12028301 Roldin, Maria (Technical University of Denmark, Department of Environmental Engineering, Lyngby, Denmark); Mark, Ole; Kuczera, G.; Mikkelsen, P. S. and Binning, P. J. Representing soakaways in a physically distributed urban drainage model; upscaling individual allotments to an aggregated scale: Journal of Hydrology, 414-415, p. 530-538, illus. incl. 1 table, 31 ref., January 11, 2012.
The increased load on urban stormwater systems due to climate change and growing urbanization can be partly alleviated by using soakaways and similar infiltration techniques. However, while soakaways are usually small-scale structures, most urban drainage network models operate on a larger spatial scale and the simulation of individual soakaways in these models is therefore often not readily feasible. This study describes the coupling of a soakaway model to a physically distributed urban drainage model, and investigates different upscaling methods. The soakaway component calculates the infiltration rate based on water depth and soil properties for each time step, and controls the removal of water from the urban drainage model. The model is intended to be used to assess the impact of soakaways on urban drainage networks. The model is tested using field data and shown to simulate the behavior of individual soakaways well. Six upscaling methods to aggregate individual soakaway units with varying saturated hydraulic conductivity (K) in the surrounding soil have been investigated. In the upscaled model, the weighted geometric mean hydraulic conductivity of individual allotments is found to provide the best match to an individual allotment model when comparing total outflow volume and peak flow rate. The error introduced by upscaling is found to be in the range of a few percent, and is relatively small compared to the uncertainty of typical field estimates of hydraulic conductivity.
12022665 Stotler, R. L. (University of Kansas, Department of Geology, Lawrence, KS); Frape, S. K.; Ruskeeniemi, T.; Pitkanen, P. and Blowes, D. W. The interglacial-glacial cycle and geochemical evolution of Canadian and Fennoscandian Shield ground waters: Geochimica et Cosmochimica Acta, 76, p. 45-67, illus. incl. 1 table, 165 ref., January 1, 2012. Includes appendices.
Results from cryogenic column experiments are compared with the geochemical data collected in the Canadian and Fennoscandian Shields over the past 25 years to investigate the relative influence of the glacial-interglacial cycle; specifically, the impact of continental glaciers, permafrost, and methane hydrate, on the evolution of groundwater from crystalline shield environments. Several different geochemical indicators of freezing processes (either glacial or permafrost-related) were utilized: comparisons of Na/Cl and Br/Cl ratios, d18O and d2H values, and d18O values and Cl- concentration. During freezing, fluids with different dominant cations follow distinctly different linear trends when Na/Cl and Br/Cl ratios are compared. Significantly, none of the freezing trends follows the trend hypothesized by Herut et al. (1990) for the evolution of seawater chemistry during freezing. Intrusion of glacial meltwater and in situ freezing (i.e., permafrost formation) result in a similar end-member when comparing d18O values and Cl- concentration. The geochemical influence of a freezing process on fresh, brackish, and some saline fluids was identified at some, but not all Canadian Shield sites, regardless of site location with respect to modern-day permafrost. Appreciably, physical and geochemical data do not support the formation of brines through any freezing process in the Canadian and Fennoscandian Shields, as hypothesized by Starinsky and Katz (2003). Rather, on all diagnostic freezing plots, brines are an end-member, indicating a different evolutionary pathway. Significant depletions in 18O with respect to modern precipitation, an indication of either glacial meltwater or a freezing process, were identified at depths of up to 1 km at some sites in the Canadian Shield, and to shallower depths in the Fennoscandian Shield. The potential of this fluid to reach such depths could be attributable to artificial gradients and mixing, glacial recharge, permafrost or paleo-permafrost formation, or methane hydrate or paleo-methane hydrate formation. At most locations it was not possible to distinguish between the different scenarios using the current geochemical database.
12022606 Dagesse, Daryl (Brock University, Geography Department, St. Catharines, ON, Canada). Effect of freeze-drying on soil aggregate stability: Soil Science Society of America Journal, 75(6), p. 2111-2121, illus. incl. 7 tables, 85 ref., December 2011.
12024371 Lin Zhijia (Chinese Academy of Sciences, Guangzhou Institute of Chemistry, Key Laboratory of Marginal Sea Geology, Guangzhou, China); Wang Qinxian; Feng Dong; Liu Qian and Chen Duofu. Post-depositional origin of highly 13C-depleted carbonate in the Doushantuo cap dolostone in south China; insights from petrography and stable carbon isotopes: Sedimentary Geology, 242(1-4), p. 71-79, illus. incl. strat. col., 2 tables, geol. sketch map, 47 ref., December 15, 2011. Chinese Academy of Sciences, Guangzhou Institute of Chemistry GIGCAS Contrib. No. IS-1401.
Extremely negative carbon isotope values from the Doushantuo cap dolostone succession in the Yangtze Gorges, South China were interpreted as direct evidence of the hypothesis of methane hydrate destabilization during the Marinoan deglaciation. However, this suggestion remains uncertain due to the obscurity of the paragenetic sequence of carbonate minerals with diverse carbon isotopic compositions. Here, we conducted macroscopic and microscopic petrographic and carbon isotopic investigations of the cap dolostone succession at the Jiulongwan section in the Yangtze Gorges. Our results show that extreme d13C values down to -44 ppm exclusively occur in calcite, whereas d13C values for the host dolomite range mostly between -4 ppm and -2 ppm, and clearly reveal that the host dolomite were locally dissolved and/or replaced by the calcite bearing highly 13C-depleted signals. This finding suggests that methane-oxidation activity as indicated by the strongly depleted d13C signals did not occur until after the cap dolostone deposition. Thus, the presence of the extremely negative d13C values could not be taken as evidence for the proposed methane hypothesis. Nevertheless, this conclusion is not contradictory to the scenario that massive releases of methane from permafrost hydrates during deglaciation, much prior to methane oxidation documented here, could drive substantial negative d13C shifts well exhibited by the Doushantuo cap dolostone and others around the world.
12022604 Meerschman, Eef (Ghent University, Department of Soil Management, Gent, Belgium); van Meirvenne, Marc; de Smedt, Philippe; Saey, Timothy; Monirul Islam, Mohammad; Meeuws, Fun; van de Vijver, Ellen and Ghysels, Gunther. Imaging of polygonal network of ice-wedge casts with an electromagnetic induction sensor: Soil Science Society of America Journal, 75(6), p. 2095-2100, illus. incl. 1 table, 30 ref., December 2011.
12022610 Pronk, Geertje Johanna (Technische Universität München, Lehrstuhl für Bodenkunde, Freising-Weihenstephan, Germany); Heister, Katja and Kögel-Knabner, Ingrid. Iron oxides as major available interface component in loamy arable topsoils: Soil Science Society of America Journal, 75(6), p. 2158-2168, illus. incl. 5 tables, 37 ref., December 2011.
12027938 Johnson, Kristofer D. (U. S. Geological Survey, Fairbanks, AK); Harden, Jennifer; McGuire, A. David; Bliss, Norman B.; Bockheim, James G.; Clark, Mark; Nettleton-Hollingsworth, Teresa; Jorgenson, M. Torre; Kane, Evan S.; Mack, Michelle; O'Donnell, Jonathan; Ping, Chien-Lu; Schuur, Edward A. G.; Turetsky, Merritt R. and Valentine, David W. Soil carbon distribution in Alaska in relation to soil-forming factors: in mplete, Geoderma, 167-168, p. 71-84, illus. incl. 4 tables, sketch map, 87 ref., November 2011. Includes appendix.
The direction and magnitude of soil organic carbon (SOC) changes in response to climate change remain unclear and depend on the spatial distribution of SOC across landscapes. Uncertainties regarding the fate of SOC are greater in high-latitude systems where data are sparse and the soils are affected by sub-zero temperatures. To address these issues in Alaska, a first-order assessment of data gaps and spatial distributions of SOC was conducted from a recently compiled soil carbon database. Temperature and landform type were the dominant controls on SOC distribution for selected ecoregions. Mean SOC pools (to a depth of 1-m) varied by three, seven and ten-fold across ecoregion, landform, and ecosystem types, respectively. Climate interactions with landform type and SOC were greatest in the uplands. For upland SOC there was a six-fold non-linear increase in SOC with latitude (i.e., temperature) where SOC was lowest in the Intermontane Boreal compared to the Arctic Tundra and Coastal Rainforest. Additionally, in upland systems mineral SOC pools decreased as climate became more continental, suggesting that the lower productivity, higher decomposition rates and fire activity, common in continental climates, interacted to reduce mineral SOC. For lowland systems, in contrast, these interactions and their impacts on SOC were muted or absent making SOC in these environments more comparable across latitudes. Thus, the magnitudes of SOC change across temperature gradients were non-uniform and depended on landform type. Additional factors that appeared to be related to SOC distribution within ecoregions included stand age, aspect, and permafrost presence or absence in black spruce stands. Overall, these results indicate the influence of major interactions between temperature-controlled decomposition and topography on SOC in high-latitude systems. However, there remains a need for more SOC data from wetlands and boreal-region permafrost soils, especially at depths>1m in order to fully understand the effects of climate on soil carbon in Alaska.
12024429 Wada, Tomoyuki (Hokkaido University, Sapporo, Japan); Chikita, K. A.; Kim, Y. and Kudo, I. Glacial effects on discharge and sediment load in the subarctic Tanana River basin, Alaska: Arctic, Antarctic, and Alpine Research, 43(4), p. 632-648, illus. incl. 5 tables, geol. sketch maps, 47 ref., November 2011.
About 5.6% of the drainage area of the Tanana River, Alaska, is covered by mountainous glacierized regions, and most of the other area by forests (51%) and wetlands (9%) with discontinuous permafrost. The water discharge and sediment load from glacierized and non-glacierized regions within the drainage area were represented by observed data of the proglacial Phelan Creek and the non-glacial Chena River, respectively, which are both the tributaries of the Tanana River and ultimately drain to the Yukon river basin. In the glacier-melt periods of 2007 and 2008, the runoff rate and suspended sediment concentration in Phelan Creek was 15 times and 36 times as high as those in the non-glacial Chena River, respectively. As a result, the mean sediment yield in the glacier-melt periods of 2007 and 2008 for Phelan Creek (24.8 t km-2 day-1) was estimated to be 640 times as high as that in the Chena River (0.039 t km-2 day-1). Hence, the glacierized regions were considered to be a major source of the fluvial sediment. In order to quantify the contribution of water discharge and sediment load from the glacierized regions to those of the Tanana River, the time series of water discharge, Q, and sediment load, L, in the glacier-melt periods were simulated by a tank model coupled with the L-Q equations (Nash-Sutcliffe efficiency coefficients, 0.41 to 0.82). The model indicates that the glacier-melt discharge accounted for 26-57% of the Tanana discharge, while the sediment load from the glacierized regions solely accounted for 76-94% of the Tanana sediment load. The remaining contribution (6-24%) of the sediment load was probably due to the fluvial resuspension of glacial sediment deposited previously in the river channels.
12024251 Woods, Gwen C. (University of Toronto, Department of Chemistry, Toronto, ON, Canada); Simpson, Myrna J.; Pautler, Brent G.; Lamoureux, Scott F.; Lafrenière, Melissa J. and Simpson, André J. Evidence for the enhanced lability of dissolved organic matter following permafrost slope disturbance in the Canadian High Arctic: Geochimica et Cosmochimica Acta, 75(22), p. 7226-7241, illus. incl. 5 tables, sketch map, 78 ref., November 15, 2011.
Arctic landscapes are believed to be highly sensitive to climate change and accelerated disturbance of permafrost is expected to significantly impact the rate of carbon cycling. While half the global soil organic matter (SOM) is estimated to reside in Arctic soils, projected warmer temperatures and permafrost disturbance will release much of this SOM into waterways in the form of dissolved organic matter (DOM). The spring thaw and subsequent flushing of soils releases the highest contributions of DOM annually but has historically been undersampled due to the difficulties of sampling during this period. In this study, passive samplers were placed throughout paired High Arctic watersheds during the duration of the 2008 spring flush in Nunavut, Canada. The watersheds are very similar with the exception of widespread active layer detachments (ALDs) that occurred within one of the catchments during a period of elevated temperatures in the summer of 2007. DOM samples were analyzed for structural and spectral characteristics via nuclear magnetic resonance (NMR) and fluorescence spectroscopy as well as vulnerability to degradation with simulated solar exposure. Lignin-derived phenols were further assessed utilizing copper(II) oxide (CuO) oxidation and gas chromatography/mass spectrometry (GC/MS). The samples were found to have very low dissolved lignin phenol content (~0.07% of DOC) and appear to originate from primarily non-woody angiosperm vegetation. The acid/aldehyde ratios for dissolved vanillyl phenols were found to be high (up to 3.6), indicating the presence of highly oxidized lignin. Differences between DOM released from the ALD vs. the undisturbed watershed suggest that these shallow detachment slides have significantly impacted the quality of Arctic DOM. Although material released from the disturbed catchment was found to be highly oxidized, DOM in the lake into which this catchment drained had chemical characteristics indicating high contributions from microbial and/or primary productivity. The resulting pool of dissolved carbon within the lake appears to be more biologically- and photochemically-labile than material from the undisturbed system. These disturbances may have implications for projected climate warming; sustained elevated temperatures would likely perpetuate widespread ALDs and further affect carbon cycling in this environment.
12022316 Pearson, Emma J. (Newcastle University, School of Geography, Politics and Sociology, Newcastle-upon-Tyne, United Kingdom); Juggins, S.; Talbot, H. M.; Weckstrom, J.; Rosen, P.; Ryves, D. B.; Roberts, S. J. and Schmidt, R. A lacustrine GDGT-temperature calibration from the Scandinavian Arctic to Antarctic; renewed potential for the application of GDGT-paleothermometry in lakes: Geochimica et Cosmochimica Acta, 75(20), p. 6225-6238, illus. incl. 3 tables, 55 ref., October 15, 2011.
Quantitative climate reconstructions are fundamental to understand long-term trends in natural climate variability and to test climate models used to predict future climate change. Recent advances in molecular geochemistry have led to calibrations using glycerol dialkyl glycerol tetraethers (GDGTs), a group of temperature-sensitive membrane lipids found in Archaea and bacteria. GDGTs have been used to construct temperature indices for oceans (TEX86 index) and soils (MBT/CBT index). The aim of this study is to examine GDGT-temperature relationships and assess the potential of constructing a GDGT-based palaeo-thermometer for lakes. We examine GDGT-temperature relationships using core top sediments from 90 lakes across a north-south transect from the Scandinavian Arctic to Antarctica including sites from Finland, Sweden, Siberia, the UK, Austria, Turkey, Ethiopia, Uganda, Chile, South Georgia and the Antarctic Peninsula. We examine a suite of 15 GDGTs, including compounds used in the TEX86 and MBT/CBT indices and reflecting the broad range of GDGT inputs to small lake systems. GDGTs are present in varying proportions in all lakes examined. The TEX86 index is not applicable to our sites because of the large relative proportions of soil derived and methanogenic components. Similarly, the MBT/CBT index is also not applicable and predicts temperatures considerably lower than those measured. We examine relationships between individual GDGT compounds and temperature, pH, conductivity and water depth. Temperature accounts for a large and statistically independent fraction of variation in branched GDGT composition. We propose a GDGT-temperature regression model with high accuracy and precision (R2 = 0.88; RMSE = 2.0°C; RMSEP = 2.1°C) for use in lakes based on a subset of branched GDGT compounds and highlight the potential of this new method for reconstructing past temperatures using lake sediments.
12022193 Peterse, Francien (Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, Den Burg, Netherlands); Hopmans, Ellen C.; Schouten, Stefan; Mets, Archélique; Rijpstra, W. Irene C. and Sinninghe Damste, Jaap S. Identification and distribution of intact polar branched tetraether lipids in peat and soil: Organic Geochemistry, 42(9), p. 1007-1015, illus. incl. 1 table, 30 ref., October 2011.
Branched glycerol dialkyl glycerol tetraether lipids (GDGTs) are membrane lipids of soil bacteria that occur ubiquitously in soil, but their occurrence as intact polar lipids (IPLs) has not been well studied. Here, we report the identification and distribution of IPL-branched GDGTs throughout a depth profile of a Swedish peat bog. In addition to two reported glycosidic IPL branched GDGTs, we identified IPL branched GDGTs with a hexose-glycuronic acid, phospho-hexose, or hexose-phosphoglycerol head group, based on mass spectrometry. A selected reaction monitoring (SRM) assay was developed to monitor changes in head group distribution with depth. The abundance of the IPL branched GDGTs increased below the water table, suggesting that they were primarily produced in this part of the peat. This was supported by the concentrations of core lipid and IPL-derived branched GDGTs, which also substantially increased below the water table. However, individual IPL trends differed, which may be due to changes in the microbial community composition with depth or to different degradation rates for the different IPL branched GDGTs. The SRM method was also applied to two different soil types, which showed that similar IPL branched GDGTs as those in peat were present, albeit with different distributions.
12024162 Yang Yonggang (Shanxi University, Institute of Loess Plateau, Taiyuan, China); Xiao Honglang; Wei, Y.; Zhao Liangju; Zou Songbing; Yin Zhenliang and Yang Qiu. Hydrologic processes in the different landscape zones of Mafengou River basin in the alpine cold region during the melting period: Journal of Hydrology, 409(1-2), p. 149-156, illus. incl. 1 table, sketch map, 20 ref., October 28, 2011.
Hydrologic processes of glacier, snow, frozen soil, groundwater, surface water and precipitation have always been the common concern of hydrologists. The purpose of this study is to identify the hydrologic processes in different landscape zones, based on the isotopic and hydrochemical analysis of glacier, snow, frozen soil and groundwater. The chemical compositions were characterized by Ca-HCO3 in the glacier snow zone, Mg-Ca-SO4-HCO3 in the alpine cold desert zone, Ca-Mg-HCO3 in the marsh meadow zone, Ca-Mg-HCO3 in the alpine shrub zone, and Na-Ca-SO4 in the mountain grassland zone. The end-member mixing model was employed for hydrograph separation. The results showed that during the melting period Mafengou River water was recharged by glacier-snow melt water about 34%, thawed frozen soil water in each of the landscape zones about 12%, and groundwater about 54%. This study suggested that Mafengou River water during the melting period was mainly recharged by glacier-snow melt water, groundwater and thawed frozen soil water.
12025691 Chasmer, L. (Wilfrid Laurier University, Cold Regions Research Center, Waterloo, ON, Canada); Quinton, W.; Hopkinson, C.; Petrone, R. and Whittington, P. Vegetation canopy and radiation controls on permafrost plateau evolution within the discontinuous permafrost zone, Northwest Territories, Canada: Permafrost and Periglacial Processes, 22(3), p. 199-213, illus. incl. geol. sketch maps, 42 ref., September 2011.
12025694 Harris, Charles (Cardiff University, School of Earth and Ocean Sciences, Cardiff, United Kingdom); Kern-Luetschg, Martina; Christiansen, Hanne H. and Smith, Fraser. The role of interannual climate variability in controlling solifluction processes, Endalen, Svalbard: Permafrost and Periglacial Processes, 22(3), p. 239-253, illus. incl. 2 tables, sketch map, 25 ref., September 2011.
12023582 Heidari, M. (Bu-Ali Sina University, Department of Geology, Hamedan, Iran); Khanlari, G. R.; Taleb Beydokhti, A. R. and Momeni, A. A. The formation of cover collapse sinkholes in north of Hamedan, Iran: Geomorphology, 132(3-4), p. 76-86, illus. incl. 3 tables, sketch maps, 48 ref., September 15, 2011.
Most sinkholes in the Hamedan region central plain in western Iran are developed in partially unconsolidated sediments overlying Oligo-Miocene limestone. Analyses of hydrologic and hydrogeologic conditions from 1988 to 2008 show that conditions were favourable for sinkhole development. These sinkholes developed in groundwater discharge areas near the base of karstic Oligo-Miocene limestone in zones with major groundwater circulation, thick overburden and a close proximity to deep-source carbon dioxide gas. High carbon dioxide partial pressures, caused by rising gases from pneumatolytic and hydrothermal phase sources, renew the aggressiveness of the water in the vicinity of the discharge zone. The acidic water dissolves limestone, especially along the fractures and joints. Moreover, the presence of large conduits below the surface allows for the transport of unconsolidated sediments and the continual development of sinkholes.
12023594 Niu Fujun (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Lin Zhanju; Liu Hua and Lu Jiahao. Characteristics of thermokarst lakes and their influence on permafrost in Qinghai-Tibet Plateau: Geomorphology, 132(3-4), p. 222-233, illus. incl. 5 tables, sketch maps, 47 ref., September 15, 2011.
About 250 thermokarst lakes, with an average size of 5580 m2 and a total size of 139 x 104 m2, are spread between the Kunlun Mountain pass and the Fenghuo Mountain pass along the Qinghai-Tibet railway, where ice-rich and warm permafrost exists. Approximately 56% of the lakes are elliptical and 23% are elongated. The water depth varies between 0.4 and 3 m. Most of the lakes in the Chumarhe High Plain and other mountain regions are shallower than the thickness of winter ice (60 to 80 cm), and are frozen to the bottom during the cold seasons. However, in the Hoh Xil Hill region and Beiluhe basin, the water depth is greater than the thickness of winter ice and the relatively warm lake bottoms can cause considerable disturbance to the surrounding continuous permafrost. The lakes in the Chumarhe High Plain are saltwater or brine lakes; and in other regions, the lakes contain freshwater or brackish water. Ages of formation, enlargement rates, water and lake-bottom temperatures, the configuration of permafrost, and active-layer thickness were measured at a typical thermokarst lake in the Beiluhe basin between 2007 and 2009. The lake formed about 890 years ago and is 150 m long, 100 m wide, with a water depth of 2.5 m now. The size of the lake is growing at a rate of about 1 m/a at some shores. The lakeshores are underlain by permafrost, which terminates almost vertically at their edge. The mean annual temperature measured at lake bottom in the centre was 5.45°C, while the temperature of permafrost at 15 m depth in the lakeshore varied from -0.84°C near the edge of the lake to -1.26°C at 80 m from the edge. The corresponding active layer depths varied from 2.45 to 1.80 m. The configuration of the talik indicates that no permafrost is found beneath the centre of the lake.
12023587 Pawelec, Halina (University of Silesia, Faculty of Earth Sciences, Bedzinska, Poland). Periglacial evolution of slopes; rock control versus climate factors (Cracow Upland, S. Poland): Geomorphology, 132(3-4), p. 139-152, illus. incl. 1 table, sketch map, 79 ref., September 15, 2011.
This paper concerns the periglacial morphogenesis of slopes occurring on typical relief forms of the Cracow Upland, namely: 1) valleys with asymmetric slopes, 2) undulating plateau with monadnocks, and 3) the edge of the tectonic graben. The research aims to reconstruct denudation processes and slope relief development based on the analysis of slope deposit distribution. The analysis was carried out in the context of climate change during the last glacial cycle (the Upper Vistulian). Evolution of slopes in the investigated area is mainly conditioned by the geological setting, i.e. facies of Jurassic limestones, tectonics, and presence of karstic forms. On the other hand, climate intensified and stimulated the type of denudation processes. Intensive denudation occurred in conditions of cold and wet climate (in the phases of increasing and decaying permafrost). During extremely frosty and dry climate (in the phases of continuous permafrost) denudation processes declined, and loess deposition predominated. In places, the presence of soft deposits protected the substratum against weathering. The following types of slope evolution dominated: lateral recession, development of convex-concave slopes, slope flattening and elongation, and development of convex slope shapes. Steep slopes were laterally retreated. Gentle slopes were: a) lowered and elongated (especially on the substratum made up of inclined bedded limestones) and b) transformed into convex-concave slopes (on substratum made up of different facies of limestones). A convex profile in the lower part of gentle (deluvial) valley slopes originated as a result of cutting-down by river erosion.
12022342 Pedersen, Joel A. (University of Wisconsin-Madison, Department of Soil Science, Madison, WI); Simpson, Myrna A.; Bockheim, James G. and Kumar, Kartik. Characterization of soil organic carbon in drained thaw-lake basins of Arctic Alaska using NMR and FTIR photoacoustic spectroscopy: in Applications and developments of magnetic resonance techniques in geosciences (Berns, Anne E., editor; et al.), Organic Geochemistry, 42(8), p. 947-954, illus. incl. 2 tables, 44 ref., September 2011.
Arctic soils contain a large fraction of Earth's stored carbon. Temperature increases in the Arctic may enhance decomposition of this stored carbon, shifting the role of Arctic soils from a net sink to a new source of atmospheric CO2. Predicting the impact of Arctic warming on soil carbon reserves requires knowledge of the composition of the stored organic matter. Here, we employ solid state 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared-photoacoustic spectroscopy (FTIR-PAS) to investigate the chemical composition of soil organic matter collected from drained thaw-lake basins ranging in age from 0 to 5500 years before present (y BP). The 13C NMR and FTIR-PAS data were largely congruent. Surface horizons contain relatively large amounts of O-alkyl carbon, suggesting that the soil organic matter is rich in labile constituents. Soil organic matter decreases with depth with the relative amounts of O-alkyl carbon decreasing and aromatic carbon increasing. These data indicate that lower horizons are in a more advanced stage of decomposition than upper horizons. Nonetheless, a substantial fraction of carbon in lower horizons, even for ancient thaw-lake basins (2000-5500 y BP), is present as O-alkyl carbon reflecting the preservation of intrinsically labile organic matter constituents. Climate change-induced increases in the depth of the soil active layer are expected to accelerate the depletion of this carbon.
12023595 Pfeiffer, M. (Universidad de Chile, Departamento de Geología, Santiago, Chile); Le Roux, J. P.; Solleiro-Rebolledo, Elizabeth; Kemnitz, H.; Sedov, S. and Seguel, Oscar. Preservation of beach ridges due to pedogenic calcrete development in the Tongoy Palaeobay, north-central Chile: Geomorphology, 132(3-4), p. 234-248, illus. incl. 1 table, sketch map, 109 ref., September 15, 2011. Includes appendices.
At the Tongoy palaeobay in north-central Chile, a series of beach ridges developed during seaward progradation that took place after the MIS 11 sea-level highstand (412 ka). The microrelief left by this succession of beach ridges has been well preserved from erosion due to the development of a calcrete (petrocalcic horizons), which was resistant to the chemical and physical weathering that characterized the area during humid phases of the late Pleistocene and middle Holocene. Macro- and micro-morphological analysis shows that the calcrete is of pedogenic origin and formed during two stages: in the first stage a massive (beta) calcrete developed, followed during the second stage by a laminar (alpha) calcrete. Each event in the development of the calcrete was intimately related to the foregoing process, mainly due to changes in the permeability of the profile horizons. During the first stages of development, organisms played an important role in the precipitation of calcite, which made the calcrete less permeable and favored the accumulation of ponded water during the wet season. As a result of this increased humidity, calcium carbonate with a laminar structure was precipitated. The development of the calcrete was also intimately associated with the evolution of the drainage network, which is characterized by a trellis pattern of tributaries parallel to the beach ridges. This study demonstrates the importance of soil genesis in the geomorphological evolution of landscapes.
12025695 Sattler, K. (University of Vienna, Department of Geography, Vienna, Austria); Keiler, M.; Zischg, A. and Schrott, L. On the connection between debris flow activity and permafrost degradation; a case study from the Schnalstal, south Tyrolean Alps, Italy: Permafrost and Periglacial Processes, 22(3), p. 254-265, illus. incl. 6 tables, geol. sketch maps, 54 ref., September 2011.
12023593 Scapozza, C. (University of Lausanne, Institute of Geography, Lausanne, Switzerland); Lambiel, C.; Baron, L.; Marescot, L. and Reynard, E. Internal structure and permafrost distribution in two Alpine periglacial talus slopes, Valais, Swiss Alps: Geomorphology, 132(3-4), p. 208-221, illus. incl. sketch maps, 71 ref., September 15, 2011.
In order to determine the spatial extension and the characteristics of permafrost within alpine talus slopes, two sites located in the western part of the Swiss Alps were studied using borehole drilling and electrical resistivity tomography (ERT) profiles. Three boreholes were drilled along an upslope-downslope transect in both talus slopes. In both sites, frozen sediments are present only in the two lowest boreholes, whereas the upper borehole does not present ice. This stratigraphy is confirmed by ground temperatures registered in the boreholes. In each site, three upslope-downslope ERT profiles were crossed with five, respectively four horizontal ERT profiles. All the upslope-downslope profiles show a difference in resistivities between the upper and lower parts of the slope, where a large resistive body with values higher than 35 kWm is present. In the uppermost part of the profiles, the resistivities are lower than 10-15 kWm. The borehole data allowed the stratigraphy obtained from the ERT inverted profiles to be validated, with regards to the distribution of frozen sediments as well as the depth of the detected structures. The results confirm that, in the two studied sites, permafrost is present in the lower sections of the talus slopes, whereas it is absent in the upper parts. Finally, the analysis of the talus structure showed that the permafrost stratigraphy, and in particular the ice content, may be an important element of interpretation of the palaeoclimatic significance of an alpine talus slope.
12025692 Woronko, Barbara (University of Warsaw, Department of Geomorphology, Warsaw, Poland) and Hoch, Malgorzata. The development of frost-weathering microstructures on sand-sized quartz grains; examples from Poland and Mongolia: Permafrost and Periglacial Processes, 22(3), p. 214-227, illus. incl. sketch map, 42 ref., September 2011.
12023876 Curtis, Aaron (New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, Socorro, NM) and Kyle, Philip. Geothermal point sources identified in a fumarolic ice cave on Erebus Volcano, Antarctica using fiber optic distributed temperature sensing: Geophysical Research Letters, 38(16), Citation L16802, illus. incl. geol. sketch map, 45 ref., 2011.
Degassing of CO2 on the flanks of the active Erebus volcano is thought to occur mainly through fumarolic ice caves (FIC) and associated fumarolic ice towers. There is also minor CO2 degassing from isolated areas of warm ground. The mechanism supplying heat and CO2 gas into the FIC is poorly understood. To investigate this system, a fiber optic distributed temperature sensing (DTS) system was deployed in a FIC to obtain temperature measurements every meter. The DTS data reveal that localized gas vents (GV) supply heat to the FIC air mass and are an important component of the FIC microclimate. FIC temperature is anti-correlated with local atmospheric pressure, indicating barometric pumping of the GV. These results enable the use of FIC temperature as a proxy for flank degassing rate on Erebus, and represent the first application of DTS for monitoring an active volcano.
12023679 Ge, Shemin (University of Colorado at Boulder, Department of Geological Sciences, Boulder, CO); McKenzie, Jeffrey; Voss, Clifford and Wu Qingbai. Exchange of groundwater and surface-water mediated by permafrost response to seasonal and long term air temperature variation: Geophysical Research Letters, 38(14), Citation L14402, illus. incl. 2 tables, sketch maps, 28 ref., 2011. Supplemental information/data is available in the online version of this article.
Permafrost dynamics impact hydrologic cycle processes by promoting or impeding groundwater and surface water exchange. Under seasonal and decadal air temperature variations, permafrost temperature changes control the exchanges between groundwater and surface water. A coupled heat transport and groundwater flow model, SUTRA, was modified to simulate groundwater flow and heat transport in the subsurface containing permafrost. The northern central Tibet Plateau was used as an example of model application. Modeling results show that in a yearly cycle, groundwater flow occurs in the active layer from May to October. Maximum groundwater discharge to the surface lags the maximum subsurface temperature by two months. Under an increasing air temperature scenario of 3°C per 100 years, over the initial 40-year period, the active layer thickness can increase by three-fold. Annual groundwater discharge to the surface can experience a similar three-fold increase in the same period. An implication of these modeling results is that with increased warming there will be more groundwater flow in the active layer and therefore increased groundwater discharge to rivers. However, this finding only holds if sufficient upgradient water is available to replenish the increased discharge. Otherwise, there will be an overall lowering of the water table in the recharge portion of the catchment.
12022266 Nyadjro, Ebenezer S. (University of South Carolina, Marine Science Program, Columbia, SC); Subrahmanyam, Bulusu and Shriver, Jay F. Seasonal variability of salt transport during the Indian Ocean monsoons: Journal of Geophysical Research, 116(C8), Citation C08036, illus. incl. 1 table, sketch map, 34 ref., 2011.
The seasonal variability of salinity transport in the Indian Ocean is investigated using the high-resolution global HYbrid Coordinate Ocean Model (HYCOM). Mechanisms and physical parameters that control the salinity budget are examined. Results show the influence of freshwater forcing and zonal advection as the dominant mechanisms of sea surface salinity (SSS) variability. Precipitation is highest in the eastern Bay of Bengal (BoB), where it shows seasonal variation, and in the south equatorial eastern Indian Ocean (EIO), where it was consistently high year-round. These patterns result in significant seasonal variation in the SSS in the BoB and almost no variation in the EIO. Zonal SSS transport was higher than meridional SSS transport with the strongest seasonality observed along the Sri Lankan region. Results of depth-integrated transport show northward salt transport in the bottom layers and a southward salt transport in the surface layers. The 4 year mean net flux of depth-integrated salt transport was southward (-154.8 ´ 106 kg/s to -552.4 ´ 106 kg/s) at all latitudes except at 20°N, where it was northward (396 ´ 106 kg/s). Transport generally increases southward with the highest transports occurring in the south (10°S-35°S) and a maximum at 30°S. Analyses of meridional Ekman volume and salt transport show a predominantly southward transport, an indication of the strong influence of SW monsoonal winds. It is anticipated that this study will be useful in computing salt transport using satellite-derived salinity data from the European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) and NASA Aquarius salinity missions.
12023912 Rowland, J. C. (Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM); Travis, B. J. and Wilson, C. J. The role of advective heat transport in talik development beneath lakes and ponds in discontinuous permafrost: Geophysical Research Letters, 38(17), Citation L17504, illus. incl. 2 tables, 30 ref., 2011.
Regions of warm, thin, discontinuous permafrost have been observed to be experiencing rapid changes in lake and pond dynamics in recent decades. Even though surface water and groundwater interactions are thought to play a significant role in heat transport in these regions, the effect of these interactions on permafrost remains largely unquantified. In order to examine the influence of groundwater flow on permafrost dynamics, we modeled the development of a sub-lake talik under permafrost conditions similar to those observed in the southern-central Seward Peninsula region of Alaska using a numerical solution that couples heat transport and groundwater flow, including the effect of water phase changes on soil permeability and latent heat content. A comparison of model simulations, with and without near surface subpermafrost groundwater flow, indicates that stable permafrost thicknesses are 2 to 5 times greater in the absence of groundwater flow. Simulations examining the thermal influence of lakes on underlying permafrost suggest that a through-going talik can develop in a matter of decades and that the incorporation of advective heat transport reduces the time to complete loss of ice beneath the lake by half, relative to heat transport by conduction alone. This work presents the first quantitative assessment of the rates of sub-lake permafrost response to thermal disturbances, such as talik development, in systems with near-surface groundwater flow. The results highlight the importance of coupled thermal and hydrologic processes on discontinuous permafrost dynamics.
12024530 van Husen, Dirk and Reitner, Jürgen M. An outline of the Quaternary stratigraphy of Austria: in Glaciations and periglacial features in Central Europe (Böse, Margot, editor; et al.), Eiszeitalter und Gegenwart - Quarternary Science Journal, 60(2-3), p. 366-387 (German sum.), 124 ref., 2011.
An overview of the Quaternary stratigraphy in Austria is given. The subdivision of the mappable depositional units is based partly on criteria of lithostratigraphy (lithic properties) and allostratigraphy (e.g. unconformities). Traces of glaciations are missing for the Early Pleistocene period (2.58-0.78 Ma). The few and isolated sediment bodies are documenting fluvial accumulation and loess deposition along the rivers. Paleomagnetically correlated loess-paleosol-sequences like the profil at Stranzendorf including the Gauss/Matuyama boundary respectively Neogen/Quaternary are documenting slightly warmer condition than during during the Middle Pleistocene (0.78-0.13 Ma) which is in accordance with the global ?18O record. Four major glaciations (Günz, Mindel, Rib, Würm) are proved during Middle and Late Pleistocene. All of these are documented by proglacial sediments topped by basal till, terminal moraines linked with terrace bodies and loess accumulation as well. This allows to recognize the climatic steering of sedimentation in context with advancing glaciers and the dispersion of permafrost and congelifraction as far as into the Alpine foreland. Both youngest major glaciations (Rib and Würm) are correlated according to geochronological data with the Marine Isotope Stages (MIS) 6 and 2. The simultaneousness of Günz and Mindel with the phases of massive global climatic deterioration during MIS 16 and 12 seems plausible. Phases of less climatic deterioration and consequently glaciations have been found only in loess profiles like Krems Schiebstätte so far.
12024979 Maksimov, F. E. (Saint Petersburg State University, St. Petersburg, Russian Federation); Laukhin, S. A.; Arslanov, Kh. A.; Kuznetsov, V. Yu.; Shilova, G. N.; Chernov, S. B.; Zherebtsov, I. E. and Levchenko, S. B. The first uranium-thorium dating of the middle Neopleistocene peat in West Siberia: Doklady Earth Sciences, 433(1), p. 915-919, illus. incl. 1 table, 14 ref., July 2010.
For a sample from the roof of peat (0-2 cm) located in a reference section for the Middle Neopleistocene in West Siberia near the village of Krivosheino, we obtained an exorbitant value of 14C date >&eq;53.9 ka B.P. (LU-6024). In the peat proper, the 230Th/U dates obtained by the isochronous method are 195.2 ± 10.8/9.1 ka B.P. for the L/L model and 204.1 ± 17/13 ka B.P. for the TSD model. The palynospectra of the peat characterize, from the bottom up, birch forests with fir and spruce participation; then spruce forests with fir; next spruce-cedar forests, similar to the middle taiga subzone. In the clay, the following palynospectra have been examined: forb-gramineous grasslands and light forests with spruce and Betula fruticosa. In the upper part of clays, the palynospectra reflect the evolution of swampy, birch, light forests with spruce participation. The conclusion is made that the studied part of the section formed at the end of the Samarovo Ice Age and in the last third of the Taz Ice Age. The break in sedimentation related to the erosion contact covers a part of the Samarovo Ice Age and the first two-thirds of the Taz Ice Age. Copyright 2010 Pleiades Publishing, Ltd.
12024990 Vasil'chuk, A. C. (Moscow State University, Moscow, Russian Federation) and Vasil'chuk, Yu. K. Local pollen spectra as a new criterion for nonglacial origin of massive ice: Doklady Earth Sciences, 433(1), p. 985-990, illus. incl. 1 table, 14 ref., July 2010.
12028070 Lara, Marisol (Universidad de Chile, Departamento de Geología, Santiago, Chile) and Sepúlveda, Sergio A. Landslide susceptibility and hazard assessment in San Ramón Ravine, Santiago de Chile, from an engineering geological approach: Environmental Earth Sciences, 60(6), p. 1227-1243, illus. incl. 8 tables, geol. sketch maps, 35 ref., May 2010.
Debris flows and soil and rock slides are among the main geological hazards in the mountain foothills of Central Chile. Geological risk associated with the development of landslides, especially debris flows triggered in the basins of ravines that drain into the capital city, Santiago, has increased in time due to accelerated urban expansion. A landslide hazard evaluation in the San Ramon Ravine, located within the foothills of Santiago is presented. Hazard evaluation is based on a methodology that combines the determination of landslide susceptibility calculated by integration of conditioning factors, with the assessment of slope failure and runout probabilities incorporating geotechnical engineering approaches. The methodology is appropriate for medium or subregional scale studies with limited data. The results show that in San Ramon Ravine the landslide hazard consists mainly of debris flows, rock block slides, rock falls and shallow soil slides. Among these, debris flows are the most important due to the urban area that can be affected. Other case studies show that the method can be used in other regions with minor adaptations for territorial planning or for engineering and environmental purposes. Copyright 2009 Springer-Verlag
12024851 Aksenov, V. I. (Fundamentproyekt, Moscow, Russian Federation); Bubnov, N. G.; Klinova, G. I.; Iospa, A. V. and Gevorkyan, S. G. Fazovyye prevrashcheniya vody v merzlykh gruntakh pod vozdeystviyem kriopegov [Phase transitions of water in frozen grounds in the presence of cryopegs]: Geoekologiya (Moskva), 2010(1), p. 40-51, illus. incl. 4 tables, sketch map, 9 ref., February 2010.
12024852 Mikhaylov, V. M. (Russian Academy of Sciences, Siberian Division, P. I. Melnikov Permafrost Institute, Yakutsk, Russian Federation). Otsenka rasprostraneniya poymennykh talikov v basseyne verkhney Kolymy [Analysis of taliks distribution in floodplains of the upper Kolyma River basin]: Geoekologiya (Moskva), 2010(1), p. 52-61, illus. incl. 1 table, 30 ref., February 2010.
12021558 Cull, Selby C. (Washington University in Saint Louis, Department of Earth and Planetary Sciences, St. Louis, MO); Arvidson, Raymond E.; Mellon, Michael T.; Skemer, Philip; Shaw, Amy and Morris, Richard V. Compositions of subsurface ices at the Mars Phoenix landing site: Geophysical Research Letters, 37(24), Citation L24203, illus. incl. sketch map, 30 ref., 2010.
NASA's Phoenix Lander uncovered two types of ice at its 2008 landing site on the northern plains of Mars: a brighter, slab-like ice that broke during Robotic Arm operations; and a darker icy deposit. Spectra from the Phoenix Surface Stereo Imager (SSI) are used to demonstrate that the brighter material consists of nearly pure water ice, which probably formed by migration and freezing of liquid water. The darker icy material consists of ~30 ± 20 wt% ice, with the remainder composed of fine-grained soil, indicating that it probably formed as pore ice. These two types of ice represent two different emplacement mechanisms and periods of deposition.
12021380 Zillén, Lovisa (Lund University, Department of Earth and Ecosystem Sciences, Lund, Sweden) and Conley, Daniel J. Hypoxia and cyanobacteria blooms; are they really natural features of the late Holocene history of the Baltic Sea?: Biogeosciences, 7(8), p. 2567-2580, illus. incl. strat. col., 1 table, sketch map, 86 ref., 2010. Published in Biogeosciences Discussion: 15 March 2010, URL: http://www.biogeosciences-discuss.net/7/1783/2010/bgd-7-1783-2010.html; accessed in Dec., 2011.
During the last century (1900s) industrialized forms of agriculture and human activities have caused eutrophication of Baltic Sea waters. As a consequence, the hypoxic zone in the Baltic Sea has increased, especially during the last 50 years, and has caused severe ecosystem disturbance. Climate forcing has been proposed to be responsible for the reported trends in hypoxia (<2 mg/l O2) both during the last c. 100 years (since c. 1900 AD) and the Medieval Period. By contrast, investigations of the degree of anthropogenic forcing on the ecosystem on long time-scales (millennial and greater) have not been thoroughly addressed. This paper examines evidence for anthropogenic disturbance of the marine environment beyond the last century through the analysis of the human population growth, technological development and land-use changes in the drainage area. Natural environmental changes, i.e. changes in the morphology and depths of the Baltic basin and the sills, were probably the main driver for large-scale hypoxia during the early Holocene (8000-4000 cal yr BP). We show that hypoxia during the last two millennia has followed the general expansion and contraction trends in Europe and that human perturbation has been an important driver for hypoxia during that time. Hypoxia occurring during the Medieval Period coincides with a doubling of the population (from c. 4.6 to 9.5 million) in the Baltic Sea watershed, a massive reclamation of land in both established and marginal cultivated areas and significant increases in soil nutrient release. The role of climate forcing on hypoxia in the Baltic Sea has yet to be demonstrated convincingly, although it could have helped to sustain hypoxia through enhanced salt water inflows or through changes in hydrological inputs. In addition, cyanobacteria blooms are not natural features of the Baltic Sea as previously deduced, but are a consequence of enhanced phosphorus release from the seabed that occurs during hypoxia.