14061976 Baumann, Frank (Eberhard Karls Universität Tübingen, Department of Geosciences, Tubingen, Germany); Schmidt, Karsten; Dörfer, Corina; He Jinsheng; Scholten, Thomas and Kühn, Peter. Pedogenesis, permafrost, substrate and topography; plot and landscape scale interrelations of weathering processes on the central-eastern Tibetan Plateau: Geoderma, 226-227, p. 300-316, illus. incl. 7 tables, sketch map, 94 ref., August 2014.
Weathering indices (WI) and pedogenic oxides ratios (POR) were used to describe patterns of weathering intensities and pedogenesis along climatic gradients, mainly affected by varying influences of the Asian and Indian Monsoon. These climate settings induce particular soil moisture (SM) conditions, in turn closely related to permafrost state, substrate, and topography. Nine sites including a total of 30 soil profiles were examined along an eastern and a western transect across the central-eastern Qinghai-Tibet Plateau. Additionally, differences between four soil groups were analysed. According to our knowledge, the presented study is the first attempt of a comprehensive application of different WI and POR to substrates of currently permafrost-affected soils. It provides an evaluation of various tools in terms of chemically describing and differentiating the related processes to distinct environmental settings in low-weathering regions. We found that weathering trends along the climatic gradients could be clearly outlined by WI, whereas POR rather account for small scale variations, describing significant differences of pedogenesis between continuous and discontinuous permafrost conditions. Pyrophosphate soluble iron (Fep) proved to be useful for differentiating permafrost and ground water influenced soils, showing a strong correlation to total organic carbon (r=0.89). The chemical index of alteration (CIA) is the most suitable WI, whereas Ca-free CPA is more easily biased by salinity variations of topsoils at sites with negative water balance, thus pretending lower weathering intensities. Regression analyses for WI and POR with main independent variables underline the specific characteristics: climatic parameters best explain WI, while SM is dominant for POR. The ratio (Fed-Feo)/Fet proved as the most appropriate POR with 64% explained variation by a multiple linear regression model, implying significantly lower iron release with higher SM and pH values. Variation of Fep can be explained by 63% with soil acidity being most important, followed by SM. Importantly, the presented research provides tools for investigating past and future stability or respective degradation processes of permafrost ecosystems on the Tibetan Plateau and may be applicable to other permafrost-affected environments. Abstract Copyright (2014) Elsevier, B.V.
14062641 Peterson, Ronald C. (Queen's University, Department of Geological Sciences and Geological Engineering, Kingston, ON, Canada); Williamson, Marie-Claude and Rainbird, Robert H. Gossan Hill, Victoria Island, Northwest Territories; an analogue for mine waste reactions within permafrost and implication for the subsurface mineralogy of Mars: Earth and Planetary Science Letters, 400, p. 88-93, illus. incl. geol. sketch map, 27 ref., August 15, 2014.
Gossan Hill is located within the Minto Inlier in central Victoria Island, Northwest Territories (N 71.36697°, W 114.95155°). A study of the mineralogical associations and geological setting of this deposit indicates that it is an arrested hydrothermal system frozen in permafrost. From above, the hill stands out because of the topographic relief of 75 m and the orange-brown color of the surficial material. The surface of the hill is marked by areas of concentric color zonation up to 3 m across, with light gray centers surrounded by a yellow-orange ring that is surrounded by an orange-brown color that covers the rest of the surface of the hill. Trenches dug into these areas reveal that the central zone contains quartz and pyrite +/- native sulfur in a loose aggregate of sand-sized grains. This central area is surrounded by a zone dominated by gypsum and quartz with some jarosite. Beyond this, the surrounding surface consists of quartz, hematite, and amorphous iron oxides. The radial arrangement of the mineral assemblage indicates an increase in oxidation of sulfur from the center outward. Analysis of isotopic composition of the sulfur indicates the source of sulfur could be the underlying strata. The hill is underlain by inter-bedded carbonate and sulfate-evaporite sedimentary rocks of the Kilian formation in the upper part of the Neoproterozoic Shaler Super group. The sedimentary rocks were intruded by diabase sills of the 720 Ma Franklin igneous event, which crop out 2 km to the south of Gossan Hill. The soft friable nature of the deposit and the topographic relief of the hill indicate a post-glacial (Pleistocene) age of formation. Permafrost has maintained the disequilibrium mineral assemblage since the cessation of fluid flow. Extraction of the permafrost ice from the central zone yields a liquid with a pH of 2.3. The observed long-term persistence of pyrite encased within the acidic permafrost indicates that oxidation and dissolution reactions common in mine waste are slowed, if not stopped, in such an environment. The predicted rise of Arctic temperatures will cause the active layer to move deeper and result in the release of the acidic solutions frozen in the permafrost. Water ice or frozen CO2 just below the Martian surface would also preserve such mineral disequilibrium for very long periods of time. No region exists on Earth where ice has existed continuously for millions of years, but the Gossan Hill deposit is an excellent terrestrial analogue. On Mars, the subsurface ice may be very old. Ancient reactive Martian mineral assemblages and the fluids associated with them will reflect conditions that existed in the past. Abstract Copyright (2014) Elsevier, B.V.
14062395 Bischoff, Juliane (Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute, Potsdam, Germany); Mangelsdorf, Kai; Schwamborn, Georg and Wagner, Dirk. Impact of lake-level and climate changes on microbial communities in a terrestrial permafrost sequence of the El'gygytgyn Crater, Far East Russian Arctic: Permafrost and Periglacial Processes, 25(2), p. 107-116, illus. incl. sketch maps, 44 ref., June 2014.
Microbial permafrost communities play an important role in carbon cycling and greenhouse gas fluxes. Despite the importance of these processes, there is a lack of knowledge about how environmental and climatic changes affect the abundance and composition of microorganisms. Here, we investigated the changing distribution of permafrost microorganisms in response to climate and lake-level changes. The permafrost core was drilled at the near shore of Lake El'gygytgyn, Far East Russian Arctic, and a combined microbiological and lipid biomarker approach was applied. The lower part of the permafrost core, deposited under subaquatic conditions, contains only small amounts of microbial signals; total organic carbon (TOC) content is sparse. After exposure of the site to subaerial conditions during the Allerod, the abundance of Bacteria and Archaea started to increase and the lake-level change is especially evidenced by the relative proportion of archaeal biomarkers. This increase is supported by rising bacterial and archaeal 16S ribosomal ribonucleic acid (rRNA) gene copy numbers and significant amounts of TOC during the late Allerod. After a small decrease during the colder Younger Dryas, the TOC content and the microbial signals strongly increase during the Holocene, presumably stimulated by pedogenesis. The occurrence of intact phospholipids indicates the presence of living microorganisms in these deposits. Our data suggest that methane formation is mainly expected for the subaerial interval, especially the Holocene where methanogens were identified by fingerprinting. This study emphasizes the role of the uppermost permafrost deposits as a hotspot of carbon cycling in arctic environments, especially in the light of expected future global warming. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14062399 Gao, Cunhai (Ontario Geological Survey, Sudbury, ON, Canada). Relict thermal-contraction-crack polygons and past permafrost south of the late Wisconsinan glacial limit in the Mid-Atlantic Coastal Plain, USA: Permafrost and Periglacial Processes, 25(2), p. 144-149, illus. incl. sketch map, 28 ref., June 2014.
The paucity of reports on relict thermal contraction crack polygons in the mid-Atlantic Coastal Plain and many other areas in eastern North America has hampered our understanding of the extent and nature of past permafrost south of the Late Wisconsinan glacial limit. Examination of Google EarthTM imagery revealed orthogonal to hexagonal polygons, mostly 10-30 m in diameter, at more than 160 sites in sand and gravel deposits in southern New Jersey and the Delmarva Peninsula. The polygons are interpreted to indicate that continuous permafrost extended to 38.5°N in a zone more than 250 km wide to the south of the glacial limit under a mean annual air temperature of ≤&eq; -6°C probably during the late Wisconsinan. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14062397 Roy-Léveillée, P. (Carleton University, Department of Geography and Environmental Studies, Ottawa, ON, Canada); Burn, C. R. and McDonald, I. D. Vegetation-permafrost relations within the forest-tundra ecotone near Old Crow, northern Yukon, Canada: Permafrost and Periglacial Processes, 25(2), p. 127-135, illus. incl. 3 tables, sketch map, 35 ref., June 2014.
Old Crow Flats is a 5600 km2 glaciolacustrine plain that straddles the forest-tundra ecotone in northern Yukon. Continuous taiga corridors occur in the entrenched river valleys, where annual mean ground temperatures (Tg) at the depth of zero annual amplitude at two locations were -3.1 and -4.0°C in 2013. On the Flats, the vegetation cover is patchy, and Tg varied between -5.1 and -2.6°C. Annual mean near-surface permafrost temperatures (Tps) measured on the Flats between 2008 and 2011 in patches of taiga, tall shrubs and low shrubs were correlated with local snow depth. Snow depth was controlled by vegetation height if the snow supply was not limited, for example, where low shrubs and large lakes dominate the landscape. In this setting, snow depths and, hence, Tps in taiga patches were higher (-2.6 to -2.9°C) than in the surrounding shrub vegetation (-3.5 to -5.5°C). Where taiga patches were more extensive, redistributed snow was trapped at the patch edge and Tps in taiga was lower (-4.1 to -4.3°C) than in the surrounding shrub patches (-3.2 to -3.6°C). The permafrost temperature field is heterogeneous under patchy vegetation in the forest-tundra ecotone. Our data suggest that it is governed by both the snow-holding capacity of local vegetation patches and the spatial configuration of vegetation in the surrounding landscape, which controls snow supply. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14066106 Schreiner, Kathryn M. (Texas A&M University, Department of Oceanography, College Station, TX); Bianchi, Thomas S. and Rosenheim, Brad E. Evidence for permafrost thaw and transport from an Alaskan North Slope watershed: Geophysical Research Letters, 41(9), p. 3117-3126, illus. incl. 2 tables, sketch map, 40 ref., May 16, 2014.
Burial of organic carbon (OC) in marine sediments is one of the most important linkages between the short-term biologic carbon cycle and the long-term geologic carbon cycle. Yet much is still unknown about the fate of terrigenous OC in marine coastal margins. Here the delivery of particulate OC (POC) to the Colville River deltaic region in the Alaskan Beaufort Sea by particulates of varying densities is studied through the use of ramped temperature pyrolysis and radiocarbon analyses. The Colville River is the largest river in North America whose watershed is underlain completely by high Arctic permafrost tundra. A variety of sources of POC are considered, including terrestrial soils, Pleistocene-aged yedoma-like sediments, coastal peat erosion, and marine POC. We provide the first evidence that riverine POC from the Colville River contains old (Pleistocene-sourced) OC, suggesting ongoing thaw and mobilization of yedoma-like permafrost OC from this northern Alaskan watershed. Additionally, much of this OC appears to be fairly labile and therefore could be readily oxidized and returned to the atmosphere. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14069046 Briggs, Martin A. (U. S. Geological Survey, Office of Groundwater, Storrs, CT); Walvoord, Michelle A.; McKenzie, Jeffrey M.; Voss, Clifford I.; Day-Lewis, Frederick D. and Lane, John W. New permafrost is forming around shrinking Arctic lakes, but will it last?: Geophysical Research Letters, 41(5), p. 1585-1592, illus., 30 ref., March 16, 2014.
Widespread lake shrinkage in cold regions has been linked to climate warming and permafrost thaw. Permafrost aggradation, however, has been observed within the margins of recently receded lakes, in seeming contradiction of climate warming. Here permafrost aggradation dynamics are examined at Twelvemile Lake, a retreating lake in interior Alaska. Observations reveal patches of recently formed permafrost within the dried lake margin, colocated with discrete bands of willow shrub. We test ecological succession, which alters shading, infiltration, and heat transport, as the driver of aggradation using numerical simulation of variably saturated groundwater flow and heat transport with phase change (i.e., freeze-thaw). Simulations support permafrost development under current climatic conditions, but only when net effects of vegetation on soil conditions are incorporated, thus pointing to the role of ecological succession. Furthermore, model results indicate that permafrost aggradation is transitory with further climate warming, as new permafrost thaws within seven decades. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
14065742 Lacelle, Denis (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Fontaine, Marielle; Forest, Alex P. and Kokelj, Steve. High-resolution stable water isotopes as tracers of thaw unconformities in permafrost; a case study from western Arctic Canada: Chemical Geology, 368, p. 85-96, illus. incl. 1 table, sketch map, 49 ref., March 12, 2014.
The knowledge of past permafrost conditions is of importance to assess the potential magnitude of changes that periglacial environments may experience as a result of climate warming or disturbance. To assess if past thaw unconformities may be preserved from isotopic and geochemical discontinuities within permafrost, this study investigates the distribution of ground ice, stable water isotopes and major cations in two permafrost cores collected in a hummocky terrain site near Inuvik, Northwest Territories, Canada; a site where the evolution of the active layer during a recent period of permafrost degradation and subsequent aggradation was documented. Based on the high-resolution isotope geochemistry profiles, closed-system Rayleigh-type ionic segregation and isotope fractionation occurred during thermally-induced water migration into shallow permafrost and its freezing along a negative soil temperature gradient. Due to thermally-induced water migration into permafrost, d18O may not always be able to identify thaw unconformities; however the calculation of the 18O enrichment factors between ice and water (e18Oi-w) may be used to determine position of thaw unconformities in permafrost, if thaw events are followed by permafrost aggradation. The approach of using e18Oi-w provides additional information regarding past permafrost conditions that can complement change in cryostructures observed along natural exposures. Abstract Copyright (2014) Elsevier, B.V.
14065744 Routh, Joyanto (Linkoping University, Department of Water and Environmental Studies, Linkoping, Sweden); Hugelius, Gustaf; Kuhry, Peter; Filley, Timothy; Tillman, Paivi Kaislahti; Becher, Marina and Crill, Patrick. Multi-proxy study of soil organic matter dynamics in permafrost peat deposits reveal vulnerability to climate change in the European Russian Arctic: Chemical Geology, 368, p. 104-117, illus. incl. 2 tables, sketch map, 65 ref., March 12, 2014.
Soil organic carbon (SOC) in permafrost terrain is vulnerable to climate change. Perennially frozen peat deposits store large amounts of SOC, but we know little about its chemical composition and lability. We used plant macrofossil and biomarker analyses to reconstruct the Holocene paleovegetation and paleoenvironmental changes in two peat plateau profiles from the European Russian Arctic. Peat plateaus are the main stores of permafrost soil C in the region, but during most of the Holocene peats developed as permafrost-free rich fens with woody vegetation, sedges and mosses. Around 2200 cal BP, permafrost aggraded at the site resulting in frost heave and a drastic reduction in peat accumulation under the drier uplifted surface conditions. The permafrost dynamics (aggradation, frost-heave and thaw) ushered changes in plant assemblages and carbon accumulation, and consequently in the biomarker trends too. Detailed biomarker analyses indicate abundant neutral lipids, which follow the general pattern: n-alkanols>sterols>&eq;n-alkanes>&eq;triterpenols. The lignin monomers are not as abundant as the lipids and increase with depth. The selected aliphatic and phenolic compounds are source specific, and they have different degrees of lability, which is useful for tracing the impact of permafrost dynamics (peat accumulation and/or decay associated with thawing). However, common interpretation of biomarker patterns, and perceived hydrological and climate changes, must be applied carefully in permafrost regions. The increased proportion (selective preservation) of n-alkanes and lignin is a robust indicator of cumulative decomposition trajectories, which is mirrored by functional compounds (e.g. n-alkanol, triterpenol, and sterol concentrations) showing opposite trends. The distribution of these compounds follows first order decay kinetics, and concurs with the downcore diagenetic changes. In particular, some of the biomarker ratios (e.g. stanol/sterol and higher plant alkane index) seem promising for tracing SOC decomposition despite changes in botanical imprint, and sites spanning across different soil types and locations. Carbon accumulation rate calculated at these sites varies from 18.1 to 31.1gCm-2yr-1, and it's evident selective preservation, molecular complexity of organic compounds, and freezing conditions enhance the long-term stability of SOC. Further, our results suggest that permafrost dynamics strongly impact the more undecomposed SOC that could be rapidly remobilized through ongoing thermokarst expansion. Abstract Copyright (2014) Elsevier, B.V.
14067363 Lebrouc, V. (Université de Grenoble I, Institut des Sciences de la Terre, Grenoble, France); Schwartz, S.; Baillet, L.; Jongmans, D. and Gamond, J. F. Modeling permafrost extension in a rock slope since the last glacial maximum; application to the large Sechilienne Landslide (French Alps): Geomorphology, 198, p. 189-200, illus. incl. 3 tables, geol. sketch maps, 56 ref., September 15, 2013. Includes appendices.
Recent dating performed on large landslides in the Alps has revealed that the initiation of instability did not immediately follow deglaciation but occurred several thousand years after ice down-wastage in the valleys. This result indicates that debuttressing is not the immediate cause of landslide initiation. The period of slope destabilization appears to coincide with the wetter and warmer Holocene Climatic Optimum, indicating a climatic cause of landslide triggering, although the role of seismic activity cannot be ruled out. A phenomenon which may partly explain the delay between valley deglaciation and gravitational instability is the temporal persistence of thick permafrost layers developed in the Alps since the Last Glacial Maximum (LGM). This hypothesis was tested through 2D thermal numerical modeling of the large Sechilienne landslide (Romanche valley, French Alps) using plausible input parameter values. Simulation results suggest that permafrost vanished in the Sechilienne slope at 10 to 11 ka, 3000 to 4000 years following the total ice down-wastage of the Romanche valley at 14.3 ka. Permafrost persistence could have contributed to the failure delay by temporally strengthening the slope. Numerical simulations also show that the permafrost depth expansion approximately fits the thickness of ground affected by gravitational destabilization, as deduced from geophysical investigations. These results further suggest that permafrost development, associated with an ice segregation mechanism, damaged the rock slope and influenced the resulting landslide geometry. Abstract Copyright (2013) Elsevier, B.V.
14067384 Kraev, G. N. (Russian Academy of Sciences, Center for Ecology and Forest Productivity, Moscow, Russian Federation); Schultze, E. D. and Rivkina, E. M. Cryogenesis as a factor of methane distribution in layers of permafrost: Doklady Earth Sciences, 451(2), p. 882-885, illus., 15 ref., August 2013.
The gas seeps in Kolyma lowland are associated with methane inclusions in permafrost. These inclusions are formed by methane squeezed by epigenetic freezing of methane saturated deposits. This is proved by the biological genesis of the methane, by the isotopic data and the lower radiocarbon age of the methane from the gas seep in comparison with the radiocarbon age of the host deposits. The experimental data and observations of methane distribution in permafrost indicate that the methane distribution in the stratum of frozen deposits is a result of methane migration during cryolithogenesis. The regularities of methane distribution in the deposits and formation of methane inclusions may change the idea of the character and volumes of emission of greenhouse gases into the atmosphere upon degradation of permafrost. Copyright 2013 Pleiades Publishing, Ltd.
14059212 Bonnaventure, P. P. (Queen's University, Department of Geography, Kingston, ON, Canada) and Lewkowicz, A. G. Impacts of mean annual air temperature change on a regional permafrost probability model for the southern Yukon and northern British Columbia, Canada: The Cryosphere (Online), 7(3), p. 935-946, illus. incl. 2 tables, sketch maps, 55 ref., 2013.
Air temperature changes were applied to a regional model of permafrost probability under equilibrium conditions for an area of nearly 0.5 ´ 106 km2 in the southern Yukon and northwestern British Columbia, Canada. Associated environmental changes, including snow cover and vegetation, were not considered in the modelling. Permafrost extent increases from 58% of the area (present day: 1971-2000) to 76% under a -1 K cooling scenario, whereas warming scenarios decrease the percentage of permafrost area exponentially to 38% (+ 1 K), 24% (+ 2 K), 17% (+ 3 K), 12% (+ 4 K) and 9% (+ 5 K) of the area. The morphology of permafrost gain/loss under these scenarios is controlled by the surface lapse rate (SLR, i.e. air temperature elevation gradient), which varies across the region below treeline. Areas that are maritime exhibit SLRs characteristically similar above and below treeline resulting in low probabilities of permafrost in valley bottoms. When warming scenarios are applied, a loss front moves to upper elevations (simple unidirectional spatial loss). Areas where SLRs are gently negative below treeline and normal above treeline exhibit a loss front moving up-mountain at different rates according to two separate SLRs (complex unidirectional spatial loss). Areas that display high continentally exhibit bidirectional spatial loss in which the loss front moves up-mountain above treeline and down-mountain below treeline. The parts of the region most affected by changes in MAAT (mean annual air temperature) have SLRs close to 0 K km-1 and extensive discontinuous permafrost, whereas the least sensitive in terms of areal loss are sites above the treeline where permafrost presence is strongly elevation dependent.
14059218 Luetscher, M. (University of Innsbruck, Institute of Geology, Innsbruck, Austria); Borreguero, M.; Moseley, G. E.; Spötl, C. and Edwards, R. L. Alpine permafrost thawing during the Medieval Warm Period identified from cryogenic cave carbonates: The Cryosphere (Online), 7(4), p. 1073-1081, illus. incl. 1 table, sect., 49 ref., 2013.
Coarse crystalline cryogenic cave carbonates (CCCcoarse) dated to the last glacial period are common in central European caves and provide convincing evidence of palaeo-permafrost during this time. Little is known, however, about the exact nature of the environment in which CCCcoarse formed as no modern analogue setting is known. Here, we report the first findings of sub-recent, albeit inactive, CCCcoarse from a cave of the Western Alps which is located in the present-day permafrost zone. The globular shape and the presence of ubiquitous euhedral crystal terminations are comparable to previously reported aggregates from the last glacial period and strongly suggest that these aggregates formed subaqueously in pools lacking agitation. Furthermore, stable isotope values of mm-sized spheroids point to calcite precipitation in a closed system with respect to CO2, strongly supporting the hypothesis of a cryogenic origin associated with the freezing of water ponds. U-series analyses revealed three clusters of late Holocene calcite precipitation intervals between 2129 and 751 a b2k. These ages correlate with known periods of elevated summer temperatures, suggesting that warming and thawing of the frozen catchment above the cave allowed water infiltration into the karst system. The growth of CCCcoarse resulted from the re-freezing of this water in the still cold karst cavities.
14059222 Zhang, Y. (Natural Resources Canada, Canada Centre for Remote Sensing, Ottawa, ON, Canada); Wang, X.; Fraser, R.; Olthof, I.; Chen, W.; McLennan, D.; Ponomarenko, S. and Wu, W. Modelling and mapping climate change impacts on permafrost at high spatial resolution for an Arctic region with complex terrain: The Cryosphere (Online), 7(4), p. 1121-1137, illus. incl. 4 tables, sketch maps, 45 ref., 2013. Includes appendices.
Most spatial modelling of climate change impacts on permafrost has been conducted at half-degree latitude/longitude or coarser spatial resolution. At such coarse resolution, topographic effects on insolation cannot be considered accurately and the results are not suitable for land-use planning and ecological assessment. Here we mapped climate change impacts on permafrost from 1968 to 2100 at 10 m resolution using a process-based model for Ivvavik National Park, an Arctic region with complex terrain in northern Yukon, Canada. Soil and drainage conditions were defined based on ecosystem types, which were mapped using SPOT imagery. Leaf area indices were mapped using Landsat imagery and the ecosystem map. Climate distribution was estimated based on elevation and station observations, and the effects of topography on insolation were calculated based on slope, aspect and viewshed. To reduce computation time, we clustered climate distribution and topographic effects on insolation into discrete types. The modelled active-layer thickness and permafrost distribution were comparable with field observations and other studies. The map portrayed large variations in active-layer thickness, with ecosystem types being the most important controlling variable, followed by climate, including topographic effects on insolation. The results show deepening in active-layer thickness and progressive degradation of permafrost, although permafrost will persist in most of the park during the 21st century. This study also shows that ground conditions and climate scenarios are the major sources of uncertainty for high-resolution permafrost mapping.
14058777 Rödder, Tobias (University of Wurzburg, Institute of Geography and Geology, Wurzburg, Germany) and Kneisel, Christof. Influence of snow cover and grain size on the ground thermal regime in the discontinuous permafrost zone, Swiss Alps: Geomorphology, 175-176, p. 176-189, illus. incl. 3 tables, 59 ref., November 15, 2012.
The presence or absence of frozen ground within the discontinuous mountain permafrost zone is on a small scale largely determined by local site characteristics. Snow cover changes spatially at short distances caused by relief and temporally from year to year. Substrate grain size influences the heat exchange processes between air and surface and causes differences in the ground thermal properties. Based on data of four shallow boreholes and 25 temperature loggers, the effect of these factors on the ground thermal regime in two recently deglaciated forefields in the Engadin, Swiss Alps is investigated. The annual depth of the cold wave is dependent on the characteristics of the snow cover and can be twice as deep in winters with a snow height below 0.8 m. In contrast, the active layer thickness is constant even though the duration of the snow-free period changes substantially from year to year. A difference in mean annual ground surface temperatures of 4.3°C is registered over distances of 50m. The postulated negative thermal anomaly in blocky surfaces is confirmed by our data. However, permafrost conditions are also recorded at one site with fine-grained debris (sand/gravel) that is attributed to its geomorphological position and a strong coupling between air and ground surface temperatures in early winter. Thus, the ground thermal regime shows a large spatial and temporal variability as a function of snow cover evolution, snow height, surface substrate, and relief. The short data record does not yet enable us to detect any climatic signal within the discontinuous permafrost.
14062393 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Gurney, Kirsty and Wipfli, Mark S. Morphology-dependent water budgets and nutrient fluxes in arctic thaw ponds: Permafrost and Periglacial Processes, 25(2), p. 79-93, illus. incl. 3 tables, 48 ref., June 2014.
Thaw ponds on the Arctic Coastal Plain of Alaska are productive ecosystems, providing habitat and food resources for many fish and bird species. Permafrost in this region creates unique pond morphologies: deep troughs, shallow low-centered polygons (LCPs) and larger coalescent ponds. By monitoring seasonal trends in pond volume and chemistry, we evaluated whether pond morphology and size affect water temperature and desiccation, and nitrogen (N) and phosphorus (P) fluxes. Evaporation was the largest early-summer water flux in all pond types. LCPs dried quickly and displayed high early-summer nutrient concentrations and losses. Troughs consistently received solute-rich subsurface inflows, which accounted for 12 to 42 percent of their volume and may explain higher P in the troughs. N to P ratios increased and ammonium concentrations decreased with pond volume, suggesting that P and inorganic N availability may limit ecosystem productivity in older, larger ponds. Arctic summer temperatures will likely increase in the future, which may accelerate mid-summer desiccation. Given their morphology, troughs may remain wet, become warmer and derive greater nutrient loads from their thawing banks. Overall, seasonal- to decadal-scale warming may increase ecosystem productivity in troughs relative to other Arctic Coastal Plain ponds. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14060429 Raschke, Ulli (Museum für Naturkunde Berlin, Berlin, Germany); Zaag, Patrice Tristan; Schmitt, Ralf Thomas and Reimold, Wolf Uwe. The 2011 expedition to the El'gygytgyn impact structure, northeast Russia; toward a new geological map for the crater area: Meteoritics & Planetary Science, 49(6), p. 978-1006, illus. incl. 4 tables, sketch maps, 56 ref., June 2014.
El'gygytgyn is a 3.6 Ma, 18 km diameter, impact crater formed in an approximately 88 Ma old volcanic target in Northeast Siberia. The structure has been the subject of a recent ICDP drilling project. In parallel to those efforts, a Russian-German expedition was undertaken in summer 2011 to investigate the permafrost soil, lake terraces, and the volcanic rocks of the southern and eastern crater rim. This provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure. Samples from 43 outcrops were collected and analyzed petrographically and geochemically. The results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs, at the scale of 1:50,000. Compositions of our rock suites are compared with the lithologies of the 2009 ICDP drill core. The ignimbrite described as lower bedrock in the ICDP drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface. The suevite sequence exposed in the ICDP drill core is a mixture of all observed target rocks at their respective proportions in the area. In contrast to previous studies, the calculated average target composition of El'gygytgyn takes the contribution of the basic target rocks into consideration: mafic and intermediate rocks approximately 7.5%, and felsic rocks approximately 92.5%. Abstract Copyright The Meteoritical Society, 2014.
14064380 Zimov, Sergey (Russian Academy of Sciences, Pacific Institute for Geography, Cherskii, Russian Federation) and Zimov, Nikita. Role of megafauna and frozen soil in the atmospheric CH4 dynamics: PloS One, 2014(E93331), illus. incl. 1 table, 50 ref., April 2, 2014.
Modern wetlands are the world's strongest methane source. But what was the role of this source in the past? An analysis of global 14C data for basal peat combined with modelling of wetland succession allowed us to reconstruct the dynamics of global wetland methane emission through time. These data show that the rise of atmospheric methane concentrations during the Pleistocene-Holocene transition was not connected with wetland expansion, but rather started substantially later, only 9 thousand years ago. Additionally, wetland expansion took place against the background of a decline in atmospheric methane concentration. The isotopic composition of methane varies according to source. Owing to ice sheet drilling programs past dynamics of atmospheric methane isotopic composition is now known. For example over the course of Pleistocene-Holocene transition atmospheric methane became depleted in the deuterium isotope, which indicated that the rise in methane concentrations was not connected with activation of the deuterium-rich gas clathrates. Modelling of the budget of the atmospheric methane and its isotopic composition allowed us to reconstruct the dynamics of all main methane sources. For the late Pleistocene, the largest methane source was megaherbivores, whose total biomass is estimated to have exceeded that of present-day humans and domestic animals. This corresponds with our independent estimates of herbivore density on the pastures of the late Pleistocene based on herbivore skeleton density in the permafrost. During deglaciation, the largest methane emissions originated from degrading frozen soils of the mammoth steppe biome. Methane from this source is unique, as it is depleted of all isotopes. We estimated that over the entire course of deglaciation (15,000 to 6,000 year before present), soils of the mammoth steppe released 300-550 Pg (1015 g) of methane. From current study we conclude that the Late Quaternary Extinction significantly affected the global methane cycle.
14058821 Ravanel, Ludovic (Université de Savoie, EDYTEM Lab, Le Bourget-du-Lac, France); Deline, Philip; Lambiel, Christophe and Vincent, Christian. Instability of a high alpine rock ridge; the lower Arête des Cosmiques, Mont Blanc Massif, France: Geografiska Annaler. Series A: Physical Geography, 95(1), p. 51-66, illus. incl. 1 table, sketch map, 31 ref., March 2013.
Rockfalls are dominant in the rock slopes and rock ridge morphodynamics in high mountain areas and endanger people who pass along or stay there, as well as infrastructure that host them (cable cars, refuges). Risks are probably greater now because of fast permafrost degradation and regression of surface ice, two consequences of the atmospheric warming of the last decades. These two commonly associated factors are involved in the instability of rock slopes by modifying the mechanical behaviour of often ice-filled rock fractures and the mechanical constraints in the rock masses. This paper examines over 15 years the instability of the lower Arête des Cosmiques on the French side of the Mont Blanc massif. Its vulnerability is due to the presence of a high-capacity refuge on its top (3613 m a.s.l.). In 1998, a part of the refuge was left without support when a collapse of 600 m3 occurred immediately below it. Since this date, reinforcement work has been carried out in this area, but the whole ridge has been affected by around 15 relatively shallow rockfalls. Through a multidisciplinary approach, this article assesses the role of the cryospheric factors in the triggering of these rockfalls. Abstract Copyright (2012), Swedish Society for Anthropology and Geography.
14063783 Bussmann, I. (Alfred Wegener Institute for Polar and Marine Research, Helgoland, Germany). Distribution of methane in the Lena Delta and Buor-Khaya Bay, Russia: Biogeosciences, 10(7), p. 4641-4652, illus. incl. 1 table, sketch maps, 61 ref., 2013.
The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The permafrost areas surrounding the Lena are predicted to thaw at increasing rates due to global temperature increases. With this thawing, large amounts of carbon - either organic or in the gaseous forms carbon dioxide and methane - will reach the waters of the Lena and the adjacent Buor-Khaya Bay (Laptev Sea). Methane concentrations and the isotopic signal of methane in the waters of the Lena Delta and estuary were monitored from 2008 to 2010. Creeks draining from permafrost soils produced hotspots for methane input into the river system (median concentration 1500 nM) compared with concentrations of 30-85 nM observed in the main channels of the Lena. No microbial methane oxidation could be detected; thus diffusion is the main process of methane removal. We estimated that the riverine diffusive methane flux is 3-10 times higher than the flux from surrounding terrestrial environment. To maintain the observed methane concentrations in the river, additional methane sources are necessary. The methane-rich creeks could be responsible for this input. In the estuary of Buor-Khaya Bay, methane concentrations decreased to 26-33 nM. However, within the bay no consistent temporal and spatial pattern could be observed. The methane-rich waters of the river were not diluted with marine water because of a strong stratification of the water column. Thus, methane is released from the estuary and from the river mainly by diffusion into the atmosphere.
14059228 Nagai, H. (Nagoya University, Graduate School of Environmental Studies, Nagoya, Japan); Fujita, K.; Nuimura, T. and Sakai, A. Southwest-facing slopes control the formation of debris-covered glaciers in the Bhutan Himalaya: The Cryosphere (Online), 7(4), p. 1303-1314, illus. incl. sketch maps, 80 ref., 2013.
To understand the formation conditions of debris-covered glaciers, we examined the dimension and shape of debris-covered areas and potential debris-supply (PDS) slopes of 213 glaciers in the Bhutan Himalaya. This was undertaken using satellite images with 2.5 m spatial resolution for manual delineation of debris-covered areas and PDS slopes. The most significant correlation exists between surface area of southwest-facing PDS slopes and debris-covered area. This result suggests that the southwest-facing PDS slopes supply the largest quantity of debris mantle. The shape of debris-covered areas is also an important variable, quantitatively defined using a geometric index. Elongate or stripe-like debris-covered areas on north-flowing glaciers are common throughout the Bhutan Himalaya. In contrast, south-flowing glaciers have large ablation zones, entirely covered by debris. Our findings suggest that this difference is caused by effective diurnal freeze-thaw cycles rather than seasonal freeze-thaw cycles, permafrost degradation, or snow avalanches. In terms of geographic setting, local topography also contributes to glacier debris supply and the proportion of debris cover on the studied glaciers is suppressed by the arid Tibetan climate, whereas the north-to-south asymmetric topography of the Bhutan Himalaya has less influence on the proportion of debris cover.
14065680 Guil-Guerrero, José L. (University of Almeria, Food Technology Division, Almeria, Spain); Tikhonov, Alexei; Rodríguez-García, Ignacio; Protopopov, Albert; Grigoriev, Semyon and Ramos-Bueno, Rebeca P. The fat from frozen mammals reveals sources of essential fatty acids suitable for Palaeolithic and Neolithic humans: PloS One, 2014(E84480), illus. incl. 4 tables, 31 ref., January 8, 2014.
The elucidation of the sources of n-3 fatty acids available for the humans in the Upper Palaeolithic and Neolithic is highly relevant in order to ascertain the availability of such nutrients in that time frame as well as to draw useful conclusions about healthy dietary habits for present-day humans. To this end, we have analysed fat from several frozen mammals found in the permafrost of Siberia (Russia). A total of 6 specimens were included in this study: 2 mammoths, i.e. baby female calf called "Lyuba" and a juvenile female called "Yuka", both specimens approximately from the same time, i.e. Karginian Interstadial (41,000 and 34,000 years BP); two adult horses from the middle Holocene (4,600 and 4,400 years BP); and two bison very close to the Early Holocene (8,200 and 9,300 years BP). All samples were analysed by gas-liquid chromatography-mass spectrometry (GLC-MS) and GLC-flame ionization detector (GLC-FID). As demonstrated in this work, the fat of single-stomached mammals often consumed by Palaeolithic/Neolithic hunters contained suitable amounts of n-3 and n-6 fatty acids, possibly in quantities sufficient to meet the today's recommended daily intake for good health. Moreover, the results also suggest that mammoths and horses at that time were hibernators.
14061868 Hopcroft, P. O. (University of Bristol, Bristol Research Initiative for the Dynamic Global Environment, Bristol, United Kingdom); Valdes, P. J.; Wania, R. and Beerling, D. J. Limited response of peatland CH4 emissions to abrupt Atlantic Ocean circulation changes in glacial climates: Climate of the Past, 10(1), p. 137-154, illus. incl. 4 tables, 71 ref., 2014.
Ice-core records show that abrupt Dansgaard-Oeschger (D-O) climatic warming events of the last glacial period were accompanied by large increases in the atmospheric CH4 concentration (up to 200 ppbv). These abrupt changes are generally regarded as arising from the effects of changes in the Atlantic Ocean meridional overturning circulation and the resultant climatic impact on natural CH4 sources, in particular wetlands. We use two different ecosystem models of wetland CH4 emissions to simulate northern CH4 sources forced with coupled general circulation model simulations of five different time periods during the last glacial to investigate the potential influence of abrupt ocean circulation changes on atmospheric CH4 levels during D-O events. The simulated warming over Greenland of 7-9 °C in the different time periods is at the lower end of the range of 11-15 °C derived from ice cores, but is associated with strong impacts on the hydrological cycle, especially over the North Atlantic and Europe during winter. We find that although the sensitivity of CH4 emissions to the imposed climate varies significantly between the two ecosystem emissions models, the model simulations do not reproduce sufficient emission changes to satisfy ice-core observations of CH4 increases during abrupt events. The inclusion of permafrost physics and peatland carbon cycling in one model (LPJ-WHyMe) increases the climatic sensitivity of CH44 emissions relative to the Sheffield Dynamic Global Vegetation Model (SDGVM) model, which does not incorporate these processes. For equilibrium conditions this additional sensitivity is mostly due to differences in carbon cycle processes, whilst the increased sensitivity to the imposed abrupt warmings is also partly due to the effects of freezing on soil thermodynamics. These results suggest that alternative scenarios of climatic change could be required to explain the abrupt glacial CH4 variations, perhaps with a more dominant role for tropical wetland CH4 sources.
14063650 Lyons, W. Berry (Ohio State University, Byrd Polar Research Center, Columbus, OH); Welch, Kathleen A.; Gardner, Christopher B.; Jaros, Chris; Moorhead, Daryl L.; Knoepfle, Jennifer L. and Doran, Peter T. The geochemistry of upland ponds, Taylor Valley, Antarctica: Antarctic Science, 24(1), p. 3-14, illus. incl. 2 tables, 36 ref., February 2012. Includes 1 appendix.
The McMurdo Dry Valleys of Antarctica are the largest ice-free region on the continent. These valleys contain numerous water bodies that receive seasonal melt from glaciers. For forty years, research emphasis has been placed on the larger water bodies, the permanent ice-covered lakes. We present results from the first study describing the geochemistry of ponds in the higher elevations of Taylor Valley. Unlike the lakes at lower elevations, the landscape on which these ponds lie is among the oldest in Taylor Valley. These upland ponds wax and wane in size depending on the local climatic conditions, and their ionic concentrations and isotopic composition vary annually depending on the amount of meltwater generated and their hydrologic connectivity. This study evaluates the impact of changes in summer climate on the chemistry of these ponds. Although pond chemistry reflects the initial meltwater chemistry, dissolution and chemical weathering within the stream channels, and possibly permafrost fluid input, the primary control is the dilution effect of glacier melt during warmer summers. These processes lead to differences in solute concentrations and ionic ratios between ponds, despite their nearby proximity. The change in size of these ponds over time has important consequences on their geochemical behaviour and potential to provide water and solutes to the subsurface.
14069085 Marciniak, Marek (Adam Mickiewicz University, Institute of Physical Geography, Poznan, Poland); Dragon, Krzysztof and Chudziak, Lukasz. Water circulation within a high Arctic glaciated valley (Petunia Bay, central Spitsbergen); recharge of a glacial river: Journal of Hydrology, 513, p. 91-100, illus. incl. 6 tables, sketch map, 28 ref., May 26, 2014.
This article presents an investigation of the runoff of a glacial river located in the high Arctic region of Spitsbergen. The Ebba River runoff was measured during three melting seasons of 2007, 2008 and 2009. The most important component of the river recharge is the flow of melting water from glaciers (76-82% of total river runoff). However, the other components (surface water and groundwater) also made a significant contribution to the river recharge. The contribution of groundwater flow in total river runoff was estimated by measurements performed in four groups of piezometers located in different parts of the valley. The hydrogeological parameters that characterize shallow aquifer (thickness of the active layer, hydraulic conductivity, groundwater level fluctuations) were recognized by direct field measurements. The groundwater recharging river was the most variable recharge component, and ranged from 1% of the total runoff at the beginning of the melting season to even 27% at the end of summer. Abstract Copyright (2014) Elsevier, B.V.
14069015 Soare, R. J. (Dawson College, Department of Geography, Montreal, QC, Canada); Conway, S. J. and Dohm, J. M. Possible ice-wedge polygons and recent landscape modification by "wet" periglacial processes in and around the Argyre impact basin, Mars: Icarus, 233, p. 214-228, illus. incl. 2 tables, geol. sketch maps, 91 ref., May 1, 2014.
14063781 Hanis, K. L. (University of Manitoba, Department of Soil Science, Winnipeg, MB, Canada); Tenuta, M.; Amiro, B. D. and Papakyriakou, T. N. Seasonal dynamics of methane emissions from a subarctic fen in the Hudson Bay Lowlands: Biogeosciences, 10(7), p. 4465-4479, illus. incl. 3 tables, 46 ref., 2013.
Ecosystem-scale methane (CH4) flux over a subarctic fen at Churchill, Manitoba, Canada was measured to understand the magnitude of emissions during spring and fall shoulder seasons, and the growing season in relation to physical and biological conditions. Methane flux was measured using eddy covariance with a closed-path analyser in four years (2008-2011). Cumulative measured annual methane flux (shoulder plus growing seasons) ranged from 3.0 to 9.6 g CH4 m-2 yr-1 among the four study years, with a mean of 6.5 to 7.1 g CH4 m-2 yr-1 depending upon gap-filling method. Soil temperatures to depths of 50 cm and air temperature were highly correlated with methane flux, with near-surface soil temperature at 5 cm most correlated across spring, fall, and the shoulder and growing seasons. The response of methane flux to soil temperature at the 5 cm depth and air temperature was more than double in spring to that of fall. Emission episodes were generally not observed during spring thaw. Growing season emissions also depended upon soil and air temperatures but the water table also exerted influence, with methane flux highest when water was 2-13 cm below and lowest when it was at or above the mean peat surface.
14059199 Spahni, Renato (Universität Bern, Oeschger-Zentrum für Klimaforschung, Bern, Switzerland); Joos, Fortunat; Stocker, B. D.; Steinacher, Marco and Yu, Z. C. Transient simulations of the carbon and nitrogen dynamics in northern peatlands; from the last glacial maximum to the 21st century: Climate of the Past, 9(3), p. 1287-1308, illus. incl. 3 tables, sketch maps, 74 ref., 2013. Includes appendices; published in Climate of the Past Discussion: 15 November 2012, URL: http://www.clim-past-discuss.net/8/5633/2012/cpd-8-5633-2012.html; accessed in Oct., 2013.
The development of northern high-latitude peatlands played an important role in the carbon (C) balance of the land biosphere since the Last Glacial Maximum (LGM). At present, carbon storage in northern peatlands is substantial and estimated to be 500 ± 100 Pg C (1 Pg C = 1015 g C). Here, we develop and apply a peatland module embedded in a dynamic global vegetation and land surface process model (LPX-Bern 1.0). The peatland module features a dynamic nitrogen cycle, a dynamic C transfer between peatland acrotelm (upper oxic layer) and catotelm (deep anoxic layer), hydrology- and temperature-dependent respiration rates, and peatland specific plant functional types. Nitrogen limitation down-regulates average modern net primary productivity over peatlands by about half. Decadal acrotelm-to-catotelm C fluxes vary between -20 and +50 g C m-2 yr-1 over the Holocene. Key model parameters are calibrated with reconstructed peat accumulation rates from peat-core data. The model reproduces the major features of the peat core data and of the observation-based modern circumpolar soil carbon distribution. Results from a set of simulations for possible evolutions of northern peat development and areal extent show that soil C stocks in modern peatlands increased by 365-550 Pg C since the LGM, of which 175-272 Pg C accumulated between 11 and 5 kyr BP. Furthermore, our simulations suggest a persistent C sequestration rate of 35-50 Pg C per 1000 yr in present-day peatlands under current climate conditions, and that this C sink could either sustain or turn towards a source by 2100 AD depending on climate trajectories as projected for different representative greenhouse gas concentration pathways.
14063651 Tamppari, L. K. (Jet Propulsion Laboratory, Pasadena, CA); Anderson, R. M.; Archer, Paul Douglas, Jr.; Douglas, S.; Kounaves, S. P.; McKay, C. P.; Ming, Douglas W.; Moore, Q.; Quinn, J. E.; Smith, P. H.; Stroble, S. and Zent, A. P. Effects of extreme cold and aridity on soils and habitability; McMurdo dry valleys as an analogue for the Mars Phoenix landing site: Antarctic Science, 24(3), p. 211-228, illus. incl. 4 tables, 50 ref., June 2012.
The McMurdo Dry Valleys are among the driest, coldest environments on Earth and are excellent analogues for the Martian northern plains. In preparation for the 2008 Phoenix Mars mission, we conducted an interdisciplinary investigation comparing the biological, mineralogical, chemical, and physical properties of wetter lower Taylor Valley (TV) soils to colder, drier University Valley (UV) soils. Our analyses were performed for each horizon from the surface to the ice table. In TV, clay-sized particle distribution and less abundant soluble salts both suggested vertical and possible horizontal transport by water, and microbial biomass was higher. Alteration of mica to short-order phyllosilicates suggested aqueous weathering. In UV, salts, clay-sized materials, and biomass were more abundant near the surface, suggesting minimal downward translocation by water. The presence of microorganisms in each horizon was established for the first time in an ultraxerous zone. Higher biomass numbers were seen near the surface and ice table, perhaps representing locally more clement environments. Currently, water activity is too low to support metabolism at the Phoenix site, but obliquity changes may produce higher temperatures and sufficient water activity to permit microbial growth, if the populations could survive long dormancy periods (»106 years).
14062398 Hjort, Jan (University of Oulu, Department of Geography, Oulu, Finland). Which environmental factors determine recent cryoturbation and solifluction activity in a subarctic landscape? A comparison between active and inactive features: Permafrost and Periglacial Processes, 25(2), p. 136-143, illus. incl. 1 table, sketch map, 38 ref., June 2014.
Environmental factors that affect the activity-inactivity variation of periglacial features may differ from those factors that control the distributional patterns of active features. To explore this potential difference, a statistically based modelling approach and comprehensive data on active and inactive cryoturbation and solifluction features from a subarctic area of Finnish Lapland are investigated at a landscape scale. In the cryoturbation modeling, vegetation abundance is the most important environmental variable explaining both the activity-inactivity variation and the distribution of active sites. The next most important variables are soil moisture and (micro)climatological conditions in the activity modelling, and slope angle and ground material in the distribution modeling. For solifluction, the key variables determining the activity-inactivity variation are mean annual air temperature and mean maximum snow depth, whereas vegetation abundance and slope angle control the distribution of active sites. Comparison between the environmental conditions of active and inactive periglacial features may provide new insights into activity-environment relationships, which in turn are valuable when the effects of climate change on periglacial processes are explored. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14062394 Matsuoka, Norikazu (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan). Combining time-lapse photography and multisensor monitoring to understand frost creep dynamics in the Japanese Alps: Permafrost and Periglacial Processes, 25(2), p. 94-106, illus. incl. 1 table, sketch map, 27 ref., June 2014.
Automated monitoring that combines time-lapse photography and sensor-based data logging can elucidate the environmental conditions, processes and rates of soil movement on remote periglacial hillslopes. This study presents the results from 5 years of time-lapse photography of soil movements, supported by time series data on frost heave, soil temperature, soil moisture and surface weather, on an alpine stone-banked lobe subject to frequent diurnal freeze-thaw cycles and deep seasonal frost on Mt Ainodake in the Japanese Alps. The lobe is dominated by biannual shallow soil movements, mostly originating from diurnal frost heave by needle ice or shallow ice lens formation and approximated by potential frost creep. The surface velocity shows a small interannual variation mainly reflecting snow conditions that control the spatio-temporal variability of freeze-thaw action, while it is independent of mean annual air temperature that influences the intensity of seasonal freezing. Occasional rill erosion occurs when the topmost frozen soil is rapidly thawed and super-saturated by intensive rainfall during seasonal thawing periods. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14067751 Monnier, Sébastien (Centro de Estudios Avanzados en Zonas Áridas, La Serena, Chile); Kinnard, Christophe; Surazakov, Arzhan and Bossy, William. Geomorphology, internal structure, and successive development of a glacier foreland in the semi-arid Chilean Andes (Cerro Tapado, upper Elqui Valley, 30°08'S, 69°55'W): Geomorphology, 207, p. 126-140, illus. incl. geol. sketch map, 39 ref., February 15, 2014.
We use geomorphological analysis, sedimentological survey, remote sensing, and ground penetrating radar (GPR) in order to understand the complex landform assemblage found in front of the Cerro Tapado glacier in the upper Elqui River catchment, semiarid Andes of Chile. The geomorphological analysis highlights prominent boundaries dividing the landform assemblage into (from the upper part to the lower part) an upper latero-frontal moraine complex, an upper debris-covered glacier, a lower debris-covered glacier, two rock glaciers, and a lower morainic complex. The sedimentological survey highlights the rather small size of the surface debris (in general <20cm) and the predominance of porphyritic rhyolite. Remote sensing data show that, between 1956 and 2010, considerable (>400m) receding of the glacier occurred, along with downslope displacements (dm-m.y-1) of most of the landform units and a significant evolution of the thermokarst features on the debris-covered glaciers. Considerable surface lowering occurred in the upper part of the assemblage, while localized bulging is seen along the morphological boundaries in the lower units. The GPR profiles highlight spectacular internal structure in the upper debris-covered glacier with up to 80m of buried ice. In the other landform units, the internal structure is less visible and more heterogeneous. The analysis of the radar wave velocity along the GPR profiles reveals the occurrence of air-filled and moist zones in the internal structure. The geomorphological assemblage is fundamentally characterized by its morphological, structural, and dynamical boundaries and defined as a young (probably <2000years) polygenetic construction with landform units having added to/overlapped one another. The rock glaciers do not derive from the present debris-covered glacier but preexist to it. Abstract Copyright (2014) Elsevier, B.V.
14066995 Zhao Long (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Laboratory of Tibetan Environment Changes and Land Surface Processes, Beijing, China); Yang Kun; Qin Jun; Chen Yingying; Tang Wenjun; Montzka, Carsten; Wu Hui; Lin Changgui; Han Menglei and Vereecken, Harry. Spatio-temporal analysis of soil moisture observations within a Tibetan mesoscale area and its implication to regional soil moisture measurements: Journal of Hydrology, 482, p. 92-104, illus. incl. 6 tables, sketch map, 54 ref., March 4, 2013.
A mesoscale Tibetan Plateau Soil Moisture/Temperature Monitoring Network (SMTMN) has been established to study large-scale soil-vegetation-atmosphere interactions and to validate satellite soil moisture products. Soil moisture at four layers (0-5 cm, 10 cm, 20 cm, and 40 cm) of 30 sites was monitored since July, 2010. This paper firstly introduces the network and then presents preliminary spatiotemporal analyses based on the in situ soil moisture measurements in SMTMN. Three temporal scales (half-hourly, daily, and 10-days) and three time periods corresponding to typical soil wetness conditions, including frozen soil in winter times, are discussed. Primary findings are: (a) generally 13 randomly distributed sites in the study domain are required (i.e. number of required sites) to estimate areal mean soil moisture with correlation coefficient >&eq;0.99 and root mean square difference ≤&eq;0.02 m3m-3. This provides guidance for future soil moisture network establishment in similar regions; (b) both number of required sites and the most representative site are insensitive to temporal scales while conversely sensitive to soil wetness conditions; (c) the combination of a few optimally-selected sites can give more robust estimate of areal mean soil moisture than a single site does because the former contains more information on spatial heterogeneity. These findings can provide not only a practical compromise between maintenance cost and risk on reliability for an existing soil moisture network, but also insights for soil moisture upscaling studies and satellite soil moisture products validations. Abstract Copyright (2013) Elsevier, B.V.
14061892 Matsuoka, Norikazu (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan); Imaizumi, Fumitoshi and Nishii, Ryoko. Geomorphic dynamics and sediment budget in the southern Japanese Alps; recent studies and prospects: in Changing natural environments in the Japanese Alps region (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 122(4), p. 591-614, (Japanese) (English sum.), illus. incl. block diag., sketch maps, 145 ref., 2013.
This review paper synthesizes geomorphic dynamics, sediment transport and resulting natural hazards in mountains of the southern Japanese Alps and their drainage basins, where climatic and geological situations produce highly active landform dynamics. In alpine areas above the timber line, shallow diurnal freeze-thaw action operating in the thin topsoil produces small-scale periglacial forms, and gravitational spreading leads to numerous sackung features where snow-melt and heavy rain in places promote rockslides. In subalpine and montane areas, deep-seated landslides originate from fractured sedimentary rocks, deep V-shaped valleys, and heavy rain, while shallow landslides continue with historical forest clearance. Continuous slope failures prevent vegetation recovery and maintain debris input to valleys. Steep valleys contribute to high-density debris flows. Frequent or repetitive occurrences of these mass movements promote continuous denudation of slopes, rockfall accidents along hiking trails, and sedimentation at artificial dams. They occasionally cause significant hazards to villages further downstream. Predicting and mitigating slope hazards require distinguishing among annual, low-magnitude processes, episodic high-magnitude processes and geomorphic changes associated with long-term climate change.
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