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2017011363 Mu, C. C. (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Zhang, T. J.; Zhao, Q.; Guo, H.; Zhong, W.; Su, H. and Wu, Q. B. Soil organic carbon stabilization by iron in permafrost regions of the Qinghai-Tibet Plateau: Geophysical Research Letters, 43(19), p. 10,286-10,294, illus. incl. 1 table, geol. sketch map, 41 ref., October 16, 2016.
A close relationship exists between soil organic carbon (SOC) and reactive iron; however, little is known about the role of iron in SOC preservation in permafrost regions. We determined the amount of SOC associated with reactive iron phases (OC-Fe) in the permafrost regions of the Qinghai-Tibetan Plateau (QTP). The results showed that the percentage of OC-Fe ranged between 0.9% and 59.5% in the upper 30 cm of soil and that the OC-Fe represented 19.5 ± 12.3% of the total SOC pool. No clear vertical distribution pattern in OC-Fe was present in the upper 1 m of soil. Throughout the year, the OC-Fe accounted for relatively stable proportions of the total SOC pool. This study suggests that approximately 20% of SOC is a potential rusty OC pool in the permafrost regions of the QTP. Biogeochemical processes related to the reaction of iron may play important roles in soil carbon cycles in permafrost regions. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016GL070071
2017011822 Stapel, Janina G. (German Research Centre for Geoscience, Helmholtz Centre Potsdam, Potsdam, Germany); Schirrmeister, L.; Overduin, P. P.; Wetterich, S.; Strauss, J.; Horsfield, Brian and Mangelsdorf, K. Microbial lipid signatures and substrate potential of organic matter in permafrost deposits; implications for future greenhouse gas production: Journal of Geophysical Research: Biogeosciences, 121(10), p. 2652-2666, illus. incl. sketch maps, 87 ref., October 2016.
A terrestrial permafrost core from Buor Khaya in northern Siberia comprising deposits of Late Pleistocene to Early Holocene age has been investigated to characterize living and past microbial communities with respect to modern and paleoclimate environmental conditions and to evaluate the potential of the organic matter (OM) for greenhouse gas generation. Microbial life markers-intact phospholipids and phospholipid fatty acids-are found throughout the entire core and indicate the presence of living microorganisms also in older permafrost deposits. Biomarkers for past microbial communities (branched and isoprenoid glycerol dialkyl glycerol tetraether as well as archaeol) reveal links between increased past microbial activity and intervals of high OM accumulation accompanied by increased OM quality presumably caused by local periods of moister and warmer environmental conditions. Concentrations of acetate as an excellent substrate for methanogenesis are used to assess the OM quality with respect to microbial degradability for greenhouse gas production. For this purpose two acetate pools are determined: the pore water acetate and OM bound acetate. Both depth profiles reveal similarities to the OM content and quality indicating a link between the amount of the stored OM and the potential to provide substrates for microbial greenhouse gas production. The data suggest that OM stored in the permafrost deposits is not much different in terms of OM quality than the fresh surface organic material. Considering the expected increase of permafrost thaw due to climate warming, this implies a potentially strong impact on greenhouse gas generation from permafrost areas in future with positive feedback on climate variation. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016JG003483
2017013205 Han Tianding (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Station, Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Pu Hongzheng; Cheng Peng and Jiao Keqin. Hydrological effects of alpine permafrost in the headwaters of the Urumqi River, Tianshan Mountains: Sciences in Cold and Arid Regions, 8(3), p. 241-249, illus. incl. 1 table, sketch map, 23 ref., June 2016.
Against the background of climate change, alpine permafrost active layers have shown a gradual thickening trend and the hydrothermal conditions have undergone significant changes in the Tianshan Mountains and the Qinghai-Tibet Plateau, China. At the ice-free cirque basins in the headwaters of the Urumqi River (hereafter referred to as the Ice-Free Cirque) in eastern Tianshan, China, the hydrological effects of the alpine permafrost active layers appear to have also exhibited significant changes recently. The increasing trend of local precipitation is clear in May and June. The onset of winter and spring snowmelt runoff clearly lags behind increases of air temperature, and the runoff peak appears near the beginning of the melting season, which results in the spring runoff increasing. In summer, runoff decreases strongly and the maximum runoff occurs earlier. In our analysis of meteorological and hydrologic data from 1959 to 2010, the runoff and precipitation changes are significantly correlated. In the initial stage of runoff, the runoff-producing process is mainly under the control of the soil water content and soil temperature in the 0-30 cm active layers. Spring precipitation and snowmelt water are mainly involved in the processes of infiltration and evaporation while some melt water infiltrates into the seasonal thawed layer and stays above the frozen layers. During the strong ablation period in summer, the runoff-generating process is mainly controlled by soil water content in the active layers deeper than 60 cm. In the active layer, precipitation and seasonal snowmelt water infiltrates, migrates, collects, and then forms runoff.
DOI: 10.3724/SP.j.1226.2016.00241
2017010707 Ardelean, Adrian C. (West University of Timisoara, Department of Geography, Timisoara, Romania); Onaca, Alexandru L.; Urdea, Petru; Serban, Raul D. and Sirba, Flavius. A first estimate of permafrost distribution from BTS measurements in the Romanian Carpathians (Retezat Mountains): Géomorphologie: Relief, Processus, Environnement, 21(4), p. 297-312 (French sum.), illus. incl. 5 tables, geol. sketch maps, 68 ref., December 2015.
A first estimate of permafrost distribution in the central part of the Retezat Mountains (Southern Carpathians, Romania) was computed using basal temperature measurements of winter snow cover as input data for an empirical-statistical modelling approach. During the 2012-2013 winter season, a total of 170 bottom temperature of snow cover measurements (Haeberli, 1973) were made. The permafrost distribution within the investigated area was modelled based on multiple linear regression analysis of the relationship between bottom temperature of snow cover measurements and five predictor variables: elevation, solar radiation, vegetation cover, slope and profile curvature. The final model, having an overall accuracy of 0.48, included only the first three variables as the main factors controlling permafrost occurrence within the investigated area, while slope and profile curvature proved to be statistically insignificant. Permafrost occurrence, as predicted by the model, covers 31 km2 (52% of the investigated area), of which 14 km2 is predicted as probable permafrost and the remaining 17 km2 is possible permafrost. The obtained results indicate the importance of solar radiation, elevation and vegetation cover in controlling alpine permafrost occurrence in the central part of the Retezat Mountains.
DOI: 10.4000/geomorphologie.11131
2017009378 Magnin, Florence (Université de Savoie, Laboratoire EDYTEM, Le Bourget du Lac, France); Brenning, Alexander; Bodin, Xavier; Deline, Philip and Ravanel, Ludovic. Modélisation statistique de la distribution du permafrost de paroi; application au massif du Mont Blanc [Statistical modelling of rock wall permafrost distribution; application to the Mont Blanc massif]: Géomorphologie: Relief, Processus, Environnement, 21(2), p. 145-162 (English sum.), illus. incl. 2 tables, geol. sketch maps, 60 ref., June 2015.
The study of rock wall permafrost has only started ten years ago. The understanding of the role of permafrost degradation in rock wall instabilities must be firstly based on the knowledge of its spatial distribution. The difficulties in mapping rock wall permafrost result as much from its invisibility as its extreme sensitivity to local settings. Thus its modelling becomes an essential tool. An empirico-statistical model built for the mapping of permafrost probability in the rock walls at an Alpine scale is here applied to the Mont Blanc massif, integrating local input variables with high spatial resolution. The importance of the spatial resolution for modelling rock wall permafrost is highlighted: differences in output temperature for the same model can reach up to 2°C between 4 m and 30 m spatial resolutions. A map of the permafrost in the massif rock walls is proposed. 45 to 79% of the 86 km2 of steep rock faces >&eq;40° would be underlain by permafrost. It would be present from 1900 m a.s.l in north faces and 2600 m in south faces in case of favourable local structural settings. Its presence would be more continuous from 2600 m and 3000 m, respectively, but it would occupy the totality of the rock walls, in any aspect from 3600 m a.s.l. The interpretation of the permafrost index map requires the understanding of the effects of factors that are not taken into account in the model and that favour its occurrence beyond the topoclimatic control, such as fractures and snow cover. The validation of distributed models of permafrost in rock walls, which is extremely variable in space and hardly accessible, is one of the current challenges.
DOI: 10.4000/geomorphologie.10965
2017014413 Heslop, Joanne (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Walter Anthony, Katey and Zhang, Mingchu. Utilizing pyrolysis GC-MS to characterize organic matter quality in relation to methane production in a thermokarst lake sediment core: Organic Geochemistry, 103, p. 43-50, illus. incl. 1 table, 71 ref., January 2017.
Thermokarst (thaw) lakes are an important source of atmospheric CH4; however, few studies have examined the composition and biodegradability of their sediment organic matter (OM). We have quantified the (i) composition of bulk sediment OM (bulk SOM) using pyrolysis gas chromatography-mass spectrometry (GC-MS) and (ii) statistical relationships between bulk SOM properties and anaerobic incubation CH4 production rate at 3 °C in sediment core samples from a thermokarst lake system. The study extended through the full vertically-thawed profile (0-550 cm) of Vault Lake, a small thermokarst lake near Fairbanks, Alaska, USA, and into the permafrost thawing beneath the lake (551-590 cm). Compared with the underlying mineral-dominated sediments (153-590 cm depth in core), the surface organic-rich sediment horizon (0-152 cm) had higher CH4 production rate, greater substrate availability indicated by percent organic carbon and total nitrogen, and greater proportions of terrestrially-associated bulk SOM compounds (alkanes, alkenes, lignin products, and phenols and phenolic precursors). Correlation and principal component analyses indicated that CH4 production potential values measured in the core were positively associated with initial substrate availability and terrestrially-derived OM compounds. We observed positive correlation (p ≤&eq; 0.05) between CH4 production and bulk SOM compounds classified as phenols and phenolic precursors, a pattern different from previously observed relationships in natural aquatic anaerobic environments.
DOI: 10.1016/j.orggeochem.2016.10.013
2017011828 Pirk, Norbert (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Tamstorf, Mikkel P.; Lund, Magnus; Mastepanov, Mikhail; Pedersen, Stine H.; Mylius, Maria R.; Parmentier, Frans-Jan W.; Christiansen, Hanne H. and Christensen, Torben R. Snowpack fluxes of methane and carbon dioxide from high Arctic tundra: Journal of Geophysical Research: Biogeosciences, 121(11), p. 2886-2900, illus., 66 ref., November 2016.
Measurements of the land-atmosphere exchange of the greenhouse gases methane (CH4) and carbon dioxide (CO2) in high Arctic tundra ecosystems are particularly difficult in the cold season, resulting in large uncertainty on flux magnitudes and their controlling factors during this long, frozen period. We conducted snowpack measurements of these gases at permafrost-underlain wetland sites in Zackenberg Valley (NE Greenland, 74°N) and Adventdalen Valley (Svalbard, 78°N), both of which also feature automatic closed chamber flux measurements during the snow-free period. At Zackenberg, cold season emissions were 1 to 2 orders of magnitude lower than growing season fluxes. Perennially, CH4 fluxes resembled the same spatial pattern, which was largely attributed to differences in soil wetness controlling substrate accumulation and microbial activity. We found no significant gas sinks or sources inside the snowpack but detected a pulse in the d13C-CH4 stable isotopic signature of the soil's CH4 source during snowmelt, which suggests the release of a CH4 reservoir that was strongly affected by methanotrophic microorganisms. In the polygonal tundra of Adventdalen, the snowpack featured several ice layers, which suppressed the expected gas emissions to the atmosphere, and conversely lead to snowpack gas accumulations of up to 86 ppm CH4 and 3800 ppm CO2 by late winter. CH4 to CO2 ratios indicated distinctly different source characteristics in the rampart of ice-wedge polygons compared to elsewhere on the measured transect, possibly due to geomorphological soil cracks. Collectively, these findings suggest important ties between growing season and cold season greenhouse gas emissions from high Arctic tundra. Abstract Copyright (2016), . The Authors.
DOI: 10.1002/2016JG003486
2017011824 Street, Lorna E. (Heriot-Watt University, School of Life Sciences, Edinburgh, United Kingdom); Dean, Joshua F.; Billett, Michael F.; Baxter, Robert; Dinsmore, Kerry J.; Lessels, Jason S.; Subke, Jens-Arne; Tetzlaff, Doerthe and Wookey, Philip A. Redox dynamics in the active layer of an Arctic headwater catchment; examining the potential for transfer of dissolved methane from soils to stream water: Journal of Geophysical Research: Biogeosciences, 121(11), p. 2776-2792, illus. incl. 2 tables, sketch map, 70 ref., November 2016.
The linkages between methane production, transport, and release from terrestrial and aquatic systems are not well understood, complicating the task of predicting methane emissions. We present novel data examining the potential for the saturated zone of active layer soils to act as a source of dissolved methane to the aquatic system, via soil water discharge, within a headwater catchment of the continuous permafrost zone in Northern Canada. We monitored redox conditions and soil methane concentrations across a transect of soil profiles from midstream to hillslope and compare temporal patterns in methane concentrations in soils to those in the stream. We show that redox conditions in active layer soils become more negative as the thaw season progresses, providing conditions suitable for net methanogenesis and that redox conditions are sensitive to increased precipitation during a storm event-but only in shallower surface soil layers. While we demonstrate that methane concentrations at depth in the hillslope soils increase over the course of the growing season as reducing conditions develop, we find no evidence that this has an influence on stream water methane concentrations. Sediments directly beneath the stream bed, however, remain strongly reducing at depth throughout the thaw season and contain methane at concentrations 5 orders of magnitude greater than those in hillslope soils. The extent of substreambed methane sources, and the rates of methane transport from these zones, may therefore be important factors determining headwater stream methane concentrations under changing Arctic hydrologic regimes. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016JG003387
2017013203 Harris, Stuart A. (University of Calgary, Department of Geography, Calgary, AB, Canada). Identification, characteristics and classification of cryogenic block streams: Sciences in Cold and Arid Regions, 8(3), p. 177-186, illus. incl. 1 table, 49 ref., June 2016.
Cryogenic block streams consist of a stream of rocks superficially resembling a stream deposit but lacking a matrix, usually occurring on a valley or gully floor or on slopes that are less steep than the maximum angle of repose of coarse sediments. They are usually formed on perennially frozen ground, but can also occur as relict landforms. There are three main active kinds forming today, viz., Siberian and Tibetan dynamic rock streams and lag block streams. During their formation, the blocks in the active Siberian and Tibetan dynamic block streams move downslope at up to 1 m/a. They are forming today on the Tibetan Plateau and in the more arid parts of south-central Siberia, although the processes involved in the movement are different. In the case of the Tibetan type, individual blocks slide downslope over the substrate in winter on an icy coating in areas of minimal winter precipitation. The Siberian type develops in areas of 15-80 cm of winter snow cover and an MAAT (mean annual air temperature) of -4°C to -17°C. The movement is due to creep of snow and ice and collapse of the blocks downslope during thawing. Lag block streams are formed by meltwater flowing over the surface of sediment consisting primarily of larger blocks with a limited amount of interstitial sediment. The erosion of the matrix is primarily in the spring in areas of higher winter precipitation on 10°-30° slopes. The blocks remain stationary, but the interstitial sediment is washed out by strong seasonal flows of meltwater or rain to form an alluvial fan. The boulders undergo weathering and become more rounded in the process. Lag block streams can also develop without the presence of permafrost in areas with cold climates or glaciers. Block streams also occur as relict deposits in older deposits under various climatic regimes that are unsuitable for their formation today. An example of relict lag block streams with subangular to subrounded blocks occurs in gullies on the forested mountainsides at Felsen in Germany, and is the original "felsenmeer". Similar examples occur near Vitosha Mountain in Bulgaria. The "stone runs" in the Falkland Islands are examples of the more angular relict lag block streams. In both Tasmania and the Falkland Islands, they mask a more complex history, the underlying soils indicating periods of tropical and temperate soil formation resulting from weathering during and since the Tertiary Period. Block streams have also been reported from beneath cold-based glaciers in Sweden, and below till in Canada, and when exhumed, can continue to develop.
DOI: 10.3724/SP.J.1226.2016.00177
2017013094 Ivanov, A. L. (Dokuchayev Soil Science Institute, Moscow, Russian Federation); Stolbovoy, V. S. and Savin, I. Yu. Soil resources of the Russian Arctic: Doklady Earth Sciences, 466(1), p. 105-107, illus. incl. 1 table, 6 ref., January 2016.
The soil cover of the Arctic zone of Russia is ~330 million hectares. Permafrost restricts the thickness of the active layer but does not prevent the formation of significant diversity of soils and soil complexes, including Al-Fe humic and peat soils, gleysols, and others. The available data on soil resources are sufficient for organization and participation of Russia in scientific-practical international programs. At the same time, specific soil related targets and project tasks may require additional study of soils of the Arctic region. Copyright 2016 Pleiades Publishing, Ltd.
DOI: 10.1134/S1028334X16010220
2017013087 Nikiforov, S. L. (Russian Academy of Sciences, Shirshov Institute of Oceanology, Moscow, Russian Federation); Lobkovskii, L. I.; Dmitrevskii, N. N.; Ananiev, R. A.; Sorokhtin, N. O.; Khortov, A. V. and Bogdanova, O. Yu. Expected geological and geomorphological risks along the Northern Sea Route: Doklady Earth Sciences, 466(1), p. 75-77, illus., 5 ref., January 2016.
Degradation of the underwater multiyear permafrost rocks (UMPR) together with intensification of thermal abrasion processes in the coasts are global risks on a planetary scale. Changes in the physical properties of sediments can occur after degradation of the UMPR and can lead to unpredictable consequences especially in the regions of technical development. Drifting ice bottom exaration (ice plucking of bottom sediments), which is increasing based on the data of recent expeditions, is no less dangerous. These processes are hazardous for practically all types of activity. Copyright 2016 Pleiades Publishing, Ltd.
DOI: 10.1134/S1028334X1601013X
2017008767 Peng Xiaoqing (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Frauenfeld, Oliver W.; Cao Bin; Wang, Kang; Wang Huijuan; Su Hang; Huang Zhe; Yue Dongxia and Zhang Tingjun. Response of changes in seasonal soil freeze/thaw state to climate change from 1950 to 2010 across China: Journal of Geophysical Research: Earth Surface, 121(11), p. 1984-2000, illus. incl. 1 table, sketch maps, 70 ref., November 2016.
Variations in seasonal soil freeze/thaw state are important indicators of climate change and influence ground temperature, hydrological processes, surface energy, and the moisture balance. Previous studies mainly focused on the active layer and permafrost, while seasonally frozen ground research in nonpermafrost regions has received less attention. In this study, we investigate the response of changes in seasonal soil freeze/thaw state to changes in air temperatures by combining observations from more than 800 stations with gridded mean monthly air temperature data across China. The results show that mean annual air temperature (MAAT) increased statistically significantly by 0.29 ± 0.03°C/decade from 1967 to 2013, with greater warming on the Qinghai-Tibetan Plateau. There is a statistically significant decrease in the freeze/thaw cycle (FTC) at 0.39 ± 0.05 cycles/decade. In addition, there are strong negative correlations between FTC and MAAT. Estimating the soil freeze/thaw state classification based on the number of days in the month, we find that changes of mean annual area extent of seasonal soil freeze/thaw state decreased significantly for completely frozen (CF) ground, while the area extent of partially frozen (PF) and unfrozen (UF) ground both increased. Changes in mean monthly area extent of seasonal soil freeze/thaw state indicate that the extent of CF and UF area was decreasing and increasing, respectively. But for the extent of PF areas, both increasing and decreasing trends were observed. Quantifying the spatial pattern of the seasonal soil freeze/thaw, we find that CF and PF areas are located in northern China and the Tibetan Plateau from December to March, and UF areas are located in southern China. The variations of mean annual area extent departure of soil freeze/thaw states are consistent with MAAT changes in different land cover types across China. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016JF003876
2017013434 Gaglioti, Benjamin V. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AL); Mann, Daniel H.; Jones, Benjamin M.; Wooller, Matthew J. and Finney, Bruce P. High-resolution records detect human-caused changes to the boreal forest wildfire regime in interior Alaska: Holocene, 26(7), p. 1064-1074, illus. incl. 1 table, sketch map, 77 ref., July 1, 2016.
Stand-replacing wildfires are a keystone disturbance in the boreal forest, and they are becoming more common as the climate warms. Paleo-fire archives from the wildland-urban interface can quantify the prehistoric fire regime and assess how both human land-use and climate change impact ecosystem dynamics. Here, we use a combination of a sedimentary charcoal record preserved in varved lake sediments (annually layered) and fire scars in living trees to document changes in local fire return intervals (FRIs) and regional fire activity over the last 500 years. Ace Lake is within the boreal forest, located near the town of Fairbanks in interior Alaska, which was settled by gold miners in AD 1902. In the 400 years before settlement, fires occurred near the lake on average every 58 years. After settlement, fires became much more frequent (average every 18 years), and background charcoal flux rates rose to four times their preindustrial levels, indicating a region-wide increase in burning. Despite this surge in burning, the preindustrial boreal forest ecosystem and permafrost in the watershed have remained intact. Although fire suppression has reduced charcoal influx since the 1950s, an aging fuel load experiencing increasingly warm summers may pose management problems for this and other boreal sites that have similar land-use and fire histories. The large human-caused fire events that we identify can be used to test how increasingly common megafires may alter ecosystem dynamics in the future.
DOI: 10.1177/0959683616632893
2017008771 Fisher, David A. (University of Ottawa, Department of Earth Sciences, Ottawa, ON, Canada); Lacelle, Denis; Pollard, Wayne; Davila, Alfonso and McKay, Christopher P. Ground surface temperature and humidity, ground temperature cycles and the ice table depths in University Valley, McMurdo dry valleys of Antarctica: Journal of Geophysical Research: Earth Surface, 121(11), p. 2069-2084, illus. incl. 1 table, sketch map, 47 ref., November 2016.
In the upper McMurdo Dry Valleys, 90% of the measured ice table depths range from 0 to 80 cm; however, numerical models predict that the ice table is not in equilibrium with current climate conditions and should be deeper than measured. This study explored the effects of boundary conditions (air versus ground surface temperature and humidity), ground temperature cycles, and their diminishing amplitude with depth and advective flows (Darcy flow and wind pumping) on water vapor fluxes in soils and ice table depths using the REGO vapor diffusion model. We conducted a series of numerical experiments that illustrated different hypothetical scenarios and estimated the water vapor flux and ice table depth using the conditions in University Valley, a small high elevation valley. In situ measurements showed that while the mean annual ground surface temperature approximates that in the air, the mean annual ground surface relative humidity (>85%ice) was significantly higher than in the atmosphere (~50%ice). When ground surface temperature and humidity were used as boundary conditions, along with damping diurnal and annual temperature cycles within the sandy soil, REGO predicted that measured ice table depths in the valley were in equilibrium with contemporary conditions. Based on model results, a dry soil column can become saturated with ice within centuries. Overall, the results from the new soil data and modeling have implications regarding the factors and boundary conditions that affect the stability of ground ice in cold and hyperarid regions where liquid water is rare. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016JF004054
2017007469 Qin Yue (Tsinghua University, Department of Hydraulic Engineering, Beijing, China); Lei Huimin; Yang Dawen; Gao Bing; Wang Yuhan; Cong Zhentao and Fan Wenjie. Long term change in the depth of seasonally frozen ground and its ecohydrological impacts in the Qilian Mountains, northeastern Tibetan Plateau: Journal of Hydrology, 542, p. 204-221, illus. incl. 10 tables, sketch maps, 108 ref., November 2016.
Changes in seasonally frozen ground at high elevations under the effects of global warming and their ecohydrological impacts are important for understanding changes in regional water resources and ecosystems. This study estimates the spatio-temporal variability in the maximum thickness of seasonally frozen ground (MTSFG) in the Qilian Mountains in the northeastern Tibetan Plateau from 1960 to 2014 by using a variant of the Stefan solution. The present study analyzes changes in streamflow and vegetation to reveal the ecohydrological impacts of changes in the MTSFG. Results indicate that the MTSFG shows a mean decreasing trend of 7.4 cm/10a in the past 55 years in correspondence to the significantly increasing air temperature (0.34 °C/10a). The greatest decreasing trend of the MTSFG is at elevations of 3400-3800 m. The annual baseflow has increased significantly in most of the sub-basins for which the increasing precipitation is the main factor. The MTSFG is another major factor for the increase in baseflow during the cold season (from November to April) according to the results of gray relational analysis. The leaf area index (LAI) during the growing season has increased by 0.045/10a since 2000, and the start of growing season has advanced by 1.8-2.1 d/10a at elevations of 3000-3800 m, where the vegetation cover is the densest. Furthermore, results of correlation analysis show that the topsoil moisture increases with the MTSFG decreases. Results of gray relational analysis show that the decrease in MTSFG is the main reason for the advancing green-up dates and increasing LAI in the initial period of the growing season. Our results show that the ecohydrological processes are changing along with frozen soil degradation in the northeastern Tibetan Plateau.
DOI: 10.1016/j.jhydrol.2016.09.008
2017008773 van Pelt, Ward J. J. (Uppsala University, Department of Earth Sciences, Uppsala, Sweden); Kohler, J.; Liston, G. E.; Hagen, J. O.; Luks, B.; Reijmer, C. H. and Pohjola, V. A. Multidecadal climate and seasonal snow conditions in Svalbard: Journal of Geophysical Research: Earth Surface, 121(11), p. 2100-2117, illus. incl. sketch maps, 60 ref., November 2016.
Svalbard climate is undergoing amplified change with respect to the global mean. Changing climate conditions directly affect the evolution of the seasonal snowpack, through its impact on accumulation, melt, and moisture exchange. We analyze long-term trends and spatial patterns of seasonal snow conditions in Svalbard between 1961 and 2012. Downscaled regional climate model output is used to drive a snow modeling system (SnowModel), with coupled modules simulating the surface energy balance and snowpack evolution. The precipitation forcing is calibrated and validated against snow depth data on a set of glaciers around Svalbard. Climate trends reveal seasonally inhomogeneous warming and a weakly positive precipitation trend, with strongest changes in the north. In response to autumn warming the date of snow onset increased (2 days decade-1), whereas in spring/summer opposing effects cause a nonsignificant trend in the snow disappearance date. Maximum snow water equivalent (SWE) in winter/spring shows a modest increase (+0.01 meters water equivalent (mwe) decade-1), while the end-of-summer minimum snow area fraction declined strongly (from 48% to 36%). The equilibrium line altitude is highest in relatively dry inland regions, and time series show a clear positive trend (25 m decade-1) as a result of summer warming. Finally, rain-on-snow in the core winter season, affecting ground ice formation and limiting access of grazing animals to food supplies, peaks during specific years (1994, 1996, 2000, and 2012) and is found to be concentrated in the lower lying coastal regions in southwestern Svalbard. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016JF003999
2017008654 Peng Zhenyang (Wuhan University, State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan, China); Tian Fuqiang; Wu Jingwei; Huang Jiesheng; Hu Hongchang and Darnault, Christophe J. G. A numerical model for water and heat transport in freezing soils with nonequilibrium ice-water interfaces: Water Resources Research, 52(9), p. 7366-7381, illus. incl. 3 tables, 57 ref., September 2016.
A one-dimensional numerical model of heat and water transport in freezing soils is developed by assuming that ice-water interfaces are not necessarily in equilibrium. The Clapeyron equation, which is derived from a static ice-water interface using the thermal equilibrium theory, cannot be readily applied to a dynamic system, such as freezing soils. Therefore, we handled the redistribution of liquid water with the Richard's equation. In this application, the sink term is replaced by the freezing rate of pore water, which is proportional to the extent of supercooling and available water content for freezing by a coefficient, b. Three short-term laboratory column simulations show reasonable agreement with observations, with standard error of simulation on water content ranging between 0.007 and 0.011 cm3 cm-3, showing improved accuracy over other models that assume equilibrium ice-water interfaces. Simulation results suggest that when the freezing front is fixed at a specific depth, deviation of the ice-water interface from equilibrium, at this location, will increase with time. However, this deviation tends to weaken when the freezing front slowly penetrates to a greater depth, accompanied with thinner soils of significant deviation. The coefficient, b, plays an important role in the simulation of heat and water transport. A smaller b results in a larger deviation in the ice-water interface from equilibrium, and backward estimation of the freezing front. It also leads to an underestimation of water content in soils that were previously frozen by a rapid freezing rate, and an overestimation of water content in the rest of the soils. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.
DOI: 10.1002/2016WR019116
2017012744 Vodyanitskii, Yu. N. (Lomonosov Moscow State University, Soil Science, Vorob'yevy gory, Russian Federation); Trofimov, S. Ya. and Shoba, S. A. The influence of Fe(III) on oil biodegradation in excessively moistened soils and sediments: Eurasian Soil Science, 48(7), p. 764-772, 50 ref., July 2015. Based on Publisher-supplied data.
Soils are self-purified from oil slowly, in the north, in particular, where hydromorphic conditions and low temperatures hinder the process. Oxidation of oil hydrocarbons depends on the type of electron acceptors and decreases in the following sequence: denitrification > Mn4+ reduction > Fe3+ reduction > sulfate reduction > methanogenesis. Usually, not all of these redox reactions develop in contaminated excessively moistened soils and sediments. Fe(III) reduction and methanogenesis are the most common: the latter is manifested near the contamination source, while the former develops in less contaminated areas. Fe reduction hinders the methanogenesis. In oil-contaminated areas, Fe reduction is also combined with sulfate reduction, the latter intensifying Fe reduction due to the formation of iron sulfides. Concurrently with oil degradation in excessively moistened soils and sediments, the composition of iron compounds changes due to the increasing Fe(II) share magnetite, as well as siderite and ferrocalcite (in calcareous deposits), and iron sulfides (in S-containing medium) are formed. Copyright 2015 Pleiades Publishing, Ltd.
DOI: 10.1134/S1064229315070121
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2017013640 Lininger, Katherine B. (Colorado State University, Department of Geosciences, Fort Collins, CO); Wohl, Ellen; Benshoof, Jessamyn and Rose, Joshua. The influence of channel migration rate and grain size on differences in floodplain organic carbon storage between two rivers in interior Alaska [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 36-4, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.
Research on the terrestrial carbon cycle has not adequately addressed floodplain organic carbon (OC) storage at timescales of 101-103 years. Floodplains provide a temporary storage area for sediment and associated OC, but many questions remain regarding differences in floodplain sediment OC storage across diverse river systems as a result of geomorphic influences. Rates of channel migration and floodplain erosion and the dominant grain size of the floodplain likely influence large-scale spatial patterns of floodplain OC storage and the residence time of floodplain sediment and OC. We present results of floodplain OC storage in sediment within the active layer of the floodplain along two rivers in interior Alaska: the Dall River (meandering single-thread) and Preacher Creek (multithread with braided channel characteristics). We expected the Dall River floodplain to have higher OC storage per unit area than Preacher Creek in part due to differences in rates of floodplain erosion and grain size. Floodplain OC storage was determined from sediment samples collected along transects at 5 sites along the Dall River (drainage areas 780 - 2720 km2), and 4 sites along Preacher Creek (drainage areas 1230 - 2780 km2). We estimated channel migration rates using aerial photos from the 1970s/1980s and 2011. We also used tree cores to estimate rates of channel migration, and we determined soil texture class of sediment as a measurement of dominant grain size. Average values of floodplain sediment OC along the Dall River and Preacher Creek are 243 and 176 Mg C ha-1, respectively, and the Preacher Creek dominant soil texture class is coarser than that of the Dall River. Segment-averaged rates of channel migration obtained via aerial photo analyses range from 0.08 to 0.4 m yr-1 for the Dall River and 1.9 to 2.6 m yr-1 for Preacher Creek. Rates of channel migration obtained through dendrochronology are slower and more uncertain than those found via aerial photo analysis. The smaller average value of OC storage per area along Preacher Creek is likely linked to the faster rate of floodplain turnover caused by channel migration and the differences in grain size. This work helps to constrain the large-scale spatial distribution of carbon storage within the landscape in interior Alaska, a region undergoing rapid climate change and permafrost thaw.
2017013641 Rowland, Joel C. (Los Alamos National Laboratory, Earth and Environmental Science Division, Los Alamos, NM); Muss, Jordan; Shelef, Eitan; Stauffer, Sophie J. and Sutfin, Nicholas A. Quantifying the export of floodplain soil carbon to Arctic rivers by bank erosion [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 36-5, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.
Recent efforts to quantify terrestrial carbon budgets highlight the importance of inland waters in the transport, loss to the atmosphere, and storage of carbon. Many of the estimates of carbon loss and storage along river systems are largely based on differencing the estimated input to rivers in headwaters from the outflows at measured at river mouths. However, studies of sediment exchange between river and floodplains, on systems large and small, have reported that the total amount of sediment being moved between river and floodplains can exceed the amount being discharged at the river mouth on an annual basis. This back and forth of sediment also likely impacts the storage, release and fate of particulate carbon in systems with floodplains. Here we present the results of a study that seeks to quantify the flux of soil carbon from floodplains into rivers across the Arctic. Using satellite imagery and aerial photography collected over 4 decades, we quantified rates of lateral floodplain erosion on approximately 5,000 km of rivers in 12 Arctic watersheds. An empirical model for lateral erosion rates was developed using topographic, climatological and permafrost distribution datasets. This model was then used to extrapolate erosion rates from the measured other sections of rivers across the Arctic. This extrapolation was restricted to only rivers with detectable alluvial floodplains. We then coupled these pan-Arctic erosion estimates with recently published maps of soil carbon across permafrost regions to quantify the annualized flux of soil carbon from the upper few meters of floodplains into rivers. Preliminary results indicate that annually tens of Terragrams (Tg) of carbon enter arctic rivers from their bounding floodplains. The fate of this carbon is presently unknown. Much of the carbon may be redeposited downstream or respired to the atmosphere. However, based on limited data of particulate carbon fluxes measured at the mouths of arctic rivers, it appears that more carbon is cycled between rivers and their floodplains than is exported to the ocean.
2017013419 Wiersberg, T. (GeoForschungsZentrum Potsdam, Potsdam, Germany) and Zimmer, M. Online monitoring of drilling mud gas in ICDP and IODP scientific drilling projects [abstr.]: in 35th international geological congress; abstracts, International Geological Congress, Abstracts = Congrès Géologique International, Résumés, 35, Abstract 3775, 11 ref., 2016. Meeting: 35th international geological congress, Aug. 27-Sept. 4, 2016, Cape Town, South Africa.
Continuous mud gas logging during drilling is a standard technique in oil and gas exploration since the late 1930s where it is used to to detect and validate pay horizons while drilling or coring. This technique has been modified to meet the demands of scientific drilling, e.g. sample and study the composition of crustal gases in sedimentary and crystalline formations [1]. Drilling mud that circulates in the borehole comprises air from surface, gaseous components that are mechanically released as the drill bit, including components present in the pore space of the crushed rock, and gas entering the borehole through permeable strata, either as free gas or, more likely, dissolved in liquids. At the surface, the gases are extracted from the mud in a gas-water separator and continuously pumped into a field laboratory for real time gas analysis and sampled for further studies e.g. on isotopes. Hydrocarbons, helium, radon and with limitations carbon dioxide and hydrogen are the most suitable gases for the detection of fluid-bearing horizons, shear zones, open fractures, sections of enhanced permeability. Off-site isotope studies on mud gas samples help reveal the origin, evolution, and migration mechanisms of deep-seated fluids. Beside its scientific value, the method has important applications aiding rapid decisions if and at what depth rock or fluid samples should be taken or formation testing should be performed. Until 2014, on-line mud gas monitoring was only applied in oilfield style rotary drilling. The Collisional Orogeny in the Scandinavian Caledonides (COSC) was the first project where it was successfully tested in wireline diamond coring. On-line gas monitoring of drilling mud has been proven being a reliable and inexpensive source of information on the composition and spatial distribution of fluids in the subsurface of fault zones, volcanoes and geothermal areas, permafrost regions, and other sedimentary and crystalline environments. It has been successfully applied on scientific drilling projects of the International Continental Scientific Drilling Program ICDP, the International Ocean Discovery Program IODP and other scientific drilling initiatives. On-line monitoring of fluids and gases from circulating drilling mud has been conducted in ten ICDP drilling projects in crystalline and sedimentary strata with a focus on fault zones (Corinth, Chelungpu, SAFOD, New Zealand [2-5]), volcanic systems (Unzen, Long Valley [6]), collision zones (Donghai, COSC [7]), and gas hydrates (Mallik). On-line drilling mud gas monitoring has also been applied on non-ICDP continental scientific drilling projects, e.g. the Wenchuan fault zone drilling [8], and INFLUINS Integrated Fluid Dynamics in Sedimentary Basins. After its successful introduction onboard the drilling vessel D/V Chikyu in 2009, it became a standard shipboard technique for IODP riser drilling operation and demonstrated its great value during fault zone drilling (Exp. 319, 338, 348 [9, 10]) and studies on the deep biosphere (Exp. 337 [11]).
URL: http://www.americangeosciences.org/sites/default/files/igc/3775.pdf
2017007677 Wise, Donald (University of Massachusetts, Department of Geosciences, Amherst, MA). Alternate origin of the Moon? Could big history be wrong? [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 165-1, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.
Big History lacks a credible lunar origin. Despite almost universal acceptance of giant impact models, no computer simulation has duplicated isotopic composition of lunar samples nor explained recent findings of trace water. One solution may be an upgraded 1960's scenario of core-driven fission. That Big History begins during late stages of planetary accretion when grazing merger of Proto-planet Theia spun Proto-Earth almost to its stability limit. Core/mantle segregation over the next ~50-100 m.y. finally drove whole body fission of asymmetric blobs, Moon and Vesta, each with Earth's primitive crust on one face and mantle on the other. Vesta escaped while Moon's umbilical cord collapsed as the Procellarum Basin. Moon's entrapment in close orbit allowed tidal resonance transfer of excess angular momentum to the Sun while tidal friction raised internal temperatures for a silicate atmosphere to engulf both bodies, volatiles to pass on to space, and basaltic magmas to spread new crust over both hemispheres. Doubled farside crust preserves original asymmetry with no need for a magma ocean. Escape to higher orbit ended that era at ~200 m.y., a zircon cooling age. Heavy bombardment for another 400 m.y, produced large basins and deep impact energy for another b.y. of mare lava flow. Subsequent slow global cooling formed minor thrust systems. Retrodictions test much of this scenario while radar may test its wet predictions with a sinuous rille model, substitute for a dry Moon's fatally flawed collapse of lava-tubes. Freezing regolith temperatures trap rising water vapor in shallow permafrost layers, hot volcanic gasses melt a migrating, subsurface puddle for meandering tunnel advance while melt water sinks into the regolith. The overall hypothesis produces a Moon of isotopic composition identical to Earth's mantle, explains Vesta and Moon's first order asymmetric geology, makes Procellarum the lunar navel, and predicts lunar water in volumes beyond current dreams.
2017011528 Del Vecchio, Joanmarie (Pennsylvania State University, Department of Geosciences, University Park, PA); Martin, Connor; Mount, Gregory J.; Hayes, Jorden; Comas, Xavier and DiBiase, Roman A. Surface and subsurface characteristics of periglacial landscape modification in central Pennsylvania [abstr.]: in Geological Society of America, 2016 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 48(7), Abstract no. 6-7, 2016. Meeting: Geological Society of America, 2016 annual meeting & exposition, Sept. 25-28, 2016, Denver, CO.
In slowly-eroding landscapes, critical zone architecture reflects the integrated effect of multiple Quaternary climate cycles. In the central Appalachians, south of the Last Glacial Maximum ice extent, hillslopes and headwater valleys show extensive evidence of relict periglacial erosion and sediment transport. The limited landscape modification since glaciation suggests that periglacial processes are highly efficient compared to modern, temperate processes. However, the nature and extent of inherited climatic signatures of Pleistocene conditions remains poorly constrained. Here, we use a combination of lidar topographic analysis, field mapping and sampling of colluvium, shallow geophysical surveys, and drilling to characterize regolith heterogeneity at the surface and in the shallow subsurface at Garner Run, a sandstone subcatchment of Shavers Creek in the Susquehanna Shale Hills Critical Zone Observatory, Pennsylvania. Like many sandstone landscapes in central Pennsylvania, Garner Run exhibits a patchwork of relict Pleistocene periglacial features, including solifluction lobes, block fields, and more than 9 meters of colluvial valley fill. Structural analysis and the spatial extent of solifluction lobes indicate greater sediment flux from south-facing hillslopes, in general agreement with regional observations. Additionally, shallow seismic surveys and ground penetrating radar reveal shallower depths to unweathered bedrock on southeast versus northwest-facing hillslopes. Our results suggest an aspect dependence of periglacial hillslope processes that create heterogeneity in the modern surface and subsurface critical zone architecture. Furthermore, our results highlight the potential for headwater valleys in the central Appalachians preserve a record of glacial/interglacial cycles over the Quaternary, and thus contain a sedimentary record of landscape response to climate change.
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