Permafrost Monthly Alerts (PMAs)

13091429 Malone, Laura (University of Ottawa, Department of Earth Sciences, Ottawa, ON, Canada); Lacelle, Denis; Kokelj, Steve and Clark, Ian D. Impacts of hill slope thaw slumps on the geochemistry of permafrost catchments (Stony Creek watershed, NWT, Canada): Chemical Geology, 356, p. 38-49, illus. incl. sketch maps, 36 ref., October 9, 2013. Includes appendices.

Retrogressive thaw slumps are one of the most dramatic thermokarst landforms in periglacial regions. This study investigates the impacts of one stable and two active thaw slumps on the geochemistry of streams in the Stony Creek watershed (Peel Plateau, NWT, Canada). The objective of this study is to elucidate the geochemical processes associated with ground ice ablation in retrogressive thaw slumps and the geochemical evolution of slump runoff to streams. This is accomplished by describing the geochemical composition of runoff across active mega-slumps, impacted and pristine tundra streams, as well as that of the ice-rich permafrost exposed in the slump headwalls. In the Stony Creek watershed, runoff derived from active and stable thaw slumps is characterized by a Ca(Mg)-SO₄ geochemical facies with conductivity and solute concentrations approximately one order of magnitude higher than in pristine streams. The elevated solute concentrations in the slump runoff are directly related to thawing of highly weatherable Late Pleistocene age ice-rich and solute-rich permafrost exposed in the headwalls of slumps, which has solute concentrations nearly 100 times higher than those measured in the uppermost 1-2 m (i.e., above the early Holocene thaw unconformity). An examination of ionic relations revealed a strong relation between Ca²⁺ and SO₄^2- and (Ca²⁺+Mg²⁺)-SO₄^2-, suggestive that sulfate dissolution is the main process responsible for the geochemical composition of slump impacted streams. Thaw slumps significantly impact the geochemistry of streams, by increasing their solute load well above that of pristine streams along any reach of impacted streams. Unlike shallow active layer disturbances, the thaw slumps can degrade permafrost to depths of 10 m or more and the impacts of abundant slump activity on stream geochemistry can be detected at the 10^{^2}km² watershed-scale. Abstract Copyright (2013) Elsevier, B.V.

DOI: 10.1016/j.chemgeo.2013.07.010

13095420 Portnov, Alexey (University of Tromso, Centre for Arctic Gas Hydrate, Environment and Climate, Tromso, Norway); Smith, Andrew J.; Mienert, Jürgen; Cherkashov, Georgy; Rekant, Pavel; Semenov, Peter; Serov, Pavel and Vanshtein, Boris. Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the south Kara Sea shelf: Geophysical Research Letters, 40(15), p. 3962-3967, illus. incl. sketch map, 34 ref., August 16, 2013.

Since the Last Glacial Maximum (~19 ka), coastal inundation from sea-level rise has been thawing thick subsea permafrost across the Arctic. Although subsea permafrost has been mapped on several Arctic continental shelves, permafrost distribution in the South Kara Sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood. Here we use >1300 km of high-resolution seismic data to map hydroacoustic anomalies, interpreted to record seabed gas release, on the West Yamal shelf. Gas flares are widespread over an area of at least 7500 km² in water depths >20 m. We propose that continuous subsea permafrost extends to water depths of ~ m offshore and creates a seal through which gas cannot migrate. This Arctic shelf region where seafloor gas release is widespread suggests that permafrost has degraded more significantly than previously thought. Abstract Copyright (2013), American Geophysical Union. All Rights Reserved.

DOI: 10.1002/grl.50735

13093624 Scherler, Martin (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Hauck, Christian; Hoelzle, Martin and Salzmann, Nadine. Modeled sensitivity of two alpine permafrost sites to RCM-based climate scenarios: Journal of Geophysical Research: Earth Surface, 118(2), p. 780-794, illus. incl. 3 tables, sketch map, 80 ref., June 2013.

Climate change as projected by contemporary general circulation models (GCMs) and regional climate models (RCMs) will have a great impact on high latitude and high mountain permafrost. A process-based one-dimensional permafrost model is used to evaluate the sensitivity of two characteristic alpine permafrost sites to changes in climate for a 110 year time period starting 1991 and ending 2100 using output time series of six different GCM-RCM model chains. Statistical analysis of the RCM climate variables and output of the impact model has been conducted to gain insight into the sensitivity of the active layer to changes in climatic conditions. Strong sensitivity to climate change was found for the active layer thickness (ALT) at Schilthorn, which increased by up to 100% before most of the models pointed to a degradation of the permafrost around the year 2020. The sensitivity of the ALT at the rock glacier site Murtel is less pronounced; permafrost degradation is slower and sets in only around 2070. At both sites, the thermal evolution is linked to an increase in unfrozen water content within the permafrost body. Multiple linear regression analysis shows a strong model dependency of ALT on ice content and summer soil surface temperatures and to a less significant degree on snow cover timing and duration. The ALT at Schilthorn is influenced by the ALT of the preceding year, while at Murtel, the ALT is influenced by the ALT of up to 15 preceding years. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/jgrf.20069

13093609 Zhang, Yu (Natural Resources Canada, Canada Centre for Remote Sensing, Ottawa, ON, Canada). Spatio-temporal features of permafrost thaw projected from long-term high-resolution modeling for a region in the Hudson Bay Lowlands in Canada: Journal of Geophysical Research: Earth Surface, 118(2), p. 542-552, illus. incl. sketch map, 39 ref., June 2013.

Although studies agree that climate warming will cause permafrost thaw, projected permafrost conditions differ widely, and most projections use half degree latitude/longitude or coarser spatial resolution. Using a process-based model, this study projected changes of permafrost from 2010 to 2200 at 30 m by 30 m resolution for a region in the northwest of the Hudson Bay Lowlands in Canada. This long-term spatially detailed modeling revealed some general features of permafrost dynamics with climate warming. Temporally, permafrost degradation at a site can be divided into five stages: gradual-thawing stage, increased-thawing stage, frequent-talik stage, isothermal-permafrost stage, and permafrost-free stage. This study determined the beginning or ends of the stages for each grid cell and mapped the degradation stages in this region. Spatially, permafrost was predicted to become increasingly discontinuous with climate warming. By the end of the 22nd century, only 20% to 65% of the land area in this region will be underlain by permafrost. With the formation of taliks, the maximum summer thaw depth will increase significantly, and near-surface permafrost will disappear in many areas while permafrost at depth can persist for decades. Thus, the spatial distribution of near-surface permafrost and permafrost at depth can be very different. This study also shows that climate scenarios, the depth of permafrost considered, spatial resolution and associated ground conditions used for modeling could cause significant differences in permafrost projections. Abstract Copyright (2013), . Her Majesty the Queen in Right of Canada.

DOI: 10.1002/jgrf.20045

13095039 Hunt, Stephanie (Lehigh University, Department of Earth and Environmental Sciences, Bethlehem, PA); Yu, Zicheng and Jones, Miriam. Late glacial and Holocene climate, disturbance and permafrost peatland dynamics on the Seward Peninsula, western Alaska: Quaternary Science Reviews, 63, p. 42-58, illus. incl. 3 tables, sketch map, 85 ref., March 1, 2013.

Northern peatlands have accumulated large carbon (C) stocks, acting as a long-term atmospheric C sink since the last deglaciation. How these C-rich ecosystems will respond to future climate change, however, is still poorly understood. Furthermore, many northern peatlands exist in regions underlain by permafrost, adding to the challenge of projecting C balance under changing climate and permafrost dynamics. In this study, we used a paleoecological approach to examine the effect of past climates and local disturbances on vegetation and C accumulation at a peatland complex on the southern Seward Peninsula, Alaska over the past ~15 ka (1 ka = 1000 cal yr BP). We analyzed two cores about 30 m apart, NL10-1 (from a permafrost peat plateau) and NL10-2 (from an adjacent thermokarst collapse-scar bog), for peat organic matter (OM), C accumulation rates, macrofossil, pollen and grain size analysis. A wet rich fen occurred during the initial stages of peatland development at the thermokarst site (NL10-2). The presence of tree pollen from Picea spp. and Larix laricinia at 13.5-12.1 ka indicates a warm regional climate, corresponding with the well-documented Bolling-Allerod warm period. A cold and dry climate interval at 12.1-11.1 ka is indicated by the disappearance of tree pollen and increase in Poaceae pollen and an increase in woody material, likely representing a local expression of the Younger Dryas (YD) event. Following the YD, the warm Holocene Thermal Maximum (HTM) is characterized by the presence of Populus pollen, while the presence of Sphagnum spp. and increased C accumulation rates suggest high peatland productivity under a warm climate. Toward the end of the HTM and throughout the mid-Holocene a wet climate-induced several major flooding disturbance events at 10 ka, 8.1 ka, 6 ka, 5.4 ka and 4.7 ka, as evidenced by decreases in OM, and increases in coarse sand abundance and aquatic fossils (algae Chara and water fleas Daphnia). The initial peatland at permafrost site (NL10-1) is characterized by rapid C accumulation (66 g C m^-2 yr^-1), high OM content and a peak in Sphagnum spp. at 5.8-4.6 ka, suggesting the lack of permafrost. A transition to extremely low C accumulation rates of 6.3 g C m^-2 yr^-1 after 4.5 ka at this site suggests the onset of permafrost aggradation, likely in response to Neoglacial climate cooling as documented across the circum-Arctic region. A similar decrease in C accumulation rates also occurred at non-permafrost site NL10-2. Time-weighted C accumulation rates are 21.8 g C m^-2 yr^-1 for core NL10-1 during the last ~6.5 ka and 14.8 g C m^-2 yr^-1 for core NL10-2 during the last ~15 ka. Evidence from peat-core analysis and historical aerial photographs shows an abrupt increase in Sphagnum spp. and decrease in area of thermokarst lakes over the last century, suggesting major changes in hydrology and ecosystem structure, likely due to recent climate warming. Our results show that the thermokarst-permafrost complex was much more dynamic with high C accumulation rates under warmer climates in the past, while permafrost was stabilized and C accumulation slowed down following the Neoglacial cooling in the late Holocene. Furthermore, permafrost presence at local scales is controlled by both regional climate and site-specific factors, highlighting the challenge in projecting responses of permafrost peatlands and their C dynamics to future climate change. Abstract Copyright (2013) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2012.11.019

13097565 Boike, J. (Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany); Kattenstroth, B.; Abramova, K.; Bornemann, N.; Chetverova, A.; Fedorova, I.; Fröb, K.; Grigoriev, M.; Grüber, M.; Kutzbach, L.; Langer, M.; Minke, M.; Muster, S.; Piel, K.; Pfeiffer, E. M.; Stoof, G.; Westermann, S.; Wischnewski, K.; Wille, C. and Hubberten, H. W. Baseline characteristics of climate, permafrost and land cover from a new permafrost observatory in the Lena River delta, Siberia (1998-2011): Biogeosciences, 10(3), p. 2105-2128, illus. incl. 8 tables, sketch maps, 104 ref., 2013.

Samoylov Island is centrally located within the Lena River Delta at 72° N, 126° E and lies within the Siberian zone of continuous permafrost. The landscape on Samoylov Island consists mainly of late Holocene river terraces with polygonal tundra, ponds and lakes, and an active floodplain. The island has been the focus of numerous multidisciplinary studies since 1993, which have focused on climate, land cover, ecology, hydrology, permafrost and limnology. This paper aims to provide a framework for future studies by describing the characteristics of the island's meteorological parameters (temperature, radiation and snow cover), soil temperature, and soil moisture. The land surface characteristics have been described using high resolution aerial images in combination with data from ground-based observations. Of note is that deeper permafrost temperatures have increased between 0.3 to 1.3 °C over the last five years. However, no clear warming of air and active layer temperatures is detected since 1998, though winter air temperatures during recent years have not been as cold as in earlier years. Data related to this article are archived under: htp://doi.pangaea.de/10.1594/PANGAEA.806233.

DOI: 10.5194/bg-10-2105-2013

13092945 Westermann, S. (University of Oslo, Department of Geosciences, Oslo, Norway); Schuler, T. V.; Gisnas, K. and Etzelmuller, B. Transient thermal modeling of permafrost conditions in Southern Norway: The Cryosphere (Online), 7(2), p. 719-739, illus. incl. 3 tables, sketch maps, 89 ref., 2013.

Thermal modeling is a powerful tool to infer the temperature regime of the ground in permafrost areas. We present a transient permafrost model, CryoGrid 2, that calculates ground temperatures according to conductive heat transfer in the soil and in the snowpack. CryoGrid 2 is forced by operational air temperature and snow-depth products for potential permafrost areas in Southern Norway for the period 1958 to 2009 at 1 km² spatial resolution. In total, an area of about 80 000 km² is covered. The model results are validated against borehole temperatures, permafrost probability maps from "bottom temperature of snow" measurements and inventories of landforms indicative of permafrost occurrence. The validation demonstrates that CryoGrid 2 can reproduce the observed lower permafrost limit to within 100 m at all validation sites, while the agreement between simulated and measured borehole temperatures is within 1 K for most sites. The number of grid cells with simulated permafrost does not change significantly between the 1960s and 1990s. In the 2000s, a significant reduction of about 40% of the area with average 2 m ground temperatures below 0 °C is found, which mostly corresponds to degrading permafrost with still negative temperatures in deeper ground layers. The thermal conductivity of the snow is the largest source of uncertainty in CryoGrid 2, strongly affecting the simulated permafrost area. Finally, the prospects of employing CryoGrid 2 as an operational soil-temperature product for Norway are discussed.

URL: http://www.the-cryosphere.net/7/719/2013/tc-7-719-2013.pdf

13097207 Miao, Y. (Chinese Academy of Sciences, Northeast Institute of Geography and Agroecology, Changchun, China); Song, C.; Sun, L.; Wang, X.; Meng, H. and Mao, R. Growing season methane emission from a boreal peatland in the continuous permafrost zone of northeast China; effects of active layer depth and vegetation: Biogeosciences, 9(11), p. 4455-4464, illus. incl. 2 tables, 45 ref., 2012.

Boreal peatlands are significant natural sources of methane and especially vulnerable to abrupt climate change. However, the controlling factors of CH₄ emission in boreal peatlands are still unclear. In this study, we investigated CH₄ fluxes and abiotic factors (temperature, water table depth, active layer depth, and dissolved CH₄ concentrations in pore water) during the growing seasons in 2010 and 2011 in both shrub-sphagnum- and sedge-dominated plant communities in the continuous permafrost zone of Northeast China. The objective of our study was to examine the effects of vegetation types and abiotic factors on CH₄ fluxes from a boreal peatland. In an Eriophorum-dominated community, mean CH₄ emissions were 1.02 and 0.80 mg m^-2 h^-1 in 2010 and 2011, respectively. CH₄ fluxes (0.38 mg m^-2 h^-1) released from the shrub-mosses-dominated community were lower than that from Eriophorum-dominated community. Moreover, in the Eriophorum-dominated community, CH₄ fluxes showed a significant temporal pattern with a peak value in late August in both 2010 and 2011. However, no distinct seasonal variation was observed in the CH₄ flux in the shrub-mosses-dominated community. Interestingly, in both Eriophorum- and shrub-sphagnum-dominated communities, CH₄ fluxes did not show close correlation with air or soil temperature and water table depth, whereas CH₄ emissions correlated well to active layer depth and CH₄ concentration in soil pore water, especially in the Eriophorum-dominated community. Our results suggest that CH₄ released from the thawed CH₄-rich permafrost layer may be a key factor controlling CH₄ emissions in boreal peatlands, and highlight that CH₄ fluxes vary with vegetation type in boreal peatlands. With increasing temperature in future climate patterns, increasing active layer depth and shifting plant functional groups in this region may have a significant effect on CH₄ emission.

DOI: 10.5194/bg-9-4455-2012

13096939 Strauss, Jens (Alfred Wegener Institute for Polar and Marine Research, Periglacial Research Unit, Potsdam, Germany); Schirrmeister, Lutz; Wetterich, Sebastian; Borchers, Andreas and Davydov, Sergei P. Grain-size properties and organic-carbon stock of Yedoma ice complex permafrost from the Kolyma lowland, northeastern Siberia: Global Biogeochemical Cycles, 26(3), Citation GB3003, illus. incl. sketch map, 95 ref., 2012.

The organic carbon stock in permafrost is of increasing interest in environmental research, because during the late Quaternary a large pool of organic carbon accumulated in the sedimentary deposits of arctic permafrost. Because of its potential to degrade and release organic carbon, the organic-matter inventory of Yedoma Ice Complex deposits is relevant to current concerns about the effects of global warming. In this context, it is essential to improve the understanding of preserved carbon quantities and characteristics. The paper aims to clarify the Yedoma Ice Complex origin, and to develop an approach for volumetric organic-matter quantification. Therefore, we analyzed the grain size and the organic-matter characteristics of the deposits exposed at the stratigraphic key site Duvanny Yar (lower Kolyma River, northeast Siberia). A distinct bimodal grain-size distribution confirms a polygenetic origin of the frozen sediments from a floodplain environment. The total organic-carbon content averages 1.5 ± 1.4 wt% while the volumetric organic-carbon content averages 14 ± 8 kg/m³. However, large-scale extrapolations for Yedoma Ice Complex deposits in general are not reasonable yet because of their rather unclear spatial distribution. We conclude that Yedoma Ice Complex formation at Duvanny Yar was dominated by water-related (alluvial/fluvial/lacustrine) as well as aeolian processes. The total organic-carbon content of the studied deposits is low if compared to other profiles, but it is still a significant pool.

DOI: 10.1029/2011GB004104

13090910 Gärtner-Roer, Isabelle (University of Zürich, Department of Geography, Zurich, Switzerland); Heinrich, Ingo and Gärtner, Holger. Wood anatomical analysis of Swiss willow (Salix helvetica) shrubs growing on creeping mountain permafrost: Dendrochronologia (Verona), 31(2), p. 97-104, illus., 50 ref., 2013.

DOI: 10.1016/j.dendro.2012.09.003

13098026 Lacelle, Denis (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Davila, Alfonso F.; Fisher, David; Pollard, Wayne H.; DeWitt, Regina; Heldmann, Jennifer; Marinova, Margarita M. and McKay, Christopher P. Excess ground ice of condensation-diffusion origin in University Valley, Dry Valleys of Antarctica; evidence from isotope geochemistry and numerical modeling: Geochimica et Cosmochimica Acta, 120, p. 280-297, illus. incl. sketch map, 70 ref., November 1, 2013. Includes appendices.

This study investigates the origin and age of ground ice in the uppermost 1 m of permafrost in University Valley, one of the upper valleys in the McMurdo Dry Valleys of Antarctica. In contrast to other regions in the MDV, mean daily air and soil temperatures at the coring sites are always below 0°C, which allows for unique cryogenic processes to occur. In the two cores that were analyzed, excess ground ice was measured throughout, ranging between 23% and 85%. Isotope geochemical trends in the ice-rich permafrost indicate that the ground in Core 5 (65 cm long) and the uppermost 52 cm of Core 7 originated from condensation-diffusion of water vapor; whereas the ground ice between 57-90 cm in Core 7 originated from freezing of liquid water. Using numerical modeling, we show that the excess ground ice of condensation-diffusion origin formed by the long-term thermal contraction-expansion of the cryotic sediments, which allowed for the ice content to exceed pore-filling capacity. Absolute age estimates of the sandy-loam sediments based on Optically Stimulated Luminescence dating indicate that soils have been accreting at the site for at least the last 170±36 ka years, and this places an upper limit to the age of the ground ice. Absolute soil ages allowed us to link the change in ground ice origin in Core 7, which took place around 152±12 ka years, with shifts in climate conditions since marine isotope stage 5e interglacial period. Our findings offer a new process of ground ice emplacement in sediments in cold-dry environments and allow an alternative explanation regarding the enigmatic origin of excess ground ice identified by Mars Odyssey and Phoenix in the northern martian plain, which is that overfilled pore ice can form by vapor deposition and repeated thermal cycling without the presence of melt water. Abstract Copyright (2013) Elsevier, B.V.

DOI: 10.1016/j.gca.2013.06.032

13093618 Kokelj, S. V. (Aboriginal Affairs and Northern Development Canada, Cumulative Impact Monitoring Program, Yellowknife, NT, Canada); Lacelle, D.; Lantz, T. C.; Tunnicliffe, J.; Malone, L.; Clark, I. D. and Chin, K. S. Thawing of massive ground ice in mega slumps drives increases in stream sediment and solute flux across a range of watershed scales: Journal of Geophysical Research: Earth Surface, 118(2), p. 681-692, illus. incl. 2 tables, geol. sketch map, 66 ref., June 2013.

Ice-cored permafrost landscapes are highly sensitive to disturbance and have the potential to undergo dramatic geomorphic transformations in response to climate change. The acceleration of thermokarst activity in the lower Mackenzie and Peel River watersheds of northwestern Canada has led to the development of large permafrost thaw slumps and caused major impacts to fluvial systems. Individual "mega slumps" have thawed up to 10⁶ m³of ice-rich permafrost. The widespread development of these large thaw slumps (up to 40 ha area with headwalls of up to 25 m height) and associated debris flows drive distinct patterns of stream sediment and solute flux that are evident across a range of watershed scales. Suspended sediment and solute concentrations in impacted streams were several orders of magnitude greater than in unaffected streams. In summer, slump impacted streams displayed diurnal fluctuations in water levels and solute and sediment flux driven entirely by ground-ice thaw. Turbidity in these streams varied diurnally by up to an order of magnitude and followed the patterns of net radiation and ground-ice ablation in mega slumps. These diurnal patterns were discernible at the 10³ km² catchment scale, and regional disturbance inventories indicate that hundreds of watersheds are already influenced by slumping. The broad scale impacts of accelerated slumping are indicated by a significant increase in solute concentrations in the Peel River (70,000 km²). These observations illustrate the nature and magnitude of hydrogeomorphic changes that can be expected as glaciogenic landscapes underlain by massive ice adjust to a rapidly changing climate. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/jgrf.20063

13092941 Park, H. (Japan Agency for Marine-Earth Science and Technology, Research Institute for Global Change, Yokosuka, Japan); Walsh, J.; Fedorov, A. N.; Sherstiukov, A. B.; Iijima, Y. and Ohata, T. The influence of climate and hydrological variables on opposite anomaly in active-layer thickness between Eurasian and North American watersheds: The Cryosphere (Online), 7(2), p. 631-645, illus. incl. sketch maps, 61 ref., 2013.

This study not only examined the spatiotemporal variations of active-layer thickness (ALT) in permafrost regions during 1948-2006 over the terrestrial Arctic regions experiencing climate changes, but also identified the associated drivers based on observational data and a simulation conducted by a land surface model (CHANGE). The focus on the ALT extends previous studies that have emphasized ground temperatures in permafrost regions. The Ob, Yenisey, Lena, Yukon, and Mackenzie watersheds are foci of the study. Time series of ALT in Eurasian watersheds showed generally increasing trends, while the increase in ALT in North American watersheds was not significant. However, ALT in the North American watersheds has been negatively anomalous since 1990 when the Arctic air temperature entered into a warming phase. The warming temperatures were not simply expressed to increases in ALT. Since 1990 when the warming increased, the forcing of the ALT by the higher annual thawing index (ATI) in the Mackenzie and Yukon basins has been offset by the combined effects of less insulation caused by thinner snow depth and drier soil during summer. In contrast, the increasing ATI together with thicker snow depth and higher summer soil moisture in the Lena contributed to the increase in ALT. The results imply that the soil thermal and moisture regimes formed in the pre-thaw season(s) provide memory that manifests itself during the summer. The different ALT anomalies between Eurasian and North American watersheds highlight increased importance of the variability of hydrological variables.

URL: http://www.the-cryosphere.net/7/631/2013/tc-7-631-2013.pdf

13097877 Preuss, I. (University of Hamburg, Institute of Soil Science, Hamburg, Germany); Knoblauch, C.; Gebert, J. and Pfeiffer, E. M. Improved quantification of microbial CH₄ oxidation efficiency in arctic wetland soils using carbon isotope fractionation: Biogeosciences, 10(4), p. 2539-2552, illus. incl. 4 tables, 77 ref., 2013.

Permafrost-affected tundra soils are significant sources of the climate-relevant trace gas methane (CH₄). The observed accelerated warming of the arctic will cause deeper permafrost thawing, followed by increased carbon mineralization and CH₄ formation in water-saturated tundra soils, thus creating a positive feedback to climate change. Aerobic CH₄ oxidation is regarded as the key process reducing CH₄ emissions from wetlands, but quantification of turnover rates has remained difficult so far. The application of carbon stable isotope fractionation enables the in situ quantification of CH₄ oxidation efficiency in arctic wetland soils. The aim of the current study is to quantify CH₄ oxidation efficiency in permafrost-affected tundra soils in Russia's Lena River delta based on stable isotope signatures of CH₄. Therefore, depth profiles of CH₄ concentrations and d¹³CH₄ signatures were measured and the fractionation factors for the processes of oxidation (a_ox) and diffusion (a_diff) were determined. Most previous studies employing stable isotope fractionation for the quantification of CH₄ oxidation in soils of other habitats (such as landfill cover soils) have assumed a gas transport dominated by advection (a_trans = 1). In tundra soils, however, diffusion is the main gas transport mechanism and diffusive stable isotope fractionation should be considered alongside oxidative fractionation. For the first time, the stable isotope fractionation of CH₄ diffusion through water-saturated soils was determined with an a_diff = 1.001 1.001 ± 0.000 (n = 3). CH₄ stable isotope fractionation during diffusion through air-filled pores of the investigated polygonal tundra soils was a_diff = 1.013 ± 0.003 (n = 18). Furthermore, it was found that a_ox differs widely between sites and horizons (mean a_ox = 1.017 ± 0.009) and needs to be determined on a case by case basis. The impact of both fractionation factors on the quantification of CH₄ oxidation was analyzed by considering both the potential diffusion rate under saturated and unsaturated conditions and potential oxidation rates. For a submerged, organic-rich soil, the data indicate a CH₄ oxidation efficiency of 50% at the anaerobic-aerobic interface in the upper horizon. The improved in situ quantification of CH₄ oxidation in wetlands enables a better assessment of current and potential CH₄ sources and sinks in permafrost-affected ecosystems and their potential strengths in response to global warming.

DOI: 10.5194/bg-10-2539-2013

13095001 Schober, Andreas (Geoconsult ZT, Wals, Austria); Bannwart, Carsten and Keuschnig, Markus. Rockfall modelling in high alpine terrain; validation and limitations--Steinschlagsimulation in hochalpinem Raum; Validierung und Limitationen: Geomechanik und Tunnelbau = Geomechanics and Tunnelling, 5(4), p. 368-378, (English, German), 18 ref., August 2012.

The Kitzsteinhorn, Salzburg, represents an ideal environment for rockfall simulations in high mountains due to its local infrastructure, the geological conditions and the presence of permafrost. Through climate change and the associated alteration of the glacier and the distribution of permafrost, mass movements increasingly occur in the form of rockfalls and rock slides. In order to improve the understanding and prediction of these gravitational processes, existing models have to be calibrated and adapted or their results have to be verified. As part of the MOREXPERT project, "Monitoring Expert System for Hazardous Rock Walls" (Rockfall 7.1) and 3D (Rockyfor3D 4.1) rockfall simulations were performed. The results of the 3D simulations could be validated directly using orthophotos. It turned out that the modelling results fit very well with the deposits below the investigation area on the glacier and also with the accumulation of debris in the channels and ledges in the face. The largest factor of uncertainty for both programmes is the coverage of snow and ice, respectively the surface of the glacier. As these parameters change with various time scales (hours to years), any simulation of events in the high mountains only represents a snapshot. In order to obtain an overview of the rockfall danger of the entire investigation area, 3D modelling has proved advantageous in addition to the detailed mapping of the terrain. 2D modelling is also useful for a more detailed understanding of rockfall processes in individual zones of the rock face, and its results are ideal for the design of protection measures.

DOI: 10.1002/geot.201200025

13094746 Fischer, L. (University of Zurich, Department of Geography, Zurich, Switzerland); Purves, R. S.; Huggel, C.; Noetzli, J. and Haeberli, W. On the influence of topographic, geological and cryospheric factors on rock avalanches and rockfalls in high-mountain areas: Natural Hazards and Earth System Sciences (NHESS), 12(1), p. 241-254, illus. incl. 1 table, geol. sketch map, 68 ref., 2012.

The ongoing debate about the effects of changes in the high-mountain cryosphere on rockfalls and rock avalanches suggests a need for more knowledge about characteristics and distribution of recent rock-slope instabilities. This paper investigates 56 sites with slope failures between 1900 and 2007 in the central European Alps with respect to their geological and topographical settings and zones of possible permafrost degradation and glacial recession. Analyses of the temporal distribution show an increase in frequency within the last decades. A large proportion of the slope failures (60%) originated from a relatively small area above 3000 m a.s.l. (i.e. 10% of the entire investigation area). This increased proportion of detachment zones above 3000 m a.s.l. is postulated to be a result of a combination of factors, namely a larger proportion of high slope angles, high periglacial weathering due to recent glacier retreat (almost half of the slope failures having occurred in areas with recent deglaciation), and widespread permafrost occurrence. The lithological setting appears to influence volume rather than frequency of a slope failure. However, our analyses show that not only the changes in cryosphere, but also other factors which remain constant over long periods play an important role in slope failures.

DOI: 10.5194/nhess-12-241-2012

13092566 Kehew, Alan E. (Western Michigan University, Department of Geosciences, Kalamazoo, MI); Piotrowski, Jan A. and Jorgensen, Flemming. Tunnel valleys; concepts and controversies; a review: Earth-Science Reviews, 113(1-2), p. 33-58, illus. incl. sketch maps, 117 ref., June 2012.

Although erosion of valleys by subglacial meltwater was first proposed more than 100 years ago, the processes that produced these valleys under past ice sheets have remained a topic of vigorous debate. The most commonly hypothesized mechanisms have included gradual formation by sediment deformation into the incipient valleys under steady state conditions and subsequent transport by meltwater to the ice margin; time-transgressive formation along a retreating ice margin by drainage of surface meltwater to the bed or release of impounded meltwater behind a marginal permafrost wedge, probably catastrophically; and rapid erosion during widespread, catastrophic basal sheetflood events. Recent application of new and enhanced imaging techniques has led to the identification of many new tunnel valleys both on land and offshore throughout the regions glaciated during former ice ages. In addition, new advances in understanding of subglacial hydrology, both from modelling and field instrumentation have helped to constrain the drainage of meltwater from past ice sheet beds. This work elucidates the role of subglacial groundwater flow systems in evacuating meltwater from the bed, but also shows that groundwater flow alone was not enough to maintain ice bed meltwater pore pressures below the level of ice flotation. Both modelling and field observations indicate that subglacial conduits oriented parallel to glacial flow lines reorganize groundwater flow systems into basins containing lateral flow toward conduits cut upward into the ice or downward into the bed. Because of the inability of groundwater flow to account for all the meltwater produced by basal melting, other drainage mechanisms involving both non-channelized and channelized meltwater flow have been proposed. The notion of catastrophic drainage of impounded basal meltwater is still favored by many, and the discovery of hundreds of subglacial lakes beneath the Antarctic Ice Sheet and the likelihood of similar lakes beneath Pleistocene ice sheets provides a source of water for those advocating catastrophic formation for tunnel valleys. Proponents of catastrophic drainage consider the valleys to be channels reflecting the width and perhaps depths of flows that formed them. Tunnel valleys produced by the Scandinavian Ice Sheet have been described and mapped on land as well as on the sea bed. Valleys and networks of valleys, some of which are totally buried, have been linked to 3 or more glaciations. Tunnel valley networks from the last (Weichselian) glaciation in Denmark can be related to specific ice margins developed during ice retreat. In North America, most research has focused on tunnel valleys associated with ice margins formed by the last (Wisconsin) glaciation along the southern margin of the Laurentide Ice Sheet. Abstract Copyright (2012) Elsevier, B.V.

DOI: 10.1016/j.earscirev.2012.02.002

13097559 Zürcher, S. (University of Bern, Climate and Environmental Physics, Bern, Switzerland); Spahni, R.; Joos, F.; Steinacher, M. and Fischer, H. Impact of an abrupt cooling event on interglacial methane emissions in northern peatlands: Biogeosciences, 10(3), p. 1963-1981, illus. incl. 2 tables, 104 ref., 2013.

Rapid changes in atmospheric methane (CH₄), temperature and precipitation are documented by Greenland ice core data both for glacial times (the so called Dansgaard-Oeschger (D-O) events) as well as for a cooling event in the early Holocene (the 8.2 kyr event). The onsets of D-O warm events are paralleled by abrupt increases in CH₄ by up to 250 ppb in a few decades. Vice versa, the 8.2 kyr event is accompanied by an intermittent decrease in CH₄ of about 80 ppb over 150 yr. The abrupt CH₄ changes are thought to mainly originate from source emission variations in tropical and boreal wet ecosystems, but complex process oriented bottom-up model estimates of the changes in these ecosystems during rapid climate changes are still missing. Here we present simulations of CH₄ emissions from northern peatlands with the LPJ-Bern dynamic global vegetation model. The model represents CH₄ production and oxidation in soils and transport by ebullition, through plant aerenchyma, and by diffusion. Parameters are tuned to represent site emission data as well as inversion-based estimates of northern wetland emissions. The model is forced with climate input data from freshwater hosing experiments using the NCAR CSM1.4 climate model to simulate an abrupt cooling event. A concentration reduction of ~10 ppb is simulated per degree K change of mean northern hemispheric surface temperature in peatlands. Peatland emissions are equally sensitive to both changes in temperature and in precipitation. If simulated changes are taken as an analogy to the 8.2 kyr event, boreal peatland emissions alone could only explain 23% of the 80 ppb decline in atmospheric methane concentration. This points to a significant contribution to source changes from low latitude and tropical wetlands to this event.

DOI: 10.5194/bg-10-1963-2013

13099918 Krivonogov, S. K. (Korea Institute of Geoscience and Mineral Resources, Daejeon, South Korea); Yi, S.; Kashiwaya, K.; Kim, J. C.; Narantsetseg, T.; Oyunchimeg, T.; Safonova, I. Y.; Kazansky, A. Y.; Sitnikova, T.; Kim, J. Y. and Hasebe, N. Solved and unsolved problems of sedimentation, glaciation and paleolakes of the Darhad Basin, northern Mongolia: Quaternary Science Reviews, 56, p. 142-163, illus. incl. geol. sketch maps, 76 ref., November 21, 2012.

The paper reviews previously published and presents new data on the Darhad Basin, Mongolia, which is a key locality for reconstruction of Quaternary glaciation and environmental changes in northern Central Asia. The previously published data include those obtained in the 20th century by Soviet geological surveys and academic researches of the Darhad Basin, which are, as a rule, not accessible for an international reader, and those obtained by several international teams during the last decade. The new results include geomorphologic, sedimentological and geochronological data obtained prior to and within the International Darhad Drilling Project (DDP-2010). These data show that the Darhad sedimentary sequence has been formed since the Pliocene and represents a detailed archive of environmental changes due to a high content of lacustrine beds. Lakes formed several times in the Darhad Basin by basaltic, glacial and sedimentary dams, which blocked the water outlet of the basin. Of special interest in this paper are the late Pleistocene damming events, which are well-documented in the sediments and landforms, however, their chronology is still obscure. There have been two stages of deep lake. The first lake was dammed by a glacier during late MIS 5 (Krivonogov et al., 2005) or, alternatively, during early to middle MIS 3 (Gillespie et al., 2008a). The second damming, glacial or sedimentary, formed another deep lake during MIS 4 or MIS 2. The level of the lake was greatly variable up to its complete disappearance. Our new data from the DDP10-3 and DN-1 boreholes and from the Hodon outcrop illustrate the Holocene history of the paleolake, which was dammed by the sediments and was kept at low levels. We propose a first sedimentation model for the Holocene part of the lacustrine sedimentary sequence. The lake was minimal or disappeared at ca 12-9.6 and after 4.5 ka cal. BP, relatively deep at 9.6-7.1 and 6.4-4.5 ka cal. BP and shallow at 7.1-6.4 ka cal. BP. Conclusively, we highlighted solved and unsolved geological problems of the Darhad Basin, the most important of which are our recognized stages of the paleolake development (solved) and the detailed chronology and environments of the lacustrine and glacial events (unsolved). Abstract Copyright (2012) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2012.08.013

13092924 Krupoderov, V. S. (Russian Research Institute of Hydrogeology and Engineering Geology, Moscow, Russian Federation); Luk'yanchikov, V. M. and Sokolovskiy, L. G. Rezul'taty i aktual'nyye napravleniya gidrogeologicheskikh, inzhenerno-geologicheskikh i geokriologicheskikh rabot [Results and trends of hydrogeological, engineering-geological and geocryological surveys]: Razvedka i Okhrana Nedr, 2012(9), p. 112-117 (English sum.), illus., September 2012.

This paper describes results and basic directions of the hydro-geological, engineering-geological and geocryological investigations of the subsurface space aimed at evaluation of the groundwater resource potential, geoenvironmental state, prediction of consequences from industrial and civil development of territories and for other purposes.

13090195 Pimentel, E. (Eidgenössische Technische Hochschule Zürich, Institute for Geotechnical Engineering, Zurich, Switzerland); Sres, A. and Anagnostou, G. Large-scale laboratory tests on artificial ground freezing under seepage-flow conditions: Géotechnique, 62(3), p. 227-241 (French sum.), illus. incl. 4 tables, 19 ref., March 2012.

A high seepage-flow velocity represents a potential problem for artificial ground freezing (AGF), as it may hinder the growth of an ice body and the development of a closed ice wall. To avoid such difficulties, careful thermal hydraulic analysis is necessary. This presupposes, of course, that the reliability of the underlying computational models has been verified by means of comparisons with the results of appropriate field tests or physical models. As there are scarcely any results of such tests available in the literature, a new large-scale physical model for AGF under conditions of high seepage-flow velocities has been developed. The present paper documents in detail the experimental set-up, the thermodynamic properties of the soil material, the boundary conditions, and the results of six experiments. These data are valuable as a reliable basis for the evaluation of numerical or analytical prediction models. Additionally, the paper discusses existing closed-form solutions for AGF with and without seepage flow in the light of the experimental results, from the perspective of the refrigeration time and the cooling power required for the merger of a freeze-pipe row.

DOI: 10.1680/geot.9.P.120

13092345 Hartlen, Jan (JH GeoConsulting, Limhamn, Sweden); Christensen, Henrik and Jansson, Sven. Citytunneln, Malmo; geotechnical hazards and opportunities: Proceedings of the Institution of Civil Engineers. Geotechnical Engineering, 165(1), p. 35-44, illus. incl. 4 tables, chart, 10 ref., February 2012.

Penetrating limestone in Malmo, Sweden, the underground works at Citytunneln comprise two parallel 7.8 m internal diameter railway tunnels, 6 km long, excavated with tunnel-boring machines. Triangeln Station, halfway along the tunnels, is a 30 m wide cavern with 15 m soil/rock cover and a row of pillars for central support. Malmo C Station at the northern end is an open cut-and-cover structure. There are two contracts, one for the tunnels and cavern (Lot E201) and another for Malmo C Station (Lot E101). Differing risk management techniques maintained an appropriate balance in the risk distribution. Groundwater lowering close to the harbour and the stability of adjacent historic buildings were the main hazards in E101. The design was based on the client's geotechnical interpretative report (GIR), and encountered deviations were compensated within a unit rate contract (E101). By contrast, the tunnelling risks in E201 were handled in a design-build contract (Lot E201), with the contractor responsible for the GIR. The geotechnical risk management was based on contractual geotechnical reference conditions. The observational method was used successfully to mitigate geotechnical hazards as well as to exploit opportunities.

DOI: 10.1680/geng.9.00079

13095236 Sanders, Diethard (University of Innsbruck, Institute for Geology and Paleotology, Innsbruck, Austria). Talus accumulation in detachment scars of late Holocene rock avalanches, Eastern Alps (Austria); rates and implications: Geo.Alp, 9, p. 82-99, illus. incl. 3 tables, geol. sketch maps, 87 ref., 2012.

In mountain ranges, under the present interglacial conditions, active scree slopes tend to cluster within a certain range of altitude, probably because of an altitudinal/climatic span with maximum efficiency of frost cracking ('talus window'). In the Northern Calcareous Alps, large active scree slopes within the detachment scars of two late Holocene rock avalanches accumulated at mean rates of 7-18 mm/a over a time interval of ~1.7-3.8 ka. A plot of sedimentation rates as a function of time interval (Sadler plot) shows: (a) that the two scree slopes accumulated at comparatively high rates, and that (b) the rate of deposition must have been much higher (up to >1 meter/a) shortly after rock avalanching, but then diminished. The apex of each scree slopes is located close to 1400 m a.s.l., i. e. some 400-1000 meters lower in altitude than the apices of most other scree slopes of the Eastern Alps. At the time of rock avalanching, the mountain flank laterally adjacent to the scree slopes was forested up to its crest, as it is today. Climatic data (1971-2000) of stations ranging from 498-3105 m a.s.l. in altitude suggest that the intense scree production is not readily explained by the annual number of ice days (ID; days with T<0°C). The annual number of freeze-thaw days (FTD), in contrast, remains nearly constant from station Haiming (695 m a.s.l.; 130 FTD) up to Obervermunt (2040 m a.s.l.; 125 FTD). Thus, scree production may have been mainly controlled by FTD or by, both, FTD and ID compensating in effect each other with increasing altitude. In addition, processes unrelated to freezing probably significantly contributed to scree production, such as 'scraping' off scree by heavy rainfalls and snow cascading or avalanching down cliffs, spalling of rock by increased pore-water pressure, and rock cracking/loosening by thermal stress fatigue well-above the freezing point. I suggest that the prevalence of presently-active scree slopes in a certain altitude range (slope apex between ~1800 to ~2600 m a.s.l.) of the Eastern Alps results from: (a) the gross topography across the orogen, with internides (Central Alps) the highest, (b) medium-scale morphology produced mainly by glacial erosion (cirques and glacially-carved valleys flanked by cliffs), (c) post-glacial climb of vegetation, superposed with (d) an optimal combination of all processes (irrespective of their total altitude range) capable to (i) liberate scree from cliffs, and (ii) at a combined rate high enough to sustain a sizeable, active scree slope. This interpretation does not invalidate, but embeds the concept of the 'frost-cracking window'. In the Northern Calcareous Alps, observations on the long-term (here: >10 ka) and short term (here: tens of years) dynamics of talus accumulations indicate that the role of vegetation for scree shedding from cliffs (technically, rock flanks with dip >&eq;45°) has been underestimated. In the Alps, the scarcity of presently active talus below about 1600-2000 m a.s.l. mainly results from slope stabilization by vegetation rather than by lack of processes capable to liberate scree from bare rocky slopes. The two scree slopes described herein indicate that, under certain geological circumstances, rapid talus accumulation in comparatively low topographic position is possible also under interglacial climatic conditions.

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13100698 Douglas, Thomas A. (U.S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK). Dramatic seasonality of biogeochemical signatures in watersheds underlain by continuous and discontinuous permafrost [abstr.]: in Goldschmidt abstracts 2013, Mineralogical Magazine, 77(5), p. 1006, 2013. Meeting: Goldschmidt 2013, Aug. 25-30, 2013, Florence, Italy.

High latitude watersheds experience two extreme seasons: 6-9 months of cold, snow covered winter and a warm, bright, summer. Between these seasons is the spring freshet, a dramatic two to three week period when up to three quarters of the yearly precipitation runs off. The summer to winter transition is far less remarkable as temperatures and light slowly decrease until winter arrives. The intense seasonality and transitions in Arctic rivers are associated with unique biogeochemical signatures, a landscape scale "view" of vegetation, soil, weathering, and water column processes. Discerning sources or fluxes of compounds out of Arctic rivers is difficult in large rivers because they represent the combined effect of innumerable plot-scale melt water sources, each coming from different soil and vegetation types, each experiencing a slightly different melt timing and evolution, and each following its own timing. Work at Arctic sites typically means field work in remote locations with sparse ancillary data and this provides added challenges. Spring melt is characterized by an ionic pulse of solutes, dissolved organic carbon and other nutrients (ammonium, phosphate and nitrate) leached by snow melt water from the surface organic mat of vegetation and near-surface soil. Summer and fall flows are comprised largely of shallow flow from a deepening seasonally thawed ("active") layer. During late summer with an expanded active layer or at sites where permafrost is degrading these processes may be associated with an increasing mineral weathering signal into watersheds. The watershed biogeochemical response to precipitation in continuous and discontinuous terrains may also yield insight into subsurface permafrost geomorphological characteristics. Winter processes are the least studied or understood but overflow ice ("aufeis") provides access to deep, old waters. This presentation will focus on using water stable isotopes, major ion concentrations, and permafrost delineation to identify biogeochemical sources in watersheds draining continuous and discontinuous permafrost. Field sites represent permafrost terrains in Alaska from the North Slope to the Interior. Biogeochemical processes associated with scaling, meteorology, and climate warming will be discussed.

DOI: 10.1180/minmag.2013.077.5.4

13099644 Mitrofanov, I. G. (Institute for Space Research, Moscow, Russian Federation); Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Malakhov, A. A. and Sanin, A. B. Solar water permafrost; is it detected on the Moon? Is it expected on the Mercury?: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2083, illus., 5 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on Sept. 7, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2083.pdf

13101045 Walker, Laurel A. (University of Kentucky, Earth and Environmental Sciences, Lexington, KY); Bemis, Sean P. and DeVore, Joshua R. The effects of global climate change on landscape evolution in the Boreal forest of the central Alaska Range [abstr.]: in Geological Society of America, 2013 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 45(7), p. 118, 2013. Meeting: Geological Society of America, 2013 annual meeting & exposition, Oct. 27-30, 2013, Denver, CO.

Glaciation cycles during the Quaternary produced major shifts in vegetation patterns in subarctic regions. Predicted rapid changes in global climate at high latitudes could produce vegetative shifts not previously recognized during the Quaternary. Global climate change could specifically affect the subarctic region by shifting the boreal forest biome north, which could alter ecological and geomorphic processes particularly exhibited in landscape evolution. To investigate hillslope processes operating in the boreal forest environment and how this may vary between glacial and interglacial cycles, we target the extensive sequence of fluvial terraces along the Nenana River valley in Alaska. We hypothesize that factors causing higher soil shear strength such as depth to permafrost, slope angle, slope aspect, rooting depth, and soil moisture content act as primary controls on diffusion rates at higher-latitudes. Limited existing age control, coupled with correlation to the Marine Isotope Stages (MIS), are being used to date the fluvial terrace sequence of the Nenana River valley and derive a nonlinear sediment flux equation for this boreal forest environment. Preliminary observations suggest that high-latitude hillslopes diffuse at slower rates and appear younger than they are when compared to arid, mid-latitude regions. This behavior and resultant appearance is due to controlling factors which heighten soil shear strength. This diffusion characteristic is exemplified in our study area by hillslope profiles transitioning from a convex to concave shape through an inflection point which migrates over time. In conclusion, diffusion rates are slower in this boreal forest environment when compared to mid-latitude regions, which makes landforms appear younger than their true age. Changes in global climate could cause shifts in vegetation, increasing diffusion rates at high latitudes not previously noted in the Quaternary. An increased rate of diffusion could not only shift the boreal forest biome north, but potentially increase hazards related to land failure and have global implications at this latitude.

URL: https://gsa.confex.com/gsa/2013AM/webprogram/Paper227630.html

13097604 Le Deit, Laetitia (German Aerospace Center, Institute of Planetary Research, Berlin, Germany); Hauber, E.; Fueten, F.; Pondrelli, M.; Rossi, A. P. and Jaumann, Ralf. Investigation of possible coastal and periglacial landforms in Gale Crater, Mars: in 44th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 44, Abstract 2187, illus., 14 ref., 2013. Meeting: 44th lunar and planetary science conference, March 18-22, 2013, Woodlands, TX. Accessed on June 13, 2013.

URL: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/2187.pdf

13097606 Oehler, D. Z. (NASA, Johnson Space Center, Houston, TX). Periglacial analog for landforms in Gale Crater, Mars: in 44th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 44, Abstract 1322, illus. incl. sketch map, 6 ref., 2013. Meeting: 44th lunar and planetary science conference, March 18-22, 2013, Woodlands, TX. Accessed on June 13, 2013.

URL: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1322.pdf

13099657 Scheidegger, J. M. (University of East Anglia, School of Environmental Sciences, Norwich, United Kingdom) and Bense, V. F. Potential inflow of sub-glacial groundwater to proglacial lakes along the western margin of the Greenland ice sheet [abstr.]: in European Geosciences Union general assembly 2012, Geophysical Research Abstracts, 14, Abstract EGU2012-990-1, 2012. Meeting: European Geosciences Union general assembly 2012, April 22-27, 2012, Vienna, Austria.

URL: http://meetingorganizer.copernicus.org/EGU2012/EGU2012-990-1.pdf

13099675 Séjourné, A. (Université Paris-Sud, Laboratory of Interactions and Dynamics of Surface Geology, Orsay, France); Costard, F.; Gargani, J. and Marmo, C. Formation and evolution of periglacial landforms in context of global warming; comparison Earth-Mars [abstr.]: in European Geosciences Union general assembly 2012, Geophysical Research Abstracts, 14, Abstract EGU2012-1047-1, 2012. Meeting: European Geosciences Union general assembly 2012, April 22-27, 2012, Vienna, Austria.

URL: http://meetingorganizer.copernicus.org/EGU2012/EGU2012-1047-1.pdf

13097581 van Hardenbroek, M. (Utrecht University, Institute of Environmental Biology, Utrecht, Netherlands); Heiri, O.; Parmentier, F. J. W.; Bastviken, D.; Ilyashuk, B. P.; Wiklund, J. A.; Hall, R. I. and Lotter, A. F. Evidence for past variations in methane availability in a Siberian thermokarst lake based of d¹³C of chitinous invertebrate remains: in International Association of Limnogeology; Isotopes and lakes (Leng, Melanie J., editor; et al.), Quaternary Science Reviews, 66, p. 74-84, illus. incl. 3 tables, sketch map, 62 ref., April 15, 2013. Meeting: 5th international limnogeology congress, Aug. 31-Sept. 3, 2011, Konstanz, Germany.

Understanding past methane dynamics in arctic wetlands and lakes is crucial for estimating future methane release. Methane fluxes from lake ecosystems have increasingly been studied, yet only few reconstructions of past methane emissions from lakes are available. In this study, we develop an approach to assess changes in methane availability in lakes based on d¹³C of chitinous invertebrate remains and apply this to a sediment record from a Siberian thermokarst lake. Diffusive methane fluxes from the surface of ten newly sampled Siberian lakes and seven previously studied Swedish lakes were compared to taxon-specific d¹³C values of invertebrate remains from lake surface sediments to investigate whether these invertebrates assimilated ¹³C-depleted carbon typical for methane. Remains of chironomid larvae of the tribe Orthocladiinae that, in the study lakes, mainly assimilate plant-derived carbon had higher d¹³C than other invertebrate groups. d¹³C of other invertebrates such as several chironomid groups (Chironomus, Chironomini, Tanytarsini, and Tanypodinae), cladocerans (Daphnia), and ostracods were generally lower. d¹³C of Chironomini and Daphnia, and to a lesser extent Tanytarsini was variable in the lakes and lower at sites with higher diffusive methane fluxes. d¹³C of Chironomini, Tanytarsini, and Daphnia were correlated significantly with diffusive methane flux in the combined Siberian and Swedish dataset (r = -0.72, p = 0.001, r = -0.53, p = 0.03, and r = -0.81, p < 0.001, respectively), suggesting that d¹³C in these invertebrates was affected by methane availability. In a second step, we measured d¹³C of invertebrate remains from a sediment record of Lake S1, a shallow thermokarst lake in northeast Siberia. In this record, covering the past ca 1000 years, d¹³C of taxa most sensitive to methane availability (Chironomini, Tanytarsini, and Daphnia) was lowest in sediments deposited from ca AD 1250 to ca AD 1500, and after AD 1970, coinciding with warmer climate as indicated by an independent local temperature record. As a consequence the offset in d¹³C between methane-sensitive taxa and bulk organic matter was higher in these sections than in other parts of the core. In contrast, d¹³C of other invertebrate taxa did not show this trend. Our results suggest higher methane availability in the study lake during warmer periods and that thermokarst lakes can respond dynamically in their methane output to changing environmental conditions. Abstract Copyright (2013) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2012.04.009

13097608 Pedersen, G. B. M. (University of Iceland, Institute of Earth Sciences, Nordic Volcanological Center, Reykjavik, Iceland) and Head, James W. Frozen Martian lahars? Emplacement mechanisms and geologic impact of Utopia-Elysium flows: in 44th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 44, Abstract 1514, illus. incl. geol. sketch map, 23 ref., 2013. Meeting: 44th lunar and planetary science conference, March 18-22, 2013, Woodlands, TX. Accessed on June 28, 2013.

URL: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1514.pdf

13097611 Sizemore, H. G. (Montani Consulting, Hillsboro, WV); Zent, A. P. and Rempel, A. W. Initiation and growth of Martian ice lenses: in 44th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 44, Abstract 1368, illus., 11 ref., 2013. Meeting: 44th lunar and planetary science conference, March 18-22, 2013, Woodlands, TX. Accessed on June 28, 2013.

URL: http://www.lpi.usra.edu/meetings/lpsc2013/pdf/1368.pdf

13100883 Herzog, Franziska. Untersuchungen zum Gefriersog und der Eislinsenbildung bei der Bodenfrostung [Freezing suction and ice lens formation during soil freezing]: in 32. Baugrundtagung; Forum für junge Geotechnik-Ingenieure; Beiträge der Spezialsitzung (Deutsche Gesellschaft für Geotechnik), Deutsche Gesellschaft für Geotechnik, Essen, Germany, p. 37-44, 7 ref., 2012. Meeting: 32. Baugrundtagung; Forum für junge Geotechnik-Ingenieure, Sept. 26, 2012, Mainz, Germany.

13099469 Hooper, Donald M. (Southwest Research Institute, Geosciences and Engineering Division, San Antonio, TX); Dinwiddie, Cynthia L.; McGinnis, Ronald N.; Smart, Kevin J. and Roberts, Marla M. Observations of debris flows at the Great Kobuk Sand Dunes, Alaska; implications for analogous features on Mars: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2040, illus., 21 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 19, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2040.pdf

13099470 Souness, C. J. (Aberystwyth University, Institute of Geography and Earth Sciences, Ceredigion, United Kingdom) and Abramov, A. The volcanic terrains of Kamchatka, eastern Russia; a glacial and periglacial environment with potential for Mars analog-based research: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 1071, illus. incl. sketch map, 13 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 19, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1071.pdf

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13091311 Blais-Stevens, A.; Smith, S. L.; Kremer, M.; Bonnaventure, P.; Lewkowicz, A. G.; Lipovsky, P.; Duguay, M.; Ednie, M. and Koch, J. Geohazard information and permafrost characterization surveys along the Yukon-Alaska Highway corridor: Scientific Presentation - Geological Survey of Canada, Rep. No. 16, 1 sheet, illus., 9 ref., 2013. Poster. Accessed on Nov. 15, 2013.

URL: http://geoscan.ess.nrcan.gc.ca/cgi-bin/starfinder/0?path=geoscan.downloade.fl&id ...

13095544 Grosse, Guido (University of Alaska, Fairbanks, AK); Robinson, Joel E.; Bryant, Robin; Taylor, Maxwell D.; Harper, William; DeMasi, Amy; Kyker-Snowman, Emily; Veremeeva, Alexandra; Schirrmeister, Lutz and Harden, Jennifer. Distribution of late Pleistocene ice-rich syngenetic permafrost of the Yedoma Suite in east and central Siberia, Russia: Open-File Report - U. S. Geological Survey, Rep. No. OF 2013-1078, 24 p., illus. incl. 3 tables, geol. sketch maps, 81 ref., 2013. Accessed on Oct. 29, 2013; includes appendices.

This digital database is the product of collaboration between the U.S. Geological Survey, the Geophysical Institute at the University of Alaska, Fairbanks; the Los Altos Hills Foothill College GeoSpatial Technology Certificate Program; the Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany; and the Institute of Physical Chemical and Biological Problems in Soil Science of the Russian Academy of Sciences. The primary goal for creating this digital database is to enhance current estimates of soil organic carbon stored in deep permafrost, in particular the late Pleistocene syngenetic ice-rich permafrost deposits of the Yedoma Suite. Previous studies estimated that Yedoma deposits cover about 1 million square kilometers of a large region in central and eastern Siberia, but these estimates generally are based on maps with scales smaller than 1:10,000,000. Taking into account this large area, it was estimated that Yedoma may store as much as 500 petagrams of soil organic carbon, a large part of which is vulnerable to thaw and mobilization from thermokarst and erosion. To refine assessments of the spatial distribution of Yedoma deposits, we digitized 11 Russian Quaternary geologic maps. Our study focused on extracting geologic units interpreted by us as late Pleistocene ice-rich syngenetic Yedoma deposits based on lithology, ground ice conditions, stratigraphy, and geomorphological and spatial association. These Yedoma units then were merged into a single data layer across map tiles. The spatial database provides a useful update of the spatial distribution of this deposit for an approximately 2.32 million square kilometers land area in Siberia that will (1) serve as a core database for future refinements of Yedoma distribution in additional regions, and (2) provide a starting point to revise the size of deep but thaw-vulnerable permafrost carbon pools in the Arctic based on surface geology and the distribution of cryolithofacies types at high spatial resolution. However, we recognize that the extent of Yedoma deposits presented in this database is not complete for a global assessment, because Yedoma deposits also occur in the Taymyr lowlands and Chukotka, and in parts of Alaska and northwestern Canada.

URL: http://pubs.usgs.gov/of/2013/1078/

13091308 Ednie, M.; Chartrand, J.; Smith, S. L.; Duchesne, C. and Riseborough, D. W. Report on 2012 field activities and collection of ground thermal and active layer data in the Mackenzie Corridor completed under Northwest Territories Science Licence 053: Open-File Report - Geological Survey of Canada, Rep. No. 7416, 69 p., illus. incl. tables, 9 ref., 2013. Accessed on Nov. 15, 2013.

This report presents a summary of field activities conducted in 2011 in the Mackenzie Corridor under N.W.T. Science Licence 918. Air temperature, ground thermal and active layer data acquired from permafrost monitoring sites visited in 2011 throughout the corridor are provided in graphical and tabular format. This report will be distributed to community organizations and stakeholders in the study region to provide an update on field activities. The ground thermal and active layer data presented provide essential baseline information that can be utilized by stakeholders and others for various purposes such as land management activities, regulatory processes and design of northern infrastructure.

URL: http://geoscan.ess.nrcan.gc.ca/cgi-bin/starfinder/0?path=geoscan.downloade.fl&id ...

13093754 Lech, Megan E. (Geoscience Australia, Canberra, A.C.T., Australia) and Trewin, Cindy L. Weathering, erosion, landforms and regolith; teacher notes and student activities: Record - Geoscience Australia, Rep. No. 2013/16, 104 p., illus. incl. block diags., geol. sketch maps, 4 p. ref., 2013. ISBN: 978-1-922201-41-6. GeoCat no. 75055. Accessed on Nov. 21, 2013.

Weathering, erosion and deposition are all around us. Without these processes we would not have our mountains, river valleys, sandy beaches or even the soil in which we grow our food. This booklet outlines the processes of weathering, erosion and deposition for the information of teachers and students. Includes case studies about the formation of many Australian landforms such as Uluru, the Warrumbungles and the Bungle Bungles. The booklet also includes reproducible student activities that provide students with fun and easy ways to learn about the processes that shape the Earth. 50 page booklet 8 student activities suggested answers. A comprehensive resource to introduce your students to the concept of regolith, an important way of looking at, and mapping, the landscape. Suitable for primary Years 5-6 and secondary Years 7-12.

URL: https://www.ga.gov.au/products/servlet/controller?event=GEOCAT_DETAILS&catno=750 ...

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