the most intense CO2 sinks of the oceanic realm due to the low temperature and relatively high primary productivity of its waters . Nevertheless, the Arctic Ocean is prone to rapid transformations in response to climate change, such as changes in sea-ice melt and freezing rates, increased freshwater, nutrient, and particulate input due to higher riverine discharge, as well as changing carbon and sediment fluxes caused by coastal erosion and permafrost thawing. Given the complex interplay between these factors, predicting how the strength of the Arctic Ocean atmospheric CO2 sink will vary in the future is still a matter of debate . In this context, we address how CO2 in the surface mixed layer (SML) of the Arctic Ocean may change in response to increased sea-ice melt and riverine inputs. During the summer of 2009, we conducted high resolution water column sampling on the Mackenzie and Beaufort Shelves (Canadian Arctic) to examine the impact of sea-ice melt and river runoff on surface ocean CO2 chemistry. We used a combination of natural tracers (salinity, total alkalinity (TA) and stable oxygen isotopic composition (d18O-H2O)) to distinguish between sea-ice melt (SIM) and meteoric water (MW) . SIM is characterised by a low TA (415 ± 35 mmol kg-1), a relatively high d18O-H2O (-2.0 ± 0.5 ppm) and relatively low CO2 partial pressure (pCO2»300 matm). MW is characterised by a high TA (1618 ± 55 mmol kg-1), low d18O-H2O (-18.9 ± 0.1 ppm), and relatively high pCO2 (>450 matm). In addition, we analysed the stable carbon isotopic composition (d13C) of dissolved inorganic carbon (DIC) to determine the origin of the CO2, i.e. metabolic or atmospheric. During the study period, significant contributions of MW (>50%) to the SML were only observed on the inner Mackenzie Shelf. In contrast, SIM contribution to the SML reached 30% close to the ice pack, located beyond the shelf break. The admixture of SIM to the SML may therefore allow for the absorption of atmospheric CO2. A preliminary analysis of the d13C-DIC data reveals two distinct patterns indicating that CO2 was either taken up from the atmosphere or produced in situ by microbial respiration.
14005814 Ledesma, J. L. J. (Swedish University of Agricultural Sciences, Department of Aquatic Sciences and Assessment, Uppsala, Sweden); Grabs, T.; Bishop, K. H. and Kohler, S. J. The turnover time of organic carbon in boreal riparian zones; a hydrological approach [abstr.]: in Goldschmidt abstracts 2013, Mineralogical Magazine, 77(5), p. 1563, 4 ref., 2013. Meeting: Goldschmidt 2013, Aug. 25-30, 2013, Florence, Italy.
Boreal regions are large stores of organic carbon (OC). The majority of the OC found in boreal inland waters is allochthonous, i.e. originally from terrestrial sources. Allochthonous carbon is especially dominant in headwater streams, which also show high concentration and fluxes. The link between the terrestrial and the aquatic compartments in these headwaters is dominated by organic matter-rich riparian zones (RZ). RZ have been described as near-infinite organic matter sources because large amounts of OC originate here and are exported to streams by lateral fluxes. But, how long can RZ sustain the high lateral OC fluxes in boreal catchments? To answer this question we estimate the turnover times of OC in 13 RZ profiles in a boreal catchment in northern Sweden by comparing pools and lateral fluxes. The lateral fluxes can be mathematically estimated using the Riparian Flow-Concentration Integration Model (RIM) approach, in which lateral discharge and concentration profiles in the RZ are combined. Our calculations with this approach indicate that 90% of the lateral OC fluxes come from a 36 ± 18 cm (± SD) shallow soil layer accounting in all the 13 studied riparian profiles. Preliminary analyses suggest long turnover times of OC in these 'active' layers. That would imply that there is no long term supply shortage. The results from this study will have implications for the global carbon cycle in relation to human perturbations.
14005177 Buchroithner, M. (Dresden University of Technology, Institute for Cartography, Dresden, Germany) and Trombotto, D. Cryophenomena in the cold desert of Atacama [abstr.]: in European Geosciences Union general assembly 2012, Geophysical Research Abstracts, 14, Abstract EGU2012-654, 2012. Meeting: European Geosciences Union general assembly 2012, April 22-27, 2012, Vienna, Austria.
14005666 Chwalek, Thomas (Swiss Federal Institute for Environmental Science and Technology, Kastanienbaum, Switzerland); Torres, Natascha; Furrer, Gerhard; Brandl, Helmut; Müller, Beat and Hauser, Peter C. The influence of frost weathering on the release of readily available ions from granite surfaces [abstr.]: in Goldschmidt abstracts 2013, Mineralogical Magazine, 77(5), p. 888, 2013. Meeting: Goldschmidt 2013, Aug. 25-30, 2013, Florence, Italy.
Hundreds of research studies concerning frost weathering of minerals were conducted during the last century. Regardless of a long history of inquiries, the quantitative insights of frost weathering products are still elusive. Frost weathering is mainly attributed to the increase of surface area without any chemical changes. This study represents the first attempt to evaluate readily available ions released by frost weathering with the use of capillary electrophoresis (CE) and a capacitively coupled contactless conductivity detection (C4D) detector. An new easy-to-handle sampling technique called "Drop-on-Stone" (DoS) was used to sample rock surface areas. Are Granite samples undergoing different amounts of freeze-thaw cycles were analyzed for a continuous increase of cations and anions. Particular attention was given to the first weathering steps. Complementary SEM pictures of the sampled areas were taken during the weathering experiments. The results illustrate the initial release of ions during the first few freeze-thaw cycles. This indicates that frost weathering is able to raise surface concentrations of readily soluble cations and anions. These ions serve as the primary nutrient source for organisms and are essential for initial soil formation in arctic and high altitude areas.
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