|
14094306 Stiegler, Christian (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Rode, Matthias; Sass, Oliver and Otto, Jan-Christoph. An undercooled scree slope detected by geophysical investigations in sporadic permafrost below 1000 M ASL, central Austria: Permafrost and Periglacial Processes, 25(3), p. 194-207, illus. incl. 1 table, sketch map, 40 ref., September 2014.
Multi-method geophysical investigations, accompanied by microclimatic measurements and vegetation mapping, were performed at an undercooled scree slope near Schladming (Austria) in the eastern Alps in order to detect, map and monitor mountain permafrost. The study site, at an elevation of 990 m asl, is one of the lowest-lying examples of a cold, undercooled scree slope in the Alps. Geophysical measurements with electrical resistivity tomography, ground-penetrating radar and seismic refraction indicate the presence of several isolated areas of frozen ground over a full year, far below the regional lower limit of mountain permafrost. Frozen sediments identified at shallow depths (beneath 1-3 m) were 5-20 m thick and ice-rich. Near-surface temperatures at the foot of the scree slope were strongly influenced by pronounced cooling. Vegetation mapping showed a dominance of cryophilic plant species. The results suggest that the scree slope is strongly influenced by the interplay of vegetation cover, ground thermal regime and the distribution of frozen sediments. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1813
14098556 Blikra, Lars Harald (Aknes/Tafjord Early Warning Centre, Stranda, Norway) and Christiansen, Hanne H. A field-based model of permafrost-controlled rockslide deformation in Northern Norway: Geomorphology, 208, p. 34-49, illus. incl. sketch maps, 36 ref., March 1, 2014.
Knowledge about the detailed processes linked to the existence of permafrost in rockslide fractures is sparse. Large parts of the Jettan rockslide are located right below the discontinuous permafrost limit in the arctic part of the alpine landscape of northern Norway. Combining four years of meteorological and rockslide deformation data with temperature measurements from different parts of open fractures, shallow bedrock boreholes and air, as well as daily snow cover observations, allows a detailed identification of the key processes involved. These field data are the basis for the development of a permafrost controlled rockslide model. Seasonally, the deformation has a very distinctive pattern with high deformation starting abruptly right after snowmelt in May, and lasting until snow isolation in winter. Then there is a gradual transition to medium deformation as the ground is cooled further for another 1-2 months. Finally, the winter period, when maximum snow occurs in the fractures, is characterized by limited or almost no deformation. The primary controlling deformation process is meltwater percolation into fractures in summer with significant refreezing, ice formation and temperature increase in the lower part of the fractures from -1°C to 0°C. Sporadic permafrost exists below the discontinuous permafrost limit, and may extend into open fractures and sliding planes. Another primary process is the significant cold air accumulation in fractures in early winter, due to the Balch effect, which significantly cools the fracture and surrounding rock promoting permafrost development. Finally, the cold air effect is stopped by snow isolation once enough snow has accumulated in the fracture by late winter. The deformation itself is thought to be controlled by changing shear strength of the brecciated sliding planes due to either changing ice temperatures and/or variations in water infiltration to the unsaturated sliding zones. The overall system is very locally controlled driving itself, and the effect of a future climate change can thus be of minor importance. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.geomorph.2013.11.014
14101731 Klapstein, Sara J. (University of Guelph, Department of Integrative Biology, Guelph, Canada); Turetsky, Merritt R.; McGuire, A. David; Harden, Jennifer W.; Czimczik, Claudia I.; Xu, Xiaomei; Chanton, Jeffrey P. and Waddington, James M. Controls on methane released through ebullition in peatlands affected by permafrost degradation: Journal of Geophysical Research: Biogeosciences, 119(G3), p. 418-431, illus. incl. 3 tables, 50 ref., March 2014.
Permafrost thaw in peat plateaus leads to the flooding of surface soils and the formation of collapse scar bogs, which have the potential to be large emitters of methane (CH4) from surface peat as well as deeper, previously frozen, permafrost carbon (C). We used a network of bubble traps, permanently installed 20 cm and 60 cm beneath the moss surface, to examine controls on ebullition from three collapse bogs in interior Alaska. Overall, ebullition was dominated by episodic events that were associated with changes in atmospheric pressure, and ebullition was mainly a surface process regulated by both seasonal ice dynamics and plant phenology. The majority (>90%) of ebullition occurred in surface peat layers, with little bubble production in deeper peat. During periods of peak plant biomass, bubbles contained acetate-derived CH4 dominated (>90%) by modern C fixed from the atmosphere following permafrost thaw. Post-senescence, the contribution of CH4 derived from thawing permafrost C was more variable and accounted for up to 22% (on average 7%), in the most recently thawed site. Thus, the formation of thermokarst features resulting from permafrost thaw in peatlands stimulates ebullition and CH4 release both by creating flooded surface conditions conducive to CH4 production and bubbling as well as by exposing thawing permafrost C to mineralization. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2013JG002441
14092048 Tarbeyeva, A. M. (Moskovskiy Gosudarstvennyy Universitet im. M. V. Lomonosova, Moscow, Russian Federation) and Surkov, V. V. Chetkovidnyye rusla malykh rek mnogoletney merzloty [Braided channels of small rivers in permafrost zones]: Geografiya i Prirodnyye Resursy, 2013(3), p. 27-32 (English sum.), illus. incl. sketch map, 9 ref., September 2013.
The authors examine the factors that are responsible for the formation of the beaded structure of channels in the permafrost zone. It is found that formation of beaded channels in the permafrost zone is possible only in the case of small gradients and water flow rates. The existence of such channels in the permafrost zone is unstable; hence there is little likelihood that they have persisted in a relict form to date.
14102430 Vaks, A. (Oxford University, Oxford, United Kingdom); Gutareva, O. S.; Breytenbach, S. F. M.; Avirmed, Ye.; Meyson, A. D.; Tomas, A. L.; Osintsev, A. V.; Kononov, A. M. and Khenderson, G. M. Stalaktity i stalagmity otkryvayut tayny istorii mnogoletney merzloty Sibiri [Stalactites and stalagmites reveal mysteries of the permafrost in Siberia]: in Kak my rosli i v tvorchestve vzrosleli 1984-2014 gg. (Melnikov, V. S., editor), Kholod'OK!, 1(11), p. 57-61, illus., 2014.
14094307 Duca, Silvia (ENI, Upstream and Technical Services, Petroleum Engineering Laboratories, Milan, Italy); Occhiena, C.; Mattone, M.; Sambuelli, L. and Scavia, C. Feasibility of ice segregation location by acoustic emission detection; a laboratory test in gneiss: Permafrost and Periglacial Processes, 25(3), p. 208-219, illus. incl. 3 tables, 30 ref., September 2014.
Large slope failures in steep alpine bedrock present significant geological hazards. Ice segregation is thought to be one of the mechanisms involved in high-mountain bedrock fracture but has not been reproduced experimentally in hard, intact rock. Here, we report results from a 3 month freezing experiment that aimed to reproduce ice-lens growth at the interface between the active layer and permafrost in a 15 cm cube of hard, intact rock (Arolla gneiss). Monitoring of acoustic emissions (AEs) recorded the propagation of microcracks horizontally through the block, resulting in a continuous and thick macrocrack near the base of the artificial active layer. Microcracking occurred within an approximate temperature range of -0.5°C to -2.7°C, consistent with ice segregation theory. Hypocentres of recorded AE events were concentrated in a 40 mm thick band between depths of 4.5 and 8 cm in the block. The band approximately coincides with the frozen fringe and indicates that ice segregation can induce micro- and macrocracking in gneiss. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1814
14094302 Ulrich, Mathias (Leipzig University, Institute for Geography, Leipzig, Germany); Grosse, Guido; Strauss, Jens and Schirrmeister, Lutz. Quantifying wedge-ice volumes in Yedoma and thermokarst basin deposits: Permafrost and Periglacial Processes, 25(3), p. 151-161, illus. incl. 1 table, sketch map, 20 ref., September 2014.
Wedge-ice volume (WIV) is a key factor in assessing the response of ice-rich permafrost landscapes to thaw and in quantifying deep permafrost soil carbon inventories. Here, we present a method for calculating WIV in late Pleistocene Yedoma deposits and Holocene thermokarst basin deposits at four study areas in Siberia and Alaska. Ice-wedge polygons and thermokarst mound (baydzherakh) patterns were mapped on different landscape units using very high-resolution (0.5 m/pixel) satellite imagery (WorldView-1 and GeoEye-1). In a geographic information system (GIS) environment, Thiessen polygons were automatically created to reconstruct relict ice-wedge polygonal networks, and field and published data on ice-wedge dimensions were used to generate three-dimensional subsurface models that distinguish between epi- and syngenetic ice-wedge geometry. The results reveal significant variations in WIV between the study sites and within certain terrain units. Calculated maximum WIV ranges from 31.4 to 63.2 vol% for Yedoma deposits and from 6.6 to 13.2 vol% for thermokarst basin deposits. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1810
14104428 Kneisel, C. (University of Wurzburg, Institute of Geography and Geology, Wurzburg, Germany); Emmert, A. and Kastl, J. Application of 3D electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies: Geomorphology, 210, p. 71-82, illus. incl. 1 table, 27 ref., April 1, 2014.
Periglacial landscapes comprise landforms that are inherently 3D structures, often exhibiting small-scale spatial heterogeneity of surface and subsurface conditions. The objectives of the present paper are to illustrate the potential of the novel application of 3D electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies with different geomorphological problems to be addressed and to consider the efficacy of the 3D approach to geomorphological investigations in mid-latitude high alpine and high latitude lowland permafrost environments. The approach described in the three case studies includes reconnaissance surveys using two-dimensional electrical resistivity tomography (2D ERT) followed by a detailed mapping using three-dimensional electrical resistivity imaging (3D ERI). The latter approach enables a spatial imaging of the subsurface resistivity distribution and clearly improves the delineation and characterization of subsurface structures compared to state-of-the-art 2D ERT that is limited to findings gained along single profiles or extrapolation between several profiles. Although it can be challenging and time-consuming to apply this technique in periglacial environments, the promising results demonstrate its value for the 3D delineation of frozen ground conditions. In the case of the described case study sites, characterizing the subsurface heterogeneity is close to impossible using drilling or 2D geophysical surveying alone because of the complex 3D nature of the frozen ground characteristics comprising permafrost and permafrost-free areas (alpine permafrost test site) as well as permafrost with variable characteristics (subarctic lowland permafrost test site) at close distance. Even in environments that seem homogeneous at first sight, this method allows us to detect substantial subsurface property variations that can be attributed to different frozen ground conditions. Furthermore, 3D ERI allows the linking of different data sources (e.g., site-specific geomorphology and hydrology) to enhance the spatial understanding of surface and subsurface characteristics and dynamics in permafrost environments. The improved knowledge of the geophysical anatomy and subsurface architecture of the permafrost occurrences revealed by this study suggests a more widespread use for glacial and periglacial landform studies in the future. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.geomorph.2013.12.022
14098558 Liaudat, Dario Trombotto (Instituto Argentino de Nivologa, Glaciología y Ciencias Ambientales, Mendoza, Argentina); Penas, Pablo and Aloy, Gustavo. Impact of volcanic processes on the cryospheric system of the Peteroa Volcano, Andes of southern Mendoza, Argentina: Geomorphology, 208, p. 74-87, illus. incl. 3 tables, sketch map, 25 ref., March 1, 2014.
Soil temperatures of the active Volcanic Complex Peteroa situated in the Cordillera Principal between Chile and Argentina at 35°15' S and 70°35' W (approximately) were monitored in the area, and local geomorphology (periglacial geomorphology, presence of permafrost, and cryoforms) was studied. The present contribution also resulted in a comparison of two consecutive analyses of the volcano peak carried out with special thermocameras (AGEMA TVH 550, FUR P660) in order to study the thermal range of different hot and cold sites selected in 2009. The thermocameras were used ascending by foot and also during flights with a Cessna 180. A night expedition to the volcanic avalanche caldera, at up to 3900masl (approximately), completed the monitoring activity of 2010. Hot zones were associated to present volcanism and cold zones to the presence of glacier ice and shadowy slopes with possible presence of permafrost. Identifying and mapping uncovered and covered ice was possible with the help of monitoring and geomorphological interpretation related to the upper englacement, which is severely affected by volcanism. Glaciers are retreating toward the north or approaching the rims of the volcanic avalanche caldera leaving islands of ice associated with superficial permafrost. The cryogenic area with slope permafrost was identified through active protalus and sedimentary cryogenic slopes. Craters have undergone considerable thermal changes in comparison to the year 2009; and new, much more vigorous fumaroles have appeared in hot areas detected in 2009 following a tendency toward the west. New subaquatic heat columns that appeared in crater 3, crater walls, and glaciated areas vanished, supplying cold water and thus contributing to the formation of a new lake in crater 4. A possible post-seismic shift of the volcanic activity may provide geodynamical evidence of the changes registered in other areas after the earthquake of 27 February 2010. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.geomorph.2013.11.016
14104646 Kaab, A. (University of Oslo, Department of Geosciences, Oslo, Norway); Girod, L. and Berthling, I. Surface kinematics of periglacial sorted circles using structure-from-motion technology: The Cryosphere (Online), 8(3), p. 1041-1056, illus. incl. 1 table, sketch map, 39 ref., 2014. Includes appendices.
Sorted soil circles are a form of periglacial patterned ground that is commonly noted for its striking geometric regularity. They consist of an inner fine domain bordered by gravel rings that rise some decimetres above the fine domain. Field measurements and numerical modelling suggest that these features develop from a convection-like circulation of soil in the active layer of permafrost. The related cyclic burial and exhumation of material is believed to play an important role in the soil carbon cycle of high latitudes. The connection of sorted circles to permafrost conditions and its changes over time make these ground forms potential palaeoclimatic indicators. In this study, we apply for the first time photogrammetric structure-from-motion technology (SfM) to large sets of overlapping terrestrial photos taken in August 2007 and 2010 over three sorted circles at Kvadehuksletta, western Spitsbergen. We retrieve repeat digital elevation models (DEMs) and orthoimages with millimetre resolution and precision. Changes in microrelief over the 3 yr are obtained from DEM differencing and horizontal displacement fields from tracking features between the orthoimages. In the fine domain, surface material moves radially outward at horizontal rates of up to ~2 cm yr-1. The coarse stones on the inner slopes of the gravel rings move radially inward at similar rates. A number of substantial deviations from this overall radial symmetry, both in horizontal displacements and in microrelief, shed new light on the spatio-temporal evolution of sorted soil circles, and potentially of periglacial patterned ground in general.
DOI: 10.5194/tc-8-1041-2014
14104638 Liu, L. (Stanford University, Department of Geophysics, Stanford, CA); Schaefer, K.; Gusmeroli, A.; Grosse, G.; Jones, B. M.; Zhang, T.; Parsekian, A. D. and Zebker, H. A. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska: The Cryosphere (Online), 8(3), p. 815-826, illus. incl. 1 table, 60 ref., 2014.
Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3-4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10-35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.
DOI: 10.5194/tc-8-815-2014
14105182 Scherler, Dirk (California Institute of Technology, Geological and Planetary Sciences, Pasadena, CA). Climatic limits to headwall retreat in the Khumbu Himalaya, eastern Nepal: Geology (Boulder), 42(11), p. 1019-1022, illus. incl. sketch map, 32 ref., November 2014. GSA Data Repository item 2014355.
Ice-free bedrock headwalls are widespread landforms of many glacial landscapes, but their formation and evolution are not well understood. Here, I present observations from the Khumbu Himalaya, eastern Nepal, of a distinct elevation zone that aligns the base of many steep headwalls with the highest predicted frost-cracking intensity (FCI). Below this zone, median ice-free hillslope angles are ≤&eq;40° and similar to those of other areas in the Himalaya, where threshold hillslopes that are close to the critical angle of stability have been inferred. At higher elevations, ice-free hillslopes of different rock types have median slope angles of ~50°-55°, suggesting threshold hillslopes with higher rock mass strength, possibly related to the presence of deep-reaching permafrost. High-altitude meteorological data combined with FCI models support frost cracking as a mechanism for headwall retreat by undercutting of threshold headwalls, while glacial transport inhibits the accumulation of scree deposits at their base. This mechanism could account for continued headwall retreat as long as climatic conditions enable frost cracking near the base of headwalls that are high enough to sustain glaciers at their base, even if subglacial erosion is minor.
DOI: 10.1130/G35975.1
14098660 Müller, Johann (University of Zurich, Department of Geography, Zurich, Switzerland); Gärtner-Roer, Isabelle; Kenner, Robert; Thee, Patrick and Morche, David. Sediment storage and transfer on a periglacial mountain slope (Corvatsch, Switzerland): in Sediment flux and sediment budget studies in cold environments; new approaches and techniques (Beylich, Achim A., editor; et al.), Geomorphology, 218, p. 35-44, illus. incl. 2 tables, sketch maps, 63 ref., August 1, 2014.
High mountain geomorphology is mostly characterized by high elevation, steep gradients, rocky terrain, the presence of snow and ice and the related processes occurring in a high energy environment. Large sources of sediment and sediment storages often exist within high mountain systems and are controlled by the processes occurring within this setting. The purpose of this study is to describe sediment paths on a periglacial mountain slope and quantify geomorphic work within one example year in order to analyze and compare sediment budgets in high mountain geosystems. This energy-related approach helps to characterize a periglacial slope on account of the effectiveness of its geomorphological processes and might help to understand the complex dynamic behavior of its constituent subsystems. A periglacial mountain slope is investigated in Eastern Switzerland (Corvatsch). The environment is characterized by a typical coarse debris cascade: rock wall®rock fall®talus slope®permafrost creep®rockglacier. Rockglaciers are considered to be sediment traps of the coarse debris system, reflecting the erosion history of the corresponding catchment. Headwall recession and creep processes of the talus slopes and rockglaciers are quantified by a multi-method-approach combining remote sensing and terrestrial methods. Multitemporal DEMs of the last two decades enabled the quantification of sediment transfer of the slow moving landforms (frozen talus slopes and rockglaciers). Sediment input from the rock wall is quantified by repeated laser scanning over the last 4 years. With the introduced cascading approach it is possible to assess dynamics within the coarse debris system. The mountain slope is divided into three subsystems (headwall, talus cone and rockglacier) and their dynamics are analyzed individually but also in relation to the entire mountain slope on a yearly base. A backweathering rate of 2mm can be derived for the headwall and an energy transfer of 29.8GJ from the headwall to the slope, 4GJ from the talus slope to rockglacier where 1.44GJ of geomorphic work are released by the downwards creep of the landform. This study is the first to include an analysis of the geomorphic work generated on the basis of vertically differentiated sediment production and transport processes. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.geomorph.2013.12.002
14101428 Tridico, Silvana R. (Murdoch University, School of Veterinary and Life Sciences, Perth, West. Aust., Australia); Rigby, Paul; Kirkbride, K. Paul; Haile, James and Bunce, Michael. Megafaunal split ends; microscopical characterisation of hair structure and function in extinct woolly mammoth and woolly rhino: Quaternary Science Reviews, 83, p. 68-75, illus. incl. sketch map, 23 ref., January 1, 2014.
The large extinct megafaunal species of the Late Pleistocene, Mammuthus primigenius (woolly mammoth) and Coelodonta antiquitatis (woolly rhino) are renowned for their pelage. Despite this, very little research has been conducted on the form and function of hair from these iconic species. Using permafrost preserved hair samples from seven extinct megafaunal remains, this study presents an in-depth microscopical characterisation of preservation, taphonomy, microbial damage, pigmentation and morphological features of more than 420 hairs. The presence of unique structural features in hairs, from two extinct megafauna species, such as multiple medullae and unparallelled stiffness suggests evolution of traits that may have been critical for their survival in the harsh arctic environment. Lastly, despite popular depictions of red-haired and/or uniformly coloured mammoths, a closer examination of pigmentation reveals that mammoth coats may have exhibited a mottled/variegated appearance and that their 'true' colours were not the vivid red/orange colour often depicted in reconstructions. Insights gained from microscopical examination of hundreds of extinct megafauna hairs demonstrate the value of extracting as much morphological data as possible from ancient hairs prior to destructive sampling for molecular analyses. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.quascirev.2013.10.032
14094713 Hansom, J. D. (University of Glasgow, Department of Geographical and Earth Sciences, Glasgow, United Kingdom); Forbes, D. L. and Etienne, S. The rock coasts of polar and sub-polar regions: in Rock coast geomorphology; a global synthesis (Kennedy, David M., editor; et al.), Memoirs of the Geological Society of London, 40, p. 263-281, illus. incl. geol. sketch map, 159 ref., 2014.
Polar and subpolar coasts are distinctive owing to the presence of ice on land as permafrost, ground ice and glacier ice, and in the sea as tidewater glaciers, icebergs, ice shelves and sea ice. Most of these coasts remain glaciated or are recently deglaciated so their geomorphology carries a strong glacial signature. The morphogenetic environment of polar and subpolar coasts is dominated by extreme seasonality with winter development of sea ice and a shore-fast ice foot that excludes wave activity and is primarily protective. However, sea ice may also be erosional at any time of year but is most effective as an erosional agent on polar coasts between freeze-up and break-up, when wave activity forces sea ice to repeatedly impact the shore. Depending on latitude, the short summers are characterized by wave and sea ice erosion at high latitudes and by wave activity at lower latitudes. The contribution of frost weathering to cliff and shore platform development in polar and subpolar rock coasts is unclear, but is likely to be an important influence. Rock coasts are widespread in the Arctic and sub-Arctic, including Iceland, and in the Antarctic and sub-Antarctic the limited ice-free coast is almost entirely rock-dominated.
DOI: 10.1144/M40.16
14094303 Costard, François (Université Paris-Sud XI, Laboratoire Interactions et Dynamique des Environnements de Surface, Orsay, France); Gautier, E.; Fedorov, A.; Konstantinov, P. and Dupeyrat, L. An assessment of the erosion potential of the fluvial thermal process during ice breakups of the Lena River (Siberia): Permafrost and Periglacial Processes, 25(3), p. 162-171, illus. incl. 1 table, sketch map, 22 ref., September 2014.
Fluvial thermal erosion following ice breakups of the Lena River (Yakutia, Siberia) is a significant geomorphic process. During the initial stage of ice breakup, ice pushes up onto the river banks and produces large accumulations of ice and sediments that protect the islands' heads against the mechanical and thermal effects of the river's flow. This initial stage is relatively short and terminates only a few days after breakup begins. In the second phase of flooding, after the river ice has melted, the island heads become free of ice. Hence, when water levels are high, the floodwaters are in sustained contact with the frozen banks of the islands, causing efficient thermal and mechanical erosion of their banks. Such erosion may also occur later in summer, if there is a second discharge peak. Between 2009 and 2012, the retreat of the banks of the river islands displayed high interannual variation that is attributed to the variability of the duration and timing of the flood season. For a given island, the annual rate varied from 2 m to 40 m and the duration of active thermal erosion of the frozen islands varied from 6 days to 39 days. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1812
14094305 Klaminder, Jonatan (Umea University, Department of Ecology and Environmental Science, Abisko, Sweden); Yoo, K.; Olid, C.; Rameback, H. and Vesterlund, A. Using short-lived radionuclides to estimate rates of soil motion in frost boils: Permafrost and Periglacial Processes, 25(3), p. 184-193, illus. incl. 4 tables, 36 ref., September 2014.
Cryoturbation in high-latitude soils is crucial for the long-term cycling of elements, but the rates of soil motion are poorly constrained. Here, we test whether the rate of frost creep, soil erosion and vertical soil mixing in frost boils can be estimated using short-lived radionuclides (137Cs and 210Pb). We find a small-scale variation in 137Cs and 210Pb inventories in the lower levels of the eroding regions of frost boils in comparison to the expected depositional sites; hence, the distribution of the radionuclides appears to reflect a lateral transport of atmospheric fallout from the centre of the boil (inner domain) towards the surrounding soil (outer domain). 14C dating of the soil indicates that fallout of 137Cs was mobile in the soil and that 210Pb moved with the soil matrix. A soil creep model and a surface soil erosion model are derived and applied to the lateral and vertical distributions of 210Pb in the frost boil. Both models predict the expected trajectories of soil motion and provide rates of creep, erosion and mixing at a mm yr-1 to cm yr-1 scale. The distribution of 210Pb provides new insights about the processes and rates of soil mass movement in frost boils, if sound mass-balance models are applied. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1811
14102428 Brown, Jerry (International Permafrost Association, International). Geokriologicheskiye issledovaniya v arkticheskikh regionakh; Yamburg, 1989 g. [Geocryological studies in the Arctic region; Yamburg, 1989]: in Kak my rosli i v tvorchestve vzrosleli 1984-2014 gg. (Melnikov, V. S., editor), Kholod'OK!, 1(11), p. 26-33, illus., 4 ref., 2014.
14102427 Melnikov, V. S., editor (Russian Academy of Sciences, Siberian Division, Institute of the Cryosphere, Tyumen, Russian Federation). Kak my rosli i v tvorchestve vzrosleli 1984-2014 gg. [The story of our growth and creative maturation, 1984-2014]: Kholod'OK!, 1(11), 98 p., illus., 2014. Individual papers within scope are cited separately.
14102429 Sheynkman, V. S. (Russian Academy of Sciences, Siberian Division, Institute of the Cryosphere, Tyumen, Russian Federation). Kholod kak predmet izucheniya nauk o zemle i faktor, kontroliruyushchiy proyavleniya krioraznoobraziya [Cold as a subject of geosciences and factor of cryodiversity]: in Kak my rosli i v tvorchestve vzrosleli 1984-2014 gg. (Melnikov, V. S., editor), Kholod'OK!, 1(11), p. 44-56, illus., 17 ref., 2014.
14094100 Eriksson, Bert (Uppsala University, Department of Social and Economic Geography, Uppsala, Sweden) and Eldridge, David J. Surface destabilisation by the invasive burrowing engineer Mus musculus on a sub-Antarctic island: Geomorphology, 223, p. 61-66, illus. incl. 1 table, 41 ref., October 15, 2014.
Invasive species are known to have substantial trophic effects on ecosystems and ecosystem processes. The invasion of the house mouse (Mus musculus) onto sub-Antarctic islands has had a devastating effect on plants, invertebrates, and birds with substantial changes in ecosystem functions. Less well understood, however, are the nontrophic, geomorphic effects of mice resulting from their burrowing activities. We examined the extent of burrow construction by M. musculus across an area of about 20 ha on Marion Island and the effects of burrows on water flow and sediment movement. We recorded a density of 0.59 ± 0.48 (mean ± SD) burrows m- 2, with more burrows at lower altitudes and shallower slopes, and twice the density in the solifluction risers (0.86 ± 0.54 m- 2) than the intervening terraces or treads (0.40 ± 0.51 m- 2). Most burrows were dug horizontally into the slope and tended to extend about 20 cm deep before turning. A very conservative estimate of sediment removed from burrows from this depth is 2.4 t ha- 1. However, taking into account more detailed data on burrow morphology based on excavations, actual amounts may be closer to 8.4 t ha- 1. Average soil displacement rate for a single burrow, measured over 5 days, was 0.18 kg burrow- 1 day- 1. Burrows acted as conduits for water and warmer air. Stones at burrow entrances were moved eight times farther by water (10.4 cm) than those not associated with burrows. Similarly, temperatures adjacent to burrow entrances were 4.1 °C higher than sites 10 cm away. Together our data indicate that mice are having substantial deleterious and geomorphic effects on sub-Antarctic ecosystems through their burrowing. With lower rates of mouse mortality resulting from warmer climates predicted under global climate models, we can expect an increase in damage resulting from mouse activity. Abstract Copyright (2014) Elsevier, B.V.
DOI: 10.1016/j.geomorph.2014.06.026
14094304 Sánchez-García, Laura (Stockholm University, Department of Applied Environmental Science, Stockholm, Sweden); Vonk, J. E.; Charkin, A. N.; Kosmach, D.; Dudarev, O. V.; Semiletov, I. P. and Gustafsson, O. Characterisation of three regimes of collapsing Arctic ice complex deposits on the SE Laptev Sea coast using biomarkers and dual carbon isotopes: Permafrost and Periglacial Processes, 25(3), p. 172-183, illus. incl. 2 tables, sketch maps, 47 ref., September 2014.
Arctic amplification of climate warming is intensifying the thaw and coastal erosion of the widespread and carbon-rich Siberian Ice Complex Deposits (ICD). Despite the potential for altering long-term carbon dynamics in the Arctic, the susceptibility of organic carbon (OC) to degradation as the ICD thaw is poorly characterised. This study identifies signs of OC degradation in three Siberian ICD regimes of coastal erosion through elemental, isotopic and molecular analyses. The degree of erosion appears to determine the extent of degradation. The moisture-limited and beach-protected ICD bluff near Buor-Khaya Cape, characterised by thermokarst mounds (baydzherakhs), represents a dormant regime with limited ongoing degradation. Conversely, the more exposed ICD scarps on eroding riverbanks (Olenek Channel, Lena Delta) and coastal slopes (Muostakh Island) showed more pronounced signs of ongoing OC decay. Different parameters suggest that degradation can partially explain the shift of the OC signature with 14C age in the thawing ICD. Exposure time, degree of erosion, slope gradient and moisture conditions appear to be key factors determining the degradation propensity of OC in exposed ICD. These field results document the lability of OC in ICD upon thaw and illustrate the potential for transferring old OC into the rapidly cycling atmosphere-biosphere carbon pools. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1815
|
|
14094464 Merritts, Dorothy J. (Franklin and Marshall College, Department of Earth and Environment, Lancaster, PA); Potter, Noel; Schulte, Kayla; Weiserbs, Benjamin; Markey, Erin and Blair, Aaron. Paleo-analog evidence of permafrost thaw in southeastern Pennsylvania [abstr.]: in Geological Society of America, Northeastern Section, 49th annual meeting, Abstracts with Programs - Geological Society of America, 46(2), p. 113, 2014. Meeting: Geological Society of America, Northeastern Section, 49th annual meeting, March 23-25, 2014, Lancaster, PA.
During the last glacial maximum 33,300 to 26,500 years BP, areas now encompassed within southeastern Pennsylvania and northern Maryland were not covered by the Laurentide ice sheet, but earlier work indicates that the region was subject to periglacial environmental conditions and processes. Previous analysis of macrofossils from a sediment core in a vernal pool at Kings Gap Pond, northern slope of South Mt, indicate that tundra vegetation persisted until at least 14,000 yrs BP. Using slope analysis of lidar data, we document widespread evidence of periglacial landforms that are indicative of permafrost thaw, and we attribute the youngest of these to the last glacial maximum. These fossil landforms include gelifluction lobes and sheets produced by a combination of bedrock fracturing and downslope mass movement over a frozen inactive layer of permafrost during climate induced seasonal freeze-thaw cycles. In places, sheets and lobes dominate the landscape and commonly are stepped, with multiple cases of younger lobes over-riding older ones. Along ridge lines we have identified numerous relics of nivation hollows, concave features on hill slopes that are the product of snow patch accumulation, freeze-thaw and mass wasting. We also document massive paleo-slumps along mid- to lower parts of hillslopes that we attribute to permafrost thaw, and suggest that their origin is similar to well-known examples of retrogressive thaw slump in the Arctic today, such as the Sewalik thaw slump in Alaska. Finally, the massive amounts of downslope movement of material during times of permafrost thaw impacted valley bottoms, in places leading to development of extensive debris and alluvial fans, and in some places these landforms blocked valley bottoms. We developed a website that provides examples of these features and describes their origin in the context of climate change and permafrost thaw (www.fandmgeo-breakingtheice).
URL: https://gsa.confex.com/gsa/2014NE/webprogram/Paper236417.html
14096979 Weiserbs, Benjamin (Franklin and Marshall College, Department of Earth and Environment, Lancaster, PA); Merritts, Dorothy J.; Schulte, Kayla; Walter, Robert C. and Potter, Noel, Jr. Evidence of gelifluction lobes at the Gettysburg Battlefield, Pennsylvania [abstr.]: in Geological Society of America, Northeastern Section, 49th annual meeting, Abstracts with Programs - Geological Society of America, 46(2), p. 71, 2014. Meeting: Geological Society of America, Northeastern Section, 49th annual meeting, March 23-25, 2014, Lancaster, PA.
Previous workers have noted that the diabase boulder-strewn slopes at the Gettysburg Civil War battlefield (Gettysburg National Military Park) in southeastern Pennsylvania are the result of periglacial processes, and focused in particular on freeze-thaw activity as a mechanism for producing boulders up to 8 m in length. Here we use analysis of lidar data to demonstrate that these boulders moved downslope primarily as a result of gelifluction, a form of mass movement within the active layer of permafrost. This layer typically is a half meter or so thick and overlies a frozen inactive layer of permafrost. Gelifluction occurs during seasonal freeze-thaw cycles in periglacial landscapes. During thaw, drainage of excess water is limited by the frozen substrate and the strength of the overlying thawed mass is reduced, leading to elasto-plastic deformation. At the Gettysburg battlefield, the most prominent examples of gelifluction occur on hills formed of Triassic diabase, part of the Gettysburg sill, which is characterized by extensive joints. Elevation of the diabase hills is about 200 m above sea level, and gelifluction lobes are prominent on multiple low tors left behind as boulders moved downslope from outcrop sources. Hills that are well known for playing crucial roles in the Union defense, including Little Roundtop, are rimmed with multiple, stepped gelifluction lobes that extend for tens of meters outward from the hill tops. Some lobes are stacked atop older lobes, and some appear to have flowed around large blocks, possibly intact bedrock (i.e., braking blocks). Permafrost must have existed during at least one cold full glacial period, perhaps as recently as the last glacial maximum (33,300 to 26,500 years BP).
URL: https://gsa.confex.com/gsa/2014NE/webprogram/Paper236628.html
14104522 Cadieux, S. B. (Indiana University, Department of Geological Sciences, Bloomington, IN); Goldman, A. E.; Young, S. E.; Peng, Y.; Pratt, L. M. and White, J. R. Methane dynamics and microbial communities in small, seasonally ice-covered Arctic lakes in western Greenland; insights into early pluvial periods on Mars: in 45th lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 45, Abstract 2223, sketch map, 13 ref., 2014. Meeting: 45th lunar and planetary science conference, March 17-21, 2014, Woodlands, TX. Accessed on May 22, 2014.
URL: http://www.hou.usra.edu/meetings/lpsc2014/pdf/2223.pdf
14093973 Ruppel, C. (U. S. Geological Survey, Woods Hole, MA). Natural methane hydrates; energy resource and climate implications [abstr.]: in Goldschmidt abstracts 2014, V.M. Goldschmidt Conference - Program and Abstracts, 24, p. 2131, 2014. Meeting: Goldschmidt 2014, June 8-13, 2014, Sacramento, CA.
14094465 Sevon, William D. (East Lawn Research Center, Harrisburg, PA). Boulder colluvium on the southeast-facing slope of Blue Mountain in Cumberland County, Pennsylvania [abstr.]: in Geological Society of America, Northeastern Section, 49th annual meeting, Abstracts with Programs - Geological Society of America, 46(2), p. 114, 2014. Meeting: Geological Society of America, Northeastern Section, 49th annual meeting, March 23-25, 2014, Lancaster, PA.
Blue Mountain (BM) extends southwestward across PA from the Delaware River in the north-east to the MD-PA state line and beyond in the southwest. The mountain ridge is broken only by several water gaps. The crest and upper southeast-facing slope of BM is composed of quartzite of the Silurian Tuscarora Fm. This upper slope is considerably steeper than the lower slope that is underlain by shale and siltstone of the Ordovician Martinsburg Fm. All of the BM slope is covered with boulder colluvium (BC) derived from the Tuscarora quartzite (TQ). Where exposed, naturally or artificially, such as at Wagoner's Gap, the TQ shows bedding planes that are separated by beds several to many cm thick. In addition, the TQ has numerous structurally generated fracture planes that are generally approximately normal to bedding and occurring at intervals up to a meter or more apart. The underlying Martinsburg is almost never exposed on the slope. During the Pleistocene, freeze and thaw action in the periglacial climate that affected all of the non-glaciated parts of PA utilized the numerous bedrock parting planes to break down the TQ into a multitude of boulders and blocks. This material gradually descended the slope of BM to create a covering of BC. The upper, steep-slope BC comprises, basically, broken rock that fell, slid, and rolled down slope assisted by snow and ice and additional freeze-thaw breakdown action. There is no surface pattern in the upper slope BC. Once the downward moving BC achieved the lower, gentler, Martinsburg slope, the movement process changed to one controlled by solifluction in an often water-saturated environment. This BC moved in masses generally having the form of low, rounded, elongate, curved mounds with steep fronts, rounded tops, and less steep backs. These masses are called solifluction lobes. This BC generally has more, smaller pieces of rock and some dirt that contributed to its lobe-forming tendency. Solifluction lobes are very common in PA on lower, gentler slopes of mountains. Multiple soil profiles on the BM mountain slope indicate that at least 3 periglacial episodes occurred during which BC movement took place.
URL: https://gsa.confex.com/gsa/2014NE/webprogram/Paper236469.html
|
