13026749 Arnalds, Olafur (Agricultural University of Iceland, Hvanneyri, Iceland); Orradottir, Berglind and Aradottir, Asa L. Carbon accumulation in Icelandic desert Andosols during early stages of restoration: Geoderma, 193-194, p. 172-179, illus. incl. 8 tables, 52 ref., February 2013.
Carbon accumulation in soils is an important method to offset the release of carbon based GHG into the atmosphere. We investigated carbon accumulation during early stages of ecological restoration of a desertified area in Iceland. The study site, a part of a larger experimental area, consisted of 24 1ha experimental plots with nine different restoration treatments and untreated control, all replicated 2-3 times. The barren desert soils were sandy with unstable surface conditions subjected to intense cryoturbation and wind erosion. Initial carbon stocks in soils of eroded, untreated areas were 0.1-0.3kgm-2, largely consisting of inert metal-humus and/or clay-humus complex characteristic of Andosols. Carbon content in the 5cm surface layer increased from <0.3% up to >0.7% in some treated plots. Annual carbon accumulation of 0.04-0.063kgCm-2yr-1 was observed over the first seven years after initiation of restoration efforts, highest in treatments seeded with grasses and fertilized but no accumulation was observed in untreated controls. Carbon accumulation rate of >0.05kgCm-2yr-1 can potentially be maintained over >100yr due to the nature of Andosols and a steady burial by an influx of eolian materials. There are large areas of desertified surfaces in Iceland (thousands of km2), many of which are undergoing restoration treatments. Restoration efforts in Iceland can play a significant role in sequestering carbon in ecosystems to balance national greenhouse gas emissions as well as restoring biodiversity and important ecosystem services. Abstract Copyright (2013) Elsevier, B.V.
13023721 Boyle, John (University of Liverpool, School of Environmental Science, Liverpool, United Kingdom); Chiverrell, Richard; Plater, Andrew; Thrasher, Ian; Bradshaw, Emily; Birks, Hilary and Birks, John. Soil mineral depletion drives early Holocene lake acidification: Geology (Boulder), Pre-Issue Publication, illus. incl. geol. sketch map, 28 ref., February 20, 2013.
In recent decades, explanations for post-glacial lake acidification have focused on changing climate and biotic factors. Here we present a unique lake sediment data set combining diatom-inferred acidity reconstruction with detailed quantitative assessment of soil base dynamics that challenges this view. We show, at Krakenes Lake in Norway, that historical development of soil mineral depletion inferred from the lake sediment record is consistent with the extent and timing of early Holocene acidification. The lake-water acidification can be fully accounted for by abiotic soil mineral depletion, suggesting a lesser role for alternative acidifying mechanisms, such as direct climate impacts and successional changes in organic acid production. There are at present few comparable data sets, but those that exist suggest similar rates of soil base depletion. As this acidification is not confined to water, abiotic mineral depletion is likely also to impact terrestrial ecosystems, and dynamic vegetation models that exclude irreversible mineral depletion will fail to capture an important element of global ecology.
13025206 Cameron, Eion M. (Eion Cameron Geochemical, Carp, ON, Canada). From Chile to Nevada to the Athabasca Basin; earthquake-induced geochemical anomalies from near-field to far-field: Geochemistry - Exploration, Environment, Analysis, 13(1), p. 41-51, illus. incl. sketch maps, 47 ref., February 2013.
In northern Chile, geochemical anomalies are present above porphyry copper deposits buried beneath thick piedmont gravels. Reactivation of basement faults that originally focussed deposits created fracture zones in the indurated gravels, providing a channel along which earthquakes forced groundwater to the surface. The composition of the groundwater had been modified by interaction with the deposits, generating anomalies. Northern Chile lies directly above a subduction zone, can similar anomalies be formed in regions of lesser seismicity? Seismologists have described the phenomenon of "triggered earthquakes", where passage of dynamic surface waves from major earthquakes can cause other earthquakes hundreds or thousands of kilometres distant. These waves remove blockages along faults, releasing high pressure water to rise and replace lower pressure water. The resulting increase in pore pressure lowers the effective normal stress, allowing the fault to slip: upsurge of water and fault reactivation are linked. In Nevada, part of the Great Basin, there is inherent seismicity from crustal extension and triggered earthquakes from major earthquakes as far distant as Alaska. Case studies show distinct geochemical anomalies above deeply buried deposits, attributed to groundwater with elements derived from the deposits reaching the surface. The Proterozoic Athabasca Basin contains the largest concentration of high grade uranium deposits in the world; it is within a cratonic setting. Deposits lie near the unconformity between Athabasca sandstones and a metamorphic basement along faults that were repeatedly reactivated by remote earthquakes. Reactivation of faults, coupled with fluid movement, continued long after the formation of the deposits. This allowed the upward movement of material from the deposits during the Proterozoic, including radiogenic lead, which had accumulated in the uranium ore. In places, this material reached several hundred metres to the upper levels of the sandstones, from which elements were transferred to tills, soils and vegetation during Quaternary time.
13021309 Cnudde, Veerle (Ghent University, Department of Geology and Soil Science, Ghent, Belgium); de Boever, W.; Dewanckele, J.; de Kock, T.; Boone, M.; Boone, M. N.; Silversmit, G.; Vincze, L.; van Ranst, E.; Derluyn, H.; Peetermans, S.; Hovind, J.; Modregger, P.; Stampanoni, M.; de Buysser, K. and de Schutter, G. Multi-disciplinary characterization and monitoring of sandstone (Kandla Grey) under different external conditions: Quarterly Journal of Engineering Geology and Hydrogeology, 46(1), p. 95-106, illus., 68 ref., February 2013.
Nowadays there is an increase of imported natural building stones, often used as replacement of local, more traditional building stones. The durability of these traditional stones is generally well known; however, when new imported materials are used, it is essential to study their behaviour under the current and local climatological conditions to predict their weathering resistance. In addition to water exposure, these building materials have to be resistant to significant mechanical stress created by the imbibition of de-icing salt solutions, frequently used during winter in Western Europe, with temperature periodically changing from freeze to thaw conditions. Porous network modifications related to the materials" chemical composition are very complex when different forces are acting on the stone itself. Therefore it is crucial to determine the internal structure of the building stone under changing external conditions with and without the presence of de-icing salts, to understand the influence of these additional salts. In this paper, particular attention was paid to the multi-characterization of compact Kandla Grey laminated sandstone, a building stone frequently imported from India to Belgium recently. Traditional as well as highly advanced research techniques were used for the characterization and monitoring of changes under different external conditions. This study demonstrates that the structural characteristics of the laminations have an effect on the frost resistance of the stone and its response to salt weathering. From the experiments carried out, it can be concluded that Kandla Grey can be sensitive to frost and salt weathering under the current climatic conditions in Western Europe.
13026758 Pereira, Thiago T. C. (Universidade Federal de Vicosa, Departamento de Solos, Vicosa, Brazil); Schaefer, Carlos Ernesto G. R.; Ker, Joao C.; Almeida, Cecilia C. and Almeida, Ivan C. C. Micromorphological and microchemical indicators of pedogenesis in ornithogenic Cryosols (Gelisols) of Hope Bay, Antarctic Peninsula: Geoderma, 193-194, p. 311-322, illus. incl. 4 tables, sketch map, 28 ref., February 2013.
Micromorphological investigations of Antarctic soils are comparatively scarce, however, they could help understand the genesis of cryogenic soils under extreme polar conditions and different biotic factors. In most areas of Maritime Antarctica, the soil structure is apparently influenced by the local lithology, cryoturbation, guano deposition and reaction of guano solutions. The present study was carried out in Hope Bay, in the northern part of the Antarctic Peninsula, possibly one of the oldest sites of penguin occupation in the region. We describe and analyze the most important micro and sub-microscopic features of selected Ornithogenic Cryosols (Gelisols) from this part of Antarctic Peninsula, representing a transitional climatic zone between the wetter South Shetlands and the much drier Weddell Sea sector. Nine pedons representing the main ornithogenic soils found in ice-free areas of Hope Bay were selected for the micromorphological study. Undisturbed soil blocks were sampled at different depths, ranging between 0 and 30cm. The microstructure and sub-microstructure were further investigated using a JEOL 8200 and a Zeiss scanning electron microscopes, both coupled with an microprobe (SEM/WDS). These pedons have a very limited surface accumulation of organic matter formed by mosses and lichens, changing abruptly to a mineral phosphatic horizon of bleached colors, and usually hardcemented by ice. A small to medium-sized granular structure is generally observed, with ovoidal, subrounded forms, including several well-defined ornithogenic materials, such as P-rich organic remains, nodular phosphates forms and minute fragments of bone apatite. The chemical composition of ornithogenic materials and phosphatic coatings indicates the presence of discrete forms of taranakite, minyulite, leucophosphite, struvite and fluorapatite, typical of phosphatization process in these soils. Phosphatization and enhanced chemical alteration of the substrate and is one of the main soil-forming process in ornithogenic soils, resulting in P-rich ovoidal aggregates formation. P-rich solutions penetrate desiccation fractures and cleavage planes in large clasts and react preferably with plagioclases. P reacts with Al and Fe to form various amorphous and crystalline P phases. Present day permafrost cementation of deeper phosphate layers indicate that warmer/wetter conditions occurred in the past, during which P was leached downwards and reacted with the rock substrates, developing stable ovoidal aggregates, now incorporated in ice-cemented subsurface horizon. Abstract Copyright (2013) Elsevier, B.V.
13026751 Walpersdorf, Eva (University of Copenhagen, Department of Plant and Environmental Sciences, Copenhagen, Denmark); Koch, C. Bender; Heiberg, Lisa; O'Connell, David W.; Kjaergaard, C. and Bruun Hansen, H. C. Does vivianite control phosphate solubility in anoxic Meadow soils?: Geoderma, 193-194, p. 189-199, illus. incl. 3 tables, 72 ref., February 2013.
Vivianite (Fe3(PO4)2.8H2O) may precipitate in anoxic wetland soils where it may control orthophosphate (Pi) equilibrium solution concentrations at micromolar levels, and thus be of key importance in reducing excessive P from agricultural sources and eutrophication. However, vivianite equilibria and kinetics under in situ conditions are not fully understood and the occurrence of vivianite in wetland soils is rarely documented. In the present investigation we have monitored the temporal (November to June) variation in the pore water chemistry of a wet meadow soil (Sapric Medihemist) including a vivianite-containing gyttja layer. Pore water concentrations of Ca, FeII, HCO3, and NH4 in the gyttja layer were higher than in adjacent horizons. In contrast, dissolved Pi concentrations were the lowest observed in the profile and showed only minor fluctuations (between 0.1 and 6mM). Pore water composition in the gyttja layer was close to equilibrium with vivianite (saturation index, SIviv, 2.01±0.53) at constant pH (~6.8). Dissolution and precipitation experiments in the laboratory with soil suspensions from the gyttja layer demonstrated that vivianite solubility equilibria were only slowly restored. Even after 120 days following perturbation the supersaturation was still high (SIviv~6). It seems that vivianite does contribute to Pi immobilization in anoxic soil horizons, but due to slow precipitation kinetics such soils cannot maintain Pi concentrations at levels below critical thresholds for eutrophication (~1mM), except if pore water geochemistry is kept stable. Abstract Copyright (2013) Elsevier, B.V.
13025084 Wu Xiaodong (Chinese Academy of Sciences, Cryosphere Research Station on the Qinghai-Tibetan Plateau, Lanzhou, China); Zhao Lin; Wu Tonghua; Chen Ji; Pang Qiangqiang; Du Erji; Fang Hongbing; Wang Zhiwei; Zhao Yonghua and Ding Yongjian. Observation of CO2 degassing in Tianshuihai Lake basin of the Qinghai-Tibetan Plateau: Environmental Earth Sciences, 68(3), p. 865-870, illus. incl. sketch map, 24 ref., February 2013.
A large volume of underground gas in the permafrost region of the Qinghai-Tibetan Plateau has been identified. Although many studies were performed to investigate the soil organic carbon dynamics and Earth degassing in volcanic areas, this is the first report of a large amount of non-volcanic CO2 contained in permafrost. The gas was mostly CO2 (81.76 vol.%) and nitrogen (14.59 vol.%). The gas composition and the evidence from carbon stable isotope values (-23.9 ppm, PDB) suggested that the gases possibly had a deep origin. The gas emissions may be triggered by permafrost degradation, which means mitigation of the barrier effect of permafrost for the gas. In addition, plate tectonic processes may also lead to gas emissions, as the tectonic activity is strong in the area. Therefore, particular attention should be paid to the underground gases in the study of global change and permafrost degradation. Copyright 2013 Springer-Verlag Berlin Heidelberg and 2012 Springer-Verlag
13021099 Akesson, M. (Lund University, Department of Geology, Lund, Sweden); Sparrenbom, C. J.; Carlsson, C. and Kreuger, J. Statistical screening for descriptive parameters for pesticide occurrence in a shallow ground water catchment: Journal of Hydrology, 477, p. 165-174, illus. incl. 2 tables, sketch map, 92 ref., January 16, 2013.
We have assessed the ability of a range of pesticide, site and climate parameters to discriminate between detected and non-detected pesticides as observed by long-term monitoring data of pesticide use and groundwater occurrence in a small catchment in southern Sweden. Of seventeen investigated parameters, six demonstrated such an ability: dosage applied, the Henry's Law Constant (HLC), the octanol-water partitioning coefficient (logPow), the amount of precipitation the week before application, the amount of precipitation the month after application, and the substance degradation potential (DT50). The apparent influence of the investigated parameters on pesticide occurrence in groundwater, and their apparent suitability as descriptive parameters in terms of assessment of related risks, is accordingly discussed. We conclude that knowledge of actual pesticide use appear fundamental for risk assessment of groundwater contamination potential. We further suggest that chemical property-parameters of specific pesticides, although clearly valuable, should be applied in groundwater contamination risk assessments with care. If site-specific values are unattainable, tabular values of log Pow, HLC and water solubility (Ws) are demonstrated to exhibit a superior explanatory ability than those of substance adsorption potential (Koc) and DT50 which, in the latter case, is shown to be able to lead to misleading conclusions on actual risks. The demonstrated explanatory ability of precipitation both before and after application suggests that relatively greater precipitation amounts occur in relation to application of non-detected substances. Increased dilution and run-off as well as decreased soil matrix retainment and decreased top-soil cracking are potential explanations although higher-resolution monitoring records are needed in order to confirm these hypotheses. Abstract Copyright (2013) Elsevier, B.V.
13021124 Douglas, Thomas A. (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Blum, Joel D.; Guo, Laodong; Keller, Katy and Gleason, James D. Hydrogeochemistry of seasonal flow regimes in the Chena River, a subarctic watershed draining discontinuous permafrost in interior Alaska (USA): Chemical Geology, 335, p. 48-62, illus. incl. 4 tables, sketch map, 113 ref., January 6, 2013.
Thawing of permafrost and a shift in the timing of major seasonal transitions (spring melt and fall freeze-up) are two anticipated effects of climate warming in northern regions. These fundamental changes in terrestrial ecosystems could have major ramifications for the timing and fluxes of carbon and nutrient exports from watersheds and the geochemical signatures of northern rivers. Discontinuous permafrost, which underlies watersheds in Interior Alaska (USA), is expected to degrade rapidly in response to climate warming and this will likely alter subsurface flows and flow paths, water residence times, water-soil, and water-rock interactions. This study of the Chena River in Interior Alaska was undertaken to quantify dissolved organic carbon (DOC), total dissolved nitrogen (TDN), major ion, strontium isotope, and stable oxygen and hydrogen isotope values during two year-long time series sampling periods. Our goal was to identify the hydrogeochemical signatures associated with the major seasonal flow regimes. Periods of increased discharge such as spring melt and major summer precipitation events yielded elevated DOC and TDN concentrations, diluted major ion concentrations, and shifted stable oxygen and hydrogen isotope ratios from base flow toward precipitation values. During dry summer periods nutrient concentrations decreased and strontium isotope values were indicative of a higher proportion of silicate versus carbonate mineral dissolution. Winter base flow had a unique geochemical signal with a slight increase in TDN concentrations compared to typical summer conditions, and a lower proportion of silicate versus carbonate mineral dissolution. Since flow paths in subarctic watersheds can change dramatically over the course of a year we interpreted our results within the context of a schematic model for subsurface flow to identify how permafrost degradation might affect nutrient exports and hydrogeochemical patterns in these watersheds. Abstract Copyright (2013) Elsevier, B.V.
13025146 Elbert, Julie (University of Bern, Oeschger Center for Climate Change Research, Bern, Switzerland); Wartenburger, Richard; von Gunten, Lucien; Urrutia, Roberto; Fischer, Daniela; Fujak, Marian; Hamann, Yvonne; Greber, Nicolas David and Grosjean, Martin. Late Holocene air temperature variability reconstructed from the sediments of Laguna Escondida, Patagonia, Chile (45°30'S): Palaeogeography, Palaeoclimatology, Palaeoecology, 369, p. 482-492, illus. incl. 1 table, sketch map, 54 ref., January 1, 2013.
Climate and environmental reconstructions from natural archives are important for the interpretation of current climatic change. Few quantitative high-resolution reconstructions exist for South America which is the only land mass extending from the tropics to the southern high latitudes at 56°S. We analyzed sediment cores from two adjacent lakes in Northern Chilean Patagonia, Lago Castor (45°36'S, 71°47'W) and Laguna Escondida (45°31'S, 71°49'W). Radiometric dating (210Pb, 137Cs, 14C-AMS) suggests that the cores reach back to c. 900BC (Laguna Escondida) and c. 1900BC (Lago Castor). Both lakes show similarities and reproducibility in sedimentation rate changes and tephra layer deposition. We found eight macroscopic tephras (0.2-5.5cm thick) dated at 1950BC, 1700BC, at 300BC, 50BC, 90AD, 160AD, 400AD and at 900AD. These can be used as regional time-synchronous stratigraphic markers. The two thickest tephras represent known well-dated explosive eruptions of Hudson volcano around 1950 and 300BC. Biogenic silica flux revealed in both lakes a climate signal and correlation with annual temperature reanalysis data (calibration 1900-2006AD; Lago Castor r=0.37; Laguna Escondida r=0.42, seven years filtered data). We used a linear inverse regression plus scaling model for calibration and leave-one-out cross-validation (RMSEv=0.56°C) to reconstruct sub decadal-scale temperature variability for Laguna Escondida back to AD 400. The lower part of the core from Laguna Escondida prior to AD 400 and the core of Lago Castor are strongly influenced by primary and secondary tephras and, therefore, not used for the temperature reconstruction. The temperature reconstruction from Laguna Escondida shows cold conditions in the 5th century (relative to the 20th century mean), warmer temperatures from AD 600 to AD 1150 and colder temperatures from AD 1200 to AD 1450. From AD 1450 to AD 1700 our reconstruction shows a period with stronger variability and on average higher values than the 20th century mean. Until AD 1900 the temperature values decrease but stay slightly above the 20th century mean. Most of the centennial-scale features are reproduced in the few other natural climate archives in the region. The early onset of cool conditions from c. AD 1200 onward seems to be confirmed for this region. Abstract Copyright (2013) Elsevier, B.V.
13021074 Ilina, Svetlana M. (University Paul Sabatier, Géosciences Environnement Toulouse, Toulouse, France); Poitrasson, Franck; Lapitskiy, Sergey A.; Alekhin, Yuriy V.; Viers, Jérôme and Pokrovsky, Oleg S. Extreme iron isotope fractionation between colloids and particles of boreal and temperate organic-rich waters: Geochimica et Cosmochimica Acta, 101, p. 96-111, illus. incl. 2 tables, sketch maps, 130 ref., January 15, 2013. Includes appendices.
Significant and systematic variations of iron isotopic composition in surface water sample fractions obtained by frontal cascade filtration and ultrafiltration have been recorded in (1) subarctic organic-rich boreal river and stream, mire, lake and soil solutions in northern taiga zone (Karelia, NW Russia) and (2) temperate river and lake waters of the southern boreal zone (Central Russia). Water samples were filtered in the field employing progressively decreasing pore size from 100mm to 1 kDa followed by iron isotope analysis. In all river samples, there was a gradual increase of d57Fe relative to IRMM-14 with decreasing pore size, from +0.4±0.1 ppm at 100mm up to +4.2±0.1 ppm at 10 kDa fraction in the subarctic zone and from -0.024±0.2 ppm at 100mm up to +1.2±0.2 ppm at 10 kDa in the temperate zone. In the series of filtrates/ultrafiltrates of subarctic and temperate streams and rivers, the d57Fe value decreases with increasing molar Fe/Corg ratio. Therefore, small-size, Fe-poor, C-rich colloids (1-10 kDa) and Low Molecular Weight (LMW) fractions of oxygenated water exhibit strong enrichment in heavy isotope whereas High Molecular Weight Fe-rich colloids (100 kDa-0.22mm) and particles (1-100mm) are isotopically lighter and closer to the continental crust Fe isotope composition. The relative enrichment of 1-10 kDa ultrafiltrates in heavy isotopes suggests that low molecular weight ligands bind Fe more strongly (Fe-O-C bonds) than Fe(III)oxy(hydr)oxides (Fe-O-Fe bonds), in accord with quantum mechanics principles. Highly positive d57Fe of the LMW fraction of labile and potentially bioavailable Fe in small subarctic rivers may turn out to be a very important source of isotopically heavy Fe in the Arctic Ocean. The mechanisms involved in the production of this isotopically heavy Fe may lead this tracer to become a new indicator of environmental changes occurring in the boreal zone. Abstract Copyright (2013) Elsevier, B.V.
13021091 Luo Yi (Chinese Academy of Sciences, Xinjiang Institute of Ecology and Geography, Laboratory of Oasis and Desert Ecology, Urumqi, China); Arnold, Jeff; Liu Shiyin; Wang, Xiuying and Chen Xi. Inclusion of glacier processes for distributed hydrological modeling at basin scale with application to a watershed in Tian Shan Mountains, northwest China: Journal of Hydrology, 477, p. 72-85, illus. incl. 2 tables, sketch map, 94 ref., January 16, 2013.
In this paper we proposed: (1) an algorithm of glacier melt, sublimation/evaporation, accumulation, mass balance and retreat; (2) a dynamic Hydrological Response Unit approach for incorporating the algorithm into the Soil and Water Assessment Tool (SWAT) model; and (3) simulated the transient glacier retreat and its impacts on streamflow at basin scale. Application of the enhanced SWAT model in the Manas River Basin (MRB) in the Tianshan Mountains in northwest China, shows that the approach is viable as evidenced by a Nash-Sutcliff efficiency of 0.65 and a percent bias of -3.7% for daily streamflow and water balance, respectively. The results indicate that the glacier area decreased by 11% during the simulation period from 1961 to 1999, which is within the range of records from other glaciers. On average, glacier melt contributed 25% to streamflow, although glacier area accounts for only 14% of the catchment drainage area in the MRB. Glacier melt was positively correlated to temperature change (R2=0.70, statistical significance P<0.001) and negatively correlated to precipitation (R2=0.20, statistical significance P<0.005). The results indicate that glacier melt was more sensitive to temperature change than to precipitation change, implying that modeling the effects of climate change with increasing temperatures and decreasing precipitation should be further studied. Abstract Copyright (2013) Elsevier, B.V.
13020970 Viles, Heather A. (University of Oxford, School of Geography, Oxford, United Kingdom). Linking weathering and rock slope instability; non-linear perspectives: Earth Surface Processes and Landforms, 38(1), p. 62-70, illus. incl. 3 tables, 60 ref., January 2013.
Weathering is linked complexly to the erosion and evolution of rock slopes. Weathering influences both the strength of rock slopes and the stresses that act upon them. While weathering has often been portrayed in an over-simplified way by those studying rock slope instability, in reality it consists of multiple processes, acting over different spatial and temporal scales, with many complex inter-linkages. Through a demonstration of the sources of non-linearities in rock slope weathering systems and their implications for rock slope instability, this paper proposes five key linkages worthy of further study. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13023571 Warsta, Lassi (Aalto University School of Engineering, Department of Civil and Environmental Engineering, Aalto, Finland); Karvonen, Tuomo; Koivusalo, Harri; Paasonen-Kivekas, Maija and Taskinen, Antti. Simulation of water balance in a clayey, subsurface drained agricultural field with three-dimensional FLUSH model: Journal of Hydrology, 476, p. 395-409, illus. incl. 8 tables, sketch map, 85 ref., January 7, 2013. Includes appendices.
Water flow is a key component in the evaluation of soil erosion and nutrient loads from agricultural fields. Field cultivation is the main non-point pollution source threatening water quality of surface waters in Nordic and many other countries. Few models exist that can describe key hydrological processes in clayey soils, i.e. overland flow, preferential flow in macropores and soil shrinkage and swelling. A new three-dimensional (3-D) distributed numerical model called FLUSH is introduced in this study to simulate these processes. FLUSH describes overland flow with the diffuse wave simplification of the Saint Venant equations and subsurface flow with a dual-permeability approach using the Richards equation in both macropore and matrix pore systems. A method based on the pentadiagonal matrix algorithm solves flow in both macropore and matrix systems directly in a column of cells in the computational grid. Flow between the columns is solved with iteration accelerated with OpenMP parallelisation. The model validity is tested with data from a 3-D analytical model and a clayey subsurface drained agricultural field in southern Finland. According to the simulation results, over 99% of the drainflow originated from the macropore system and drainflow started in some cases within the same hour when precipitation started indicating preferential flow in the profile. The moisture content of the clay soil had a profound effect on runoff distribution between surface runoff and drainflow. In summer, when the soil was dry and cracked, drainflow dominated the total runoff, while in autumn, when the shrinkage crack network had swollen shut, surface runoff fraction clearly increased. Observed differences in surface runoff fraction before and after tillage indicated that the operation decreased hydraulic conductivity of the profile. Abstract Copyright (2013) Elsevier, B.V.
13020896 Zhao Qiudong (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Ye Baisheng; Ding Yongjian; Zhang Shiqiang; Yi Shuhua; Wang Jian; Shangguan Donghui; Zhao Chuancheng and Han Haidong. Coupling a glacier melt model to the Variable Infiltration Capacity (VIC) model for hydrological modeling in north-western China: Environmental Earth Sciences, 68(1), p. 87-101, illus. incl. 2 tables, sketch map, 83 ref., January 2013.
For the sustainable utilization of rivers in the mid and downstream regions, it is essential that land surface hydrological processes are quantified in high cold mountains regions, as it is in these regions where most of the larger rivers in China acquire their headstreams. Glaciers are one of the most important water resources of north-west China. However, they are seldom explicitly considered within hydrological models, and climate-change effects on glaciers, permafrost and snow cover will have increasingly important consequences for runoff. In this study, an energy-balance ice-melt model was integrated within the Variable Infiltration Capacity (VIC) macroscale hydrological model. The extended VIC model was applied to simulate the hydrological processes in the Aksu River basin, a large mountainous and glaciered catchment in north-west China. The runoff components and their response to climate change were analyzed based on the simulated and observed data. The model showed an acceptable performance, and achieved an efficiency coefficient R2 » 0.8 for the complete simulation period. The results indicate that a large proportion of the catchment runoff is derived from ice meltwater and snowmelt water. In addition, over the last 38 years, rising temperature caused an extension in the snow/ice melting period and a reduction in the seasonality signal of runoff. Due to the increased precipitation runoff, the Aksu catchment annual runoff had a positive trend, increasing by about 40.00 ´ 106 m3 per year, or 25.7 %. Copyright 2013 Springer-Verlag Berlin Heidelberg and 2012 Springer-Verlag
13024922 Li Ren (Research Station on Cryosphere of Qinghai-Xizang Plateau, Lanzhou, China); Zhao Lin; Ding Yongjian; Wu Tonghua; Xiao Yao; Du Erji; Liu Guangyue and Qiao Yongping. Temporal and spatial variations of the active layer along the Qinghai-Tibet Highway in a permafrost region: Chinese Science Bulletin, 57(35), p. 4609-4616, illus. incl. 2 tables, 31 ref., December 2012. This article is published with open access at Springerlink.com.
Using monitored active layer thickness (ALT) and environmental variables of 10 observation fields along the Qinghai-Tibet Highway in permafrost region of the Qinghai-Tibetan Plateau (QTP), a model for ALT estimation was developed. The temporal and spatial characteristics of the ALT were also analyzed. The results showed that in the past 30 years ALT in the study region increased at a rate of 1.33 cm a-1. Temperatures at the upper limit of permafrost and at 50 cm depth, along with soil cumulative temperature at 5 cm depth also exhibited a rising trend. Soil heat flux increased at a rate of 0.1 W m-2 a-1. All the above changes demonstrated that the degradation of permafrost happened in the study region on the QTP. The initial thawing date of active layer was advanced, while the initial freezing date was delayed. The number of thawing days increased to a rate of 1.18 d a-1. The variations of active layer were closely related to the permafrost type, altitude, underlying surface type and soil composition. The variations were more evident in cold permafrost region than in warm permafrost region, in high-altitude region than in low-altitude region, in alpine meadow region than in alpine steppe region; and in fine-grained soil region than in coarse-grained soil region. Copyright 2012 The Author(s)
13025088 Tabuchi, Hiroshi (Hosei University, Department of Physical Geography, Tokyo, Japan) and Seppala, Matti. Surface temperature inversion in the palsa and pounu fields of northern Finland: Polar Science, 6(3-4), p. 237-251, illus. incl. 6 tables, sketch map, 32 ref., November 2012.
13022872 Kvaerno, Sigrun H. (Norwegian Institute for Agricultural and Environmental Research, Soil and Environment Division, As, Norway) and Stolte, Jannes. Effects of soil physical data sources on discharge and soil loss simulated by the LISEM model: Catena (Giessen), 97, p. 137-149, illus. incl. 3 tables, sketch map, 52 ref., October 2012.
The source of input data for soil physical properties may contribute to uncertainty in simulated catchment response. The objective of this study was to quantify the uncertainty in catchment surface runoff and erosion predicted by the physically based model LISEM, as influenced by uncertainty in soil texture and SOM content, and the pedotransfer function derived soil water retention curve, hydraulic conductivity, aggregate stability and cohesion. LISEM was first calibrated using measured data in a sub-catchment, and then run for the whole catchment for a summer storm event with basic input data from two data sources: soil series specific generic data from the national soil survey database, and measured data collected in a grid within the catchment. The measured data were assigned in two ways: mean values per map unit, or random distribution (50 realizations) per map unit. The model was run both for a low risk situation (crop covered surface) and a high risk situation (without crop cover and with reduced aggregate stability and cohesion). The main results were that 1) using non-local database data yielded much higher peak discharge and five to six times higher soil loss than using locally measured data, 2) there was little difference in simulated runoff and soil loss between the two approaches (mean value versus random distribution) to assign locally measured data, 3) differences between the 50 random realizations were insignificant, for both low-risk and high-risk situations, and 4) uncertainty related to input data could result in larger differences between runs with different input data source than between runs with the same input data source but extreme differences in erosion risk. The main conclusion was that inadequate choice of input data source can significantly affect general soil loss and the effect of measures. Abstract Copyright (2012) Elsevier, B.V.
13022934 Abramovich, Reut Sorek (University of New South Wales, Sydney, N.S.W., Australia); Pomati, Francesco; Jungblut, Anne D.; Guglielmin, Mauro and Neilan, Brett A. T-RFLP fingerprinting analysis of bacterial communities in debris cones, northern Victoria Land, Antarctica: Permafrost and Periglacial Processes, 23(3), p. 244-248, illus. incl. 2 tables, 30 ref., September 2012.
The debris cones known as Amorphous Glacier and Boulder Clay are located in an ice-free region in Northern Victoria Land, Antarctica, and differ in their isotopic composition, mechanisms of ice distribution, geological formation and age. However, to date it is not known if bacterial community profiles within ice and permafrost can be established for these environments, and then whether glaciological differences between the two areas would be reflected in the bacterial community composition. In order to gather first evidence for the bacterial communities in these glacial zones, we carried out terminal-restriction fragment length polymorphism (T-RFLP) analysis on the 16S rRNA gene using a universal bacterial amplification protocol on two permafrost cores. The DNA yields from ice-core samples ranged from 0.29 ng mL-1 in Amorphous Glacier to 88 ng mL-1 in Boulder Clay. Bray-Curtis cluster analysis suggested Boulder Clay bacterial profiles were similar to each other, but cluster separately from the Amorphous Glacier bacterial profile. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022932 Bockheim, J. G. (University of Wisconsin, Department of Soil Science, Madison, WI) and Hinkel, Kenneth M. Accumulation of excess ground ice in an age sequence of drained thermokarst lake basins, Arctic Alaska: Permafrost and Periglacial Processes, 23(3), p. 231-236, illus. incl. 1 table, 21 ref., September 2012.
The excess ice content of near-surface permafrost near Barrow, Alaska, was estimated using cores collected from 57 drained thermokarst-lake basins and additional cores from a nearby landform unaffected by thaw-lake processes. The excess ice content, estimated using soil cryostructures, increased with surface age: from 20 per cent in young basins <50 years in age to 40 per cent in ancient basins that drained 2000-5500 years ago. The frequency of ice wedges encountered during coring increased from 0 per cent in young basins to 50 per cent in ancient basins. These results indicate that the volume of ground ice increases rapidly immediately following lake drainage, as permafrost aggrades into unfrozen basin sediments. Ice enrichment continues over time by incorporating meteoric water as ice veins and lenses, and expanding networks of ice wedges. To test the efficacy of visually estimating excess ice content, the ice content was measured on a subsample of cores; measured volumetric values were strongly correlated (r2=0.72; p<0.001) to the estimated excess ice content. The results of this study have important implications for estimating soil organic carbon content of soils with abundant excess ice, and for evaluating the susceptibility of these soils to thermokarst. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022928 Edenborn, Harry M. (U. S. Department of Energy, National Energy Technology Laboratory, Pittsburgh, PA); Sams, James I. and Kite, J. Steven. Thermal regime of a cold air trap in central Pennsylvania, USA; the Trough Creek ice mine: Permafrost and Periglacial Processes, 23(3), p. 187-195, illus. incl. 1 table, sketch map, 34 ref., September 2012.
Air temperatures internal and external to a talus cave ("ice mine") in central Pennsylvania were measured hourly for three years. Despite its location near the base of a talus slope, the cave demonstrated the thermal characteristics of an apparently static cave, with limited connections to the external environment other than through the cave entrance. Congelation ice that lasted until late spring formed as drip or flowstone and ponded ice from the limited influx of infiltrating water during late winter/early spring. A closed period of thermal stratification and slow warming of cave air was followed by an open period in winter months during which the cave was cooled by the influx of cold dry air. Unlike the occasionally strong and localised cooling induced by the flow of cold air from vents at the base of talus slopes, static cold traps retain their cold air and have little apparent effect on surrounding biota, instead providing potential refugia for organisms that prefer colder temperatures. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022930 Hinkel, Kenneth M. (University of Cincinnati, Department of Geography, Cincinnati, OH); Lenters, John D.; Sheng, Yongwei; Lyons, Evan A.; Beck, Richard A.; Eisner, Wendy R.; Maurer, Eric F.; Wang, Jida and Potter, Brittany L. Thermokarst lakes on the Arctic Coastal Plain of Alaska; spatial and temporal variability in summer water temperature: Permafrost and Periglacial Processes, 23(3), p. 207-217, illus. incl. 1 table, sketch map, 54 ref., September 2012.
In summer 2010, water temperature profile measurements were made in 12 thermokarst lakes along a 150-km long north-south transect across the Arctic Coastal Plain of northern Alaska. In shallow lakes, gradual warming of the water column to 1-4°C begins at the lake bed during decay of the ice cover in spring. Rapid warming follows ice-off, with water temperature responding synchronously to synoptic weather variations across the area. Regionally, ice-off occurs 2-4 weeks later on lakes near the coast. Inland lakes are warmer (13°C) in mid-summer than those near the coast (7°C), reflecting the regional climate gradient and the maritime effect. All lakes are well mixed and largely isothermal, with some thermal stratification (< 2°C) occurring during calm, sunny periods in deeper lakes. In deep (6-9 m) lake-bed depressions that are likely ice-wedge troughs, water cools by conduction to the colder sediments below, while concurrent warming occurs in the upper water column. A spatially dense sample of near-surface temperature measurements was collected from one lake over a short period and shows warmer (2-3°C) temperatures on the upwind, sheltered end of the lake. This study demonstrates that climatic gradients, meteorological conditions and basin characteristics impact lake temperature dynamics. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022931 Hinkel, Kenneth M. (University of Cincinnati, Department of Geography, Cincinnati, OH); Sheng, Yongwei; Lenters, John D.; Lyons, Evan A.; Beck, Richard A.; Eisner, Wendy R. and Wang, Jida. Thermokarst lakes on the Arctic Coastal Plain of Alaska; geomorphic controls on bathymetry: Permafrost and Periglacial Processes, 23(3), p. 218-230, illus. incl. 2 tables, sketch map, 67 ref., September 2012.
Detailed bathymetric data were collected for 28 thermokarst lakes across the Arctic Coastal Plain (ACP) of northern Alaska from areas with distinctly different surficial sediments and topography. Lakes found in the low-relief coastal area have developed in marine silts that are ice-rich in the upper 6-10 m. The lakes tend to be shallow (~ 2 m), of uniform depth and lack prominent littoral shelves. Further inland on the ACP, lakes have formed in relatively ice-poor aeolian sand deposits. In this hilly terrain, average lake depth is less (~ 1 m) despite deeper (3-5 m) central pools. This bathymetry reflects the influence of broad, shallow littoral shelves where sand, eroded from bluffs at the lake margin, is deposited concurrently with deep penetration of the talik beneath the basin center. Lakes in the ACP-Arctic Foothills transition zone to the south have developed in loess uplands. These yedoma deposits are extremely ice-rich, and residual lakes found inside old lake basins (alases) are generally 2-4 m deep, reflecting continued talik development and ground subsidence following drainage of the original lake. However, where the expanding lake encroaches on the flanks of the upland at actively eroding bluffs, near-shore pools develop that can be 6-9 m deep. It appears that thawing of ice-rich permafrost during lake expansion causes ground subsidence and formation of deep pools above ablating ice wedges. These data suggest that thermokarst lake morphometry largely depends on the characteristics of the substrate beneath the lake and the availability of sediments eroded at the lake margin. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022929 Kelley, Alexia M. (University of Virginia, Department of Environmental Sciences, Charlottesville, VA); Epstein, Howard E.; Ping, Chien-Lu and Walker, Donald A. Soil nitrogen transformations associated with small patterned-ground features along a North American Arctic transect: Permafrost and Periglacial Processes, 23(3), p. 196-206, illus. incl. 2 tables, 68 ref., September 2012.
Small patterned-ground features (PGFs) in the Arctic have unique soil properties that vary with latitude and may greatly affect tundra biogeochemistry. Because nitrogen availability can strongly limit arctic vegetation growth, we examined how soil nitrogen transformations differ between PGFs and the surrounding inter-PGF tundra along an arctic latitudinal gradient. We collected soils at eight sites from the Alaskan Low Arctic to the Canadian High Arctic. The soils were incubated for 21 days at 9 °C and 15 °C and analyzed for changes in total inorganic nitrogen, nitrate and extractable organic nitrogen (EON). We found greater nitrogen immobilization in the surrounding inter-PGF soils than in the PGF soils. Along the latitudinal gradient, differences in net nitrogen mineralization and EON cycling between PGF and inter-PGF soils were strongly influenced by the presence of a pH boundary within the Low Arctic and the transition between the High and Low Arctic, with greater immobilization in the nonacidic and Low Arctic sites, respectively. Incubation temperature affected EON flux but did not affect net nitrogen mineralization or nitrification. These results show that spatial heterogeneity at several scales can influence soil nitrogen dynamics, and is therefore an important influence on arctic ecosystem function. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022933 Nagare, Ranjeet M. (University of Western Ontario, Department of Earth Sciences, London, ON, Canada); Schincariol, Robert A.; Quinton, William L. and Hayashi, Masaki. Moving the field into the lab; simulation of water and heat transport in subarctic peat: Permafrost and Periglacial Processes, 23(3), p. 237-243, illus. incl. 1 table, 27 ref., September 2012.
Large climate chambers are suitable to simulate, at or close to field scale, the annual freezing and thawing of layered peat in subarctic active layers above permafrost. An experiment in a climate chamber at the University of Western Ontario was designed to freeze and thaw four peat cores 60 cm in diameter. This paper describes the climate chamber and experimental setup, and evaluates their ability to maintain one-dimensional change in soil moisture and temperature profiles. Preliminary results on soil water content (liquid and total) indicate that active-layer freezing resulted in an upward movement of water towards a freezing front that propagated downward. The physical simulations will contribute towards improving conceptual and mathematical hydrological models for permafrost regions. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13020639 Pestryakova, Luidmila A. (North-Eastern Federal University of Yakutsk, Department for Geography and Biology, Yakutsk, Russian Federation); Herzschuh, Ulrike; Wetterich, Sebastian and Ulrich, Mathias. Present-day variability and Holocene dynamics of permafrost-affected lakes in central Yakutia (eastern Siberia) inferred from diatom records: Quaternary Science Reviews, 51, p. 56-70, illus. incl. 4 tables, sketch map, 88 ref., September 19, 2012.
Thermokarst lakes are assumed to develop cyclically, driven by processes that are triggered by climate and maintained by internal feedbacks that may trigger lake drainage. However, the duration of these cycles remains uncertain, as well as whether or not they affect the stabilization of lake ecosystems in permafrost regions over millennial time scales. Our research has combined investigations into modern lake-to-lake variability with a study of the long-term development of individual lakes. We have investigated the physico-chemical and diatom compositions of a set of 101 lakes with a variety of different origins in central Yakutia (Eastern Siberia), including thermokarst lakes, fluvial-erosion thermokarst lakes, fluvial-erosion lakes, and dune lakes. We found a significant relationship between lake genesis and the present-day variability in environmental and diatom characteristics, as revealed by multi-response permutation procedures, indicator species analyses, and redundancy analyses. Environmental parameters also exhibit a significant correlation with variations in the diatom data, for which they may have been to a substantial extent responsible. Mg and SO4 concentrations, together with pH and water depth, were identified as the most important parameters, influencing the variations in the diatom data almost as much as the entire environmental parameter set. We were therefore able to establish a robust Mg-diatom transfer function, which was then applied to three Holocene lake records. From these reconstructions, together with a general interpretation of the diatom record (including, e.g., the ratio between benthic/epiphytic and planktonic taxa), we have been able to infer that all three of these lakes show (1) a continuous record with no desiccation events, (2) high lake water-levels during the early Holocene, (3) centennial to millennial scale variability, and (4) high levels of variability during the early Holocene but rather stable conditions during the late Holocene (a feature that is also known from other sites around the world). We therefore concluded that the development of these three lakes was mainly driven directly by the climate, rather than by thaw lake cycling. Abstract Copyright (2012) Elsevier, B.V.
13022857 Bhreasail, A. Ní (Imperial College London, Department of Civil and Environmental Engineering, London, United Kingdom); Lee, P. D.; O'Sullivan, C.; Fenton, C. H.; Hamilton, R.; Rockett, P. and Connolley, T. In-situ observation of cracks in frozen soil using synchrotron tomography: Permafrost and Periglacial Processes, 23(2), p. 170-176, illus., 29 ref., June 2012.
Phase-contrast synchrotron micro-computed tomography (mCT) is well suited to studying the microstructure of frozen soil. To take advantage of the high-resolution three-dimensional images that can be generated using mCT, a specialized in-situ rig was designed and commissioned. This miniature temperature-controlled odometer is capable of controlling soil sample thermal gradients and applying uniaxial deformation while measuring stress. This system was used to apply repeated freeze-thaw cycles to water-saturated samples of Leighton Buzzard sand, Reigate sand and spherical glass ballotini (an idealized soil). High-resolution images were obtained using a monochromatic, parallel beam of x-rays generated on Beamline I12 of the Diamond Synchrotron. Cracking in the ice was directly measured utilizing the phase-contrast fringes generated by ice-air interfaces. Examination of these images revealed two modes of crack formation in the ice phase of frozen soil: micro-cracks between soil particles, and longer, well-developed cracks that follow along ice-soil particle boundaries and span across the ice between particles. Both crack types were orientated parallel to the freezing front (normal to the heat flow), affecting both the frozen soils' mechanical behavior, and we hypothesize that these cracks are potential initiation sites for ice lens development. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022852 Dugan, Hilary A. (University of Illinois at Chicago, Department of Earth and Environmental Sciences, Chicago, IL); Lamoureux, Scott F.; Lewis, Ted and Lafrenière, Melissa J. The impact of permafrost disturbances and sediment loading on the limnological characteristics of two High Arctic lakes: Permafrost and Periglacial Processes, 23(2), p. 119-126, illus. incl. 2 tables, sketch map, 18 ref., June 2012.
The physical and chemical characteristics of two High Arctic lakes were investigated at the Cape Bounty Arctic Watershed Observatory on Melville Island, in response to large active-layer detachments generated by extreme summer temperatures in 2007. In the two years following the permafrost disturbances, there was an elevated loading of total dissolved solids into both lakes, but no concomitant increase in suspended sediment levels. The physical dynamics of one lake were significantly altered by an internal sediment input, which was not directly related to watershed processes. The results indicate that localized permafrost disturbance in the watersheds resulted in changes to chemical conditions in these relatively deep, large lakes, while increased sediment transport from disturbances did not have a sustained impact. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022851 Iwahana, Go (Hokkaido University, Sapporo, Japan); Fukui, Kotaro; Mikhailov, Nikolai; Ostanin, Oleg and Fujii, Yoshiyuki. Internal structure of a lithalsa in the Akkol Valley, Russian Altai Mountains: Permafrost and Periglacial Processes, 23(2), p. 107-118, illus. incl. 1 table, sketch map, 41 ref., June 2012.
Perennial frost mounds are present near the edges of ponds located on the terrace between the mountain flank and a valley-bottom lake in the Akkol Valley of the Russian Altai Mountains. These mounds are 10-50 m in diameter and 3-6 m in height. We describe one mound, identified as a lithalsa, which had been eroded so as to expose almost its entire vertical cross-section, revealing its internal structure. The frozen core consisted mainly of soil segments suspended in reticulate ice lenses with a mean thickness of 11-48 mm and a maximum thickness of about 160 mm. The shapes of the soil segments matched their neighbors. Other features included soil segments suspended in the ice veins shaped like "En echelon gash veins", and the presence of a radial structure of ice-rich and sediment-rich frozen bands. These features all suggest the greater importance of a differential stress field during heaving of the mound and after ice segregation, compared to the thermal gradient and water supply. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022855 Killingbeck, James (University of Saint Andrews, School of Geography and Geosciences, Saint Andrews, United Kingdom) and Ballantyne, Colin K. Earth hummocks in west Dartmoor, SW England; characteristics, age and origin: Permafrost and Periglacial Processes, 23(2), p. 152-161, illus. incl. geol. sketch map, 48 ref., June 2012.
Extensive fields of vegetated, dome-shaped earth hummocks 5-35 cm high and typically 80-200 cm in diameter occur on slopes of up to 15° at elevations of 320-440 m asl on Dartmoor, SW England, but are limited to terrain underlain by metasedimentary rocks and dolerite, and absent from granite areas. Hummocks occur within archaeological sites, implying formation within the last ~ 3000 years and ruling out development over permafrost. The hummocks are composed of frost-susceptible silty soil (modal grain size 10-100 mm) with occasional clasts, but exhibit no evidence for cryoturbation or diapirism. Hummock size and spacing are fairly consistent at particular sites but vary between sites. Hummock age, distribution and characteristics are incompatible with non-frost action origins and most proposed frost action origins (cryostatic pressure, soil circulation, permafrost aggradation, soil injection), but regular spacing and granulometry favor initiation by differential frost heave under conditions of periodic shallow (0.2-0.4 m) seasonal ground freezing. We suggest that hummock growth may reflect migration of silt in advance of inclined freezing planes until equilibrium is achieved with soil loss down hummock sides. Our results confirm that hummock formation by frost action occurs on silty soils in humid cool temperate climates with only limited seasonal frost penetration. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022850 Utting, Nicholas (University of Ottawa, Department of Earth Science, Ottawa, ON, Canada); Clark, Ian; Lauriol, Bernard; Wieser, Martin and Aeschbach-Hertig, Werner. Origin and flow dynamics of perennial groundwater in continuous permafrost terrain using isotopes and noble gases; case study of the Fishing Branch River, northern Yukon, Canada: Permafrost and Periglacial Processes, 23(2), p. 91-106, illus. incl. 6 tables, geol. sketch map, 45 ref., June 2012.
Perennially flowing groundwater discharges along a 15-km section of the Fishing Branch River, Yukon causing open water during winter and numerous discrete springs near Bear Cave Mountain. Groundwater flow occurs in karstified marine carbonate rocks as well as in alluvial river talik(s). The PCO2 and d13C indicate groundwater dissolves CO2 during recharge in organic soils and weathers limestone in the aquifer. These analyses show three groundwater chemistry groups and variability in surface water chemistry. The variations in water chemistry are related to differences in the rocks exposed in the recharge area. The d18O and d2H results show that groundwater represents approximately the annual average of precipitation based on samples collected in the region. Noble gases were used to determine that the recharge temperature lies between 0 and 5 °C which suggests that recharge happens during the summer. Groundwater ages, calculated using 3H-3He dating, were found to be between 0 and 17.7 years. River discharge was measured during spring and summer under different water-level conditions. Winter baseflow was calculated based on summer discharge measurements and the width of the river channel in winter. Although river flow decreases in winter, groundwater discharge maintains open water. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022853 Vespremeanu-Stroe, Alfred (Bucharest University, Faculty of Geography, Bucharest, Romania); Urdea, Petru; Popescu, Razvan and Vasile, Mirela. Rock glacier activity in the Retezat Mountains, Southern Carpathians, Romania: Permafrost and Periglacial Processes, 23(2), p. 127-137, illus. incl. 2 tables, sketch maps, 37 ref., June 2012.
Thermal conditions in seven rock glaciers (RGs) in the Retezat Mountains were examined using ground surface temperature, the bottom temperature of snow (BTS) and late-summer water temperature at springs. Direct current resistivity profiles were used to detect ice-rich layers and to estimate RG volume. These parameters were supplemented by measurements of RG surface movement and morphological characteristics in order to develop a RG typology. RG activity is suggested based on BTS values and the mean annual surface temperature. The lower altitudinal limits for permafrost occurrence and the activity of RGs were found to be at 2000 m and 2100 m asl, respectively. The two highest and most active RGs are younger than 8 ka and developed following a cold climate event at 8.2 ka when a last isolated glacial episode occurred in their hosting cirques, while the remaining RGs date from 11.5-8.7 ka. Calculated rockwall denudation rates to produce these forms range from 0.8-1.1 mm/yr. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022856 Wu Xiaodong (Chinese Academy of Sciences, Cryosphere Research Station on the Qinghai-Tibetan Plateau, Lanzhou, China); Zhao Lin; Chen Meijun; Fang Hongbing; Yue Guangyang; Chen Ji; Pang Qiangqiang; Wang Zhiwei and Ding Yongjian. Soil organic carbon and its relationship to vegetation communities and soil properties in permafrost areas of the central western Qinghai-Tibet Plateau, China: Permafrost and Periglacial Processes, 23(2), p. 162-169, illus. incl. 4 tables, sketch map, 30 ref., June 2012.
Soil organic carbon (SOC) contents were examined beneath two grassland vegetation communities and cold desert sites in permafrost areas of the central western part of the Qinghai-Tibet Plateau. Mean SOC stocks in the top 150 cm were 7.73 kg m-2 for Stipa roborowskyi communities and 3.72 kg m-2 for Carex moorcroftii communities, but only 1.84 kg m-2 for cold alpine desert. More than 80 per cent of SOC stocks beneath the grasslands were in the top 100 cm. Correlation analyses showed that SOC stocks in the top 150 cm are linked to soil moisture content, and the vertical distribution of SOC is mainly affected by depth and soil moisture content. Moisture content and vegetation communities are therefore important factors associated with SOC content in this cold, arid area, while active-layer thickness, vegetation cover and topographical factors play non-significant roles in SOC distribution. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13022854 Zenklusen Mutter, Evelyn (WSL Institute for Snow and Avalanche Research, Davos Dorf, Switzerland) and Phillips, Marcia. Active layer characteristics at ten borehole sites in Alpine permafrost terrain, Switzerland: Permafrost and Periglacial Processes, 23(2), p. 138-151, illus. incl. 4 tables, sketch map, 55 ref., June 2012.
This study investigates and compares active layer characteristics determined from ground temperature measurements at ten borehole sites in various types of Alpine permafrost terrain. Active layer thickness (ALT) remained fairly constant at the individual boreholes over the past five to 14 years, but was highly variable among the sites due to local terrain characteristics. To allow intra-site comparisons, a characteristic depth within the active layer was determined for each site. The temperature series either measured or interpolated for that depth were used to investigate different thermal stages during the annual thawing and refreezing cycle. The relation between air temperature thawing-degree days and ALT was investigated on an annual, seasonal and daily basis. The results show that at least daily data are required to establish the relevant characteristics of active layer development. Periods of slow advance of the thaw plane, interpreted as being due to the presence of ice-bearing layers within the active layer, are particularly important to the final ALT. Rapid active layer deepening, however, can occur due to the formation of taliks caused by lateral thermal disturbances below the active layer. Abstract Copyright (2010), John Wiley & Sons, Ltd.
13024808 Pontefract, Alexandra (University of Western Ontario, Department of Earth Sciences, London, ON, Canada); Osinski, Gordon R.; Lindgren, Paula; Parnell, John; Cockell, Charles S. and Southam, Gordon. The effects of meteorite impacts on the availability of bioessential elements for endolithic organisms: Meteoritics & Planetary Science, 47(10), p. 1681-1691, illus. incl. 1 table, geol. sketch map, 48 ref., 2012. Supplemental information/data is available in the online version of this article.
Meteorite impacts, one of the most ubiquitous processes in the solar system, have the ability to destroy as well as create habitats for life. The impact process can increase the translucency and porosity of the target substrate, as well as mobilize biologically relevant elements within the substrate. For endolithic organisms, this process has important implications, especially in extreme environments where they are forced to seek refuge in the interior of rocks. Here, we show that unshocked target rocks and rocks that have experienced pressures up to about 80 GPa from the Haughton impact structure, Devon Island, Canada, possess a small, but discernible change in bulk chemistry within the major oxide analysis. However, changes in the distribution of elements did occur with increasing shock level for both the sedimentary and crystalline target. Both the crystalline and sedimentary target rocks contain significant amounts of glasses at higher shock levels (up to about 95% by volume), which would improve the availability of these elements to potential microbial endoliths as glasses are more easily dissolved by organic acids. The implication that impact events do not impoverish their capacity to serve as a "substrate" through volatilization is important with respect to analogous impact structures on Mars. After the deleterious effects of the direct meteorite impact, any microorganisms on Mars would have benefited from the input of heat, the mobilization of a possible frozen groundwater system, as well as increased translucency, porosity, and trace nutrient availability of the target substrate.
13024747 Walker, Tony R. (Dillon Consulting, Halifax, NS, Canada). Properties of selected soils from the sub-arctic region of Labrador, Canada: Polish Polar Research, 33(3), p. 207-224, illus. incl. 13 tables, sketch map, 29 ref., 2012.
A total of 212 soil profiles were described and assessed for physical and chemical properties during July 2006 as part of an Ecological Land Classification study along the Churchill River in central Labrador. Two major soil types were found in the study area along the Churchill River: Podzols and Organic soils. Podzolic soils covered approximately 60% and Organic soils occurred in 24% of the study area. Approximately 15% of the study area was classified as rock and other unconsolidated material. Summary results and a sub-set of the following soil units (from 10 soil profiles) are presented here and were distinguished according to the Canadian System of Soil Classification (CSSC) (Soil Classification Working Group 1998): Orthic Humo-Ferric Podzol, Placic Ferro-Humic Podzol, Gleyed Humo-Ferric Podzol, Sombric Humo-Ferric Podzol, Gleyed Regosol and Orthic Luvic Gleysol. The basic properties of the soil units identified above included: (i) morphological descriptions of soil profiles with differentiated horizons; (ii) field-texture tests were used to determine classes and physical properties of sands, silts, loams and occurrence of mottles; and (iii) a range of soil chemical composition of different horizons (e.g., pH, total organic carbon [TOC] and select metal concentrations) which indicated no anthropogenic contamination above background concentrations in the area.
13026282 Lozhkin, Anatoly V. (Russian Academy of Sciences, Far East Branch, North East Interdisciplinary Science Research Center, Magadan, Russian Federation); Anderson, Patricia; Eisner, Wendy R. and Solomatkina, Tatiana B. Late glacial and Holocene landscapes of central Beringia: Quaternary Research, 76(3), p. 383-392, illus. incl. 3 tables, sketch map, 70 ref., November 2011.
New palynological and sedimentological data from St. Lawrence Island present a rare view into late-glacial and Holocene environments of the central Bering Land Bridge. The late glaciation was a time of dynamic landscape changes in south-central Beringia, with active thermokarst processes, including the formation and drainage of thaw lakes. The presence of such a wet, unstable substrate, if widespread, probably would have had an adverse impact on food sources and mobility for many of the large mammal populations. The establishment of Betula shrub tundra on the island suggests late-glacial summers that were warmer than present, consistent with regional paleoclimatic interpretations. However, the increasing proximity to the Bering Sea, as postglacial sea levels rose, modified the intensity of warming and prevented the establishment of deciduous forest as found in other areas of Beringia at this time. The mid- to late Holocene is marked by more stable land surfaces and development of Sphagnum and Cyperaceae peat deposits. The accumulation of organic deposits, decline of shrub Betula, and decrease in thermokarst disturbance suggest that conditions were cooler than the previous. A recent decline in peat accumulation at the study sites may relate to local geomorphology, but similar decreases have been noted for other arctic regions. Abstract Copyright (2011) Elsevier, B.V.
13020315 Andreev, Andrei A. (Alfred Wegener Institute for Polar and Marine Research, Research Unit Potsdam, Potsdam, Germany); Schirrmeister, Lutz; Tarasov, Pavel E.; Ganopolski, Andrey; Brovkin, Viktor; Siegert, Christine; Wetterich, Sebastian and Hubberten, Hans-Wolfgang. Vegetation and climate history in the Laptev Sea region (Arctic Siberia) during late Quaternary inferred from pollen records: in Beringia and beyond; papers celebrating the scientific career of Andrei Vladimirovich Sher, 1939-2008 (Edwards, Mary E., editor; et al.), Quaternary Science Reviews, 30(17-18), p. 2182-2199, illus. incl. 2 tables, sketch map, 124 ref., August 2011.
Paleoenvironmental records from a number of permafrost sections and lacustrine cores from the Laptev Sea region dated by several methods (14C-AMS, TL, IRSL, OSL and 230Th/U) were analyzed for pollen and palynomorphs. The records reveal the environmental history for the last ca 200 kyr. For interglacial pollen spectra, quantitative temperature values were estimated using the best modern analogue method. Sparse grass-sedge vegetation indicating arctic desert environmental conditions existed prior to 200 kyr ago. Dense, wet grass-sedge tundra habitats dominated during an interstadial ca 200-190 kyr ago, reflecting warmer and wetter summers than before. Sparser vegetation communities point to much more severe stadial conditions ca 190-130 kyr ago. Open grass and Artemisia communities with shrub stands (Alnus fruticosa, Salix, Betula nana) in more protected and moister places characterized the beginning of the Last Interglacial indicate climate conditions similar to present. Shrub tundra (Alnus fruticosa and Betula nana) dominated during the middle Eemian climatic optimum, when summer temperatures were 4-5°C higher than today. Early-Weichselian sparse grass-sedge dominated vegetation indicates climate conditions colder and dryer than in the previous interval. Middle Weichselian Interstadial records indicate moister and warmer climate conditions, for example, in the interval 40-32 kyr BP Salix was present within dense, grass-sedge dominated vegetation. Sedge-grass-Artemisia-communities indicate that climate became cooler and drier after 30 kyr BP, and cold, dry conditions characterized the Late Weichselian, ca 26-16 kyr BP, when grass-dominated communities with Caryophyllaceae, Asteraceae, Cichoriaceae, Selaginella rupestris were present. From 16 to 12 kyr BP, grass-sedge communities with Caryophyllaceae, Asteraceae, and Cichoriaceae indicate climate was significantly warmer and moister than during the previous interval. The presence of Salix and Betula reflect temperatures about 4°C higher than present at about 12-11 kyr BP, during the Allerod interval, but shrubs were absent in the Younger Dryas interval, pointing to a deterioration of climate conditions. Alnus fruticosa, Betula nana, Poaceae, and Cyperaceae dominate early Holocene spectra. Reconstructed absolute temperature values were substantially warmer than present (up to 12°C). Shrubs gradually disappeared from coastal areas after 7.6 kyr BP when vegetation cover became similar to modern. A comparison of proxy-based paleoenvironmental reconstructions with the simulations performed by an Earth system model of intermediate complexity (CLIMBER-2) show good accordance between the regional paleodata and model simulations, especially for the warmer intervals. Abstract Copyright (2011) Elsevier, B.V.
13020313 Kienast, Frank (Senckenberg Research Institute and Natural History Museum, Research Station for Quaternary Palaeontology, Weimar, Germany); Wetterich, Sebastian; Kuzmina, Svetlana A.; Schirrmeister, Lutz; Andreev, Andrei A.; Tarasov, Pavel E.; Nazarova, Larisa; Kossler, Annette; Frolova, Larisa and Kunitsky, Viktor V. Paleontological records indicate the occurrence of open woodlands in a dry inland climate at the present-day Arctic coast in western Beringia during the last interglacial: in Beringia and beyond; papers celebrating the scientific career of Andrei Vladimirovich Sher, 1939-2008 (Edwards, Mary E., editor; et al.), Quaternary Science Reviews, 30(17-18), p. 2134-2159, illus. incl. 7 tables, sketch map, 146 ref., August 2011.
Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleo-lake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch (Larix dahurica), tree alder (Alnus incana), birch and alder shrubs (Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13°C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4°C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5m above sea level and in a position where they should have been under sea during the Last Interglacial when the global sea level was 6-10m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence. Abstract Copyright (2011) Elsevier, B.V.
13020312 Schweger, Charles (University of Alberta, Department of Anthropology, Edmonton, AB, Canada); Froese, Duane G.; White, James M. and Westgate, John A. Pre-glacial and interglacial pollen records over the last 3 Ma from northwest Canada; why do Holocene forests differ from those of previous interglaciations?: in Beringia and beyond; papers celebrating the scientific career of Andrei Vladimirovich Sher, 1939-2008 (Edwards, Mary E., editor; et al.), Quaternary Science Reviews, 30(17-18), p. 2124-2133, illus. incl. 2 tables, sketch map, 82 ref., August 2011.
We synthesize pollen spectra from eleven dated stratigraphic sections from central and northern Yukon. Palaeomagnetic and tephra dating indicates the earliest assemblages, representing closed canopy Pinus and Picea forest, are middle-late Pliocene age. More open forest conditions, indicated by increased Poaceae and with evidence of permafrost, are dated at ca 3 Ma. While Pinus pollen is abundant at 3 Ma, it is reduced in records after 2.6 Ma, and subsequent Pleistocene interglacial forest records are repeatedly dominated by Picea, along with Alnus and small but significant amounts of Abies. Surface sample comparisons indicate that Abies was more widespread and abundant in past interglaciations than at present and that Middle-Pleistocene Picea-Abies forest grew in the northern Yukon Porcupine Basin, 500 km beyond modern Abies limits. In contrast, Pinus, which occurs today in southern and central Yukon, was not a significant component of these Pleistocene interglacial forests. Late-Holocene pollen assemblages with rare Abies and high Pinus are the most distinct in the past 2.6 Ma. Possible factors driving Holocene difference are paleoclimate, paludification, changes in megafaunal herbivory and an unusual fire regime. Anthropogenic burning is a factor unique to the Holocene, and if it is shown to be important in this case, it would challenge our notion of what constitutes boreal wilderness. Abstract Copyright (2011) Elsevier, B.V.
13020311 Zanina, Oksana G. (Russian Academy of Sciences, Institute of Physicochemical and Biological Problems in Soil Science, Pushchino, Russian Federation); Gubin, S. V.; Kuzmina, Svetlana A.; Maximovich, S. V. and Lopatina, D. A. Late-Pleistocene (MIS 3-2) palaeoenvironments as recorded by sediments, palaeosols, and ground-squirrel nests at Duvanny Yar, Kolyma Lowland, northeast Siberia: in Beringia and beyond; papers celebrating the scientific career of Andrei Vladimirovich Sher, 1939-2008 (Edwards, Mary E., editor; et al.), Quaternary Science Reviews, 30(17-18), p. 2107-2123, illus. incl. 4 tables, sketch map, 64 ref., August 2011.
A detailed study of the Duvanny Yar section in the Kolyma Lowland (Yakutia) provides the most extensive knowledge to date about late-Pleistocene soil formation processes and environments in the North-East Siberian Arctic. Late-Quaternary palaeoenvironmental changes were reconstructed using paleopedological data and a range of palaeoecological bio-indicators (palynomorphs, plant macrofossils and insects). The frozen sediments representing marine isotope stage 3 (MIS-3), which encompasses the Karginsky interstadial, include profiles of four palaeosols of different ages. The oldest palaeosol is early Karginskian, and three overlying soil horizons represent a late-Karginskian pedocomplex. Palaeopedological data indicate a change of from synlithogenic soil formation processes to epigenic ones during these intervals. The intervening periods of synlithogenic pedogenesis were accompanied by active accumulation of eolian deposits. The Earlier Karginskian period of pedogenesis occurred in the absence of eolian sedimentation and when summer conditions were warm. The wide spectrum of peaty and peaty-gley soils observed in the late-Karginskian deposits developed under conditions of progressive cooling. The structure and content of fossil rodent burrows dated to approximately 30 000 yr BP from frozen late-Pleistocene deposits at Duvanny Yar indicate an arid and severe climate, a depth of active layer of 60-80 cm, and a wide distribution of disturbed habitats with pioneer and steppe vegetation. Abstract Copyright (2011) Elsevier, B.V.
13024758 Reyes, Alberto V. (University of Ablerta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada) and Cooke, Colin A. Northern peatland initiation lagged abrupt increases in deglacial atmospheric CH4: Proceedings of the National Academy of Sciences of the United States of America, 108(12), p. 4748-4753, illus. incl. sketch map, 48 ref., March 22, 2011. Supplemental information/data is available in the online version of this article.
Peatlands are a key component of the global carbon cycle. Chronologies of peatland initiation are typically based on compiled basal peat radiocarbon (14C) dates and frequency histograms of binned calibrated age ranges. However, such compilations are problematic because poor quality 14C dates are commonly included and because frequency histograms of binned age ranges introduce chronological artefacts that bias the record of peatland initiation. Using a published compilation of 274 basal 14C dates from Alaska as a case study, we show that nearly half the 141C dates are inappropriate for reconstructing peatland initiation, and that the temporal structure of peatland initiation is sensitive to sampling biases and treatment of calibrated 14C dates. We present revised chronologies of peatland initiation for Alaska and the circumpolar Arctic based on summed probability distributions of calibrated 14C dates. These revised chronologies reveal that northern peatland initiation lagged abrupt increases in atmospheric CH4 concentration at the start of the Bolling-Allerod interstadial (Termination 1A) and the end of the Younger Dryas chronozone (Termination 1B), suggesting that northern peatlands were not the primary drivers of the rapid increases in atmospheric CH4. Our results demonstrate that subtle methodological changes in the synthesis of basal 14C ages lead to substantially different interpretations of temporal trends in peatland initiation, with direct implications for the role of peatlands in the global carbon cycle.
13024269 Böhlert, Ralph (University of Zurich, Department of Geography, Zurich, Switzerland); Compeer, Michael; Egli, Markus; Brandova, Dagmar; Maisch, Max; Kubik, Peter W. and Haeberli, Wilfried. A combination of relative-numerical dating methods indicates two high alpine rock glacier activity phases after the glacier advance of the Younger Dryas: The Open Geography Journal, 4, p. 115-130, illus. incl. 4 tables, geol. sketch map, 71 ref., 2011.
To exploit the potential of rock glaciers as indicators of past climate condition it is first necessary to date them. The combined application of both relative and absolute dating techniques is a promising approach. In this study, we present Schmidt-hammer rebound value measurements and weathering rind thicknesses on four active and one relict rock glacier in the Albula area of the eastern Swiss Alps. Associated landforms such as the moraines in front of rock glaciers and glacially polished bedrock also were used to set up the temporal framework. This was done using soil chemical analyses, radiocarbon dating of the stable fraction of soil organic matter and surface exposure dating of boulders. Schmidt-hammer and weathering rind measurements showed, in most cases, well-pronounced trends with increasing surface ages. These values are in line with measurements from other nearby rock glaciers with comparable lithologies. Use of this information together with the numeric ages makes it possible to derive two main activity phases: one started soon after the ice retreat following the Younger Dryas, the main activity occurred most likely in the early Holocene and lasted approximately until the Holocene climate optimum. The second activity phase continues today and had an unclear start between 10 to 6 cal ky BP.
13024566 Francani, Vincenzo (Politecnico di Milano, DIIAR, Milan, Italy); Gattinoni, Paola and Rampazzo, Raffaele. Conseguenze del cambiamento climatico sull'assetto idrogeologico delle aree peroglaciali--Slope instability triggered by climate change in periglacial areas: Italian Journal of Engineering Geology and Environment (Testo Stampato), 11(2), p. 39-62, (Italian, English), illus. incl. 4 tables, sketch map, 60 ref., 2011.
The paper deals with slope instabilities triggered by the thaw of mountain permafrost related to climate change. Warming-induced permafrost degradation is likely to lead an increasing in scale and frequency of slope failures and may cause thaw settlement damages to foundations. At the same time, human settlements, infrastructural development and tourism in high mountain areas are expanding, which intensifies permafrost-related risks. The aim of the study was the understanding of the geomorphologic and climatic critical characteristics, through a hydrogeological and geomechanical modeling of mountain slopes interested by thawing permafrost. At this aim, the typical features of the areas exposed to thawing permafrost-related slope instabilities were identified, with reference to a specific study area located in Italian Alps (Valmalenco, Sondrio District). Thus, considering different permafrost typology, a hydrogeological and geomechanical modeling was carried out to simulate the tenso-deformative response of the slope and to point out the effects of thawing permafrost on stability, with particular attention to the definition of triggering thresholds and the identification of typical kinematisms. At this regard, modeling results showed that, because of the high water content, the kinematisms triggered by thawing permafrost are mostly debris flows and they are often concomitant with piping phenomena and liquefaction.
13024369 Leppala, Mirva (Finnish Forest Research Institute, Muhos, Finland); Laine, Anna M. and Tuittila, Eeva-Stiina. Winter carbon losses from a boreal mire succession sequence follow summertime patterns in carbon dynamics: Suo, 62(1), p. 1-11 (Finnish sum.), 42 ref., 2011.
Although carbon (C) gas exchange during the summer largely determines the annual C balance of mires, the wintertime fluxes cannot be ignored. Decomposition continues as long as the soil is not frozen and a proportion of the gases produced during summer are also released during winter. We measured carbon dioxide (CO2) and methane (CH4) fluxes along a successional mire sequence during two winters following growing seasons with divergent weather conditions. We studied the successional trends in wintertime C release in boreal mires, and quantified the contribution of wintertime C fluxes to annual fluxes. Wintertime CO2 and CH4 fluxes from the successional mire sequence were related to the flux rates during the previous summer. Average winter CO2 release along the successional sequence varied between 19.5 and 44.9 g CO2-C m-2 winter-1 (6-months), and accounted for 8-14% of the annual CO2 release. There was no clear successional trend in CO2 fluxes. Average winter CH4 release along the successional sequence varied between 0.20 and 7.29 CH4-C g m-2 winter-1 (6-months). The winter CH4 fluxes accounted for up to 38% of the annual CH4 emissions. Occasional CH4 uptake was detected at the younger successional stages during winter following the dry summer, while after the wet summer all sites emitted CH4. In general, most of the winter C losses were composed of CO2.
13022700 Niu, Guo-Yue (University of Texas at Austin, Department of Geological Sciences, Austin, TX); Yang, Zong-Liang; Mitchell, Kenneth E.; Chen, Fei; Ek, Michael B.; Barlage, Michael; Kumar, Anil; Manning, Kevin; Niyogi, Dev; Rosero, Enrique; Tewari, Mukul and Xia, Youlong. The community Noah land surface model with multiparameterization options (Noah-MP); 1, Model description and evaluation with local-scale measurements: Journal of Geophysical Research, 116(D12), Citation D12109, illus. incl. 1 table, 45 ref., 2011.
This first paper of the two-part series describes the objectives of the community efforts in improving the Noah land surface model (LSM), documents, through mathematical formulations, the augmented conceptual realism in biophysical and hydrological processes, and introduces a framework for multiple options to parameterize selected processes (Noah-MP). The Noah-MP's performance is evaluated at various local sites using high temporal frequency data sets, and results show the advantages of using multiple optional schemes to interpret the differences in modeling simulations. The second paper focuses on ensemble evaluations with long-term regional (basin) and global scale data sets. The enhanced conceptual realism includes (1) the vegetation canopy energy balance, (2) the layered snowpack, (3) frozen soil and infiltration, (4) soil moisture-groundwater interaction and related runoff production, and (5) vegetation phenology. Sample local-scale validations are conducted over the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) site, the W3 catchment of Sleepers River, Vermont, and a French snow observation site. Noah-MP shows apparent improvements in reproducing surface fluxes, skin temperature over dry periods, snow water equivalent (SWE), snow depth, and runoff over Noah LSM version 3.0. Noah-MP improves the SWE simulations due to more accurate simulations of the diurnal variations of the snow skin temperature, which is critical for computing available energy for melting. Noah-MP also improves the simulation of runoff peaks and timing by introducing a more permeable frozen soil and more accurate simulation of snowmelt. We also demonstrate that Noah-MP is an effective research tool by which modeling results for a given process can be interpreted through multiple optional parameterization schemes in the same model framework.
13024312 Ping, Chien-Lu (University of Alaska Fairbanks, School of Natural Resources and Agricultural Sciences, Palmer, AK); Michaelson, Gary J.; Guo, Laodong; Jorgenson, M. Torre; Kanevskiy, Mikhail; Shur, Yuri; Dou, Fugen and Liang, Jingjing. Soil carbon and material fluxes across the eroding Alaska Beaufort Sea coastline: Journal of Geophysical Research, 116(G2), Citation G02004, illus. incl. 4 tables, sketch maps, 44 ref., 2011.
Carbon, nitrogen, and material fluxes were quantified at 48 sampling locations along the 1957 km coastline of the Beaufort Sea, Alaska. Landform characteristics, soil stratigraphy, cryogenic features, and ice contents were determined for each site. Erosion rates for the sites were quantified using satellite images and aerial photos, and the rates averaged across the coastline increased from 0.6 m yr-1 during circa 1950-1980 to 1.2 m yr-1 during circa 1980-2000. Soils were highly cryoturbated, and organic carbon (OC) stores ranged from 13 to 162 kg OC m-2 in banks above sea level and averaged 63 kg OC m-2 over the entire coastline. Long-term (1950-2000) annual lateral fluxes due to erosion were estimated at -153 Gg OC, -7762 Mg total nitrogen, -2106 Tg solids, and -2762 Tg water. Total land area loss along the Alaska Beaufort Sea coastline was estimated at 203 ha yr-1. We found coastal erosion rates, bank heights, soil properties, and material stores and fluxes to be extremely variable among sampling sites. In comparing two classification systems used to classifying coastline types from an oceanographic, coastal morphology perspective and geomorphic units from a terrestrial, soils perspective, we found both systems were effective at differentiating significant differences among classes for most material stores, but the coastline classification did not find significant differences in erosion rates because it lacked differentiation of soil texture.
13024250 Stocker, Benjamin D. (University of Bern, Physics Institute, Climate and Environmental Physics, Bern, Switzerland); Strassmann, K. and Joos, Fortunat. Sensitivity of Holocene atmospheric CO2 and the modern carbon budget to early human land use; analyses with a process-based model: Biogeosciences, 8(1), p. 69-88, illus. incl. 2 tables, 101 ref., 2011. Published in Biogeosciences Discussion: 5 February 2010, URL: http://www.biogeosciences-discuss.net/7/921/2010/bgd-7-921-2010.html; accessed in Jan., 2012.
A Dynamic Global Vegetation model coupled to a simplified Earth system model is used to simulate the impact of anthropogenic land cover changes (ALCC) on Holocene atmospheric CO2 and the contemporary carbon cycle. The model results suggest that early agricultural activities cannot explain the mid to late Holocene CO2 rise of 20 ppm measured on ice cores and that proposed upward revisions of Holocene ALCC imply a smaller contemporary terrestrial carbon sink. A set of illustrative scenarios is applied to test the robustness of these conclusions and to address the large discrepancies between published ALCC reconstructions. Simulated changes in atmospheric CO2 due to ALCC are less than 1 ppm before 1000 AD and 30 ppm at 2004 AD when the HYDE 3.1 ALCC reconstruction is prescribed for the past 12 000 years. Cumulative emissions of 69 GtC at 1850 and 233 GtC at 2004 AD are comparable to earlier estimates. CO2 changes due to ALCC exceed the simulated natural interannual variability only after 1000 AD. To consider evidence that land area used per person was higher before than during early industrialisation, agricultural areas from HYDE 3.1 were increased by a factor of two prior to 1700 AD (scenario H2). For the H2 scenario, the contemporary terrestrial carbon sink required to close the atmospheric CO2 budget is reduced by 0.5 GtC yr-1. Simulated CO2 remains small even in scenarios where average land use per person is increased beyond the range of published estimates. Even extreme assumptions for preindustrial land conversion and high per-capita land use do not result in simulated CO2 emissions that are sufficient to explain the magnitude and the timing of the late Holocene CO2 increase.
13022724 Tape, Ken D. (University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Verbyla, David and Welker, Jeffrey M. Twentieth century erosion in Arctic Alaska foothills; the influence of shrubs, runoff, and permafrost: Journal of Geophysical Research, 116(G4), Citation G04024, illus. incl. 1 table, sketch map, 30 ref., 2011.
Recent changes in the climate of Arctic Alaska, including warmer summers and a lengthened growing season, have increased vegetation productivity and permafrost temperatures. In this study, we use (1) time series imagery to examine the landscape pattern of tall shrub distribution and expansion in Arctic Alaska and (2) lake sediments from watersheds where shrub expansion is occurring to compare twentieth century temporal trends between shrub cover, erosion, and runoff. Landsat thematic mapper data from 1986 and 2009 were used to evaluate the expansion of tall shrubs across three regional subscenes in the Arctic foothills in northeast Alaska. We found that tall shrubs occupied floodplains and streams in 1986 and have been expanding their coverage along these corridors. The interaction between shrub expansion and erosion was examined by reconstructing the last 60-100 years of erosion from sediment cores in four lakes with shrub expansion in the surrounding watersheds. Three of the four lake cores show a steadily increasing or fluctuating erosion rate until 1980, after which these cores show a synchronous decline. We postulate that the increase in shrubs since 1980 in landscape positions prone to erosion has contributed to the decline in erosion. A decrease in the magnitude and frequency of runoff events has likely also contributed to the decline in erosion. Our results indicate a general decline in erosion since 1980 that is contemporaneous with shrub expansion and peak runoff decline, punctuated by episodic erosion events in one of four catchments.
13024311 Watanabe, Shohei (Université Laval, Département de Biologie, Quebec City, QC, Canada); Laurion, Isabelle; Chokmani, Karem; Pienitz, Reinhard and Vincent, Warwick F. Optical diversity of thaw ponds in discontinuous permafrost; a model system for water color analysis: Journal of Geophysical Research, 116(G2), Citation G02003, illus. incl. 2 tables, sketch maps, 58 ref., 2011.
Permafrost thaw ponds result from the irregular melting and erosion of frozen soils, and they are active sites of greenhouse gas emissions to the atmosphere throughout the circumpolar North. In the discontinuous permafrost region of Nunavik, Canada, thaw ponds show pronounced differences in color even among nearby ponds, ranging from white to green, brown and black. To quantify this optical variation and to determine its underlying controlling mechanisms, we studied the apparent and inherent optical properties and limnological characteristics of the ponds. The pond colors were well separated on a color coordinate diagram, with axis values determined from above-water spectral reflectance measurements. Our analyses of optical properties and their empirical relationships with optically active substances showed that the differences in color could entirely be attributed to variations in the concentration of two optically active substances: dissolved organic carbon, which was a major contributor to spectral absorption, and nonalgal suspended particulate matter, which contributed to spectral scattering as well as absorption. The latter component was dominated by small sized particles that had unusually high mass-specific absorption and scattering properties. Analysis of high spatial resolution, multispectral satellite imagery of these ponds showed that these two optically important constituents could be estimated by multivariate modeling. The results indicate that remote sensing surveys will provide valuable synoptic observations of permafrost thaw ponds across the vast subarctic region, and may allow scaling up of local greenhouse gas flux measurements to regional and circumpolar scales.
13022701 Yang, Zong-Liang (University of Texas at Austin, John A. and Katherine G. Jackson School of Geosciences, Department of Geological Sciences, Austin, TX); Niu, Guo-Yue; Mitchell, Kenneth E.; Chen, Fei; Ek, Michael B.; Barlage, Michael; Longuevergne, Laurent; Manning, Kevin; Niyogi, Dev; Tewari, Mukul and Xia, Youlong. The community Noah land surface model with multiparameterization options (Noah-MP); 2, Evaluation over global river basins: Journal of Geophysical Research, 116(D12), Citation D12110, illus. incl. 3 tables, 34 ref., 2011.
The augmented Noah land surface model described in the first part of the two-part series was evaluated here over global river basins. Across various climate zones, global-scale tests can reveal a model's weaknesses and strengths that a local-scale testing cannot. In addition, global-scale tests are more challenging than local- and catchment-scale tests. Given constant model parameters (e. g., runoff parameters) across global river basins, global-scale tests are more stringent. We assessed model performance against various satellite and ground-based observations over global river basins through six experiments that mimic a transition from the original Noah LSM to the fully augmented version. The model shows transitional improvements in modeling runoff, soil moisture, snow, and skin temperature, despite considerable increase in computational time by the fully augmented Noah-MP version compared to the original Noah LSM. The dynamic vegetation model favorably captures seasonal and spatial variability of leaf area index and green vegetation fraction. We also conducted 36 ensemble experiments with 36 combinations of optional schemes for runoff, leaf dynamics, stomatal resistance, and the b factor. Runoff schemes play a dominant and different role in controlling soil moisture and its relationship with evapotranspiration compared to ecological processes such as the b factor, vegetation dynamics, and stomatal resistance. The 36-member ensemble mean of runoff performs better than any single member over the world's 50 largest river basins, suggesting a great potential of land-based ensemble simulations for climate prediction.
13023316 Sannel, A. Britta K. (Stockholm University, Department of Physical Geography and Quaternary Geology, Stockholm, Sweden) and Brown, Ian A. High-resolution remote sensing identification of thermokarst lake dynamics in a subarctic peat plateau complex: in International Polar Year (Derksen, Chris, editor; et al.), Canadian Journal of Remote Sensing (CD-ROM) = Journal Canadien de Télédétection (CD-ROM), 36(Suppl. 1), p. 26-40 (French sum.), illus. incl. 2 tables, geol. sketch map, 32 ref., 2010. compact disc.
13023022 Schramm, Herbert and Martens, Thomas. Permafrost, Phänomene im Bereich der unterpermischen Wirbeltierlagerstätte Bromacker bei Tambach-Dietharz (Thüringer Wald) [Permafrost, phenomenon in the area of the Lower Permian Bromacker vertebrate discovery site near Tambach-Dietharz, Thuringian Forest]: Beiträge zur Geologie von Thüringen. Neue Folge, 17, p. 231-238, 13 ref., 2010.
13026037 Thome, Karl N. Korrelation der marinen Gliederung des Bohrkerns V 28-239 mit nordwestdeutschen Eiszeitspuren [Correlation of the marine strata of borehole core V 28-239 with ice-age traces in northwestern Germany]: Decheniana, 163, p. 191-200, 23 ref., 2010.
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