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13012298 Apaloo, Jotham (University of Waterloo, Department of Geography and Environmental Management, Wateloo, ON, Canada); Brenning, Alexander and Bodin, Xavier. Interactions between seasonal snow cover, ground surface temperature and topography (Andes of Santiago, Chile, 33.5°S): Permafrost and Periglacial Processes, 23(4), p. 277-291, illus. incl. 5 tables, sketch map, 59 ref., December 2012.
The spatial variables which affect the surface thermal regime are explored in a valley in a high-altitude catchment of the Andes of Santiago. Two one-year (2009-10 and 2010-11) ground surface temperature (GST) time series are analysed separately and linear mixed-effects models are used to quantify the effects of site characteristics on mean GST (MGST) and ground surface thermal regimes. The effect of snow cover onset and disappearance dates on MGST is further examined in a sensitivity analysis. Elevation has the strongest effect on MGST (1°C/100 m), 30 additional days of snow cover suppress MGST by an estimated 0.1 to 0.6°C and openwork boulder surfaces are cooler by an estimated 0.6 to 0.8°C. The sensitivity analysis corroborates the effect of late snow cover in the linear models, which can overwhelm the spatial differences in radiative effects. A positive MGST found on active rock glaciers would suggest negative thermal offsets probably related to the presence of coarse blocky material at the surface, and which may also be present outside rock glaciers. We suggest that spatial patterns of MGST can serve as a proxy for spatial patterns in the lower limit of permafrost occurrence. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1753
13012297 Bommer, Christian (University of Applied Sciences, Rapperswil, Switzerland); Fitze, Philipp and Schneider, Hansruedi. Thaw-consolidation effects on the stability of alpine talus slopes in permafrost: Permafrost and Periglacial Processes, 23(4), p. 267-276, illus. incl. 3 tables, 32 ref., December 2012.
The relative contributions of thaw consolidation and slope-parallel seepage to the generation of overall porewater pressure and resultant potential changes in slope stability are determined in two case studies of thawing soils. The first study concerns experimental slopes of frozen silt inclined at 12° and 24° that thawed during scaled centrifuge modelling reported by Harris et al. (2008). The second study concerns a natural slope near Pontresina, eastern Swiss Alps, of coarse-grained talus inclined at 37° and overlying fine-grained soil that contains the permafrost table. In both cases, seepage parallel to the slope was found to contribute much more to the excess porewater pressures in the thawing soils than did thaw consolidation. This suggests that the effects of thaw consolidation on the stability of alpine talus slopes in mountain permafrost may have only minor significance. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1751
13012299 Cheng Weiming (Chinese Academy of Sciences, Institute of Geographic Sciences and Natural Resources, Laboratory of Resources and Environmental Information System, Beijing, China); Zhao Shangmin; Zhou Chenghu and Chen Xi. Simulation of the decadal permafrost distribution on the Qinghai-Tibet Plateau (China) over the past 50 years: Permafrost and Periglacial Processes, 23(4), p. 292-300, illus. incl. 6 tables, sketch maps, 36 ref., December 2012.
Decadal changes in permafrost distribution on the Qinghai-Tibet Plateau (QTP) over the past 50 years (1960-2009) were simulated with a response model that uses data from a digital elevation model, mean annual air temperature (MAAT) and the vertical lapse rate of temperature. Compared with published maps of permafrost distribution, the accuracy of the simulated results is about 85 per cent. The simulation results show: (1) with the continuously rising MAAT over the past 50 years, the simulated areas of permafrost on the QTP have continuously decreased; (2) through areal statistics, the simulated areas of permafrost were 1.60 ´ 106 km2, 1.49 ´ 106 km2, 1.45 ´ 106 km2, 1.36 ´ 106 km2 and 1.27 ´ 106 km2, respectively, in the 1960s, 1970s, 1980s, 1990s and 2000s; and (3) the rate of permafrost loss has accelerated since the 1980s, and the total area of degraded permafrost is about 3.3 ´ 105 km2, which accounts for about one-fifth of the total area of permafrost in the 1960s. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1758
13012301 Ling Feng (Zhaoqing University, School of Mathematics and Information Sciences, Zhaoqing, China); Wu Qingbai; Zhang, Tingjun and Niu Fujun. Modelling open-talik formation and permafrost lateral thaw under a thermokarst lake, Beiluhe Basin, Qinghai-Tibet Plateau: Permafrost and Periglacial Processes, 23(4), p. 312-321, illus. incl. 1 table, 54 ref., December 2012.
Thermokarst lakes on the Qinghai-Tibet Plateau cause considerable thermal disturbance to the surrounding permafrost, giving rise to anomalous ground-temperature conditions and open-talik formation below some lakes. Using in situ data and information from monitoring of a representative thermokarst lake in the Beiluhe Basin, this study simulates the rate of talik development beneath the lake, the time taken for an open talik to form, and the rate of permafrost lateral thaw after open-talik formation. The simulation uses a simplified two-dimensional unsteady finite-element model for heat transfer with phase change under a cylindrical coordinate system. The results indicate that a bowl-shaped talik forms under the lake and that the talik thickness increases substantially over time. An open talik forms below the lake 733 years after the lake formed. The average maximum thaw rates at the top and bottom of permafrost beneath the lake before the open talik forms are 5.8 cm year-1 and 0.7 cm year-1, respectively. By 1100 years after lake formation, permafrost beneath the central deep pool and shallow nearshore zone of the lake thaws completely and the heat-source effect caused by the lake becomes very limited. The volume of the open talik beneath the lake still increases gradually with time 1500 years after lake formation, but the increase is very limited. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1754
13012302 Ran Youhua (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Li Xin; Cheng Guodong; Zhang, Tingjun; Wu Qingbai; Jin Huijun and Jin Rui. Distribution of permafrost in China; an overview of existing permafrost maps: Permafrost and Periglacial Processes, 23(4), p. 322-333, illus. incl. 4 tables, geol. sketch maps, 63 ref., December 2012.
Many permafrost maps in China have been compiled since the early 1960s. The scales of these maps range from the local (1:600 000) to the regional scale (1:10 000 000). The permafrost classification systems differ among these maps. The indices for permafrost classification used in these mapping projects include spatial continuity (areal extent) and thickness of the permafrost, air and ground temperatures and ground -ice content. All of those data have been retrieved, digitised and published in the Environmental and Ecological Science Data Center for West China. These maps represent the best understanding at the time regarding the distribution of permafrost in China and its changes over the past century. An updated map of permafrost in China, including frozen ground area, is also provided. The total area of permafrost in China is estimated at ~ 1.59 ´ 106 km2 (glaciers and lakes excluded), and the area of seasonally frozen ground (excluding instantaneous frozen ground) is ~ 5.36 ´ 106 km2. The total area of high-altitude (plateau and mountain) permafrost in China is ~ 1.35 ´ 106 km2, the area of mountain permafrost is ~ 0.30 ´ 106 km2 and the area of plateau permafrost is ~ 1.05 ´ 106 km2. The latitudinal permafrost is located in the northern part of northeastern China, and its area is ~ 0.24 ´ 106 km2. Additionally, some suggestions are proposed for future mapping of permafrost in China. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1756
13012303 Stevens, Christopher W. (SRK Consulting, Anchorage, AK) and Wolfe, Stephen A. High-resolution mapping of wet terrain within discontinuous permafrost using lidar intensity: Permafrost and Periglacial Processes, 23(4), p. 334-341, illus. incl. 2 tables, sketch map, 42 ref., December 2012.
Surface hydrology is an important aspect of northern environments on account of the thermal influence of water on permafrost. In this study, we demonstrate the ability of light detection and ranging (LiDAR) to map wet terrain within an area of discontinuous permafrost adjacent to the Northwest Territories Highway 3, located west of Yellowknife, Canada. Wet terrain was identified from LiDAR intensity measurements beneath forest canopies and across vegetated surfaces, including peatlands, fens, flooded black spruce and birch forests, and terrain adjacent to the highway embankment. Surface water pathways representing hydrological connections between water bodies and wet terrain were also identified at locations otherwise indiscernible from optical imagery. Statistical separability between terrain types, and thus the ability to map them, was improved by integrating LiDAR all-return and bare-earth intensity with colour orthophotos. The average classification accuracy for wet terrain was 93 per cent. These results indicate that LiDAR intensity can be used for local-scale mapping of wet terrain, as required by northern engineers and scientists. Future integration of LiDAR intensity and elevation measurements may be used to assess changes in surface hydrological conditions impacting permafrost. Abstract Copyright Her Majesty the Queen in Right of Canada 2012.
DOI: 10.1002/ppp.1752
13012300 Zhang Mingyi (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Frozen Soil Engineering, Lanzhou, China); Min, Ki-Hong; Wu Qingbai; Zhang Jianming and Harbor, Jon. A new method to determine the upper boundary condition for a permafrost thermal model; an example from the Qinghai-Tibet Plateau: Permafrost and Periglacial Processes, 23(4), p. 301-311, illus. incl. 3 tables, sketch maps, 48 ref., December 2012.
Assessing possible permafrost degradation related to engineering projects, climate change and land use change is of critical importance for protecting the environment and in developing sustainable designs for vital infrastructure in cold regions. A major challenge in modelling the future degradation of permafrost is finding ways to constrain changes in the upper thermal boundary condition over time and space at appropriate scales. Here, we report on an approach designed to predict time series of air, ground surface and shallow ground temperatures at a spatial scale on the order of 102 m2 for engineering design of a railway or highway project. The approach uses a regional-scale atmospheric model to downscale global climate model output, and then stepwise multiple regression to develop an equation that provides a best-fit prediction of site-specific observational data using bilinearly interpolated output from the atmospheric model. This approach bridges the scale difference between atmospheric climate models and permafrost thermal models, and allows for a wider range of factors to be used in predicting the thermal boundary condition. For a research site located in Beiluhe, China, close to the Qinghai-Tibet Railway, a comparison of model predictions with observational data not used in the construction of the model shows that this method can be used with a high degree of accuracy to determine the upper boundary condition for a permafrost thermal model. Once a model is constructed, it can be used to predict future changes in boundary condition parameters under different greenhouse emission scenarios for climate change. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1755
13009213 Greipsson, Sigurdur (Kennesaw State University, Biology and Physics Department, Kennesaw, GA). Catastrophic soil erosion in Iceland; impact of long-term climate change, compounded natural disturbances and human driven land-use changes: Catena (Giessen), 98, p. 41-54, illus. incl. 2 tables, sketch maps, 72 ref., November 2012.
This study examines the interplay between long-term climate changes, compounded natural disturbances and human driven land-use changes on catastrophic soil erosion of the heathland ecosystem of Haukadalsheidi, south Iceland. Soil erosion was catastrophic for three centuries (~1660-1960 AD) and was characterized by almost total loss of vegetation and underlying soil. Soil erosion resulted in a desertified, barren landscape that had no resemblance to the original heathland ecosystem. Soil erosion was spatially reconstructed in a chronological order using information on the average progress of eroding fronts, anecdotal and historical evidence along with tephrochronological information. The progress of the fastest eroding front was rapid (29.7myr-1). Human driven land-use changes played a role in the heathland degradation: relentless free-range grazing by livestock resulted in decreased resistance of heathland communities to soil erosion. Adverse climate-change during Little Ice Age (LIA: 1550-1850 AD) intensified the effect of grazing. The catastrophic soil erosion was triggered by a massive sand encroachment ~1660 AD from three outwash sand-plains along the glacial River Far. The sand drift was sustained by dry northern glacial (katabatic) winds that drove the soil erosion. Long-term climate change resulted in glacier fluctuation that caused changes in water discharge in the River Far; sand drift was intense during periods of no water discharge (~1660-1708 AD and ~1800-1929 AD) and following glacial river floods (1708, 1884, 1902, 1929 and 1939 AD). Also, sand drift was intense due to unusually frequent volcanic tephra fallouts (1693, 1721 and 1766 AD). Information on factors that increase the risk of soil erosion and trigger and drive soil erosion is critical in understanding catastrophic soil erosion. Abstract Copyright (2012) Elsevier, B.V.
DOI: 10.1016/j.catena.2012.05.015
13009575 Haarder, Eline B. (University of Copenhagen, Department of Geography and Geology, Copenhagen, Denmark); Binley, Andrew; Looms, Majken C.; Doetsch, Joseph; Nielsen, Lars and Jensen, Karsten H. Comparing plume characteristics inferred from cross-borehole geophysical data: Vadose Zone Journal, 11(4), illus. incl. 4 tables, sketch map, 37 ref., November 2012.
We compare results of three cross-borehole geophysical approaches for imaging tracer migration arising from a point injection of water in the unsaturated zone: three-dimensional electrical resistivity tomography (ERT), two-dimensional ground-penetrating radar (GPR) tomography and quasi-three-dimensional GPR tomography. In the studied field experiment, a tracer was injected for a period of 5 d and was monitored both during injection and for 5 d during the subsequent redistribution. The three methods show similar characteristics of the plume development and movement, which has a strong lateral component and slow vertical migration. In addition to revealing the main tracer plume, two-dimensional GPR and the quasi-three-dimensional GPR results show development of secondary plumes at depth, which are not captured by the three-dimensional ERT due to lack of resolution. The flow patterns are compared to geological information from a coring obtained at the site and it is concluded that the diversion of water in the lateral direction can be caused by a few thin layers of contrasting geological composition. Mass balance calculations based on moment analysis of the moisture content changes reveal that two-dimensional and quasi-three-dimensional GPR results show similar results and that three-dimensional ERT underestimate the amount of tracer substantially. Our results further show that the analysis volume as well as threshold value for moisture content increase has significant impact on computed mass recovery. The choice of threshold value, in particular, should be method-dependent and needs to be considered carefully if the results of the moment calculations are to be used in constraining hydrological models.
DOI: 10.2136/vzj2012.0031
13010608 Matoshko, Andrei V. (National Academy of Sciences of Ukraine, Institute of Geography, Kiev, Ukraine). Balkas; a new look at a common landform of the East European Plain, from a Quaternary perspective: Earth Surface Processes and Landforms, 37(14), p. 1489-1500, illus. incl. sects., 1 table, sketch maps, 47 ref., November 2012.
Balkas (large Quaternary gullies) of the southwestern part of the East European Plain (and their analogs in Central and Western Europe) are considered in terms of their geomorphology, lithology, sedimentology, modern surface processes, stratigraphy and paleogeography. Features attributed to balkas in comparison with regular gullies and small river valleys are described. Balkas are widespread elements of the modern landscape with the same characteristic gentle-concave bottom as regular gullies, and with or without weakly incised river channels. Buried gully incisions of different ages (post-Gelasian) with the same shape are also revealed below modern Balkas. They are infilled by characteristic balka alluvial, slope and even lacustrine-bog deposits, in places representing compound sequences of fluvial-aeolian sedimentation. The fluvial part reflects multiple series of ephemeral episodes of increased water and sediment supply within temporary streams. Two conspicuous series supposedly fall within the final stages of the Dnieper (late middle Pleistocene) and Valdai (late Pleistocene) glaciations. Different ideas concerning the increase of surface runoff and erodibility of soils that might favor active balkas under conditions of land-ice decay and permafrost, including its degradation, are discussed. The development of balkas included relatively short phases of incision and accumulation interrupted by much longer periods of inactivity, when they were subjected to surface processes in a subaerial environment or left as a relic. However, during active phases they served as important and powerful depositories and arteries of rill-gully-balka sedimentation systems, collecting and transmitting eroded material to the river valleys. These phases are related to climatic oscillations and were to some degree independent of fluvial processes affecting the permanent streams. Most of the middle-late Pleistocene balkas retained their primary features, having subsequently been incorporated into the erosional network. In contrast, some of them were totally infilled and disappeared from the landscape. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/esp.3255
13009572 Rempel, Alan W. (University of Oregon, Department of Geological Sciences, Eugene, OR). Hydromechanical processes in freezing soils: Vadose Zone Journal, 11(4), illus., 53 ref., November 2012.
The study of freezing in soils has benefited immensely from analogies with physical processes that take place within the unsaturated zone. The surface energies and wetting interactions that produce differences in pressure between the pore-filling phases cause a qualitatively similar saturation dependence on geometrical characteristics, such as the pore size distribution. The ability of solid ice surfaces to support shear tractions contrasts with the fluidity of air, however, and the limited need for transport on solidification is notably different from the wholesale displacement of gas and liquid volumes that is necessary to change saturation levels in the vadose zone. This brief review outlines the main points of common ground and some of the essential differences that separate partially frozen and unsaturated soils. Particular attention is paid to an illustration of the ice and liquid saturation behavior in a two-dimensional model porous medium, both in a pure water system and with solutes present at a specified (bulk) concentration relative to the total mass of pore constituents. A derivation is developed for the net thermomolecular force exerted by sediment particles on an ice lens, and the model soil parameters are used to examine how the colligative effects of impurities modify the loads that can be supported in this way. The focus of this study is on describing and quantifying the physical interactions that underlie the vast range of hydro-mechanical processes in freezing soils.
DOI: 10.2136/vzj2012.0045
13009600 Scholer, Marie (University of Lausanne, Institute of Geophysics, Lausanne, Switzerland); Irving, James; Looms, Majken C.; Nielsen, Lars and Holliger, Klaus. Bayesian Markov-chain-Monte-Carlo inversion of time-lapse crosshole GPR data to characterize the vadose zone at the Arrenaes site, Denmark: in Model-data fusion in the vadose zone (Huisman, Johan A., editor; et al.), Vadose Zone Journal, 11(4), illus. incl. 3 tables, sketch map, 44 ref., November 2012.
The ground-penetrating radar (GPR) geophysical method has the potential to provide valuable information on the hydraulic properties of the vadose zone because of its strong sensitivity to soil water content. In particular, recent evidence has suggested that the stochastic inversion of crosshole GPR traveltime data can allow for a significant reduction in uncertainty regarding subsurface van Genuchten-Mualem (VGM) parameters. Much of the previous work on the stochastic estimation of VGM parameters from crosshole GPR data has considered the case of steady-state infiltration conditions, which represent only a small fraction of practically relevant scenarios. We explored in detail the dynamic infiltration case, specifically examining to what extent time-lapse crosshole GPR traveltimes, measured during a forced infiltration experiment at the Arreneas field site in Denmark, could help to quantify VGM parameters and their uncertainties in a layered medium, as well as the corresponding soil hydraulic properties. We used a Bayesian Markov-chain-Monte-Carlo inversion approach. We first explored the advantages and limitations of this approach with regard to a realistic synthetic example before applying it to field measurements. In our analysis, we also considered different degrees of prior information. Our findings indicate that the stochastic inversion of the time-lapse GPR data does indeed allow for a substantial refinement in the inferred posterior VGM parameter distributions compared with the corresponding priors, which in turn significantly improves knowledge of soil hydraulic properties. Overall, the results obtained clearly demonstrate the value of the information contained in time-lapse GPR data for characterizing vadose zone dynamics.
DOI: 10.2136/vzj2011.0153
13010612 Siewert, Matthias Benjamin (University of Bonn, Department of Geography, Bonn, Germany); Krautblatter, Michael; Christiansen, Hanne Hvidtfeldt and Eckerstorfer, Markus. Arctic rockwall retreat rates estimated using laboratory-calibrated ERT measurements of talus cones in Longyeardalen, Svalbard: Earth Surface Processes and Landforms, 37(14), p. 1542-1555, illus. incl. 1 table, sketch map, 82 ref., November 2012.
Holocene rockwall retreat rates quantify integral values of rock slope erosion and talus cone evolution. Here we investigate Holocene rockwall retreat of exposed arctic sandstone cliffs in Longyeardalen, central Svalbard and apply laboratory-calibrated electrical resistivity tomography (ERT) to determine talus sediment thickness. Temperature-resistivity functions of two sandstone samples are measured in the laboratory and compared with borehole temperatures from the talus slope. The resistivity of the higher and lower-porosity sandstone at relevant borehole permafrost temperatures defines a threshold range that accounts for the lithological variability of the dominant bedrock and debris material. This helps to estimate the depth of the transition from higher resistivities of ice-rich debris to lower resistivities of frozen bedrock in the six ERT transects. The depth of the debris-bedrock transition in ERT profiles is confirmed by a pronounced apparent resistivity gradient in the raw data plotted versus depth of investigation. High-resolution LiDAR-scanning and ERT subsurface information were collated in a GIS to interpolate the bedrock surface and to calculate the sediment volume of the talus cones. The resulting volumes were referenced to source areas to calculate rockwall retreat rates. The rock mass strength was estimated for the source areas. The integral rockwall retreat rates range from 0.33 to 1.96 mm yr-1, and are among the highest rockwall retreat rates measured in arctic environments, presumably modulated by harsh environmental forcing on a porous sandstone rock cliff with a comparatively low rock mass strength. Here, we show the potential of laboratory-calibrated ERT to provide accurate estimates of rockwall retreat rates even in ice-rich permafrost talus slopes. Abstract Copyright (2010), John Wiley & Sons, Ltd.
DOI: 10.1002/esp.3297
13009605 Verbist, Koen M. J. (Ghent University, Department of Soil Management, Ghent, Belgium); Pierreux, S.; Cornelis, W. M.; McLaren, R. and Gabriels, D. Parameterizing a coupled surface-subsurface three-dimensional soil hydrological model to evaluate the efficiency of a runoff water harvesting technique: in Model-data fusion in the vadose zone (Huisman, Johan A., editor; et al.), Vadose Zone Journal, 11(4), illus. incl. 7 tables, 107 ref., November 2012.
Tools are needed to quantitatively evaluate the efficiency of water harvesting techniques in dryland environments under a wide range of climatic and soil physical conditions. In a case study for the arid zone of Chile, a detailed water balance was calculated using a coupled surface-subsurface hydrological model (HydroGeoSphere). In a first step, the model was parameterized with detailed runoff and soil water content data collected during simulated rainfall to calibrate surface and subsurface flow processes simultaneously, using six responsive parameters identified by a global sensitivity analysis. The calibrated model accurately reproduced observed soil moisture contents (R2=0.92) and runoff amounts (R2=0.97), and represented the overflowing infiltration trench, which is a clear improvement over existing frameworks that do not consider surface-subsurface flow interactions. A comparative analysis with a natural slope demonstrated that the trench was efficient in capturing runoff under high rainfall intensities, such as the one simulated, resulting in a significant decrease (46%) of runoff. In the final section, a detailed water balance of the trench was calculated for four characteristic years with increasing precipitation. Significant differences in the water balance components were only observed for the very wet year (with a return period of 67 yr), where 64% of the potential runoff was effectively harvested and stored in the soil profile. As such, this test case shows the ability of HydroGeoSphere to adequately represent the water balance components of a runoff water harvesting technique and shows its potential to become an effective tool for optimal water harvesting design, while taking both soil physical and climatic constraints into account.
DOI: 10.2136/vzj2011.0141
13009117 Wang Jiaoyue (Chinese Academy of Sciences, Northeast Institute of Geography and Agroecology, Changchun, China); Song Changchun; Wang Xianwei and Song Yanyu. Changes in labile soil organic carbon fractions in wetland ecosystems along a latitudinal gradient in northeast China: Catena (Giessen), 96, p. 83-89, illus. incl. 4 tables, 50 ref., September 2012.
Wetlands in mid-high latitude regions play a vital role in climate change, due to their high organic carbon density. Nonetheless, the stabilization of soil organic carbon (SOC) and its fractions in these regions is largely unknown. The objectives of this study were to examine the changes in SOC and its fractions along a latitudinal gradient and to analyze the influencing factors in the southern margin of the permafrost region on the Eurasian continent. Topsoil (0-20cm) was collected from five wetlands along a latitudinal gradient in Northeast China. We analyzed SOC and some labile fractions. Our results demonstrated that wetland SOC and its labile fractions concentration declined with decreasing latitude. The Permafrost regions had greater organic carbon content than the regions with seasonally frozen ground. The light fraction organic carbon and particulate organic carbon accounted for 5-83% and 21-32%, respectively, of the SOC and were particularly enriched in the permafrost region. Microbial biomass carbon and dissolved organic carbon showed a similar decreasing trend to that of SOC. At the same latitude, vegetation affected SOC stock and the dynamics of its labile fractions. Therefore, wetlands in mid-high latitudes contain a large carbon pool, and carbon stock varies with latitude. Although the labile fractions were higher in the permafrost region, their activities were lower, due to low temperature and poor nutrient status. Under global warming, the labile carbon pool may be mobilized and contribute to the greenhouse effect. Moreover, vegetation differences should be considered in obtaining an accurate carbon calculation. Abstract Copyright (2012) Elsevier, B.V.
DOI: 10.1016/j.catena.2012.03.009
13011854 Arzhannikov, Sergei G. (Russian Academy of Sciences, Siberian Branch, Institute of the Earth's Crust, Irkutsk, Russian Federation); Braucher, Regis; Jolivet, Marc; Arzhannikova, Anastasia V.; Vassallo, Riccardo; Chauvet, Alain; Bourles, Didier and Chauvet, Frédéric. History of late Pleistocene glaciations in the central Sayan-Tuva Upland (southern Siberia): Quaternary Science Reviews, 49, p. 16-32, illus. incl. 5 tables, sketch map, 47 ref., August 23, 2012.
This work describes the history of late Pleistocene glaciations in the central Sayan-Tuva Upland (southern Siberia). Geological and geomorphological analysis as well as 10Be surface-exposure dating revealed the glacier fluctuations in this continental area. The available published data show that the glaciers were formed in the MIS 6 and probably survived in the MIS 5. Data are also available concerning glacial advances in different periods of MIS 4, MIS 3 and MIS 2. ELAs were 2030-2230 m. Two distinct 10Be exposure ages groups are highlighted reflecting the time of formation of glacial deposits in the MIS 2 associated to the Big Sayan Ridge outlet glaciers. The Sentsa - Sailag group (terminal moraine) has a mean exposure age of 16.44 ± 0.38 ka. The Jombolok (terminal moraine) - Jombolok (outwash plain) group has a mean exposure age of 22.80 ± 0.56 ka. The last glaciation that occurred at MIS 2 is characterized by the absence of ice cap on the Azas volcanic Plateau and of ice field in the Todza Basin. The thickness of the valley glacier was 300-400 m. At MIS 2, the terminal moraines were ~1300-1400 m a.s.l. in the Tissa, Sentsa, Jombolok and Sailag river valleys.
DOI: 10.1016/j.quascirev.2012.06.005
13009693 Desyatkin, R. V. (Russian Academy of Sciences, Siberian Branch, Institute of the Cryosphere Biology, Yakutsk, Russian Federation); Desyatkin, A. R. and Fedorov, N. P. Temperaturnyy rezhim merzlotno-tayezhnykh pochv tsentral'noy Yakutii [Thermal regime of taiga soils in the permafrost zone of central Yakutia]: Kriosfera Zemli, 16(2), p. 70-78 (English sum.), illus. incl. sketch map, 18 ref., June 2012.
Long-term dynamics of temperature regime of the frozen forest soils under the pine, larch and birch forest has been examined on the right bank of the Lena River. The obtained results have demonstrated strong diversity and high dynamics of thermal parameters of the cryosols in Central Yakutia. Drastic fluctuations of heat supply in the cryosol active layer, both in space and in time, testify to the urgency of studying of the dynamics of energy balance in boreal forest.
13009687 Galushkin, Yu. I. (Lomonosov Moscow State University, Moscow, Russian Federation); Sitar, K. A. and Frolov, S. V. Formirovaniye i degradatsiya kriogennykh tolshch na Urengoyskoy i Kuyumbinskoy ploshchadyakh Sibiri; Chast' 2, Vliyaniye teplofizicheskikh parameterov merzlykh porod na raspredeleniye temperatury i teplovogo potoka v osadochnoy tolshche s glubinoy [Formation and degradation of the permafrost in the Urengoy and Kuyumba areas, West Siberia; Part 2, Influence of frozen rocks physical properties on heat flux and vertical temperature variations]: Kriosfera Zemli, 16(2), p. 23-29 (English sum.), illus., 20 ref., June 2012.
Numerical reconstructions of variations in distributions of temperature and heat flow with depth during the Pliocene-Holocene period of great climate variations have been carried out by the example of sedimentary sections of the Urengoy field in the West Siberian basin (well 414) and the Kuyumba area in the East Siberian Platform (the Kamov swell, well 12). The calculations confirm that an increase in salt content in underground water from 1 to 30 g/l decreases the ice melting temperature just by 2 C. At the other equal conditions, it results in a decrease in permafrost thickness almost by 100 m. The calculations demonstrate that a similar effect will take place also when the form of curve of content of unfrozen water typical of sands is replaced by the one taking into consideration the change of rock lithology with depth. The modeling results demonstrate that the temperature and heat flow distributions with depth in the present-day sedimentary section of the basin, obtained with consideration of climate variations only during the last 50 000 years, will differ significantly from the distributions with consideration of climate variations during the last 200 000 or 3 400 000 years. The corresponding estimations of the lower boundary of permafrost zone will differ by 2 and more times.
13009685 Gorbunov, A. P. (Russian Academy of Sciences, High-Altitude Geocryological Laboratory, Almaty, Kazakhstan). Kamennyye gletchery, kurumy, ledniki i vechnaya merzlota gor Turtsii; geograficheskoye obozreniye [Rock glaciers, stone runs, glaciers and permafrost in Turkish mountains; geographic review]: Kriosfera Zemli, 16(2), p. 3-8 (English sum.), illus., 4 ref., June 2012.
Analysis of satellite imagery of Google revealed active, inactive and fossil rock glaciers, glaciers, chingils-kurums and permafrost. The total number of rock glaciers is about 600. Among them, there are about 200 active glaciers. Active and inactive forms are located mainly in the range of altitudes 3400-2800 m. In some places, fossil rock glaciers go down to 2200-2300 m isohypses. The largest rock glaciers can reach 1200-1300 m long. The small cirque glaciers predominate in the mountains of Turkey. Their usual length is 200-300 m. The largest reaches a length of 2000 m. The number of glaciers is at least 80. They are confined to nine mountain ranges. Kurum fields (chingils) are characteristic of mountain summits to the north-east of Turkey. They are tracked down to an altitude of 2650 m. Permafrost is confined to 40 mountain regions.
13009694 Gubin, S. V. (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems of Soil Science, Tyumen, Russian Federation) and Lupachev, A. V. Podkhody k vydeleniyu i izucheniyu pogrebennykh pochv v merzlykh tolshchakh otlozheniy ledovogo kompleksa [Approaches to identification and study of buried soils in the permafrost]: Kriosfera Zemli, 16(2), p. 79-84 (English sum.), illus., 23 ref., June 2012.
The structure and peculiar properties of soils buried in ice complex deposits have been analyzed. Due to frozen state and high ice content of these soil profiles a number of criteria and methods of investigation have been put forward.
13009692 Makarov, V. N. (Russian Academy of Sciences, Siberian Branch, P. Melnikov Permafrost Institute, Yakutsk, Russian Federation). Dinamika tekhnogennoy migratsii soyedineniy azota v deyatel'nom sloye [Dynamics of nitric compound migration in the active layer with regard to human activity]: Kriosfera Zemli, 16(2), p. 65-69 (English sum.), illus. incl. 4 tables, sketch maps, 6 ref., June 2012.
Nitrogen is an essential nutrient for all living organisms. The results of investigation on migration of mineral nitrogen compounds into the active layer and permafrost in the residential and industrial zones of the city of Yakutsk are discussed. Concentration of nitrogen compounds is relatively uniform in perennially frozen Cenozoic alluvial deposits on the Lena River terraces. Concentration of nitrogen compounds in the active layer distinctly correlates with the period of anthropogenic impact. The flux of nitrogen compounds to the active layer of the residential areas has been relatively constant over the 300 years of anthropogenic impact. In the industrial zone, accumulation of nitrogen compounds in the active layer increases by more than one order of magnitude.
13009689 Moskalenko, N. G. (Russian Academy of Sciences, Siberian Division, Institute of the Earth's Cryosphere, Tyumen, Russian Federation). Izmeneniya kriogennykh landshaftov severnoy taygi Zapadnoy Sibiri v usloviyakh menyayushchegosya klimata i tekhnogeneza [Change of cryogenic landscapes in the northern taiga of West Siberia under climate change and human activity]: Kriosfera Zemli, 16(2), p. 38-42 (English sum.), illus. incl. 1 table, 20 ref., June 2012.
The results of monitoring of cryogenic landscape changes in the West Siberia northern taiga during 1970-2010 in the conditions of the varying climate and human-induced disturbances have been presented. Process of formation of the frozen cloudberry-wild rosemary-peat moss-lichen flat peatland instead of the thawed cotton grass-wedge-moss mires has been considered. The cotton grass-peat moss bogs with the lowered permafrost table are formed after the removal of vegetation cover on flat peatlands as a result of development of thermokarst and bogging. The impact of increase in amount of atmospheric precipitation on the development of bogging on flat poorly drained sites has been examined. This bogging leads to the replacement of the pine-larch cloudberry-wild rosemary-lichen-peat moss open wood with permafrost lenses by the andromeda-cotton grass-sedge-peat moss thawed mires.
13009690 Osadchaya, G. G. (Management Information and Business Institute, Department of Ecology and Nature Management, Ukhta, Russian Federation) and Zengina, T. Yu. Vozmozhnosti sbalansirovannogo ispol'zovaniya biosfernogo i resursnogo potentsiala Bol'shezemel'skoy tundry [Possibility of rational use of biospheric and other natural resources of Bolshezemelskaya Tundra]: Kriosfera Zemli, 16(2), p. 43-51 (English sum.), illus. incl. 2 tables, sketch map, 21 ref., June 2012.
Bolshezemelskaya tundra has unique biosphere resources. It belongs to the permafrost zone (with diverse intensity) and is a part of the Northern Eurasian Center of stabilization of the environment. Its preservation is the foundation of the sustainable development of the region and the control of the biosphere equilibrium within the limits of northern Eurasia. The features of the cryolithozone landscape-differentiation within the Bolshezemelskaya tundra are described as the factor determining the degree of stability of this area to industrial disturbances. The differentiated allowable size of the area of intensive exploitation for the northern and southern parts of the region is justified. On the basis of calculations carried out for a number of deposits under long development, it has been shown that during 20-30 years of active exploitation of all the hydrocarbon reserves prepared for development there will be a significant growth of area of disturbed lands. It will lead to a loss of biospheric functions and capacity for sustainable development and to the impossibility of the existence of traditional forms of management. The ways of changing of legal and administrative elements of environmental management to ensure the balanced use of the biosphere and resource potential of landscapes of Bolshezemelskaya tundra have been examined.
13009688 Sannikov, G. S. (Promneftegeoekologiya Company, Tyumen, Russian Federation). Kartometricheskiye issledovaniya termokarstovykh ozer na territorii Bovanenkovskogo mestorozhdeniya, poluostrov Yamal [Cartometric studies of thermokarst lakes in the Bovanenkovo Field area, Yamal Peninsula]: Kriosfera Zemli, 16(2), p. 30-37 (English sum.), illus. incl. 1 table, sketch maps, 25 ref., June 2012.
The researches of changes of the sizes of thermokarst lakes have been carried out on the key site located within the territory of Bovanenkovo gas field, Central Yamal. The changes that occurred during the last 20 years have been calculated. The analyses of the nonsimultaneous cartographic, aero- and space-survey materials have been used during the investigations. The possibility of using of the relief morphological analysis for the determination of location of sites mostly exposed to thermokarst has been examined. The cartometric calculations have revealed the insignificant but stable decrease of areas of the thermokarst lakes on watershed surfaces and insignificant increase of lake areas and number of lakes on the low hypsometrical levels.
13009691 Shkol'nik, Igor M. (Voeikov Main Geophysical Observatory, Saint Petersburg, Russian Federation); Nadezhina, E. D.; Pavlova, T. V.; Khlebnikova, E. I.; Semioshina, A. A.; Mol'kentin, E. K. and Stafeyeva, E. N. Modelirovaniye regional'nykh osobennostey sezonnotalogo sloya v zone vechnoy merzloty na territorii Sibiri [Regional modeling of active layer in the Siberian permafrost zone]: Kriosfera Zemli, 16(2), p. 52-59 (English sum.), illus., 25 ref., June 2012.
The future projections of seasonal thawing layer depth in the permafrost regions of Siberia are analyzed. The experiments have been conducted using ensemble climate simulations provided by Main Geographical Observatory Regional Climatic Model. Accordingly, the ensemble approach has been used to simulate the changes in thermal state of permafrost. The influence of forest vegetation on seasonal thaw layer evolution has been evaluated. It has been demonstrated that the anthropogenic warming signal in the seasonal thaw layer depth change is not discernible above natural climate variability in the late 20th century, while in the mid-21st century it can be estimated at a reasonable level of confidence over the most part of Siberian territory.
13009686 Slagoda, E. A. (Russian Academy of Sciences, Siberian Division, Institute of the Earth's Cryosphere, Tyumen, Russian Federation); Opokina, O. L.; Rogov, V. V. and Kurchatova, A. N. Stroyeniye i genezis podzemnykh l'dov v verkhneneopleystotsen-golotsenovykh otlozheniyakh mysa Marre-Sale, zapadnyy Yamal [Structure and origin of ground ice in upper Pleistocene-Holocene sediments in the Marre-Sale Cape, western Yamal]: Kriosfera Zemli, 16(2), p. 9-22 (English sum.), illus. incl. sects., 1 table, sketch map, 25 ref., June 2012.
In 2008-2010 the polygonal ice wedges and massive ground ice were observed in the sections of coastal cliff of Marre-Sale cape. The upper ice layer was complicated by laccolites, stocks and fissures, the lower massive ice--by anticlinal folds. Analyses of lithology and deformations of the inclosing sediments, interrelation between polygonal and massive ice, chemical and isotope composition, and ice structure have been carried out. The repeated-injection genesis of the upper massive ice with laccolites and segregation genesis of the lower ice layer has been established. It has been ascertained that the formation of the upper massive ice had occurred in the Holocene during talik freezing in the khasyreys.
13010942 Smith, I. Rod (Geological Survey of Canada, Calgary, AB, Canada). The application of seismic shothole drillers' log data to petroleum exploration and development: Bulletin of Canadian Petroleum Geology, 60(2), p. 59-68, illus. incl. sketch maps, 43 ref., June 2012.
The dearth of baseline, near-surface (<20 m) geoscience knowledge represents a practical and economic limitation to seismic exploration and petroleum development in remote and northern sedimentary basins of Canada. The compilation of 343 989 seismic shothole drillers' logs from continental Northwest Territories and northern Yukon, in database and GIS formats, provides a large new source of lithostratigraphic data. Use of this previously disregarded data has enabled reconstructions and models of potential granular aggregate resources, massive and ground ice occurrences, geohazards, muskeg and drift thicknesses, and till facies. This information can be readily utilized to improve the efficiency and focus of environmental assessments, address issues of weathered zone static inferences for seismic exploration, better identify potential geohazards, and support the sustainable design and development of regional infrastructure.
DOI: 10.2113/gscpgbull.60.2.59
13009676 Galushkin, Yu. I. (Lomonosov Moscow State University, Moscow, Russian Federation); Sitar, K. A. and Frolov, S. V. Formirovaniye i degradatsiya kriogennykh tolshch na Urengoyskoy i Kuyumbinskoy ploshchadyakh Sibiri; Chast' 1, Primeneniye sistemy modelirovaniya osadochnykh basseynov GALO [Permafrost formation and degradation in the Urengoy and Kuyumba areas; Part 1, Application of GALO basin modeling system]: Kriosfera Zemli, 16(1), p. 3-11 (English sum.), illus., 6 ref., February 2012.
Application of the Basin Modeling package GALO together with its specific modification (the FROST program package) allowed authors to carry out the numerical reconstruction of temperature and heat flow distributions with depth during basin subsidence and the assessment of permafrost evolution during the Pliocene-Quaternary. Computations have been accomplished for two sedimentary sections: the Urengoy field in the West Siberian basin and Kuyumba field in the Kamov swell on the East Siberian Platform. Calculations of the thermal regime of the sedimentary stratum evidence a significant role of rock lithology in permafrost evolution. Numerical assessments point to a decrease in rock temperatures by 15-20 C within the upper 1500 m of sedimentary section due to the climate cooling in the Pliocene-Holocene. In spite of warmer climate, the cooling effect in the Kuyumba area occurs to be deeper and more intensive due to the relatively thin sedimentary cover in comparison with that one in the more northern Urengoy area.
13009679 Grechishchev, S. E. (Russian Academy of Sciences, Siberian Branch, Earth Cryosphere Institute, Tyumen, Russian Federation); Brushkov, A. V.; Pavlov, A. V. and Grechishcheva, O. V. Eksperimental'noye izucheniye kriiogennogo davleniya v promerzhayushchikh vlagonasyshchennykh zosolennykh gruntakh [Experimental studies of cryogenic pressure in freezing water-saturated saline soils]: Kriosfera Zemli, 16(1), p. 33-36 (English sum.), illus. incl. 1 table, 4 ref., February 2012.
The results of experimental laboratory investigations of cryogenic pressure of freezing water-saturated saline fine-grained soils have been presented. The first experimental data for evaluation of cryogenic pressure dependence on the salinity of freezing fine-grained soils have been obtained. It has been established that the unfrozen water content in frozen saline fine-grained soils increases with the rise of cryogenic pressure and soil salinity.
13009682 Ivanova, V. V. (Gramberg All-Russian Research Institute for Geology and Mineral Resources of the World Ocean, Saint Petersburg, Russian Federation). Geokhimiya plastovykh l'dov ostrova Novaya Sibir' (Novosibirskiye ostrova, Rossiyskaya Arktika) kak otrazheniye usloviy ikh genezisa [Geochemical features of formation of massive ground ice bodies of New Siberia Island, Russian Arctic, as the evidence of their genesis]: Kriosfera Zemli, 16(1), p. 56-70 (English sum.), illus. incl. 7 tables, sketch map, 52 ref., February 2012.
This paper presents the preliminary results of the study of macro- and trace element composition of massive ground ice and the enclosing Quaternary sediments at New Siberian Islands, carried out during the expedition "The high-latitude Arctic: Nature and Man" (Russian-American interdisciplinary research project "Zhokov-2000"). The features of the chemical composition of massive ground ice and possible mechanisms of their formation have been analyzed. All these data make possible the assumption about the injected origin of the lower horizon of massive ground ice. The upper horizon is probably of intrasoiled origin as a result of the segregation ice formation.
13009678 Streletskiy, D. A. (George Washington University, Department of Geography, Washington); Shiklomanov, N. I. and Grebenets, V. I. Izmeneniye nesushchey sposobnosti merzlykh gruntov v svyazi s potepleniyem klimata na severe Zapadnoy Sibiri [Changes of foundation bearing capacity due to climate warming in northwestern Siberia]: Kriosfera Zemli, 16(1), p. 22-32 (English sum.), illus. incl. 1 table, sketch maps, 28 ref., February 2012.
The authors present a quantitative methodology for geographic assessment of bearing capacity of permafrost foundations. The methodology was applied to evaluate the variability in bearing capacity for different physiographic regions under changing climatic conditions. The results obtained indicate an increase in permafrost temperature over 30 (1960-1990) years attributable to climatic warming. This has resulted in a 17% decrease in foundation bearing capacity in the North of West Siberia. At some locations, the decrease has been as much as 45%. Predicted climate change may lead to a further decrease in the bearing capacity of foundations built according to the passive construction principle and results in deformations of structures. This will have negative consequences for infrastructure development in permafrost regions.
13009681 Vasil'chuk, Yu. K. (Lomonosov Moscow State University, Department of Geography and Geology, Moscow, Russian Federation); Budantseva, N. A.; Vasil'chuk, A. K.; Zemskova, A. M.; Kristiansen, Kh. and Chizhova, Yu. N. Izmeneniye soderzhaniya stabil'nykh izotopov kisloroda i vodoroda v povtorno-zhil'nykh l'dakh Yamala i Sval'barda, sformirovavshikhsya za posledniye 2 tysyachi let [Oxygen and hydrogen stable isotope variation in ice-wedges in Yamal Peninsula and Svalbard formed over the last 2 kyr]: Kriosfera Zemli, 16(1), p. 43-55 (English sum.), illus. incl. 5 tables, 26 ref., February 2012.
Variations of stable oxygen isotopes in large syngenetic ice-wedges located at the Yerkutayakha River on Southern Yamal Peninsula and the Adventselva River on Svalbard have been analyzed. Stable paleotemperature conditions of ice wedge formation during the last 2 ka have been demonstrated.
13010305 Aoyama, Masafumi (Japan Map Center, Meguro, Japan). Air and shallow ground temperatures associated with the formation of gravelly lobes on a periglacial smooth slope at Mt. Minamidake, northern Japanese Alps: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 342-358, (Japanese) (English sum.), illus. incl. geol. sketch map, 52 ref., 2012.
Air and ground temperatures on a periglacial smooth slope at Mt. Minamidake (3,033 m.a.s.l.), northern Japanese Alps, were observed and used to compare periglacial conditions between alpine areas in Japan and Switzerland. These temperature data were combined with morphometric parameters to discuss periglacial processes forming a bouldery lobe and a pebbly lobe on the smooth slope. Freezing indices at the study site are smaller than indices in permafrost areas of Mt. Fuji and of the Daisetsu Mountains, Hokkaido. Mean annual air temperatures at the study site were within the boundary values for the presence of mountain permafrost. Mean annual ground surface temperatures on the studied slope are comparable to or colder than those at the lower limit of permafrost in the Swiss Alps. Thus, ground surface temperatures on the studied slope indicate the presence of permafrost, unless an advective heat flow such as rainwater infiltration disturbs subsurface temperatures. The bouldery lobe has a smaller riser height than a typical rock glacier, but a larger one than a typical solifluction lobe. The morphometric parameters of the pebbly lobe are comparable to typical solifluction lobes, which originate from annual frost creep and gelifluction. The surface of the bouldery lobe lacks interstitial fine materials, and that of the pebbly lobe is partly composed of a fine debris layer. These conditions suggest that permafrost creep is responsible for the development of the bouldery lobe, while the pebbly lobe originates from annual frost creep and gelifluction.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13010070 Brovkin, Victor (Max Planck Institute for Meteorology, Hamburg, Germany); Ganopolski, Andrey; Archer, David and Munhoven, Guy. Glacial CO2 cycle as a succession of key physical and biogeochemical processes: Climate of the Past, 8(1), p. 251-264, illus., 66 ref., 2012. Includes appendices; published in Climate of the Past Discussion: 30 May 2011, URL: http://www.clim-past-discuss.net/7/1767/2011/cpd-7-1767-2011.html;accessed in April 2012.
During glacial-interglacial cycles, atmospheric CO2 concentration varied by about 100 ppmv in amplitude. While testing mechanisms that have led to the low glacial CO2 level could be done in equilibrium model experiments, an ultimate goal is to explain CO2 changes in transient simulations through the complete glacial-interglacial cycle. The computationally efficient Earth System model of intermediate complexity CLIMBER-2 is used to simulate global biogeochemistry over the last glacial cycle (126 kyr). The physical core of the model (atmosphere, ocean, land and ice sheets) is driven by orbital changes and reconstructed radiative forcing from greenhouses gases, ice, and aeolian dust. The carbon cycle model is able to reproduce the main features of the CO2 changes: a 50 ppmv CO2 drop during glacial inception, a minimum concentration at the last glacial maximum 80 ppmv lower than the Holocene value, and an abrupt 60 ppmv CO2 rise during the deglaciation. The model deep ocean d13C also resembles reconstructions from deep-sea cores. The main drivers of atmospheric CO2 evolve in time: changes in sea surface temperatures and in the volume of bottom water of southern origin control atmospheric CO2 during the glacial inception and deglaciation; changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycle, respectively. These feedback mechanisms could also significantly impact the ultimate climate response to the anthropogenic perturbation.
URL: http://www.clim-past.net/8/251/2012/cp-8-251-2012.pdf
13010303 Ikeda, Atsushi (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan); Iwahana, Go and Sueyoshi, Tetsuo. Year-round monitoring of shallow ground temperatures at high altitudes of Mt. Fuji with a critical discussion on the popular belief of rapid permafrost degradation: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 306-331, (Japanese) (English sum.), illus., 44 ref., 2012.
On September 2010, the Japanese mass media reported that permafrost had disappeared throughout the altitudes of 3300-3600 m asl. on the south-facing slope of Mt. Fuji (3776 m asl.) within 12 years because of climatic warming. However, no evidence (data and analyses) has been published in scientific journals. In this paper, we show ground freeze-thaw patterns above the tree line of Mt. Fuji based on recent year-round records of temperatures at shallow depths at 22 sites. The shallow ground temperatures became significantly warmer from the 2008-2009 period to the 2009-2010 period because the latter period had irregular snow accumulation at several sites and extremely sunny hot summer. The snow cover on Mt. Fuji generally prevented the ground from cooling rather than from warming. In addition, records for some locations show rapid ground warming in late 'summer, which accompanied heavy rainfall events. The mean annual temperatures at the ground surface on the south-facing slope were 1.5 to 3°C higher than those on the north-facing slope at the same altitude. Considering these characteristics, we interpret that the presence of permafrost is probable only at 5 sites on north- to west-facing windy locations above 3500 m asl., although studies in the 1970s suggest that the lower boundary lay at around 3000 m asl. on both north- and south-facing slopes. However, it is clear that, in the 1970s, the estimation of permafrost distribution on Mt. Fuji was based not on thaw depths at the end of thawing period (late September to mid October), but on those in the middle of thawing period (late July to August). The resulting overestimation of the permafrost distribution may have led to tales of extremely rapid permafrost degradation. Permafrost research on Mt. Fuji is still at its initial stage and long-term monitoring of ground temperatures is required to evaluate the impacts of changes of climate and volcanic activity on the surrounding environment.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13011503 Jones, Miriam C. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Grosse, Guido; Jones, Benjamin M. and Walter Anthony, Katey M. Peat accumulation in drained thermokarst lake basins in continuous, ice-rich permafrost, northern Seward Peninsula, Alaska: Journal of Geophysical Research, 117(G), Citation G00M07, illus. incl. 3 tables, 55 ref., 2012.
Thermokarst lakes and peat-accumulating drained lake basins cover a substantial portion of Arctic lowland landscapes, yet the role of thermokarst lake drainage and ensuing peat formation in landscape-scale carbon (C) budgets remains understudied. Here we use measurements of terrestrial peat thickness, bulk density, organic matter content, and basal radiocarbon age from permafrost cores, soil pits, and exposures in vegetated, drained lake basins to characterize regional lake drainage chronology, C accumulation rates, and the role of thermokarst-lake cycling in carbon dynamics throughout the Holocene on the northern Seward Peninsula, Alaska. Most detectable lake drainage events occurred within the last 4,000 years with the highest drainage frequency during the medieval climate anomaly. Peat accumulation rates were highest in young (50-500 years) drained lake basins (35.2 g C m-2yr-1) and decreased exponentially with time since drainage to 9 g C m-2 yr-1 in the oldest basins. Spatial analyses of terrestrial peat depth, basal peat radiocarbon ages, basin geomorphology, and satellite-derived land surface properties (Normalized Difference Vegetation Index (NDVI); Minimum Noise Fraction (MNF)) from Landsat satellite data revealed significant relationships between peat thickness and mean basin NDVI or MNF. By upscaling observed relationships, we infer that drained thermokarst lake basins, covering 391 km2 (76%) of the 515 km2 study region, store 6.4-6.6 Tg organic C in drained lake basin terrestrial peat. Peat accumulation in drained lake basins likely serves to offset greenhouse gas release from thermokarst-impacted landscapes and should be incorporated in landscape-scale C budgets.
DOI: 10.1029/2011JG001766
13011502 Kessler, M. A. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Plug, L. J. and Walter Anthony, Katey M. Simulating the decadal- to millennial-scale dynamics of morphology and sequestered carbon mobilization of two thermokarst lakes in NW Alaska: Journal of Geophysical Research, 117(G), Citation G00M06, illus., 30 ref., 2012. Includes appendix.
Thermokarst lakes alter landscape topography and hydrology in widespread permafrost regions and mobilize significant permafrost carbon pools, including releasing methane (CH4) to the atmosphere. Despite this, the dynamics of lake evolution, permafrost thawing, and carbon mobilization are not well known. We present a 3-D numerical model of thermokarst lakes on organic-rich yedoma permafrost terrains with surface water flow and pooling naturally defining lakes that deepen, expand laterally, and drain due to talik formation, bank retreat, and both gradual and catastrophic drainage. We predict the 3-D pattern of microbial methane production within the talik over time. As a first model test and calibration, beginning with small protolakes, we simulated 10,000 years of evolution of Pear and Claudi lakes, two neighboring thermokarst features on the northern Seward Peninsula, Alaska. Simulated lakes approximated observed bathymetry, but results are sensitive to initial topography and soil ice content. Local topography caused markedly different dynamics for the two lakes. Pear expanded rapidly across low-relief topography, fully drained multiple times, and released little methane in later stages due to Pleistocene carbon depletion by the first and largest lake generation. Claudi grew slowly and continuously across high-relief topography, forming high subaerial banks; partial drainages left remnant horseshoe lakes that continued to expand into virgin yedoma, mobilizing carbon at roughly the same rate irrespective of lake drainage. The ~2´ discrepancy between simulated CH4 production and observed emission rates in Claudi likely results from misestimation of hot spot ebullition, labile carbon content, CH4:CO2 production ratio, or microbial CH4 oxidation.
DOI: 10.1029/2011JG001796
13010302 Matsuoka, Norikazu (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan) and Ikeda, Atsushi. Research frontier in periglacial processes: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 269-305, (Japanese) (English sum.), illus., 298 ref., 2012.
Periglacial process studies, which began in the mid-20th century, have greatly advanced in recent years following several breakthroughs. This paper reviews the latest breakthroughs supported by new technologies, themes, and international projects. New technologies have enabled small, high-resolution data loggers to monitor rock and soil movements, and thermal and hydrological properties in polar and alpine areas; enabled geophysical instruments to visualize two-and three- dimensional subsurface structures below periglacial features; and, enabled numerical simulations to predict future landform evolution. In particular, dramatic progress has been achieved in understanding bedrock shattering and falls, soil movements induced by freeze-thaw oscillations, controls on rock glacier creep, critical conditions for icewedge cracking, and biogeophysical impacts on non-sorted circles. Two key words, global warming and Mars, are appearing often in periglacial research. High mountains and polar lowlands face the fate of potential natural hazards associated with rock slides, debris flows and thermokarst subsidence, possibly originating from permafrost thawing. High-resolution orbital images and on-site explorations on Mars provide detailed information on small-scale, potential periglacial features, which are the morphologically equivalent of terrestrial counterparts. International collaboration is expected to further promote modeling various periglacial features on a global scale, improve the resolutions of periglacial climate indicators, and increase understanding of past and present Martian environments.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13010304 Sawaguchi, Shin-ichi (Niigata University of International and Information Studies, Niigata, Japan). Ground temperature, frost heave, and slow mass movement measurements at Eagle Summit, central Alaska: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 332-341, (Japanese) (English sum.), illus. incl. 2 tables, geol. sketch map, 19 ref., 2012.
Ground temperature, frost heave, and slow mass movement were measured on a debris-mantled slope at Eagle Summit, central Alaska from 2004 to 2008. The maximum and minimum temperatures at the ground surface during the measurement period were 25.7°C on 4 July 2007 and -32.7°C on 28 February. The mean annual ground surface temperature was 3.1°C. Subsurface isotherms indicate that seasonal freezing starts from late September to early November, and that seasonal frost begins to melt in mid-May. The thawing front reached a depth of 80 cm in 8 days. The maximum height of the seasonal frost heave at the ground surface reached about 2.0 cm during the early period of seasonal freezing. Twenty diurnal freeze-thaw cycles occurred in spring, but less than 10 in autumn. Short-term frost heave corresponded to diurnal freeze-thaw cycles at the ground surface. The cumulative amount of short-term and seasonal frost heave between 2004 and 2008 was 22.1 cm. Using this value, the potential frost creep is calculated to be 2.5 cm/yr on the 20° slope. On the other hand, the annual average movements measured with two painted stone-lines were only 0.3 mm and 0.4 mm, which is considerably smaller than potential frost creep. The small surface movement probably reflects the presence of vegetation patches and uneven subsurface materials. Therefore, the value of potential frost creep (2.5 cm/yr) probably represents the average surface movement in this area. In terms of the frequency of freeze thaw-cycles and the value of potential frost creep, mountains in central Alaska have intermediate characteristics between the mid-latitude alpine area and Arctic.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13010306 Shimizu, Chousei (Komazawa University, Department of Geography, Tokyo, Japan); Yamakawa, Nobuyuki; Ishii, Masaki; Fujimori, Misae and Endo, Kaito. Ground ice and temporary crater lake in Jigokudani Crater, Kita-yatsugatake, central Japan: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 359-366, (Japanese) (English sum.), illus., 17 ref., 2012.
Ground ice and temporary lake were studied in the Jigokudani Crater (N36°03'44.82", E138°20'45.82") in a northern area of the Yatsugatake Volcanic Chain (Kita-yatsugatake). The crater, which is about 30 m deep, is located at 2108 m a.s.l., and is surrounded by subalpine coniferous forest where the mean annual air temperature is about 3°C. The ground ice survived in summer mainly because cold air blew down through voids between andesite blocks composing the crater wall. The ice remained throughout 2009, although it melted completely in September 2010. In 2010, a crater lake appeared in May and disappeared in early August. This survival period of the lake was probably much longer than in other years. We consider that the melting of ground ice was promoted by the long-lasting lake having a slightly positive temperature which contacted the ice directly.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13010309 Takaoka, Sadao (Senshu University, Department of Geography, Kanagawa, Japan); Kariya, Yoshihiko and Sato, Go. Influence of landslide activities on the origin and spatial distribution of alpine ponds in the northern Japanese Alps: in Earth surface dynamics in the cryosphere; review and outlook (Matsuoka, Norikazu, editor; et al.), Chigaku Zasshi = Journal of Geography, 121(2), p. 402-410, (Japanese) (English sum.), illus. incl. 2 tables, sketch map, 30 ref., 2012.
Little is known about the biotic and abiotic characteristics of alpine ponds and lakes even though they are prominent and important features of alpine landscape. This study examines the influence of gravitational landforms on the origins and spatial distribution of alpine ponds in a landslide-prone area in central Japan. Ninety-four ponds were detected by aerial-photo interpretation in an area above 2000 m a.s.l. (7838 ha) in a northern area of the Northern Japanese Alps. Of these, 60 ponds occurred inside or at the outer boundaries of gravitationally displaced masses, and 27 ponds occurred in linear depressions that were formed outside masses displaced by gravitational force; the remainder of the ponds were formed by volcanic activities. A logistic regression analysis was performed to determine whether environmental variables explain the presence of ponds in linear depressions. The results indicate that presence of ponds is related to the depth of a depression, snow-cover duration, and bedrock geology. Deeper depressions have ponds more frequently, and ponds tend to be found in depressions on snowy slopes underlain with ultramafic rocks. The concentration of alpine ponds in snowy slopes underlain with ultramafic rocks. The concentration of alpine ponds in snowy, ultramafic rock areas suggests ponds are mainly fed by snow melt, and that soil material from weathered ultramafic rocks supports the water storage of ponds.
URL: https://www.jstage.jst.go.jp/A_PRedirectJournalInit?sryCd=jgeography&noVol=121&n ...
13008981 Jirakova, Hana (Université de Bordeaux, UFR des Sciences de la Terre et de la Mer, Talence, France); Huneau, Frédéric; Celle-Jeanton, Hélène; Hrkal, Zbynek and Le Coustumer, Philippe. Insights into palaeorecharge conditions for European deep aquifers: Hydrogeology Journal, 19(8), p. 1545-1562, illus. incl. 2 tables, 125 ref., December 2011. Based on Publisher-supplied data.
Climatic instability during the late Pleistocene has been reflected in the pattern of groundwater recharge. This report summarizes palaeoclimate knowledge during the late Weichselian in Europe. During this period the majority of northern Europe was covered by thick ice sheets and permafrost, preventing aquifers from recharging. In contrast, southern Europe was generally free of these palaeoclimatic features. Palaeoclimatic information has been combined with isotope data to better understand the palaeorecharge conditions and recharge timing across the European continent. The 18O and 2H relationship shows latitudinal plus climatic influences. Radiocarbon data show that while southern European aquifers have generally been recharged continuously during the last 40,000 years, northern European aquifers typically show a recharge gap during the Last Glacial Maximum. Areas that underwent continuous recharge during the entire late Pleistocene period can also be distinguished from areas where recharge to aquifers was prevented during the Last Glacial Maximum. Finally, several examples are presented of melt-water recharge or subglacial recharge. The identification of such diversity in the groundwater palaeorecharge in Europe is of great importance for modellers developing management schemes for groundwater resources. Copyright 2011 Springer-Verlag
DOI: 10.1007/s10040-011-0765-7
13009927 Monnier, Sébastien (Centro de Estudios Avavnzados en Zonas Áridas, La Serena, Chile); Camerlynck, Christian; Rejiba, Fayçal; Kinnard, Christophe; Feuillet, Thierry and Dhemaied, Amine. Structure and genesis of the Thabor rock glacier (northern French Alps) determined from morphological and ground-penetrating radar surveys: Geomorphology, 134(3-4), p. 269-279, illus. incl. 1 table, sects., 32 ref., November 15, 2011.
Landform analysis and ground-penetrating radar (GPR) were used to investigate the Thabor rock glacier, in the Northern French Alps. The surface features of the rock glacier were classified and described, with emphasis on massive ice exposures. The retreat of the former Thabor glacier since the Little Ice Age (LIA) was documented through an analysis of historical sources, and recent movements of the rock glacier were inferred from orthophoto-based measurements. Two-dimensional (2-D) models of the radar wave velocity were derived from the raw GPR data, using the numerous diffraction hyperbolae for local determinations of the velocity and kriging interpolation techniques. Subsequently, the profiles were migrated through a 2-D Kirchhoff migration method using the interpolated velocities. The 2-D velocity models exhibit pronounced spatial variations and, in several locations, high values (>0.15 m ns-1) potentially corresponding to massive ice. On the other hand, while the migrated profiles show numerous layers, the internal stratigraphy of the rock glacier is dominated by a few prominent internal boundaries. The integration of morphology, radar wave velocity, and internal stratigraphy allowed us to identify the main structural units of the rock glacier as well as to explain its genesis: the rock glacier was formed by the imbrication of a massive ice core, originating from the retreat of the former Thabor glacier since the LIA, into pre-existing glacial deposits.
DOI: 10.1016/j.geomorph.2011.07.004
13009921 Ulrich, M. (Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany); Hauber, E.; Herzschuh, U.; Härtel, S. and Schirrmeister, L. Polygon pattern geomorphometry on Svalbard (Norway) and western Utopia Planitia (Mars) using high-resolution stereo remote sensing data: Geomorphology, 134(3-4), p. 197-216, illus. incl. 5 tables, sketch maps, 95 ref., November 15, 2011.
Polygonal systems formed by thermal contraction cracking are complex landscape features widespread in terrestrial periglacial regions. The manner in which cracking occurs is controlled by various environmental factors and determines dimension, shape, and orientation of polygons. Analogous small-scale features are ubiquitous in Martian mid- and high-latitudes, and they are also inferred to originate from thermal contraction cracking. We studied the geomorphometry of polygonally-patterned ground on Svalbard to draw a terrestrial analogy to small-scale polygonal structures in scalloped terrain in Martian mid-latitudes. We performed a comparative quantitative terrain analysis based on high-resolution stereo remote-sensing data (HRSC-AX and HiRISE) in combination with terrestrial field data and multivariate statistics to determine the relationship of polygon geomorphometry to local environmental conditions. Results show that polygonal structures on Svalbard and in Utopia Planitia on Mars are similar with respect to their size and shape. A comparable thermal contraction cracking genesis is likely. Polygon evolution, however, is strongly related to regional and local landscape dynamics. Individual polygon dimensions and orthogonality vary according to age, thermal contraction cracking activity, and local subsurface conditions. Based on these findings, the effects of specific past and current environmental conditions on polygon formation on Mars must be considered. On both Earth and Mars, the smallest polygons represent young, recently-active low-centered polygons that formed in fine-grained ice-rich material. Small, low-centered Martian polygons show the closest analogy to terrestrial low-centered ice-wedge polygons. The formation of composite wedges could have occurred as a result of local geomorphological conditions during past Martian orbital configurations. Larger polygons reflect past climate conditions on both Earth and Mars. The present degradation of these polygons depends on relief and topographical situation. On Svalbard the thawing of ice wedges degrades high-centered polygons; in contrast, the present appearance of polygons in Utopia Planitia is primarily the result of contemporary dry degradation processes.
DOI: 10.1016/j.geomorph.2011.07.002
13009919 Vandenberghe, J. (Vrije Universiteit University Amsterdam, Institute of Earth Sciences, Amsterdam, Netherlands); Wang, X. and Lu, H. Differential impact of small scaled tectonic movements on fluvial morphology and sedimentology (the Huang Shui catchment, NE Tibet Plateau): Geomorphology, 134(3-4), p. 171-185, illus. incl. 1 table, geol. sketch map, 63 ref., November 15, 2011.
The aim of this paper is to investigate the morphological implications of the interplay between tectonic movements at different rates, timescales, and spatial extent in a catchment of intermediate size, the Huang Shui River (a main tributary of the Yellow River in the NE Tibet Plateau). River incision started from a peneplain-like surface that developed in post-Miocene-Pliocene times. At the end of the Tertiary, a general tectonic uplift of the Tibetan Plateau initiated river incision. This general uplift also caused local fragmentation of the Huang Shui catchment into blocks (kilometers or maximally, a few tens of kilometers) of local extent that have subsided and/or uplifted relative to one another. Fluvial deposition of >30 m in the subsiding blocks contrasts with erosion and formation of gorges in the uplifted blocks. Incision into the former peneplain was not continuous but a staircase of terraces developed under climatic influences. Terrace deposits are sometimes capped by interglacial soils or soil-derived material. Apparently, terrace incision occurred at the transition to the next cold period. The different rates of uplift and subsidence of the individual blocks resulted in the simultaneous development of erosion and accumulation terraces of different sizes within the same catchment, even within the same tectonic block. This makes it impossible to connect the terraces of the different blocks, except for the three youngest terraces (representing the last 300,000 years), thus illustrating the uniform tectonic history of the catchment since that time.
DOI: 10.1016/j.geomorph.2011.06.020
13011341 Clymans, Wim (Catholic University of Louvain, Department of Earth and Environmental Sciences, Heverlee, Belgium); Struyf, Eric; Govers, Gerard; Vandevenne, Floor and Conley, Daniel J. Anthropogenic impact on amorphous silica pools in temperate soils: Biogeosciences, 8(8), p. 2281-2293, illus. incl. 2 tables, 60 ref., 2011. Published in Biogeosciences Discussion: 5 May 2011, URL: http://www.biogeosciences-discuss.net/8/4391/2011/bgd-8-4391-2011.html; accessed in Aug., 2012.
Human land use changes perturb biogeochemical silica (Si) cycling in terrestrial ecosystems. This directly affects Si mobilisation and Si storage and influences Si export from the continents, although the magnitude of the impact is unknown. A major reason for our lack of understanding is that very little information exists on how land use affects amorphous silica (ASi) storage in soils. We have quantified and compared total alkali-extracted (PSia) and easily soluble (PSie) Si pools at four sites along a gradient of anthropogenic disturbance in southern Sweden. Land use clearly affects ASi pools and their distribution. Total PSia and PSie for a continuous forested site at Siggaboda Nature Reserve (66 900±22 800 kg SiO2 ha-1 and 952±16 kg SiO2 ha-1) are significantly higher than disturbed land use types from the Rashult Culture Reserve including arable land (28 800±7200 kg SiO2 ha-1 and 239±91 kg SiO2 ha-1), pasture sites (27 300±5980 kg SiO2 ha-1 and 370±129 kg SiO2 ha-1) and grazed forest (23 600±6370 kg SiO2 ha-1 and 346±123 kg SiO2 ha-1). Vertical PSia and PSie profiles show significant (p<0.05) variation among the sites. These differences in size and distribution are interpreted as the long-term effect of reduced ASi replenishment, as well as changes in ecosystem specific pedogenic processes and increased mobilisation of the PSia in disturbed soils. We have also made a first, though rough, estimate of the magnitude of change in temperate continental ASi pools due to human disturbance. Assuming that our data are representative, we estimate that total ASi storage in soils has declined by ca. 10% since the onset of agricultural development (3000 BCE). Recent agricultural expansion (after 1700 CE) may have resulted in an average additional export of 1.1±0.8 Tmol Si yr-1 from the soil reservoir to aquatic ecosystems. This is ca. 20% to the global land-ocean Si flux carried by rivers. It is necessary to update this estimate in future studies, incorporating differences in pedology, geology and climatology over temperate regions, but data are currently not sufficient. Yet, our results emphasize the importance of human activities for Si cycling in soils and for the land-ocean Si flux.
URL: http://www.biogeosciences.net/8/2281/2011/bg-8-2281-2011.pdf
13009905 Gustafsson, O. (Stockholm University, Bert Bolin Climate Research Centre, Stockholm, Sweden); van Dongen, Bart E.; Vonk, Jorien E.; Dudarev, O. V. and Semiletov, Igor P. Widespread release of old carbon across the Siberian Arctic echoed by its large rivers: Biogeosciences, 8(6), p. 1737-1743, illus. incl. 2 tables, sketch map, 39 ref., 2011. Includes supplement, URL: http://www.biogeosciences.net/8/1737/2011/bg-8-1737-2011-supplement.pdf; part of special issue no. 76, Land-shelf-basin interactions of the Siberian Arctic, edited Gustafsson, O., et al., URL: http://www.biogeosciences.net/special_issue76.html; published in Biogeosciences Discussion: 17 February 2011, URL: http://www.biogeosciences-discuss.net/8/1445/2011/bgd-8-1445-2011.html; accessed in Jul., 2012.
Over decadal-centennial timescales, only a few mechanisms in the carbon-climate system could cause a massive net redistribution of carbon from land and ocean systems to the atmosphere in response to climate warming. The largest such climate-vulnerable carbon pool is the old organic carbon (OC) stored in Arctic permafrost (perennially frozen) soils. Climate warming, both predicted and now observed to be the strongest globally in the Eurasian Arctic and Alaska, causes thaw-release of old permafrost carbon from local tundra sites. However, a central challenge for the assessment of the general vulnerability of this old OC pool is to deduce any signal integrating its release over larger scales. Here we examine radiocarbon measurements of molecular soil markers exported by the five Great Russian-Arctic Rivers (Ob, Yenisey, Lena, Indigirka and Kolyma), employed as natural integrators of carbon release processes in their watersheds. The signals held in estuarine surface sediments revealed that average radiocarbon ages of n-alkanes increased east-to-west from 6400 yr BP in Kolyma to 11 400 yr BP in Ob. This is consistent with westwards trends of both warmer climate and more degraded organic matter as indicated by the ratio of high molecular weight (HMW) n-alkanoic acids to HMW n-alkanes. The dynamics of Siberian permafrost can thus be probed via the molecular-radiocarbon signal as carried by Arctic rivers. Old permafrost carbon is at present vulnerable to mobilization over continental scales. Climate-induced changes in the radiocarbon fingerprint of released permafrost carbon will likely depend on changes in both permafrost coverage and Arctic soil hydraulics.
URL: http://www.biogeosciences.net/8/1737/2011/bg-8-1737-2011.pdf
13009899 O'Donnell, Jonathan A. (University of Alaska Fairbanks, Biology & Wildlife Department, Fairbanks AK); Harden, Jennifer W.; McGuire, A. David and Romanovsky, Vladimir E. Exploring the sensitivity of soil carbon dynamics to climate change, fire disturbance and permafrost thaw in a black spruce ecosystem: Biogeosciences, 8(5), p. 1367-1382, illus. incl. 4 tables, 75 ref., 2011. Includes supplement, URL: http://www.biogeosciences.net/8/1367/2011/bg-8-1367-2011-supplement.pdf; published in Biogeosciences Discussion: 6 December 2010, URL: http://www.biogeosciences-discuss.net/7/8853/2010/bgd-7-8853-2010.html; accessed in Jul., 2012.
In the boreal region, soil organic carbon (OC) dynamics are strongly governed by the interaction between wildfire and permafrost. Using a combination of field measurements, numerical modeling of soil thermal dynamics, and mass-balance modeling of OC dynamics, we tested the sensitivity of soil OC storage to a suite of individual climate factors (air temperature, soil moisture, and snow depth) and fire severity. We also conducted sensitivity analyses to explore the combined effects of fire-soil moisture interactions and snow seasonality on OC storage. OC losses were calculated as the difference in OC stocks after three fire cycles (~500 yr) following a prescribed step-change in climate and/or fire. Across single-factor scenarios, our findings indicate that warmer air temperatures resulted in the largest relative soil OC losses (~5.3 kg C m-2), whereas dry soil conditions alone (in the absence of wildfire) resulted in the smallest carbon losses (~0.1 kg C m-2). Increased fire severity resulted in carbon loss of ~3.3 kg C m-2, whereas changes in snow depth resulted in smaller OC losses (2.1-2.2 kg C m-2). Across multiple climate factors, we observed larger OC losses than for single-factor scenarios. For instance, high fire severity regime associated with warmer and drier conditions resulted in OC losses of ~6.1 kg C m-2, whereas a low fire severity regime associated with warmer and wetter conditions resulted in OC losses of ~5.6 kg C m-2. A longer snow-free season associated with future warming resulted in OC losses of ~5.4 kg C m-2. Soil climate was the dominant control on soil OC loss, governing the sensitivity of microbial decomposers to fluctuations in temperature and soil moisture; this control, in turn, is governed by interannual changes in active layer depth. Transitional responses of the active layer depth to fire regimes also contributed to OC losses, primarily by determining the proportion of OC into frozen and unfrozen soil layers.
DOI: 10.5194/bg-8-1367-2011
13009845 Pokrovsky, Oleg S. (Université de Toulouse, Laboratoire des Mechanismes et Transfers en Geologie, Toulouse, France); Shirokova, Liudmila; Kirpotin, Sergey N.; Audry, Stéphane; Viers, Jérôme and Dupré, Bernard. Effect of permafrost thawing on organic carbon and trace element colloidal speciation in the thermokarst lakes of western Siberia: Biogeosciences, 8(3), p. 565-583, illus. incl. 1 table, sketch maps, 107 ref., 2011. Includes supplement, URL: http://www.biogeosciences.net/8/565/2011/bg-8-565-2011-supplement.pdf; part of special issue no. 76, Land-shelf-basin interactions of the Siberian Arctic, edited by Gustafsson, O., et al., URL: http://www.biogeosciences.net/special_issue76.html; published in Biogeosciences Discussion: 2 November 2010, URL: http://www.biogeosciences-discuss.net/7/8041/2010/bgd-7-8041-2010.html; accessed in Jan., 2012.
To examine the mechanisms of carbon mobilization and biodegradation during permafrost thawing and to establish a link between organic carbon (OC) and other chemical and microbiological parameters in forming thermokarst (thaw) lakes, we studied the biogeochemistry of OC and trace elements (TEs) in a chronosequence of small lakes that are being formed due to permafrost thawing in the northern part of western Siberia. Twenty lakes and small ponds of various sizes and ages were sampled for dissolved and colloidal organic carbon, metals and culturable heterotrophic bacterial cell number. We observed a sequence of ecosystems from peat thawing and palsa degradation due to permafrost subsidence in small ponds to large, km-size lakes that are subject to drainage to, finally, the khasyrey (drained lake) formation. There is a systematic evolution of both total dissolved and colloidal concentration of OC and TEs in the lake water along with the chronosequence of lake development that may be directly linked to the microbial mineralization of dissolved organic matter and the liberation of the inorganic components (Fe, Al, and TEs) from the organo-mineral colloids. In this chronosequence of lake development, we observed an apparent decrease in the relative proportion of low molecular weight <1 kDa (1 kDa ~1 nm) OC concentration along with a decrease in the concentration of total dissolved (<0.45 mm) OC. This decrease was accompanied by an increase in the small size organic ligands (probably autochthonous exometabolites produced by the phytoplankton) and a simultaneous decrease in the proportion of large-size organic (humic) complexes of allochthonous (soil) origin. This evolution may be due to the activity of heterotrophic bacterioplankton that use allochthonous organic matter and dissolved nutrients originating from peat lixiviation. Most insoluble TEs demonstrate a systematic decrease in concentration during filtration (5 mm, 0.45 mm) exhibiting a similar pattern among different samples. At the same time, there is an increase in the relative proportion of large size particles over the <1 kDa fraction for most insoluble elements along the chronosequence of lake evolution. TEs are likely to be bound to colloidal OC and coprecipitate with the mineral (Fe, Al) part of the colloids. Upon progressive consumption of dissolved OC by the heterotrophic bacteria, there is liberation of Fe, Al, and insoluble TEs in the water column that may be subjected to coagulation in the form of particles or large-size mineral colloids.
URL: http://www.biogeosciences.net/8/565/2011/bg-8-565-2011.pdf
13009794 Agren, Annali (Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umea, Sweden); Haei, M.; Kohler, S. J.; Bishop, Kevin and Laudon, Hjalmar. Regulation of stream water dissolved organic carbon (DOC) concentrations during snowmelt; the role of discharge, winter climate and memory effects: Biogeosciences, 7(9), p. 2901-2913, illus. incl. 1 table, sketch map, 73 ref., 2010. Published in Biogeosciences Discussion: 23 June 2010, URL: http://www.biogeosciences-discuss.net/7/4857/2010/bgd-7-4857-2010.html; accessed in Dec., 2011.
Using a 15 year stream record from a northern boreal catchment, we demonstrate that the inter-annual variation in dissolved organic carbon (DOC) concentrations during snowmelt was related to discharge, winter climate and previous DOC export. A short and intense snowmelt gave higher stream water DOC concentrations, as did long winters, while a high previous DOC export during the antecedent summer and autumn resulted in lower concentrations during the following spring. By removing the effect of discharge we could detect that the length of winter affected the modeled soil water DOC concentrations during the following snowmelt period, which in turn affected the concentrations in the stream. Winter climate explained more of the stream water DOC variations than previous DOC export during the antecedent summer and autumn.
URL: http://www.biogeosciences.net/7/2901/2010/bg-7-2901-2010.pdf
13009752 Bou Kheir, Rania (Aarhus University, Department of Agroecology and Environment, Tjele, Denmark); Bocher, Peder Klith; Greve, Mette Balslev and Greve, Mogens Humlekrog. The application of GIS based decision-tree models for generating the spatial distribution of hydromorphic organic landscapes in relation to digital terrain data: Hydrology and Earth System Sciences (HESS), 14(6), p. 847-857, illus. incl. 4 tables, sketch maps, 50 ref., 2010. Part of special issue no. 114, Quantitative analysis of DEMs for hydrology and Earth system science, edited by Purves, R., Molnar, P., and Gruber, S., URL: http://www.hydrol-earth-syst-sci.net/special_issue114.html; published in Hydrology and Earth System Sciences Discussion: 18 January 2010, URL: http://www.hydrol-earth-syst-sci-discuss.net/7/389/2010/hessd-7-389-2010 .html; accessed in Apr., 2012.
Accurate information about organic/mineral soil occurrence is a prerequisite for many land resources management applications (including climate change mitigation). This paper aims at investigating the potential of using geomorphometrical analysis and decision tree modeling to predict the geographic distribution of hydromorphic organic landscapes in unsampled area in Denmark. Nine primary (elevation, slope angle, slope aspect, plan curvature, profile curvature, tangent curvature, flow direction, flow accumulation, and specific catchment area) and one secondary (steady-state topographic wetness index) topographic parameters were generated from Digital Elevation Models (DEMs) acquired using airborne LIDAR (Light Detection and Ranging) systems. They were used along with existing digital data collected from other sources (soil type, geological substrate and landscape type) to explain organic/mineral field measurements in hydromorphic landscapes of the Danish area chosen. A large number of tree-based classification models (186) were developed using (1) all of the parameters, (2) the primary DEM-derived topographic (morphological/hydrological) parameters only, (3) selected pairs of parameters and (4) excluding each parameter one at a time from the potential pool of predictor parameters. The best classification tree model (with the lowest misclassification error and the smallest number of terminal nodes and predictor parameters) combined the steady-state topographic wetness index and soil type, and explained 68% of the variability in organic/mineral field measurements. The overall accuracy of the predictive organic/inorganic landscapes' map produced (at 1:50 000 cartographic scale) using the best tree was estimated to be ca. 75%. The proposed classification-tree model is relatively simple, quick, realistic and practical, and it can be applied to other areas, thereby providing a tool to facilitate the implementation of pedological/hydrological plans for conservation and sustainable management. It is particularly useful when information about soil properties from conventional field surveys is limited.
URL: http://www.hydrol-earth-syst-sci.net/14/847/2010/hess-14-847-2010.pdf
13009778 Gardin, Emilie (Université de Lyon, Laboratoire de Sciences de la Terre, Lyon, France); Allemand, P.; Quantin, C. and Thollot, P. Defrosting, dark flow features, and dune activity on Mars; example in Russell Crater: Journal of Geophysical Research, 115(E6), Citation E06016, illus. incl. 1 table, 33 ref., 2010.
Defrosting processes observed on Mars are among the most unusual features described on high-resolution images. A defrosting sequence has been observed near the crest of the megadune located in the Russell crater on new high-resolution images obtained from the HiRISE instrument and on hyperspectral cubes obtained from CRISM instrument, both on board MRO. Hyperspectral images show that frost overlaps the entire megadune in middle winter. This frost is composed mainly of CO2 and of a small amount of water ice. The deepest ice signatures are mainly located near the crest of the megadune. The defrosting sequence monitored by CRISM reveals spatial heterogeneity and refrosting processes. On the morphological counterpart, the defrosting sequence starts with the development of dark spots, similar to those described in the cryptic regions. After few sols, we observe the emplacement of dark linear flow features that start from the dark spots downward of the main slope of the dune. These linear flow features are 1 to 2 m wide and 50 to 100 m long. They settle on the small rills visible on the frost cover. They are interpreted as avalanches of a mixing of sand, dust, and unstable CO2 gas released under pressure. The avalanches would be triggered by the eruption of the dark spots. The flux of material transported by the flow features has been estimated to 0.25 to 0.5 m3 by meter width each year on the megadune. This flux is larger than flux transported by wind. These dark flow features are thus very efficient to transport material on slopes located in frosted areas.
DOI: 10.1029/2009JE003515
13009746 Liu, J. (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Beijing, China); Kang, S.; Gong, T. and Lu, A. Growth of a high-elevation large inland lake, associated with climate change and permafrost degradation in Tibet: Hydrology and Earth System Sciences (HESS), 14(3), p. 481-489, illus. incl. 2 tables, sketch maps, 31 ref., 2010. Part of special issue no. 105, Cold region hydrology; improved processes, parameterization and prediction, edited by Carey, S., et al., URL: http://www.hydrol-earth-syst-sci.net/special_issue105.html; published in Hydrology and Earth System Sciences Discussions: 7 August 2009, URL: http://www.hydrol-earth-syst-sci-discuss.net/6/5445/2009/hessd-6-5445-20 09.html; accessed in Oct., 2011.
This study analyzed satellite images and long term climate variables from a high-elevation meteorological station (4730 m) and streamflow records to examine hydrological response of Nam Co Lake (4718 m), the largest lake on the Tibetan Plateau, over the last 50 years. The results show the lake area extended by 51.8 km2 (2.7% of the total area) when compared with the area in 1976. This change is associated with an annual precipitation increase of 65 mm (18.6%), annual and winter mean temperature increases of 0.9°C and 2.1°C respectively, an annual runoff increase of 20% and an annual pan evaporation decrease of about 2%, during the past 20 years. The year of the change point in annual precipitation, air temperature, annual pan evaporation and runoff occurred in 1971, 1983, 1997 and 1997, respectively. The timing of the lake growth corresponds with the abrupt increase in annual precipitation and runoff since the mid-1990s.
URL: http://www.hydrol-earth-syst-sci.net/14/481/2010/hess-14-481-2010.pdf
13009755 Lyon, Steve W. (Stockholm University, Physical Geography and Quaternary Geology, Stockholm, Sweden); Mörth, Carl-Magnus; Humborg, Christoph; Giesler, Reiner and Destouni, Georgia. The relationship between subsurface hydrology and dissolved carbon fluxes for a sub-arctic catchment: Hydrology and Earth System Sciences (HESS), 14(6), p. 941-950, illus. incl. 1 table, sketch map, 56 ref., 2010. Published in Hydrology and Earth System Sciences Discussion: 3 March 2010, URL: http://www.hydrol-earth-syst-sci-discuss.net/7/1677/2010/hessd-7-1677-20 10.html; accessed in Apr., 2012.
In recent years, there has been increased interest in carbon cycling in natural systems due to its role in a changing climate. Northern latitude systems are especially important as they may serve as a potentially large source or sink of terrestrial carbon. There are, however, a limited number of investigations reporting on actual flux rates of carbon moving from the subsurface landscape to surface water systems in northern latitudes. In this study, we determined dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) fluxes from the subsurface landscape for a sub-arctic catchment located in northern Sweden. These are based on observed annual flux-averaged concentrations of DOC and DIC for the 566 km2 Abiskojokken catchment. We demonstrate the importance to correctly represent the spatial distribution of the advective solute travel times along the various flow and transport pathways. The fluxes of DOC and DIC from the subsurface landscape to the surface water system were comparable in magnitude. This balance could shift under future climatic changes that influence the hydrological and biogeochemical system.
URL: http://www.hydrol-earth-syst-sci.net/14/941/2010/hess-14-941-2010.pdf
13009791 Maljanen, Marja (Agricultural University of Iceland, Reykjavik, Iceland); Sigurdsson, Bjarni D.; Gudmundsson, J.; Oskarsson, H.; Huttunen, Jari T. and Martikainen, Pertii J. Greenhouse gas balances of managed peatlands in the Nordic countries; present knowledge and gaps: Biogeosciences, 7(9), p. 2711-2738, illus. incl. 6 tables, 186 ref., 2010. Part of special issue no. 59, Greenhouse gas exchanges, carbon balances and processes of northern ecosystems, edited by Lindroth, A., et al., URL: http://www.biogeosciences.net/special_issue59.html; published in Biogeosciences Discussion: 30 June 2009, URL: http://www.biogeosciences-discuss.net/6/6271/2009/bgd-6-6271-2009.html; accessed in Dec., 2011.
This article provides an overview of the effects of land-use on the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and from peatlands in the Nordic countries based on the field data from about 100 studies. In addition, this review aims to identify the gaps in the present knowledge on the greenhouse gas (GHG) balances associated with the land-use of these northern ecosystems. Northern peatlands have accumulated, as peat, a vast amount of carbon from the atmosphere since the last glaciation. However, the past land-use and present climate have evidently changed their GHG balance. Unmanaged boreal peatlands may act as net sources or sinks for CO2 and CH4 depending on the weather conditions. Drainage for agriculture has turned peatlands to significant sources of GHGs (mainly N2O and CO2). Annual mean GHG balances including net CH4, N2O and CO2 emissions are 2260, 2280 and 3140 g CO2 eq. m-2 (calculated using 100 year time horizon) for areas drained for grass swards, cereals or those left fallow, respectively. Even after cessetion of the cultivation practices, N2O and CO2 emissions remain high. The mean net GHG emissions in abandoned and afforested agricultural peatlands have been 1580 and 500 g CO2 eq. m-2, respectively. Peat extraction sites are net sources of GHGs with an average emission rate of 770 g CO2 eq. m-2. Cultivation of a perennial grass (e.g., reed canary grass) on an abandoned peat extraction site has been shown to convert such a site into a net sink of GHGs (-330 g CO2 eq. m-2). In contrast, despite restoration, such sites are known to emit GHGs (mean source of 480 g CO2 eq. m-2, mostly from high CH4 emissions). Peatland forests, originally drained for forestry, may act as net sinks (mean -780 g CO2 eq. m-2). However, the studies where all three GHGs have been measured at an ecosystem level in the forested peatlands are lacking. The data for restored peatland forests (clear cut and rewetted) indicate that such sites are on average a net sink (190 g CO2 eq. m-2). The mean emissions from drained peatlands presented here do not include emissions from ditches which form a part of the drainage network and can contribute significantly to the total GHG budget. Peat soils submerged under water reservoirs have acted as sources of CO2, CH4 and N2O (mean annual emission 240 g CO2 eq. m-2). However, we cannot yet predict accurately the overall greenhouse gas fluxes of organic soils based on the site characteristics and land-use practices alone because the data on many land-use options and our understanding of the biogeochemical cycling associated with the gas fluxes are limited.
URL: http://www.biogeosciences.net/7/2711/2010/bg-7-2711-2010.pdf
13009753 McClymont, Alastair F. (University of Calgary, Department of Geoscience, Calgary, AB, Canada); Hayashi, Masaki; Bentley, Lawrence Robert; Muir, D. and Ernst, E. Groundwater flow and storage within an alpine meadow-talus complex: Hydrology and Earth System Sciences (HESS), 14(6), p. 859-872, illus. incl. sects., sketch maps, 45 ref., 2010. Part of special issue no. 105, Cold region hydrology; improved processes, parameterization and prediction, edited by Carey, S., et al., URL: http://www.hydrol-earth-syst-sci.net/special_issue105.html; pPublished in Hydrology and Earth System Sciences Discussion: 25 February 2010, URL: http://www.hydrol-earth-syst-sci-discuss.net/6/3335/2009/hessd-6-3335-20 09.html; accessed in Apr., 2012.
The different types of geological deposits and rock formations found in alpine watersheds play key roles in regulating the rate and timing of runoff to mountain rivers. Talus and alpine meadows are dominant features in these areas, but scant data exist for their capacity to store and transmit groundwater. To gain further understanding of these processes, we have undertaken a combined geophysical and hydrological study of a small (2100 m2) alpine meadow and surrounding talus within the Lake O'Hara watershed in the Canadian Rockies. Several intersecting ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) profiles and a seismic refraction profile were acquired to map the thickness of the talus and to image the topography of the bedrock basin that underlies the meadow. From analysis of the GPR and seismic profiles, we estimate that the talus deposits are relatively thin (<6 m). Combined interpretations from the GPR and ERT data show that the fine-grained sediment comprising the meadow basin has a total volume of ca. 3300 m3 and has a maximum thickness of ca. 4 m. Annual snow surveys and stream gauging reveal that the total input volume of snowmelt and rainfall to the meadow basin is several times larger than its groundwater storage capacity, giving rise to low total-dissolved species concentrations (14-21 mg/L) within the meadow groundwater. Observations from four piezometers established on the meadow show that the water table fluctuates rapidly in response to spring snowmelt and precipitation events but otherwise maintains a relatively stable depth of 0.3-0.4 m below the meadow surface during summer months. A slug test performed on one of the piezometers indicated that the saturated hydraulic conductivity of the shallow meadow sediments is 2.5´10-7 m/s. We suggest that a bedrock saddle imaged underneath the southern end of the meadow forms a natural constriction to subsurface flow out of the basin and helps to maintain the stable water-table depth.
URL: http://www.hydrol-earth-syst-sci.net/14/859/2010/hess-14-859-2010.pdf
13009816 Peña-Arancibia, Jorge L. (CSIRO Land and Water, Black Mountain, A.C.T., Australia); van Dijk, Albert I. J. M.; Mulligan, Mark and Bruijnzeel, L. Adrian. The role of climatic and terrain attributes in estimating baseflow recession in tropical catchments: Hydrology and Earth System Sciences (HESS), 14(11), p. 2193-2205, illus. incl. 3 tables, sketch maps, 40 ref., 2010. Published in Hydrology and Earth System Sciences Discussion: 1 July 2010, URL: http://www.hydrol-earth-syst-sci-discuss.net/7/4059/2010/hessd-7-4059-20 10.html; accessed in Aug., 2012.
The understanding of low flows in rivers is paramount more than ever as demand for water increases on a global scale. At the same time, limited streamflow data to investigate this phenomenon, particularly in the tropics, makes the provision of accurate estimations in ungauged areas an ongoing research need. This paper analysed the potential of climatic and terrain attributes of 167 tropical and sub-tropical unregulated catchments to predict baseflow recession rates. Daily streamflow data (m3 s-1) from the Global River Discharge Center (GRDC) and a linear reservoir model were used to obtain baseflow recession coefficients (kbf) for these catchments. Climatic attributes included annual and seasonal indicators of rainfall and potential evapotranspiration. Terrain attributes included indicators of catchment shape, morphology, land cover, soils and geology. Stepwise regression was used to identify the best predictors for baseflow recession coefficients. Mean annual rainfall (MAR) and aridity index (AI) were found to explain 49% of the spatial variation of kbf. The rest of climatic indices and the terrain indices average catchment slope (SLO) and tree cover were also good predictors, but co-correlated with MAR. Catchment elongation (CE), a measure of catchment shape, was also found to be statistically significant, although weakly correlated. An analysis of clusters of catchments of smaller size, showed that in these areas, presumably with some similarity of soils and geology due to proximity, residuals of the regression could be explained by SLO and CE. The approach used provides a potential alternative for kbf parameterisation in ungauged catchments.
URL: http://www.hydrol-earth-syst-sci.net/14/2193/2010/hess-14-2193-2010.pdf
13009748 Wang, L. (University of Tokyo, Department of Civil Engineering, Tokyo, Japan); Koike, T.; Yang, K.; Jin, R. and Li, H. Frozen soil parameterization in a distributed biosphere hydrological model: Hydrology and Earth System Sciences (HESS), 14(3), p. 557-571, illus. incl. 1 table, sketch maps, 48 ref., 2010. Part of special issue no. 105, Cold region hydrology; improved processes, parameterization and prediction, edited by Carey, S., et al., URL: http://www.hydrol-earth-syst-sci.net/special_issue105.html; published in Hydrology and Earth System Sciences Discussion: 9 November 2009, URL: http://www.hydrol-earth-syst-sci-discuss.net/6/6895/2009/hessd-6-6895-20 09.html; accessed in Oct., 2011.
In this study, a frozen soil parameterization has been modified and incorporated into a distributed biosphere hydrological model (WEB-DHM). The WEB-DHM with the frozen scheme was then rigorously evaluated in a small cold area, the Binngou watershed, against the in-situ observations from the WATER (Watershed Allied Telemetry Experimental Research). First, by using the original WEB-DHM without the frozen scheme, the land surface parameters and two van Genuchten parameters were optimized using the observed surface radiation fluxes and the soil moistures at upper layers (5, 10 and 20 cm depths) at the DY station in July. Second, by using the WEB-DHM with the frozen scheme, two frozen soil parameters were calibrated using the observed soil temperature at 5 cm depth at the DY station from 21 November 2007 to 20 April 2008; while the other soil hydraulic parameters were optimized by the calibration of the discharges at the basin outlet in July and August that covers the annual largest flood peak in 2008. With these calibrated parameters, the WEB-DHM with the frozen scheme was then used for a yearlong validation from 21 November 2007 to 20 November 2008. Results showed that the WEB-DHM with the frozen scheme has given much better performance than the WEB-DHM without the frozen scheme, in the simulations of soil moisture profile at the cold regions catchment and the discharges at the basin outlet in the yearlong simulation.
URL: http://www.hydrol-earth-syst-sci.net/14/557/2010/hess-14-557-2010.pdf
13009796 Weijers, Johan W. H. (University of Bristol, School of Chemistry, Bristol Biogeochemistry Research Centre, Bristol, United Kingdom); Wiesenberg, Guido L. B.; Bol, Roland; Hopmans, Ellen C. and Pancost, Richard D. Carbon isotopic composition of branched tetraether membrane lipids in soils suggest a rapid turnover and a heterotrophic life style of their source organism(s): Biogeosciences, 7(9), p. 2959-2973, illus. incl. 3 tables, 67 ref., 2010.
Branched Glycerol Dialkyl Glycerol Tetraethers (GDGTs) are membrane spanning lipids synthesised by as yet unknown bacteria that thrive in soils and peat. In order to obtain more information on their ecological niche, the stable carbon isotopic composition of branched GDGT-derived alkanes, obtained upon ether bond cleavage, has been determined in a peat and various soils, i.e. forest, grassland and cropland, covered by various vegetation types, i.e., C3- vs. C4-plant type. These d13C values are compared with those of bulk organic matter and higher plant derived n-alkanes from the same soils. With average d13C values of -28 per mil, branched GDGTs in C3 soils are only slightly depleted (ca. 1 per mil) relative to bulk organic carbon and on average 8.5 per mil enriched relative to plant wax-derived long-chain n-alkanes (nC29-nC33). In an Australian soil dominantly covered with C4 type vegetation, the branched GDGTs have a d13C value of -18 per mil, clearly higher than observed in soils with C3 type vegetation. As with C3 vegetated soils, branched GDGT d13C values are slightly depleted (1 per mil) relative to bulk organic carbon and enriched (ca. 5 per mil) relative to n-alkanes in this soil. The d13C values of branched GDGT lipids being similar to bulk organic carbon and their co-variation with those of bulk organic carbon and plant waxes, suggest a heterotrophic life style and assimilation of relatively heavy and likely labile substrates for the as yet unknown soil bacteria that synthesise the branched GDGT lipids. However, a chemoautotrophic lifestyle, i.e. consuming respired CO2, could not be fully excluded based on these data alone. Based on a natural labelling experiment of a C3/C4 crop change introduced on one of the soils 23 years before sampling and based on a free-air CO2 enrichment experiment with labelled CO2 on another soil, a turnover time of ca. 18 years has been estimated for branched GDGTs in these arable soils.
URL: http://www.biogeosciences.net/7/2959/2010/bg-7-2959-2010.pdf
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