June 2015 Permafrost Alert
The U.S. Permafrost Association, together with the American Geosciences Institute (AGI), is pleased to provide the following Permafrost Monthly Alerts (PMA). The AGI GeoRef service regularly scans the contents of over 3500 journals in 40 languages from the global geosciences literature, comprised of approximately 345 different sources. In addition to journals, special publications such as papers in proceedings and hard-to-find publications are provided. Each PMA represents a listing of the permafrost-related materials added to GeoRef during the previous month. Where available, a direct link to the publication is included, which provides access to the full document if you or your institution have a current online subscription.
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15067947 Ernakovich, Jessica G. (Colorado State University, Ecology, Fort Collins, CO); Wallenstein, Matthew D. and Calderon, Francisco J. Chemical indicators of cryoturbation and microbial processing throughout an Alaskan permafrost soil depth profile: Soil Science Society of America Journal, 79(3), p. 783-793, illus. incl. 1 table, 61 ref., June 2015.
Although permafrost soils contain vast stores of organic C, relatively little is known about the chemical composition of their constituent soil organic matter (SOM). Mineral permafrost and organic (OAL) and mineral active layer (MAL) soils from Sagwon Hills, AK were analyzed for total C and N content and SOM chemical composition using Fourier transformed mid-infrared spectroscopy (MidIR). We also investigated techniques for proper collection of MidIR spectra on high C soils, such as permafrost. Principal Components Analysis (PCA) of the MidIR spectra revealed that the OAL was different from the MAL and permafrost based on absorbance of various organic functional groups, such as hydroxyls, alkyls, carbonyls, amines, amides, and esters. The top of the permafrost (0-15 cm below the maximum active layer thaw depth) was also differentiated from the deeper permafrost (16-40 cm below) by the same organic functional groups. Spectral data suggested that there is more chemically labile C (e.g., hydroxyl, amine groups, carbohydrates) in the OAL than the top of the permafrost, which in turn has more labile C than the MAL and deeper permafrost. The chemical similarity between the top of the permafrost and the OAL, and its differences with the MAL, suggest that organic matter (OM) is introduced into the permafrost through cryoturbation. All the soils showed evidence of microbial processing, such as organic acids and carboxylates, however the relative abundance of these compounds varied by soil depth. This study advances our understanding of permafrost C chemistry and the reactivity of constituent compounds.
15063781 Ewing, S. A. (U. S. Geological Survey, Boulder, CO); Paces, J. B.; O'Donnell, J. A.; Jorgenson, M. T.; Kanevskiy, M. Z.; Aiken, G. R.; Shur, Y.; Harden, J. W. and Striegl, R. Uranium isotopes and dissolved organic carbon in loess permafrost; modeling the age of ancient ice: Geochimica et Cosmochimica Acta, 152, p. 143-165, illus. incl. 6 tables, sketch map, 95 ref., March 1, 2015.
The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21 m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ~200 ky BP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10-100 ky BP), despite subsequent fluctuations in climate, fire disturbance and vegetation. Radiocarbon (14C) analysis of dissolved organic carbon (DOC) in thaw waters supports ages greater than ~40 ky BP below 10 m. DOC concentrations in thaw waters increased with depth to maxima of >1000 ppm, despite little change in ice content or cryostructures. These relations suggest time-dependent production of old DOC that will be released upon permafrost thaw at a rate that is mediated by sediment transport, among other factors. Abstract Copyright (2015) Elsevier, B.V.
15057364 Frederick, J. M. (Desert Research Institute, Division of Hydrologic Sciences, Reno, NV) and Buffett, B. A. Effects of submarine groundwater discharge on the present-day extent of relict submarine permafrost and gas hydrate stability on the Beaufort Sea continental shelf: Journal of Geophysical Research: Earth Surface, 120(3), p. 417-432, illus. incl. 1 table, sketch map, 22 ref., March 2015.
We investigate the role of submarine groundwater discharge on the offshore temperature and salinity field and its effect on the present-day extent of submarine permafrost and gas hydrate stability on the North American Beaufort Shelf with a two-dimensional numerical model based on the finite volume method. This study finds that submarine groundwater discharge can play a large role in submarine permafrost evolution and gas hydrate stability, suggesting that local hydrology may control the evolution of submarine permafrost as strongly as does sea level or paleoclimatic conditions. Submarine permafrost evolution shows transient behavior over potentially long time scales (e.g., several glacial cycles) before a balance of density- and pressure-driven flows is established with the permeability variations imposed by the overlying permafrost layer. The "detectable" offshore permafrost extent is related to the quasi-stationary location of the saltwater-freshwater transition. Larger values of submarine groundwater discharge allow permafrost to extend farther offshore because fresh pore water preserves relict ice. Therefore, differences in the permafrost extent at locations that share similar paleoclimatic history may be explained in part by differences in the local hydrology. Gas hydrate stability on the North American Beaufort Shelf may be more widespread than currently thought because low-ice saturation, highly degraded submarine permafrost likely exists beyond the boundary detectable by common geophysical methods. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
15067038 Lu Zhengquan (China Geological Survey, Oil and Gas Survey, Beijing, China); Rao Zhu; He Jiaxiong; Zhu Youhai; Zhang Yongqin; Liu Hui; Wang Ting and Xue Xiaohua. Geochemistry of drill core headspace gases and its significance in gas hydrate drilling in Qilian Mountain permafrost: Journal of Asian Earth Sciences, 98, p. 126-140, illus. incl. 5 tables, geol. sketch map, 49 ref., February 2015.
Headspace gases from cores are sampled in the gas hydrate drilling well DK-8 in the Qilian Mountain permafrost. Gas components and carbon isotopes of methane from headspace gas samples are analyzed. The geochemical features of the headspace gases along the well profile are compared with occurrences of gas hydrate, and with the distribution of faults or fractures. Their geochemical significance is finally pointed out in gas hydrate occurrences and hydrocarbon migration. Results show high levels of hydrocarbon concentrations in the headspace gases at depths of 149-167 m, 228-299 m, 321-337 m and 360-380 m. Visible gas hydrate and its associated anomalies occur at 149-167 m and 228-299 m; the occurrence of high gas concentrations in core headspace gases was correlated to gas hydrate occurrences and their associated anomalies, especially in the shallow layers. Gas compositions, gas ratios of C1/SC1-5, C1/(C2 + C3), iC4/nC4, and iC5/nC5, and carbon isotopic compositions of methane (d13C1, PDB ppm) indicate that the headspace gases are mainly thermogenic, partly mixed with biodegraded thermogenic sources with small amounts derived from microbial sources. Faults or fracture zones are identified at intervals of 149-167 m, 228-299 m, 321-337 m, and near 360-380 m; significantly higher gas concentrations and lower dryness ratio were found in the headspace gases within the fault or fracture zones compared with areas above these zones. In the shallow zones, low dryness ratios were observed in headspace gases in zones where gas hydrate and faults or fracture zones were found, suggesting that faults or fracture zones serve as migration paths for gases in the deep layers and provide accumulation space for gas hydrate in the shallow layers of the Qilian Mountain permafrost. Abstract Copyright (2015) Elsevier, B.V.
15060170 Arp, C. D. (University of Alaska, Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Whitman, M. S.; Jones, B. M.; Grosse, G.; Gaglioti, B. V. and Heim, K. C. Distribution and biophysical processes of beaded streams in Arctic permafrost landscapes: Biogeosciences, 12(1), p. 29-47, illus. incl. 3 tables, geol. sketch map, 58 ref., 2015.
Beaded streams are widespread in permafrost regions and are considered a common thermokarst landform. However, little is known about their distribution, how and under what conditions they form, and how their intriguing morphology translates to ecosystem functions and habitat. Here we report on a circum-Arctic survey of beaded streams and a watershed-scale analysis in northern Alaska using remote sensing and field studies. We mapped over 400 channel networks with beaded morphology throughout the continuous permafrost zone of northern Alaska, Canada, and Russia and found the highest abundance associated with medium to high ground-ice content permafrost in moderately sloping terrain. In one Arctic coastal plain watershed, beaded streams accounted for half of the drainage density, occurring primarily as low-order channels initiating from lakes and drained lake basins. Beaded streams predictably transition to alluvial channels with increasing drainage area and decreasing channel slope, although this transition is modified by local controls on water and sediment delivery. The comparisons of one beaded channel using repeat photography between 1948 and 2013 indicate a relatively stable landform, and 14C dating of basal sediments suggest channel formation may be as early as the Pleistocene-Holocene transition. Contemporary processes, such as deep snow accumulation in riparian zones, effectively insulate channel ice and allows for perennial liquid water below most beaded stream pools. Because of this, mean annual temperatures in pool beds are greater than 2 °C, leading to the development of perennial thaw bulbs or taliks underlying these thermokarst features that range from 0.7 to 1.6 m. In the summer, some pools thermally stratify, which reduces permafrost thaw and maintains cold-water habitats. Snowmelt-generated peak flows decrease rapidly by two or more orders of magnitude to summer low flows with slow reach-scale velocity distributions ranging from 0.01 to 0.1 m s-1, yet channel runs still move water rapidly between pools. The repeating spatial pattern associated with beaded stream morphology and hydrological dynamics may provide abundant and optimal foraging habitat for fish. Beaded streams may create important ecosystem functions and habitat in many permafrost landscapes and their distribution and dynamics are only beginning to be recognized in Arctic research.
15069345 Vonk, Jorien E. (Stockholm University, Department of Applied Environmental Science, Stockholm, Sweden); Semiletov, Igor P.; Dudarev, Oleg V.; Eglinton, Timothy I.; Andersson, August; Shakhova, Natalia; Charkin, Alexander; Heim, Birgit and Gustafsson, Orjan. Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters: Journal of Geophysical Research: Oceans, 119(12), p. 8410-8421, illus. incl. 1 table, 22 ref., December 2014.
The rapidly changing East Siberian Arctic Shelf (ESAS) receives large amounts of terrestrial organic carbon (OC) from coastal erosion and Russian-Arctic rivers. Climate warming increases thawing of coastal Ice Complex Deposits (ICD) and can change both the amount of released OC, as well as its propensity to be converted to greenhouse gases (fueling further global warming) or to be buried in coastal sediments. This study aimed to unravel the susceptibility to degradation, and transport and dispersal patterns of OC delivered to the ESAS. Bulk and molecular radiocarbon analyses on surface particulate matter (PM), sinking PM and underlying surface sediments illustrate the active release of old OC from coastal permafrost. Molecular tracers for recalcitrant soil OC showed ages of 3.4-13 14C-ky in surface PM and 5.5-18 14C-ky in surface sediments. The age difference of these markers between surface PM and surface sediments is larger (i) in regions with low OC accumulation rates, suggesting a weaker exchange between water column and sediments, and (ii) with increasing distance from the Lena River, suggesting preferential settling of fluvially derived old OC nearshore. A dual-carbon end-member mixing model showed that (i) contemporary terrestrial OC is dispersed mainly by horizontal transport while being subject to active degradation, (ii) marine OC is most affected by vertical transport and also actively degraded in the water column, and (iii) OC from ICD settles rapidly and dominates surface sediments. Preferential burial of ICD-OC released into ESAS coastal waters might therefore lower the suggested carbon cycle climate feedback from thawing ICD permafrost. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
15057160 O'Donnell, Jonathan A. (National Park Service, Arctic Network, Fairbanks, AK); Aiken, George R.; Walvoord, Michelle A.; Raymond, Peter A.; Butler, Kenna D.; Dornblaser, Mark M. and Heckman, Katherine. Using dissolved organic matter age and composition to detect permafrost thaw in boreal watersheds of interior Alaska: Journal of Geophysical Research: Biogeosciences, 119(11), p. 2155-2170, illus. incl. 3 tables, sketch maps, 89 ref., November 2014.
Recent warming at high latitudes has accelerated permafrost thaw, which can modify soil carbon dynamics and watershed hydrology. The flux and composition of dissolved organic matter (DOM) from soils to rivers are sensitive to permafrost configuration and its impact on subsurface hydrology and groundwater discharge. Here, we evaluate the utility of DOM composition and age as a tool for detecting permafrost thaw in three rivers (Beaver, Birch, and Hess Creeks) within the discontinuous permafrost zone of interior Alaska. We observed strong temporal controls on D14C content of hydrophobic acid isolates (D14C-HPOA) across all rivers, with the most enriched values occurring during spring snowmelt (75 ± 8 ppm) and most depleted during winter flow (-21 ± 8 ppm). Radiocarbon ages of winter flow samples ranged from 35 to 445 yr BP, closely tracking estimated median base flow travel times for this region (335 years). During spring snowmelt, young DOM was composed of highly aromatic, high molecular-weight compounds, whereas older DOM of winter flow had lower aromaticity and molecular weight. We observed a significant correlation between D14C-HPOA and UV absorbance coefficient at 254 nm (a254) across all study rivers. Using a254 as an optical indicator for D14C-HPOA, we also observed a long-term decline in a254 during maximum annual thaw depth over the last decade at the Hess Creek study site. These findings suggest a shift in watershed hydrology associated with increasing active layer thickness. Further development of DOM optical indicators may serve as a novel and inexpensive tool for detecting permafrost degradation in northern watersheds. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
15057157 Portnov, Alexey (Arctic University of Norway, Centre for Arctic Gas Hydrate Environment and Climate, Tromso, Norway); Mienert, Jurgen and Serov, Pavel. Modeling the evolution of climate-sensitive Arctic subsea permafrost in regions of extensive gas expulsion at the west Yamal shelf: Journal of Geophysical Research: Biogeosciences, 119(11), p. 2082-2094, illus. incl. sketch maps, 2 tables, block diag., 44 ref., November 2014.
Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate-sensitive Arctic environment. Expulsions of methane from shallow Russian Arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost. Here we show modeling of the permafrost evolution from the Late Pleistocene to present time at the West Yamal shelf. Modeling results suggest a highly dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g., geothermal heat flux from below and/or bottom water temperature changes from above permafrost. Scenarios of permafrost evolution show a potentially nearest landward modern extent of the permafrost at the West Yamal shelf limited by ~17 m isobaths, whereas its farthest seaward extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with a maximal thickness of 275-390 m near the shoreline. Previous field observations detected extensive emissions of free gas into the water column at the transition zone between today's shallow water permafrost (<20 m) and deeper water nonpermafrost areas (>20 m). The model adapts well to corresponding heat flux and ocean temperature data, providing crucial information about the modern permafrost conditions. It shows current locations of upper and lower permafrost boundaries and evidences for possible release of methane from the seabed to the hydrosphere in a warming Arctic. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
15066731 Makarov, V. N. (Russian Academy of Sciences, Siberian Division, Melnikov Permafrost Institute, Yakutsk, Russian Federation). Geokhimiya snezhnogo pokrova taezhnykh i gornykh merzlotnykh landshaftov Yakutii [Geochemistry of snow cover in taiga and alpine permafrost landscapes in Yakutia]: Led i Sneg = Ice and Snow, 125, p. 73-80 (English sum.), illus. incl. 9 tables, 8 ref., 2014.
The work is devoted to results of study the chemical composition of snow in mountain taiga and permafrost landscapes of Yakutia. We studied snow cover in different mountain-belt types of landscapes. The composition and calculated volumes of chemical elements and compounds are studied in snow. The chemical composition of snow in mountain taiga and permafrost landscape has remained relatively constant (hydrocarbonate chloride-bicarbonate or sodium-calcium, low sulfate content). The dominant influence on the chemical composition of snow at plains and mountain permafrost landscapes has a continental origin, mainly carbon compounds. In mountain desert, where there is predominantly regional transfer, along with the carbon significant role in atmospheric precipitation in cold season belongs to the nitrogen compounds, mainly ammonium. The total density of the entry of soluble and insoluble components in the form of snow decreases regularly with change of altitude. The distribution of trace elements in the snow cover is not a subject to altitudinal zonation. The maximum content of heavy metals (Mn, Cu, Pb, Cd), F, and Sr in the snow cover is observed in the landscapes of mountain woodlands and mountain tundra, where the route crossed research Sette-Daban metallogenic zone of stratiform Cu and Pb-Zn mineralization.
15068871 Manasypov, R. M. (Université de Toulouse, Geoscience and Environnement, Toulouse, France); Pokrovsky, O. S.; Kirpotin, S. N. and Shirokova, L. S. Thermokarst lake waters across the permafrost zones of western Siberia: The Cryosphere (Online), 8(4), p. 1177-1193, illus. incl. sketch maps, 89 ref., 2014.
This work describes the hydrochemical composition of thermokarst lake and pond ecosystems, which are observed in various sizes with different degrees of permafrost influence and are located in the northern part of western Siberia within the continuous and discontinuous permafrost zones. We analysed the elemental chemical composition of the lake waters relative to their surface areas (from 10 to 106 m2) and described the elemental composition of the thermokarst water body ecosystems in detail. We revealed significant correlations between the Fe, Al, dissolved organic carbon (DOC) and various chemical elements across a latitude gradient covering approximately 900 km. Several groups of chemical elements that reflect the evolution of the studied water bodies were distinguished. Combining the data for the studied latitude profile with the information available in the current literature demonstrated that the average dissolved elemental concentrations in lakes with different areas depend specifically on the latitudinal position, which is presumably linked to (1) the elements leached from frozen peat, which is the main source of the solutes in thermokarst lakes, (2) marine atmospheric aerosol depositions, particularly near the sea border and (3) short-range industrial pollution by certain metals from the largest Russian Arctic smelter. We discuss the evolution of the chemical compositions observed in thermokarst lakes during their formation and drainage and predict the effect that changing the permafrost regime in western Siberia has on the hydrochemistry of the lakes.
15062065 Schwamborn, G. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Meyer, H.; Schirrmeister, L. and Fedorov, G. Past freeze and thaw cycling in the margin of the El'gygytgyn crater deduced from a 141 m long permafrost record: Climate of the Past, 10(3), p. 1109-1123, illus. incl. strat. cols., 1 table, sketch map, 65 ref., 2014.
The continuous sediment record from Lake El'gygytgyn in the northeastern Eurasian Arctic spans the last 3.6 Ma and for much of this time permafrost dynamics and lake level changes have likely played a crucial role for sediment delivery to the lake. Changes in the ground-ice hydrochemical composition (d18O, dD, pH, electrical conductivity, Na+, Mg2+, Ca2+, K+, HCO3-, Cl-, SO4-) of a 141 m long permafrost record from the western crater plain are examined to reconstruct repeated periods of freeze and thaw at the lake edge. Stable water isotope and major ion records of ground ice in the permafrost reflect both a synsedimentary palaeo-precipitation signal preserved in the near-surface permafrost (0.0-9.1 m core depth) and a post-depositional record of thawing and refreezing in deeper layers of the core (9.1-141.0 m core depth). These lake marginal permafrost dynamics were controlled by lake level changes that episodically flooded the surfaces and induced thaw in the underlying frozen ground. During times of lake level fall these layers froze over again. At least three cycles of freeze and thaw are identified and the hydrochemical data point to a vertical and horizontal talik refreezing through time. Past permafrost thaw and freeze may have destabilised the basin slopes of Lake El'gygytgyn and this has probably promoted the release of mass movements from the lake edge to the deeper basin as known from frequently occurring turbidite layers in the lake sediment column.
15056214 James, Megan (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Lewkowicz, Antoni G.; Smith, Sharon L. and Miceli, Christina M. Multi-decadal degradation and persistence of permafrost in the Alaska Highway corridor, northwest Canada: Environmental Research Letters, 8(4), Paper no. 045013, illus. incl. 6 tables, sketch map, 22 ref., December 2013.
Changes in permafrost distribution in the southern discontinuous zone were evaluated by repeating a 1964 survey through part of the Alaska Highway corridor (56° N-61° N) in northwest Canada. A total of 55 sites from the original survey in northern British Columbia and southern Yukon were located using archival maps and photographs. Probing for frozen ground, manual excavations, air and ground temperature monitoring, borehole drilling and geophysical techniques were used to gather information on present-day permafrost and climatic conditions. Mean annual air temperatures have increased by 1.5-2.0° C since the mid-1970s and significant degradation of permafrost has occurred. Almost half of the permafrost sites along the entire transect which exhibited permafrost in 1964 do so no longer. This change is especially evident in the south where two-thirds of the formerly permafrost sites have thawed and the limit of permafrost appears to have shifted northward. The permafrost that persists is patchy, generally less than 15 m thick, has mean annual surface temperatures >0° C, mean ground temperatures between -0.5 and 0° C, is in peat or beneath a thick organic mat, and appears to have a thicker active layer than in 1964. Its persistence may relate to the latent heat requirements of thawing permafrost or to the large thermal offset of organic soils. The study demonstrates that degradation of permafrost has occurred in the margins of its distribution in the last few decades, a trend that is expected to continue as the climate warms. Copyright 2013 IOP Publishing Ltd.
15056219 McConnell, Nicole A. (University of Alaska Fairbanks, Department of Biology and Wildlife, Fairbanks, AK); Turetsky, Merritt R.; McGuire, A. David; Kane, Evan S.; Waldrop, Mark P. and Harden, Jennifer W. Controls on ecosystem and root respiration across a permafrost and wetland gradient in interior Alaska: Environmental Research Letters, 8(4), Paper no. 045029, illus. incl. 5 tables, 43 ref., December 2013.
Permafrost is common to many northern wetlands given the insulation of thick organic soil layers, although soil saturation in wetlands can lead to warmer soils and increased thaw depth. We analyzed five years of soil CO2 fluxes along a wetland gradient that varied in permafrost and soil moisture conditions. We predicted that communities with permafrost would have reduced ecosystem respiration (ER) but greater temperature sensitivity than communities without permafrost. These predictions were partially supported. The colder communities underlain by shallow permafrost had lower ecosystem respiration (ER) than communities with greater active layer thickness. However, the apparent Q10 of monthly averaged ER was similar in most of the vegetation communities except the rich fen, which had smaller Q10 values. Across the gradient there was a negative relationship between water table position and apparent Q10, showing that ER was more temperature sensitive under drier soil conditions. We explored whether root respiration could account for differences in ER between two adjacent communities (sedge marsh and rich fen), which corresponded to the highest and lowest ER, respectively. Despite differences in root respiration rates, roots contributed equally (»40%) to ER in both communities. Also, despite similar plant biomass, ER in the rich fen was positively related to root biomass, while ER in the sedge marsh appeared to be related more to vascular green area. Our results suggest that ER across this wetland gradient was temperature-limited, until conditions became so wet that respiration became oxygen-limited and influenced less by temperature. But even in sites with similar hydrology and thaw depth, ER varied significantly likely based on factors such as soil redox status and vegetation composition. Copyright 2013 IOP Publishing Ltd.
15065989 Quinn, P. E. (BGC Engineering, Ottawa, ON, Canada). A statistical model for presence of late-season frozen ground in discontinuous permafrost at Dublin Gulch, Yukon: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 50(8), p. 889-898, illus. incl. 4 tables, 28 ref., August 2013.
This paper describes geostatistical analyses completed at a discontinuous permafrost site in central Yukon to develop a predictive model for the presence of late-season frozen ground in support of planning and design for potential site development. The most important factors in the bivariate statistical model were soil type, as determined through terrain analysis, and slope aspect, as inferred from available topographic data. The other three factors included in the final model were profile curvature, slope angle, and ground elevation, each interpreted from available topographic data. The resulting model subdivides the site into three broad classes of frozen ground likelihood: low, where frozen ground can be expected to be encountered in late summer at 15% of observation locations; medium, where 50% of the ground is expected to remain frozen; and high, where 85% of the ground is expected to remain frozen. New test pit and borehole data from the summer of 2012 were used to verify model performance. The inferred correlations between frozen ground and soil type, aspect, curvature, slope, and elevation obtained in this case study may provide useful information relative to expected permafrost occurrence at sites in central Yukon with similar geology and physiography.
15061869 Hultman, Jenni (Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA); Waldrop, Mark P.; Mackelprang, Rachel; David, Maude M.; McFarland, Jack; Blazewicz, Steven J.; Harden, Jennifer; Turetsky, Merritt R.; McGuire, A. David; Shah, Manesh B.; VerBerkmoes, Nathan C.; Lee, Lang Ho; Mavrommatis, Kostas and Jansson, Janet K. Multi-omics of permafrost, active layer and thermokarst bog soil microbiomes: Nature (London), 521(7551), p. 208-212, illus. incl. 2 tables, 13 ref., May 14, 2015.
15067415 Bosson, Jean-Baptiste (Université de Lausanne, Institut des Dynamiques de la Surface Terrestre, Lausanne, Switzerland); Deline, Philip; Bodin, Xavier; Schoeneich, Philippe; Baron, Ludovic; Gardent, Marie and Lambiel, Christophe. The influence of ground ice distribution on geomorphic dynamics since the Little Ice Age in proglacial areas of two cirque glacier systems: Earth Surface Processes and Landforms, 40(5), p. 666-680, illus. incl. 4 tables, sects., geol. sketch maps, 61 ref., April 2015. Includes appendices.
Holocene glaciers have contributed to an abundance of unstable sediments in mountainous environments. In permafrost environments, these sediments can contain ground ice and are subject to rapid geomorphic activity and evolution under condition of a warming climate. To understand the influence of ground ice distribution on this activity since the Little Ice Age (LIA), we have investigated the Pierre Ronde and Rognes proglacial areas, two cirque glacier systems located in the periglacial belt of the Mont Blanc Massif. For the first time, electrical resistivity tomography, temperature data loggers and differential global positioning systems (dGPS) are combined with historical documents and glaciological data analysis to produce a complete study of evolution in time and space of these small landsystems since the LIA. This approach allows to explain spatial heterogeneity of current internal structure and dynamics. The studied sites are a complex assemblage of debris-covered glacier, ice-rich frozen debris and unfrozen debris. Ground ice distribution is related to former glacier thermal regime, isolating effect of debris cover, water supply to specific zones, and topography. In relation with this internal structure, present dynamics are dominated by rapid ice melt in the debris-covered upper slopes, slow creep processes in marginal glacigenic rock glaciers, and weak, superficial reworking in deglaciated moraines. Since the LIA, geomorphic activity is mainly spatially restricted within the proglacial areas. Sediment exportation has occurred in a limited part of the former Rognes Glacier and through water pocket outburst flood and debris flows in Pierre Ronde. Both sites contributed little sediment supply to the downslope geomorphic system, rather by episodic events than by constant supply. In that way, during Holocene and even in a paraglacial context as the recent deglaciation, proglacial areas of cirque glaciers act mostly as sediment sinks, when active geomorphic processes are unable to evacuate sediment downslope, especially because of the slope angle weakness. Copyright Copyright 2014 John Wiley & Sons, Ltd.
15057276 Corbett, J. Elizabeth (Florida State University, Earth, Ocean and Atmospheric Science, Tallahassee, FL); Tfaily, Malak M.; Burdige, David J.; Glaser, Paul H. and Chanton, Jeffrey P. The relative importance of methanogenesis in the decomposition of organic matter in northern peatlands: Journal of Geophysical Research: Biogeosciences, 120(2), p. 280-293, illus. incl. 1 table, sketch maps, 65 ref., February 2015.
Using an isotope-mass balance approach and assuming the equimolar production of CO2 and CH4 from methanogenesis (e.g., anaerobic decomposition of cellulose), we calculate that the proportion of total CO2 production from methanogenesis varies from 37 to 83% across a variety of northern peatlands. In a relative sense, methanogenesis was a more important pathway for decomposition in bogs (80 ± 13% of CO2 production) than in fens (64 ± 5.7% of CO2 production), but because fens contain more labile substrates they may support higher CH4 production overall. The concentration of CO2 produced from methanogenesis (CO2-meth) can be considered equivalent to CH4 concentration before loss due to ebullition, plant-mediated transport, or diffusion. Bogs produced slightly less CO2-meth than fens (2.9 ± 1.3 and 3.7 ± 1.4 mmol/L, respectively). Comparing the quantity of CH4 present to CO2-meth, fens lost slightly more CH4 than bogs (89 ± 2.8% and 82 ± 5.3%, respectively) likely due to the presence of vascular plant roots. In collapsed permafrost wetlands, bog moats produced half the amount of CO2-meth (0.8 ± 0.2 mmol/L) relative to midbogs (1.6 ± 0.6 mmol/L) and methanogenesis was less important (42 ± 6.6% of total CO2 production relative to 55 ± 8.1%). We hypothesize that the lower methane production potential in collapsed permafrost wetlands occurs because recently thawed organic substrates are being first exposed to the initial phases of anaerobic decomposition following collapse and flooding. Bog moats lost a comparable amount of CH4 as midbogs (63 ± 7.0% and 64 ± 9.3%). Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
15060003 Seppi, R. (Universita di Pavia, Dipartimento di Scienze della Terra e dell'Ambiente, Pavia, Italy); Zanoner, T.; Carton, A.; Bondesan, A.; Francese, R.; Carturan, L.; Zumiani, M.; Giorgi, M. and Ninfo, A. Current transition from glacial to periglacial processes in the Dolomites (southeastern Alps): Geomorphology, 228, p. 71-86, January 1, 2015.
A close relationship between glacial and periglacial landforms is frequently observed in alpine environments, where a transition from glacial to periglacial processes often took place after the end of the Little Ice Age (LIA). Understanding the origin of these landforms is challenging, and assessing the current spatial domain of glacial and periglacial processes may be a difficult task in high-relief areas, where thick and widespread debris cover often characterize rapidly decaying glaciers. Here we present a comprehensive study of a composite landform located in the Dolomites (South-Eastern Alps), combining geomorphological, geophysical and topographic surveys with ground surface temperature measurements. Results indicate that a debris-covered glacier persists in the upper part, rather large compared to the LIA extent, but currently inactive and rapidly losing mass. An active rock glacier exists in the lower part, surrounded by discontinuous permafrost. A frozen body about 10 m thick was detected in the rock glacier and geomorphological evidence suggests that this ice mass is completely detached from the debris-covered glacier. Our findings suggest that the lower part of the composite landform is probably a remnant of the ancient glacier tongue and is currently evolving under periglacial conditions. Periglacial processes are therefore replacing glacial processes which dominated in this site during the LIA. Abstract Copyright (2015) Elsevier, B.V.
15056218 Jones, Benjamin M. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Stoker, Jason M.; Gibbs, Ann E.; Grosse, Guido; Romanovsky, Vladimir E.; Douglas, Thomas A.; Kinsman, Nicole E. M. and Richmond, Bruce M. Quantifying landscape change in an arctic coastal lowland using repeat airborne LiDAR: Environmental Research Letters, 8(4), Paper no. 045025, illus. incl. 1 table, sketch map, 43 ref., December 2013.
Increases in air, permafrost, and sea surface temperature, loss of sea ice, the potential for increased wave energy, and higher river discharge may all be interacting to escalate erosion of arctic coastal lowland landscapes. Here we use airborne light detection and ranging (LiDAR) data acquired in 2006 and 2010 to detect landscape change in a 100 km2 study area on the Beaufort Sea coastal plain of northern Alaska. We detected statistically significant change (99% confidence interval), defined as contiguous areas (>10 m2) that had changed in height by at least 0.55 m, in 0.3% of the study region. Erosional features indicative of ice-rich permafrost degradation were associated with ice-bonded coastal, river, and lake bluffs, frost mounds, ice wedges, and thermo-erosional gullies. These features accounted for about half of the area where vertical change was detected. Inferred thermo-denudation and thermo-abrasion of coastal and river bluffs likely accounted for the dominant permafrost-related degradational processes with respect to area (42%) and volume (51%). More than 300 thermokarst pits significantly subsided during the study period, likely as a result of storm surge flooding of low-lying tundra (<1.4 m asl) as well as the lasting impact of warm summers in the late-1980s and mid-1990s. Our results indicate that repeat airborne LiDAR can be used to detect landscape change in arctic coastal lowland regions at large spatial scales over sub-decadal time periods. Copyright 2013 IOP Publishing Ltd.
15056220 Tape, Ken D. (University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Flint, Paul L.; Meixell, Brandt W. and Gaglioti, Benjamin V. Inundation, sedimentation, and subsidence creates goose habitat along the Arctic coast of Alaska: Environmental Research Letters, 8(4), Paper no. 045031, illus. incl. strat. cols., sketch map, 32 ref., December 2013.
The Arctic Coastal Plain of Alaska is characterized by thermokarst lakes and drained lake basins, and the rate of coastal erosion has increased during the last half-century. Portions of the coast are <1 m above sea level for kilometers inland, and are underlain by ice-rich permafrost. Increased storm surges or terrestrial subsidence would therefore expand the area subject to marine inundation. Since 1976, the distribution of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain has shifted from inland freshwater lakes to coastal marshes, such as those occupying the Smith River and Garry Creek estuaries. We hypothesized that the movement of geese from inland lakes was caused by an expansion of high quality goose forage in coastal areas. We examined the recent history of vegetation and geomorphological changes in coastal goose habitat by combining analysis of time series imagery between 1948 and 2010 with soil stratigraphy dated using bomb-curve radiocarbon. Time series of vertical imagery and in situ verification showed permafrost thaw and subsidence of polygonal tundra. Soil stratigraphy and dating within coastal estuaries showed that non-saline vegetation communities were buried by multiple sedimentation episodes between 1948 and 1995, accompanying a shift toward salt-tolerant vegetation. This sedimentation allowed high quality goose forage plants to expand, thus facilitating the shift in goose distribution. Declining sea ice and the increasing rate of terrestrial inundation, sedimentation, and subsidence in coastal estuaries of Alaska may portend a "tipping point" whereby inland areas would be transformed into salt marshes. Copyright 2013 IOP Publishing Ltd.
15056082 Krakauer, N. Y. (City College of New York, Department of Civil Engineering and NOAA-Cooperative Remote Sensing Science and Technology Center, New York, NY); Puma, M. J. and Cook, B. I. Impacts of soil-aquifer heat and water fluxes on simulated global climate: Hydrology and Earth System Sciences (HESS), 17(5), p. 1963-1974, illus. incl. 3 tables, 72 ref., 2013.
Climate models have traditionally only represented heat and water fluxes within relatively shallow soil layers, but there is increasing interest in the possible role of heat and water exchanges with the deeper subsurface. Here, we integrate an idealized 50 m deep aquifer into the land surface module of the GISS ModelE general circulation model to test the influence of aquifer-soil moisture and heat exchanges on climate variables. We evaluate the impact on the modeled climate of aquifer-soil heat and water fluxes separately, as well as in combination. The addition of the aquifer to ModelE has limited impact on annual-mean climate, with little change in global mean land temperature, precipitation, or evaporation. The seasonal amplitude of deep soil temperature is strongly damped by the soil-aquifer heat flux. This not only improves the model representation of permafrost area but propagates to the surface, resulting in an increase in the seasonal amplitude of surface air temperature of > 1 K in the Arctic. The soil-aquifer water and heat fluxes both slightly decrease interannual variability in soil moisture and in land-surface temperature, and decrease the soil moisture memory of the land surface on seasonal to annual timescales. The results of this experiment suggest that deepening the modeled land surface, compared to modeling only a shallower soil column with a no-flux bottom boundary condition, has limited impact on mean climate but does affect seasonality and interannual persistence.
15067952 Brummell, Martin E. (University of Saskatchewan, Department of Soil Science, Saskatoon, SK, Canada); Guy, Amanda and Siciliano, Steven D. Does diapirism influence greenhouse gas production on patterned ground in the High Arctic?: Soil Science Society of America Journal, 79(3), p. 889-895, illus. incl. 1 table, 32 ref., June 2015.
There are unusual patterns of greenhouse gas (GHG) net production in soil profiles of Arctic polar deserts. These deserts include frost boils that are symptomatic of permafrost-associated soils. Some frost boils contain diapirs, intrusions of recently thawed, carbon- and water-rich fine material pushed upward into the overlying active layer. Here we identified diapir-associated frost boils in an Arctic polar desert that we had previously found to have highly variable patterns of GHG net production, and compared patterns of GHG net production in soil profiles between diapir and non-diapir frost boils. In addition, we tested the repeatability of soil gas probes measurements and if estimates of diffusivity based on bulk density were accurate. Probes were installed in frost boils identified as including or not including diapirs, and measurements were conducted over several days to evaluate net GHG production.Soil gas probes deployed for longer than approximately 3 d showed loss of signal, and the injection of an inert tracer, SF6, validated our estimates of soil diffusivity based on bulk density. Diapir-associated frost boils showed reduced soil respiration compared with non-diapir frost boils, despite these diapir-associated frost boils having increased soil organic matter content. Thus, diapir intrusions in frost boils of the Arctic polar desert simultaneously store greater amounts of organic C and reduce soil respiration compared with non-diapir frost boils. Differences in soil organic matter quality and/or its interaction with soil texture may be an important control for carbon storage in Arctic soils.
15058284 Jolivel, Maxime (Université Laval, Centre d'Études Nordiques, Quebec City, QC, Canada); Allard, Michel and St-Onge, Guillaume. Climate change and recent sedimentation in Nastapoka Sound, eastern coast of Hudson Bay: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 52(5), p. 322-337 (French sum.), illus. incl. 3 tables, sketch map, 83 ref., May 2015.
In an attempt to determine to what extent the impact of recent climate changes that occurred east of Hudson Bay, including important reduction of areas in permafrost, had on the coastal marine environment, a series of shallow cores were extracted from the seabed off the mouth of the Sheldrake River, in Nastapoka Sound. A total of 25 cores were taken in April 2009 from the ice cover. A preliminary seafloor map was first done to help in the selection of the coring sites. Nastapoka Sound has a complex subaqueous relief, formed of asymmetric ridges and deep basins. After preliminary sedimentological analyses, six of the cores were selected for physical and chronological analyses (14C, 210Pb, and 137Cs dating); among them, three were selected for elemental (C, N, OC/TN) and isotopic (d13C, d15N) analyses to identify sedimentary organic matter sources. Sedimentation processes are complex and are primarily driven by bottom currents. This is confirmed by the absence of a clay fraction in several cores, some erosion surfaces in a few cores, and the presence of comet-like mark features on the seafloor. The highest sedimentation rates are found near the coast of the province of Quebec and Gillies Island and the lowest ones occur in the deep depocenters. Isotopic and elemental analyses reveal that Nastapoka Sound is an area of mixing between marine and terrestrial inputs and can be compared to an estuarine system similar to nearby Lac Guillaume-Delisle. Those conditions altogether make it difficult to extract a perfectly clear signal of climate change in the recent sediment record. However, the downcore application of a simple two end-member mixing model to measured d13C values strongly suggests that the fraction of sedimentary organic matter from terrestrial sources increased by 30% since about the middle of the Little Ice Age. This trend accelerated at the end of the 20th century. Rapid permafrost decay in adjacent river catchments is likely one source for this terrestrial carbon. However, it cannot be distinguished from other potential sources that are also related to environmental changes such as increase in primary productivity both on land, where peatlands, shrubs, and forest are expanding, and at sea, where sea ice cover duration is diminishing.
15060480 Roy, Srikumar (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Norway); Hovland, Martin; Noormets, Riko and Olaussen, Snorre. Seepage in Isfjorden and its tributary fjords, West Spitsbergen: Marine Geology, 363, p. 146-159, illus. incl. sketch maps, 60 ref., May 1, 2015.
This study analyses pockmark morphology and their spatial distribution in Isfjorden relative to seabed morphology, bedrock geology, fault systems, glacial landforms and processes using multibeam bathymetric data. It provides insight into the possible mechanisms of pockmark formation, high density pockmark field evolution, and fluid migration pathways. A total of 1304 pockmarks occur in the Isfjorden at water depths of 40 to 320 m, varying from circular to elongate in plan-view. Their diameter ranges from 14 to 265 m and their depths from 1 to 11 m. Elongate pockmarks are dominant in the Isfjordbanken and outer Isfjorden where the seafloor is influenced by the West Spitsbergen Current. The West Spitsbergen fold-and-thrust belt and other fault systems sub-cropping at the Isfjorden seafloor correlate spatially with the high density pockmark zones. The pockmarks are preferentially located on the marine sediments draping the bedrock of Isfjorden fjord system. They are most abundant in the areas underlain by Jurassic-Cretaceous and the Triassic-Lower Jurassic bedrock. Pockmarks found ahead of submarine slope failures may have formed due to dewatering of soft sediments as a result of rapid increase of overpressure caused by deposition of glacigenic debris lobes. Fault conduits, potential source rock and thin postglacial sediment layers are found to be crucial for the formation of pockmarks. Modeling results of the near-shore subsea permafrost and potential gas hydrate stability zone imply thawing permafrost and gas hydrate dissociation as additional possible mechanisms for pockmark formation in Isfjorden. Abstract Copyright (2015) Elsevier, B.V.
15069220 Sippel, J. (GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam, Germany); Scheck-Wenderoth, M.; Lewerenz, B. and Klitzke, P. Deep vs. shallow controlling factors of the crustal thermal field; insights from 3D modelling of the Beaufort-Mackenzie Basin (Arctic Canada): Basin Research, 27(1), p. 102-123, illus. incl. sects., 1 table, geol. sketch maps, 80 ref., February 2015.
Significant lateral variations in observed temperatures in the Beaufort-Mackenzie Basin raise the question on the temperature-controlling factors. Based on the structural configuration of the sediments and underlying crust in the area, we calculate the steady-state 3D conductive thermal field. Integrated data include the base of the relic permafrost layer representing the 0 °C-isotherm, public-domain temperature data (from 227 wells) and thermal conductivity data. For >75% of the wells the predicted temperatures deviate by <10 K from the observed temperatures, which validates the overall model setup and adopted thermal properties. One important trend reproduced by the model is a decrease in temperatures from the western to the eastern basin. While in the west, a maximum temperature of 185 °C is reached at 5000 m below sea level, in the east the maximum temperature is 138 °C. The main cause for this pattern lies in lateral variations in thermal conductivity indicating differences in the shale and sand contents of the different juxtaposed sedimentary units. North-to-south temperature trends reveal the superposition of deep and shallow effects. At the southern margin, where the insulating effect of the low-conductive sediments is missing, temperatures are lowest. Farther north, where the sub-sedimentary continental crust is thick enough to produce considerable heat and a thick pile of sediments efficiently stores heat, temperatures tend to be highest. Temperatures decrease again towards the northernmost distal parts of the basin, where thinned continental and oceanic crust produce less radiogenic heat. Wells with larger deviations of the purely conductive model from the temperature observations (>15 K at 10% of the wells) and their basin-wide pattern of misfit tendency (too cold vs. too warm temperature predictions) point to a locally restricted coupling of heat transport to groundwater flow. Abstract Copyright (2010), John Wiley & Sons, Ltd.
15062897 Moiseenko, T. I. (Vernadsky Institute of Geochemistry and Analytical Chemistry, Moscow, Russian Federation); Gashkina, N. A.; Dinu, M. I.; Kremleva, T. A. and Khoroshavin, V. Yu. Aquatic geochemistry of small lakes; effects of environment changes: Geochemistry International, 51(13), p. 1031-1148, December 2013.
This paper reports the results of an extensive investigation of water chemistry in the small lakes of European Russia and Western Siberia along a climatic gradient. It was demonstrated that small lakes unaffected by any direct contamination can be used as indicators of natural geochemical conditions of water formation, as well as global and regional fluxes of airborne pollution and climate warming. A novel concept was developed for within- and between-zone variability in water chemistry over vast areas of tundra, taiga, forest, and steppe, and contributions of natural and anthropogenic factors to its formation under present-day conditions were estimated. A proposed predictive scenario showed that climate warming will result in an increase in water salinity in southern regions and ubiquitous phosphorus enrichment in terrestrial waters; the hydrologic and geochemical conditions of water formation in northern Siberia will change significantly in response to permafrost thawing. Zonal features in the development of anthropogenically-induced processes in terrestrial surface waters (acidification, eutrophication, and metal enrichment) were determined. It was demonstrated that, in addition to naturally acidified lakes with high contents of humic acids, acid lakes of anthropogenic origin occur over the whole humid region discussed here, and acidification processes were characterized for each subregion. The trophic status of lakes and limitation of their bioproductivity with respect to nutrients were estimated. The concentrations and distribution of trace elements were analyzed in terrestrial waters from various climatic zones of European Russia and Western Siberia, and the first estimates were obtained for the mean concentrations and coefficients of migration of a wide range of elements in terrestrial freshwaters. We distinguished a group of metal (Mo, As, U, Bi, Sb, Cd, Ag, Se, Re, Pb, Cd, W, etc.) the enrichment of which in natural waters results from their global dispersion in the environment. Experimental results and natural observations are presented on the processes of metal ion complexation with humus substances, and sequences of their increasing activity in competing for organic ligands were derived. Data are presented on the speciation of metals depending on natural water chemistry in the tundra, taiga, and steppe zones. The pioneering investigations on the geochemistry of natural waters allowed us to substantiate new regional norms for water quality. Copyright 2013 Pleiades Publishing, Ltd.
15059666 Streletskaya, I. D. (Moscow State University, Geography Department, Moscow, Russian Federation); Vasiliev, A. A.; Melnikov, V. P. and Oblogov, G. E. Estimation of atmospheric paleo-circulation based on isotope composition of ice wedges: Doklady Earth Sciences, 457(2), p. 1025-1027, illus. incl. sketch map, 13 ref., August 2014.
Cryostratigraphy of frozen late-Pleistocene sediments was studied in natural exposures at the Arctic coastal area. The isotope composition of ice wedges was determined. The data base on isotope composition of syngenetic ice wedges and modern elementary ice veins was compiled for the Eurasian Arctic based on obtained data and available literature sources. Spatial distribution of the isotope composition of ice wedges, which indicates paleo-climatic conditions, was determined separately for Marine Isotope Stages (MISs) from MIS 1 to MIS 4 for the Eurasian Arctic. The pattern of this distribution has remained stable during the last 50 000 years, which indicates a stable trend in atmospheric circulation from 50 000 yr BP to the present. Copyright 2014 Pleiades Publishing, Ltd.
15058797 Watanabe, Kunio (Mie University, Graduate School of Bioresources, Mie, Japan). Knowledge of frozen soil technology of artificial frozen soil wall: Seppyo = Journal of the Japanese Society of Snow and Ice, 76(2), p. 179-192, illus., 24 ref., March 2014.
15056097 Iwata, Yukiyoshi (National Agricultural Research Center for Hokkaido Region, Hokkaido, Japan); Kuwao, Kazunobu; Hirota, Tomoyoshi and Hasegawa, Shuichi. Snowmelt infiltration into frozen ground having different frost soil structure: Seppyo = Journal of the Japanese Society of Snow and Ice, 75(3), p. 111-123, (Japanese) (English sum.), illus. incl. 1 table, 27 ref., May 2013.
Field experiments were conducted during two winters to examine the influences of the frost soil structure on snowmelt infiltration at an agricultural field of volcanic ash soil in Tokachi, Hokkaido, Japan. Two experimental plots were prepared. Snow on one plot was removed to deepen the soil freezing (treatment plot; TP). Snow on the other plot was left in its natural condition (control plot; CP). During the first winter, frost depths were 27 cm for CP and 52 cm for TP. A concrete-like structure (Concrete frost) was formed throughout the frozen layers. When snow disappeared, surface ponding was observed for Concrete frost, indicating interference of snowmelt infiltration by soil freezing, irrespective of the freezing depth. During the second year, in contrast, soil to a depth of 20 cm exhibited a honeycomb-like structure (Honeycomb frost), which included numerous macropores. Snowmelt water infiltrated freely to a frost depth of 22 cm through the Honeycomb frost for CP. In contrast, surface ponding appeared for TP after collapse of the honeycomb structure at a shallow depth because of the interference of snowmelt infiltration by the Concrete frost that formed below 20 cm depth. Results suggest that the frozen soil surface structure and deeper parts of the frozen soil structure are important to evaluate snowmelt infiltration into the frozen soil under field conditions.
15063457 Zhang Lianhai (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Frozen Soil Engineering, Lanzhou, China); Ma Wei; Yang Chengsong and Yuan Chang. Investigation of the pore water pressures of coarse-grained sandy soil during open-system step-freezing and thawing tests: Engineering Geology, 181, p. 233-248, illus. incl. 3 tables, 40 ref., October 1, 2014.
An investigation of the pore water pressure in freezing soil has been essential for exploring frost heave mechanisms such as water migration and the initiation of ice lenses. In this article, the pore water pressures of a coarse-grained sandy soil were measured during open-system laboratory testing. A total of three soil samples were tested, and the degrees of saturation were 34.78%, 61.40% and 100.00%, respectively. Each experienced a first step-freezing stage, a thawing stage and a second step-freezing stage. The results showed that changes in the pore water pressure depended on the freeze-thaw history, degree of saturation and temperature. Under the same temperature conditions, the change pattern of the pore water pressure in the first step-freezing stage differed from that in the second step-freezing stage. The pore water pressures in samples with high water content first decreased and then increased slightly as the temperature had a sudden drop in the step-freezing stage; the pore water pressures in samples with low water content were less sensitive to the temperature change. During thawing, the pore water pressures increased as the soil sample temperatures rose. In terms of the variations in the pore water pressure, we further proposed that the phase change of sandy soil occurred in a temperature range and that there was water migration when sandy soil freezes. Furthermore, the permeability between every two pore water probes was calculated, using Darcy's law, with the pore water pressures and water volumes absorbed into the soil sample. Abstract Copyright (2014) Elsevier, B.V.
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15058823 Bliss, Andy K. (University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK); Braun, Juliana Louise; Daanen, Ronald P.; Hock, Regine; Liljedahl, A.; Wolken, Gabriel J. and Zhang, J. Twenty-first century changes in the hydrology, glaciers, and permafrost of the Susitna Basin, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC23D-0960, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In South-Central Alaska, the Susitna River is the site of a proposed hydroelectric dam. The catchment of the reservoir in the upper Susitna watershed (13,289 km2, 450-4000 m a.s.l.) is 4% glacierized and is characterized by sparse vegetation, discontinuous permafrost, and little human development. Glaciers, permafrost, and the water cycle are expected to change in response to anticipated future atmospheric warming by the end of this century, thus impacting water yields to the hydroelectric reservoir. We aim to quantify future changes in glacier wastage, surface- and groundwater, permafrost, and evapotranspiration. We apply the physically-based hydrological model WaSiM using daily air temperature and precipitation data from station observations and gridded climate products. The model is calibrated with runoff and glacier mass balance measurements from the 1980s and validated with measurements from ongoing field campaigns which started in spring 2012. With the past and present data, the model is able to match both the magnitude and timing of observed river discharge. However, the scarcity of meteorological observations from the upper Susitna basin presents a major challenge to simulating the catchment hydrology. We present methods for extrapolation of the spatially-sparse long-term data across the catchment, with particular emphasis on high-elevation precipitation. To project future changes in river runoff, we run WaSiM with air temperature and precipitation downscaled from global climate models and compare results from several emission scenarios (selected from CMIP5). We discuss the anticipated changes in basin hydrology as the climate warms, permafrost thaws, and glaciers shrink.
15068775 Gong Jianming (Key Laboratory of Marine Hydrocarbon Resources and Environmental Geology, Qingdao, China); Li Yonghong; Chen Xiaohui; Li Zhigao; Li Xiaoyu; He Xingliang and Yang Zhicheng. Studies on geochemical features of Mesozoic-Paleozoic source rocks in Qinghai-Tibetan Plateau permafrost regions [abstr.]: in Goldschmidt abstracts 2014, V.M. Goldschmidt Conference - Program and Abstracts, 24, p. 831, 2014. Meeting: Goldschmidt 2014, June 8-13, 2014, Sacramento, CA.
15056898 Doner, Lisa A. (Plymouth State University, Environmental Science and Policy Department, Plymouth, NH); McGarry, Mary Ann; Perello, Melanie; Davis, P. Thompson and Foley, Kathryn. National climate literacy gaps in meteorology graduates [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 526, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Television news broadcasts are a primary source of information for the public on recent and ongoing climate changes. Unfortunately, despite new evidence that broadcast meteorologists have advanced training in meteorological and atmospheric sciences (Szymanski et al, this session), large disparities persist in their perceptions of climate change. One explanation is that meteorology students lack interdisciplinary training in bio- and geosciences, from which much of the evidence about climate is derived. Here we examine this idea, by measuring the academic preparedness of meteorology students to communicate climate information. We surveyed first-year and senior undergraduate meteorology students in 10 programs across the United States using national standards for assessing knowledge on scientific processes and climate literacy (ntotal=139, nseniors=78, nfirst years=61). A majority of students indicated that college courses were their most reliable source of climate-related information, in comparison to the media or Internet, for example. Respondents show fairly high literacy on some climate topics, such as glacial ice cores and sea ice extent as proxy climate indicators, but deficiencies appear in understanding causes and consequences of climate change, such as the affect of aerosols, feedbacks from melting permafrost, and the role of CO2 in ocean acidification. Surprisingly, 88% of all respondents indicated no concern about climate change and its impacts. Survey results indicate specific areas of climate science where curriculum revision may improve climate literacy in meteorology programs. In 2010, the American Meteorological Society made curriculum recommendations to improve coverage of climate topics; it seems clear that these measures are, thus far, inadequate. To assess student and faculty confidence in communicating climate change topics to the public, we held a workshop at the 2014 Northeast Storm Conference. This workshop included a self-assessment of preparedness to talk to the public about specific topics before and after a formal presentation by a renowned climate scientist. Many participants remarked on the importance of details in the presentation in clarifying their understanding and over 50% indicated an increased sense of preparedness following the workshop (n=83).
15057053 Shan Wei (Northeast Forestry University, Institute of Cold Regions Science and Engineering, Harbin, China). Environmental and engineering geology of the Bei'an to Heihe Expressway in China with a focus on climate change [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 716, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
The Bei'an to Heihe Expressway in China is located in southern boundary of high latitude permafrost. In recent years, this expressway has experienced increasing roadbed settlement, salutatory flow ice and cut slope landslides in the road area, which threaten the stability of the subgrade and highway operational safety. The morphological characteristics and evolution of the above phenomenon are related to permafrost distribution and degradation as well as seasonal freeze-thaw. The relationship between the annual average temperature change and the permafrost distribution are analyzed based on the annual average temperature from 1954 to 2011 in Sunwu County, and the cumulative monthly average air temperature, ground temperature, precipitation, and maximum frozen soil thickness in Sunwu County from 1971-2000. Uneven settlement of the roadbed and salutatory flow ice caused by freeze-thaw, as well as landslide mechanisms and motion characteristics were analyzed. The analysis used ground temperature, moisture, surface and landslide deformation monitoring data from 2009-2012 in the Bei'an to Heihe Expressway sections K161+440, K161+860, and K178+530, which traverses the north section of the Lesser Khin-gan Mountain. The results of this study demonstrates that in the past 50 years, the annual average temperature in the Sunwu region had an upward trend, and after 1995, when the annual average temperature in the region rose to above 0°C, the permafrost degradation process accelerated. Landslides, roadbed settlement, and salutatory flow ice in the road area are often influenced by atmospheric precipitation, melting permafrost, seepage water, air temperature, geological condition, and human activity. These geological problems are affected by seasonal temperature changes, slope water content change, and other related geological conditions, and have the characteristics of being low angle, intermittent, and creeping.
15063003 Chaouachi, M. (University of Goettingen, Department of Crystallography, Goettingen, Germany); Sell, K.; Falenty, A.; Enzmann, F.; Kersten, M.; Pinzer, Bernd; Saenger, Erik H. and Kuhs, W. F. Direct observations of gas-hydrate formation in natural porous media on the micro-scale [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract MR51A-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Gas hydrates (GH) are crystalline, inclusion compounds consisting of hydrogen-bonded water network encaging small gas molecules such as methane, ethane, CO2, etc (Sloan and Koh 2008). Natural gas hydrates are found worldwide in marine sediments and permafrost regions as a result of a reaction of biogenic or thermogenic gas with water under elevated pressure. Although a large amount of research on GH has been carried out over the years, the micro-structural aspects of GH growth, and in particular the contacts with the sedimentary matrix as well as the details of the distribution remain largely speculative. The present study was undertaken to shed light onto the well-established but not fully understood seismic anomalies, in particular the unusual attenuation of seismic waves in GH-bearing sediments, which may well be linked to micro-structural features. Observations of in-situ GH growth have been performed in a custom-build pressure cell (operating pressures up to several bar) mounted at the TOMCAT beam line of SLS/PSI. In order to provide sufficient absorption contrast between phases and reduce pressure requirements for the cell we have used Xe instead of CH4. To the best of our knowledge this represents the first direct observation of GH growth in natural porous media with sub-micron spatial resolution and gives insight into the nucleation location and growth process of GH. The progress of the formation of sI Xe-hydrate in natural quartz sand was observed with a time-resolution of several minutes; the runs were conducted with an excess of a free-gas phase and show that the nucleation starts at the gas-water interface. Initially, a GH film is formed at this interface with a typical thickness of several mm; this film may well be permeable to gas as suggested in the past - which would explain the rapid transport of gas molecules for further conversion of water to hydrate, completed in less than 20 min. Clearly, initially the growth is directed mainly into the liquid (and not into the gas phase as sometimes suggested). The observations of the 2D slices after full transformation show for all systems studied that hydrates tend to concentrate in the center of pore spaces and do not adhere in a systematic manner to quartz grains. Whether or not a thin film of water remained at the quartz-GH interface after completion of the reaction is presently under investigation.
15058809 DeStasio, J. (University of New Hampshire, Natural Resources and the Environment and Earth Sciences, Durham, NH); Halloran, M.; Erickson, L. M.; Varner, Ruth K.; Johnson, Joel E.; Setera, J.; Prado, M. F.; Wik, Martin and Crill, Patrick M. Methane and carbon dioxide production rates in lake sediments from sub-arctic Sweden [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC23B-0910, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Ecosystems at high latitudes are undergoing rapid change due to amplified arctic warming. Lakes in these regions are sources of both methane (CH4) and carbon dioxide (CO2) to the atmosphere and will likely be impacted by elevated temperatures. Because of the potential increase in the release of organic carbon due to thawing permafrost, it is believed that methanogenesis rates within neighboring fresh water sediments will display a positive feedback response, by increasing CH4 emission to the atmosphere. We studied CH4 production potential of sediments using cores from three lakes in the Stordalen Mire complex in sub-Arctic, Sweden: Inre Harrsjon, Mellan Harrsjon, and Villasjon. Sediment cores were incubated to determine CO2 and CH4 production rates and were analyzed for CH4 concentrations, dissolved inorganic carbon (DIC) concentrations, total organic carbon (TOC) concentrations, as well as carbon, nitrogen and sulfur content. Our results from the Villasjon cores indicate that CH4 production rates were highest at the same sediment depths as peak dissolved CH4 concentrations, with maximum values between depths of approximately 10 cm and 30 cm. Additionally, the highest observed CH4 production rates were in sediments from areas within Villasjon known to have the highest rates of CH4 ebullition. CO2 production rates were generally highest within surface sediments ranging from about 4 cm to 11 cm in depth, with production rates displaying a steady decrease below 11 cm. Additionally, observed CO2 production rates correlated with total organic carbon (TOC) concentrations with respect to sediment depth, but displayed no relationship with dissolved inorganic carbon (DIC). Further analysis will be conducted to determine how CH4 and CO2 production characteristics vary between sediment core samples, as well as isotopic analysis of select samples taken from each lake.
15059034 Gleeson, Tom P. (McGill University, Montreal, QC, Canada); Moosdorf, Nils; Hartmann, Jens and van Beek, L. P. High-resolution, Global Hydrogeology Maps (GHyM) of near-surface permeability, porosity and water table type [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H13O-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The lack of robust, spatially-distributed subsurface data is key obstacle limiting the implementation of complex and realistic groundwater dynamics into global land surface, hydrologic and climate models. We map and analyze permeability, porosity and water table ratio globally and at high-resolution for the first time. Permeability and porosity are crucial hydrogeologic parameters while the water table ratio is a dimensionless ratio that predicts how the water table functions, either as topography-controlled or recharge-controlled. The new permeability and porosity maps are based on a recently completed high-resolution global lithology map with important refinements in regions of weathered tropical soils and permafrost regions. We use the high-resolution global permeability map as well as other data sets to compute the high resolution water table ratio globally. The spatially-distributed mean logarithmic permeabilities for the globe (assuming permafrost regions have negligible permeability) is -13.55 ± 1.9 m2 which is consistent with previous estimates of shallow crustal permeability. The water-table type is generally contiguous over large regions rather than fragmented across the landscape and that much of the globe is topography-controlled water tables. Therefore the water table is a subdued replica of topography in many more regions than the water table is recharge controlled and disconnected from topography. We hope the new, freely-available maps of permeability, porosity and water table type, called the Global Hydrogeology Maps (GHyM), will enable further integration of groundwater dynamics into land surface, hydrologic and climate models.
15056387 Hubbard, S. S. (Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA); Dafflon, B.; Wainwright, H. M.; Tokunaga, T. K.; Ulrich, C.; Jansson, J.; Torn, M. S. and Williams, K. H. Characterizing controls on terrestrial environment functioning across scales using geophysical datasets [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H41L-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Developing an understanding of critical zone dynamics requires consideration of a broad range of processes that occur across disparate space and time scales. In this study, we combine geophysical and point-based measurements to investigate controls on terrestrial environment functioning at two contrasting sites. The first study is underway within the Arctic tundra at the DOE Next Generation Ecosystem experimental site near Barrow, AK. At this site, we are exploring relationships between land surface, active layer, and permafrost properties using remote sensing, surface geophysical (electrical, electromagnetic and ground penetrating radar), wellbore and point measurements. Early results suggest the strong correspondence between the variability of land-surface and subsurface properties relevant to carbon cycling. The second study is underway at the semi-arid, uranium contaminated DOE Rifle CO floodplain site, where we are exploring how seasonal snowmelt influences biogeochemical cycling in the heterogeneous subsurface. At this site, autonomously-collected electrical resistance tomographic data are being used to interpret variations in vadose zone infiltration and groundwater mixing. Although hydrological dynamics are interpreted to impart a significant control on biogeochemical processes at both sites, the complexity of the systems render quantification of the relationships difficult. Our findings suggest that geophysical datasets provide a useful framework for interpreting spatiotemporal variations in hydrological and biogeochemical measurements collected at discrete locations, which can in turn greatly improve the quantification of states and processes that govern system behavior across centimeter to kilometer length scales.
15059103 Karra, S. (Los Alamos National Laboratory, Los Alamos, NM); Bisht, G.; Lichtner, Peter C. and Hammond, G. E. Coupling geomechanics with flow and reactive transport in PFLOTRAN for subsurface applications [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H21E-1106, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
With increase in the number of emerging subsurface applications that involve several coupled processes such as thermal, hydrological, mechanical and chemical, there is a need for computational models that are capable of simulating these processes. Some of such applications include carbon sequestration, nuclear waste disposal, enhanced geothermal systems, degradation of permafrost in the Arctic, etc. In this work, the approach to couple geomechanics with non-isothermal flow and reactive transport in PFLOTRAN is described. PFLOTRAN (URL: http://www.pflotran.org) is a massively parallel open-source code originally developed for multiphase, non-isothermal flow and reactive transport. Details regarding the coupling algorithm, parallel framework and parallel performance is shown. Example simulations using this new multi-physics capability are also presented.
15056475 Lebedeva, L. (Nansen Environmental and Remote Sensing Centre, Saint Petersburg, Russian Federation) and Semenova, O. New perspectives of "old" data sources; the dataset of long-term research watersheds in the former Soviet Union for the task of hydrological models development, verification and comparison [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H53E-1468, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Lack of detailed process-oriented observational data is often claimed as one of the major obstacle for further advance of hydrological process understanding and development of deterministic models that do not rely on calibration. New sources of hydrological information (satellites, radars etc.) have the perspectives for the future but can not completely replace conventional and experimental observations at the moment. Long-term data-rich research catchments remain valuable if not the only source of information for development, verification, regionalization and comparison of different hydrological and environmental models. There existed the set of more than 20 such basins that were operated according to single observational program from the 1930-1950th to 1990th in the former Soviet Union. Research basins, so called water-balance stations, covered all main climatic and landscape zones such as taiga, forest-steppe, steppe, desert, mountains and permafrost regions. Each station conducted broad range of standard, special and experimental hydrometeorological field studies including spatially distributed meteorological observations, soil and snow variable states, measurements of the groundwater levels, hydrochemistry, evapotranspiration, discharges in several, often nested, slope- and small-scale watersheds, etc. The data were accompanied by the descriptions of observational techniques and landscapes allowing linking natural conditions with dominant hydrological processes. Each station is representative for larger area and the results of local studies could be transferred to other basins in similar conditions. Till recently the data existed only in hard copies in Russian language therefore they are not enough explored yet. We are currently digitizing main part of the observational and supportive materials and make it available for any scientific purpose via website URL: http://hydrograph-model.ru/. We propose to hydrological community to use the data for comprehensive intercomparison studies of our models and their modules to reject inadequate algorithms and advance our process understanding and modeling efforts in different environments.
15056453 Mann, D. H. (University of Alaska, Fairbanks, Geography Program, Fairbanks, AK); Gaglioti, Ben; Pohlmann, John W.; Rasic, Jeff T.; Jones, Benjamin M. and Wooller, M. J. Carbon inputs to Arctic streams and lakes during climate warming; lessons from prehistory [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H43B-1450, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Warming of the Arctic will cause perennially frozen ground (permafrost) to thaw and release ancient carbon into streams and lakes. How sensitive is permafrost-carbon release to warming? One way to answer this question is to quantify how permafrost C responded to prehistoric warming events. Here we use lake sediments as a long-term record of permafrost-C release from an arctic watershed. The radiocarbon-age offset is the age difference between the true age of deposition (the 14C age of delicate, terrestrial plant remains) and the apparent age of the sedimentary stratum where these plant remains were laid down (the 14C age of the surrounding bulk sediment). In many arctic lakes, true age is younger than apparent age because bulk organic sediment contains particulate and dissolved C originating from soils, peat, and permafrost. Shifts in the magnitude of the 14C-age offset over time provide a proxy for changes in the relative amount of permafrost C released from the watershed. Our age-offset record comes from the Lake of the Pleistocene (LOP), a partially-drained lake basin on the northern flank of the Brooks Range whose macrofossil-rich deposits were laid down continuously after 14,500 calendar years BP (cal yr BP). The LOP watershed is underlain by continuous permafrost and contains extensive, frozen peatlands. We excavated a wide swath of the former lake bed and collected paired samples of twigs and their enclosing sediment to construct a high-resolution age-offset chronology. Today, the radiocarbon age of dissolved and particulate organic matter being deposited in the LOP basin is 2,500 yr. During the warmer-than-present, Bolling-Allerod period (14,700-12,800 cal yr BP), and during Holocene Thermal Maximum (11,700-8500 cal yr BP), the age offset doubled to around 4,000 yr. This enhanced input of old C was interrupted during a reversion to cold conditions during the Younger Dryas (12,800-11,700 cal yr BP). Interesting, 14C-age offsets during the YD were similar to today's, suggesting that the thick peat now covering much of the LOP watershed is stabilizing permafrost C in the face of ongoing warming; however, the shielding capacity of the modern peat cover may now be approaching its limit. Enhanced permafrost thaw during the Bolling-Allerod and during the Holocene Thermal Maximum occurred despite the presence of widespread peat cover at those times, and dates on extralimital plant species suggest summer temperatures during these prehistoric warm periods were only 1-3 degrees C warmer than today. We may now be approaching a threshold leading to greatly enhanced permafrost-C release from this watershed.
15056454 Olefeldt, D. (University of Guelph, Guelph, ON, Canada); Turetsky, M.; Roulet, N. T. and Devito, K. J. Export of dissolved organic carbon from boreal peatlands in a changing climate; a song of ice and fire [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H43B-1453, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Loss of permafrost and increased wildfire occurrence are expected to affect large regions of the boreal and tundra biomes as a result of continued climate change. Peatlands are common in widespread regions along the permafrost boundary in both Eurasia and North America, where they are important sources of DOC to downstream aquatic ecosystem. Altered magnitude, timing and chemical composition of DOC export from peatlands following permafrost thaw or wildfire thus has the potential to alter C cycling in downstream aquatic ecosystems and the C balance at the catchment scale. The presence of permafrost in peatland regions has a strong influence on the organization of different peatland types. Permafrost is associated with a dominance of nutrient-poor bogs and peat plateaus that often are hydrologically disconnected from their larger catchment, while runoff is generated and conveyed through spatially discrete and nutrient-rich channel fens. Each peatland type of a sub-arctic peatland complex was accordingly found to have distinct DOC export patterns, where channel fens had higher DOC export of lower aromaticity in comparison to bogs and peat plateaus. On a larger spatial scale, we found that DOC characteristics among rivers along a 1000 km transect within a peatland-rich region of western Canada were strongly influenced by the presence of peatland permafrost. Catchments with permafrost had lower river DOC concentrations, and also exhibited a relative shift from humic/fulvic acid dominance of the DOC pool to a greater contribution from proteins/amino acids. Wildfire is known to alter soil organic matter characteristics through the combustion of recent litter and the formation of char. We found that DOC in peatland pore-water also was influenced by wildfire, causing increased DOC aromaticity, decreased biodegradability and increased photodegradability. However, this influence was only found in near-surface pore-water in peatlands - at the depth of the water table we found no difference between DOC in burned and unburned peatlands. We also sampled 30 lakes, half of which were located within a recent fire-perimeter, but could not detect any influence of wildfire on lake DOC characteristics or reactivity. Hence, while no pulse perturbation of aquatic C cycling was detected following wildfire in regions where peatlands dominate terrestrial DOC export, our results suggest that DOC of low biodegradability leached from old char layers deeper in the peat strata, likely is readily mineralized once it reaches lakes as a result of photodegradation. In order to understand the influence of terrestrial perturbations, such as permafrost thaw and wildfire, on peatland and catchment DOC export, our studies show that it is necessary to consider both effects on the source DOC characteristics as well as their hydrological connectivity to aquatic ecosystems. Regional differences in climate, surface geology and dominant ecosystems within catchments, are thus likely to moderate the response to a disturbance. Future research is needed to study interacting effects of wildfire and permafrost thaw, as their co-occurrence is likely to increase under future climate scenarios.
15066437 Smull, Erika M. (Colorado State University, Department of Civil & Environmental Engineering, Fort Collins, CO); Wlostowski, A. N.; Gooseff, M. N.; Bowden, W. B. and Wollheim, W. M. Stream tracer integrity; comparative analyses of rhodamine-WT and sodium chloride through transient storage modeling [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H33F-1456, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Solute transport in natural channels describes the transport of water and dissolved matter through a river reach of interest. Conservative tracers allow us to label a parcel of stream water, such that we can track its movement downstream through space and time. A transient storage model (TSM) can be fit to the breakthrough curve (BTC) following a stream tracer experiment, as a way to quantify advection, dispersion, and transient storage processes. Arctic streams and rivers, in particular, are continuously underlain by permafrost, which provides for a simplified surface water-groundwater exchange. Sodium chloride (NaCl) and Rhodamine-WT (RWT) are widely used tracers, and differences between the two in conservative behavior and detection limits have been noted in small-scale field and laboratory studies. This study seeks to further this understanding by applying the OTIS model to NaCl and RWT BTC data from a field study on the Kuparuk River, Alaska, at varying flow rates. There are two main questions to be answered: 1) Do differences in NaCl and RWT manifest in OTIS parameter values? 2) Are the OTIS model results reliable for NaCl, RWT, or both? Fieldwork was performed in the summer of 2012 on the Kuparuk River, and modeling was performed using a modified OTIS framework, which provided for parameter optimization and further global sensitivity analyses. The results of this study will contribute to the greater body of literature surrounding Arctic stream hydrology, and it will assist in methodology for future tracer field studies. Additionally, the modeling work will provide an analysis for OTIS parameter identifiability, and assess stream tracer integrity (i.e. how well the BTC data represents the system) and its relation to TSM performance (i.e. how well the TSM can find a unique fit to the BTC data). The quantitative tools used can be applied to other solute transport studies, to better understand potential deviations in model outcome due to stream tracer choice and/or underlying assumptions of OTIS.
15066541 Wood, J. (University of Exeter, College of Life and Environmental Sciences, Penryn, United Kingdom); Harrison, S. and Reinhardt, L. Mass movement inventories for climate research in the European Alps [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract NH21A-1508, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Climate influences landscape evolution through physical processes which affect the form of a landscape through myriad small- to large-scale mechanisms. These can manifest through mass movements and rockfalls which present an important geomorphological hazard in Alpine regions; threatening life, infrastructure and property. Modelling has shown that the response of mass movements to temperature and precipitation triggers vary over a number of timescales. Heavy rainfall events on shorter timescales (ranging from minutes to days) can exceed critical ground- and pore-water levels resulting in mass movement initiation (Iverson, 2000), whereas longer precipitation trends act as precursors to larger events. Extreme temperatures, such as the summer of 2003 which was characterised by "exceptional rockfall" (Gruber et al., 2004, p. 1) and extreme permafrost thaw in the European Alps, illustrate how short-term extreme increases in temperature can cause widespread destabilisation (Chemanda et al., 2005). Freeze-thaw action on seasonal timescales can greatly exaggerate mechanical weathering (Abele, 1997; Chigira, 2002), whilst increases in temperature (resulting from sub-annual to longer term changes) reduce both cohesive and tensile strength within slopes (Chemanda et al., 2005) leading to rock degradation. Differences in topography and geology in the region mean that the impacts of climate change are likely to vary in space and time and analysis of these is therefore required to understand the spatial patterns of mass movements through time. Here we present the development of a new regional mass movement inventory (RI) for the French and Swiss Alps. Our aim is to provide a substantial spatial picture of rockfalls and landsliding in the region through time. We discuss methods by which to improve existing inventories including the use of scaling relationships (Larsen et al., 2010) to calculate area based on a given volume for similar types of mass movement. We show that based on power-law theory (Stark and Hovius, 2001; Malamud et al., 2004), the log-linear trend which exists between area and frequency of mass movement occurrence is present for this historical dataset. We discuss the inclusion of other commonly-missed metrics such as geology and topography, and suggest open-source methods of sampling these into collated inventories (such as the RI). We present the results from a preliminary analysis of this database with COST733 synoptic weather types to suggest methods by which the influence of climate and weather on mass movements in the Alps may be investigated at the regional scale. We then conclude by discussing applications of this dataset for detection and attribution of climate change to the frequency and magnitude of mass movements and rockfalls in this region.
15059435 Carnevali, P. B. Matheus (Desert Research Institute, Reno, NV); Rohrssen, M.; Williams, M. R.; Love, G. D.; Michaud, A.; Adams, H.; Priscu, J.; Berisford, D.; Klesh, A.; Leichty, J.; Hand, K. P. and Murray, A. E. Methane sources in Arctic thermokarst lakes of the North Slope of Alaska [abstr.]: in 2014 Goldschmidt abstracts 2014, V.M. Goldschmidt Conference - Program and Abstracts, 24, p. 1621, 2014. Meeting: Goldschmidt 2014, June 8-13, 2014, Sacramento, CA.
15056371 Basnet, S. (City College of New York, New York, NY) and Shahroudi, N. A comparison of satellite land surface temperature with station measured temperature for improved detection of frozen ground [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract ED31C-0758, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The transition of the landscape between frozen and non-frozen conditions in seasonally frozen environments impacts climate and is closely linked to surface energy budget, vegetation growing season dynamics, and hydrological, ecological, and biogeochemical processes. Frozen ground occurs when the ground contains water, and the temperature of the ground goes down below 0° Celsius. In seasonally frozen environments, by the end of winter air temperatures rise above freezing, the snow pack and surface soil layer reach 0° Celsius and begin to thaw, resulting in a state change of the included water from solid to liquid. Surface temperature is one of the main factors that detects the frozen ground. In this study the land surface temperature (LST) derived from infrared (IR) radiance at International Satellite Cloud Climatology Project (ISCCP) is compared to ground surface temperature (GST) measurements from Integrated Surface Database (ISD) at National Climatic Data Center (NCDC) for 25 consecutive years (1985-2004). The analysis between LST and GST show high correlation in terms of both time and location. The research was carried out over the entire globe to study the trend between fluctuating temperature and snow cover. Number of days with temperature below zero (freezing) and above zero (thawing) were counted over a 34-year period for the GST data. Over the time winter was classified from severe to mild due to an increase in temperature. The analysis showed 2% increase in surface temperature during winter seasons and there was a decrease in the number of days with frozen ground globally. LST offers a great potential for monitoring temperature changes and is a reliable source of data for frozen ground detection.
15058832 Pourrier, Jonathan (Université Montpellier II, Hydrosciences Montpellier, Montpellier, France); Jourde, Herve; Kinnard, Christophe; Gascoin, Simon and Monnier, Sebastien. Glacier meltwater flow paths and storage in a geomorphologically complex glacial foreland; the case of the Tapado Glacier, dry Andes of Chile (30°S) [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC23D-0973, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In the Dry Andes, high altitude glacierized catchments are important contributor to streamflow and aquifer recharge. In this study we focused on the Tapado catchment, (30°S, 9 km2, elevation range: 4000 m - 5550 m) located in the upper Elqui river basin in northern Chile. This catchment encompasses the Tapado glacial complex, composed of an assemblage of the Tapado glacier and the glacial foreland (debris-covered glacier, rock glacier and moraines). Here we present the results of intensive hydrometeorological observations conducted over the 2011 glacier melt season (February to April). Weather, discharge and water electrical conductivity were monitored near the glacier snout and at the outlet of the glacial foreland. GPR observations realized on the glacial foreland are used to verify or complete interpretations of underground transfer modalities. The results show that the water production from the Tapado glacier is highly correlated with weather conditions, in particular incoming shortwave radiation and air temperature. Resulting daily and seasonal streamflow variability is buffered by the glacial foreland, where underground transfers occur through complex flow paths. However, the development of a thermokarst drainage network in a part of the glacial foreland, allows fast and concentrated water transfers, which reduces this buffering effect. The glacial foreland is shown to act as a reservoir, storing water during period of strong ice melt and providing water to downstream areas during periods of low melt. The internal structure of the glacial foreland revealed by GPR observations corroborates these analyses. The south-western part is composed by massive ice, covered by rock debris. The north-eastern part is composed by mixed ice and rock debris, presenting spatially variable ice content. Finally, the computation of the catchment water balance shows that the Tapado catchment presents a particularly high specific discharge in summer under a dry hydro-climatic context. Hence the Tapado catchment provides important water resources to downstream cultivated areas. Our study enables to better anticipate the impacts of the ongoing glacier shrinkage on the variability of streamflow at the outlet of the Tapado catchment.
15058807 Sletten, R. S. (University of Washington, Department of Earth and Space Sciences); Hagedorn, B.; Hallet, B. and Burnham, Jennifer L. Active layer warming and deepening at Thule, Greenland during past decade; a comparison of a polar desert and a polar semi-desert site [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC23A-0906, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Microclimate and soil temperature/moisture monitoring at a Polar Desert and a Polar Semi-Desert site at Thule, Greenland reveals recent warming trends and distinct differences between these two sites. Approximately 5 C of warming occurred at the Polar Desert site from 2004 to 2009, while the Polar Semi-desert site warmed only about 3.5 C. Since 2009, the temperatures remain higher but stable. This warming trend is also reflected in the active layer, both in warming of the soil and in deepening of the active layer. Trends in soil temperatures and active layer depth are controlled substantially by the snow cover. For the Polar Semi-desert site, soil temperatures are measured both under natural snow accumulation conditions and under enhanced snow accumulation where a snow fence was installed. The insulating effect of the snow cover is effective and results in significantly warmer winter soils, as has been shown in other artificial snow cover studies. The warmer winter soils may allow greater respiration during the transition seasons thereby releasing more of the accumulated soil carbon in these sites than that we have previously documented. The trends in temperature and moisture may in part be controlled by the higher wind velocities at the Polar Desert site. These conditions are likely to be dominant controls on the ecosystem, along with differences in lithology which affects the cryoturbation of the soils. This in-depth microclimate study, along with our studies of the soils and soil water chemistry provides a detailed comparison of the adjacent ecosystems and may allow us to better predict how slight changes in climatic conditions may influence these systems and their subsequent feedback on carbon cycling.
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