15026457 Iribarren Anacona, Pablo (Victoria University of Wellington, School of Geography, Environment and Earth Sciences, Wellington, New Zealand); Mackintosh, Andrew and Norton, Kevin Patrick. Hazardous processes and events from glacier and permafrost areas; lessons from the Chilean and Argentinean Andes: Earth Surface Processes and Landforms, 40(1), p. 2-21, illus. incl. 3 tables, sketch maps, 148 ref., January 2015.
Glacier and permafrost hazards such as glacial-lake outburst floods and rock-ice avalanches cause significant socio-economic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio-economic damages in this region in historic time (including glacial lake outburst floods, ice and rock-ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice-dammed lakes and 16 moraine-dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank among the largest events ever recorded (5000 ´ 106 m3 and 229 ´ 106 m3, respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long-term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short-term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10 ´ 106 m3) have impacted lakes, glaciers, and snow-covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far-reaching (> 50 km) flows. The eruption of ice-covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 ´ 106 m3. Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events. Abstract Copyright (2010), John Wiley & Sons, Ltd.
15019534 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Kikuchi, Colin P.; Wickland, Kimberly P. and Schuster, Paul. Runoff sources and flow paths in a partially burned, upland boreal catchment underlain by permafrost: Water Resources Research, 50(10), p. 8141-8158, illus. incl. 5 tables, sketch map, 70 ref., October 2014.
Boreal soils in permafrost regions contain vast quantities of frozen organic material that is released to terrestrial and aquatic environments via subsurface flow paths as permafrost thaws. Longer flow paths may allow chemical reduction of solutes, nutrients, and contaminants, with implications for greenhouse gas emissions and aqueous export. Predicting boreal catchment runoff is complicated by soil heterogeneities related to variability in active layer thickness, soil type, fire history, and preferential flow potential. By coupling measurements of permeability, infiltration potential, and water chemistry with a stream chemistry end-member mixing model, we tested the hypothesis that organic soils and burned slopes are the primary sources of runoff, and that runoff from burned soils is greater due to increased hydraulic connectivity. Organic soils were more permeable than mineral soils, and 25% of infiltration moved laterally upon reaching the organic-mineral soil boundary on unburned hillslopes. A large portion of the remaining water infiltrated into deeper, less permeable soils. In contrast, burned hillslopes displayed poorly defined soil horizons, allowing rapid, mineral-rich runoff through preferential pathways at various depths. On the catchment scale, mineral/organic runoff ratios averaged 1.6 and were as high as 5.2 for an individual storm. Our results suggest that burned soils are the dominant source of water and solutes reaching the stream in summer, whereas unburned soils may provide longer term storage and residence times necessary for production of anaerobic compounds. These results are relevant to predicting how boreal catchment drainage networks and stream export will evolve given continued warming and altered fire regimes. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
15019145 Johnston, Carmel E. (Montana State University, Department of Land Resources and Environmental Sciences, Bozeman, MT); Ewing, Stephanie A.; Harden, Jennifer W.; Varner, Ruth K.; Wickland, Kimberly P.; Koch, Joshua C.; Fuller, Christopher C.; Manies, Kristen and Jorgenson, M. Torre. Effect of permafrost thaw on CO2 and CH4 exchange in a western Alaska peatland chronosequence: Environmental Research Letters, 9(8), Paper no. 085004, illus. incl. 1 table, sketch map, 71 ref., August 2014.
Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH4), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO2) and CH4 exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH4 exchange in July (123±71 mg CH4-C m-2 d-1) was observed in features that have been thawed for 30 to 70 (<100) yr, where soils were warmer than at more recently thawed sites (14 to 21 yr; emitting 1.37±0.67 mg CH4-C m-2 d-1 in July) and had shallower water tables than at older sites (200 to 1400 yr; emitting 6.55±2.23 mg CH4-C m-2 d-1 in July). Carbon lost via CH4 efflux during the growing season at these intermediate age sites was 8% of uptake by net ecosystem exchange. Our results provide evidence that CH4 emissions following lowland permafrost thaw are enhanced over decadal time scales, but limited over millennia. Over larger spatial scales, adjacent fen systems may contribute sustained CH4 emission, CO2 uptake, and DOC export. We argue that over timescales of decades to centuries, thaw features in high-latitude lowland peatlands, particularly those developed on poorly drained mineral substrates, are a key locus of elevated CH4 emission to the atmosphere that must be considered for a complete understanding of high latitude CH4 dynamics. Copyright (Copyright) 2014 IOP Publishing Ltd
15019144 Schaefer, Kevin (University of Colorado, Cooperative Institute for Research in Environmental Sciences, Boulder, CO); Lantuit, Hugues; Romanovsky, Vladimir E.; Schuur, Edward A. G. and Witt, Ronald. The impact of the permafrost carbon feedback on global climate: Environmental Research Letters, 9(8), Paper no. 085003, illus. incl. 2 tables, sketch map, 65 ref., August 2014.
Degrading permafrost can alter ecosystems, damage infrastructure, and release enough carbon dioxide (CO2) and methane (CH4) to influence global climate. The permafrost carbon feedback (PCF) is the amplification of surface warming due to CO2 and CH4 emissions from thawing permafrost. An analysis of available estimates PCF strength and timing indicate 120±85 Gt of carbon emissions from thawing permafrost by 2100. This is equivalent to 5.7±4.0% of total anthropogenic emissions for the Intergovernmental Panel on Climate Change (IPCC) representative concentration pathway (RCP) 8.5 scenario and would increase global temperatures by 0.29±0.21°C or 7.8±5.7%. For RCP4.5, the scenario closest to the 2°C warming target for the climate change treaty, the range of cumulative emissions in 2100 from thawing permafrost decreases to between 27 and 100 Gt C with temperature increases between 0.05 and 0.15°C, but the relative fraction of permafrost to total emissions increases to between 3% and 11%. Any substantial warming results in a committed, long-term carbon release from thawing permafrost with 60% of emissions occurring after 2100, indicating that not accounting for permafrost emissions risks overshooting the 2°C warming target. Climate projections in the IPCC Fifth Assessment Report (AR5), and any emissions targets based on those projections, do not adequately account for emissions from thawing permafrost and the effects of the PCF on global climate. We recommend the IPCC commission a special assessment focusing on the PCF and its impact on global climate to supplement the AR5 in support of treaty negotiation. Copyright (Copyright) 2014 IOP Publishing Ltd
15019000 Yi Shuhua (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, State Key Laboratory of Cryospheric Sciences, Lanzhou, China); Wang Xiaoyun; Qin Yu; Xiang Bo and Ding Yongjian. Responses of alpine grassland on Qinghai-Tibetan Plateau to climate warming and permafrost degradation; a modeling perspective: Environmental Research Letters, 9(7), Paper no. 074014, illus. incl. 2 tables, sketch maps, 30 ref., July 2014.
Permafrost plays a critical role in soil hydrology. Thus, the degradation of permafrost under warming climate conditions may affect the alpine grassland ecosystem on the Qinghai-Tibetan Plateau. Previous space-for-time studies using plot and basin scales have reached contradictory conclusions. In this study, we applied a process-based ecosystem model (DOS-TEM) with a state-of-the-art permafrost hydrology scheme to examine this issue. Our results showed that 1) the DOS-TEM model could properly simulate the responses of soil thermal and hydrological dynamics and of ecosystem dynamics to climate warming and spatial differences in precipitation; 2) the simulated results were consistent with plot-scale studies showing that warming caused an increase in maximum unfrozen thickness, a reduction in vegetation and soil carbon pools as a whole, and decreases in soil water content, net primary production, and heterotrophic respiration; and 3) the simulated results were also consistent with basin-scale studies showing that the ecosystem responses to warming were different in regions with different combinations of water and energy constraints. Permafrost prevents water from draining into water reservoirs. However, the degradation of permafrost in response to warming is a long-term process that also enhances evapotranspiration. Thus, the degradation of the alpine grassland ecosystem on the Qinghai-Tibetan Plateau (releasing carbon) cannot be mainly attributed to the disappearing waterproofing function of permafrost. Copyright (Copyright) 2014 IOP Publishing Ltd
15018607 Olefeldt, D. (University of Guelph, Department of Integrative Biology, Guelph, ON, Canada); Persson, A. and Turetsky, M. R. Influence of the permafrost boundary on dissolved organic matter characteristics in rivers within the boreal and taiga plains of Western Canada: Environmental Research Letters, 9(3), Paper no. 035005, illus. incl. 2 tables, sketch map, 44 ref., March 2014.
Catchment export of terrestrial dissolved organic matter (DOM) and its downstream degradation in aquatic ecosystems are important components of landscape scale carbon balances. In order to assess the influence of peatland permafrost on river DOM characteristics, we sampled 65 rivers along a 900 km transect crossing into the southern discontinuous permafrost zone on the Boreal and Tundra Plains of western Canada. Catchment peatland cover and catchment location north or south of the permafrost boundary were found together to have strong influences on dissolved organic carbon (DOC) concentrations and DOM chemical composition. River DOC concentrations increased with catchment peatland cover, but were consistently lower for catchments north of the permafrost boundary. In contrast, protein fluorescence (PARAFAC analysis), was unrelated to catchment peatland cover but increased significantly in rivers north of the permafrost boundary. Humic and fulvic acid contribution to DOM fluorescence was lower in rivers draining catchments with large lakes than in other rivers, consistent with extensive photodegradation, but humic and fulvic acid fluorescence were also lower in rivers north of the permafrost boundary than in rivers to the south. We hypothesize that shifts in river DOM characteristics when crossing the permafrost boundary are related to the influence of permafrost on peatland hydrological connectivity to stream networks, peatland DOM characteristics and differences in DOM degradation within aquatic ecosystems. Copyright 2014 IOP Publishing Ltd
15026363 Mavromatis, Vasileios (Observatoire Midi-Pyrénées, Géosciences Environnement Toulouse, Toulouse, France); Prokushkin, Anatoly S.; Pokrovsky, Oleg S.; Viers, Jérôme and Korets, Mikhail A. Magnesium isotopes in permafrost-dominated central Siberian larch forest watersheds: Geochimica et Cosmochimica Acta, 147, p. 76-89, illus. incl. 2 tables, sketch map, 52 ref., December 15, 2014.
To unravel the Mg isotope fractionation pathways within the continuous permafrost zone in the larch deciduous forest of Central Siberia, we measured the Mg isotopic composition of two large Siberian rivers (Nizhnaya Tunguska and Kochechum, which flow into the Yenisey), a small forested stream, and the major fluid and solid sources of Mg in the watershed: atmospheric precipitates, surface suprapermafrost flow, interstitial soil solutions, plant biomass, litter and mineral soils. The obtained results indicate a significant seasonal variation in riverine water Mg isotope signatures. During the winter baseflow, the Mg isotope composition of large rivers is significantly lighter than the source basaltic rocks and the atmospheric depositions. These differences support the presence of fluids enriched in lighter Mg isotopes, such as those affected by the mineral precipitation of secondary silicates or fluids that dissolve sedimentary carbonate rocks. During the spring flood and in the summer and fall seasons, the river fluid d26Mg values increased by 0.2-0.3 ppm and approached the Mg isotope composition of the ground vegetation (dwarf shrubs, mosses) and the soil organic horizon. Overall, the riverine waters were 0.3-0.7 ppm lighter than the unaltered bedrock and the deep minerals soil horizons. The Mg isotopic compositions of Larix gmelinii organs (i.e., stem wood, roots and needles) exhibit a low variability. However, an enrichment of 0.2-0.3 ppm in the d26Mg of larch needles in the course of the growing season, from June to September can be observed. This enrichment most likely demonstrates uptake of isotopically heavier Mg by the plant in addition to the progressive thawing of the mineral soil (deepening of the active layer of the soil). Overall, the Mg isotope approach indicates the important contribution of vegetation (larch needles, mosses and dwarf shrubs) to the riverine Mg isotope signature and helps to reveal the contribution of isotopically light carbonate rocks in the large rivers of the Central Siberian Plateau. Abstract Copyright (2014) Elsevier, B.V.
15023643 Moore, Peter L. (Iowa State University of Science and Technology, Department of Natural Resource Ecology and Management, Ames, IA). Deformation of debris-ice mixtures: Reviews of Geophysics, 52(3), p. 435-467, illus. incl. 4 tables, 184 ref., September 2014.
Mixtures of rock debris and ice are common in high-latitude and high-altitude environments and are thought to be widespread elsewhere in our solar system. In the form of permafrost soils, glaciers, and rock glaciers, these debris-ice mixtures are often not static but slide and creep, generating many of the landforms and landscapes associated with the cryosphere. In this review, a broad range of field observations, theory, and experimental work relevant to the mechanical interactions between ice and rock debris are evaluated, with emphasis on the temperature and stress regimes common in terrestrial surface and near-surface environments. The first-order variables governing the deformation of debris-ice mixtures in these environments are debris concentration, particle size, temperature, solute concentration (salinity), and stress. A key observation from prior studies, consistent with expectations, is that debris-ice mixtures are usually more resistant to deformation at low temperatures than their pure end-member components. However, at temperatures closer to melting, the growth of unfrozen water films at ice-particle interfaces begins to reduce the strengthening effect and can even lead to profound weakening. Using existing quantitative relationships from theoretical and experimental work in permafrost engineering, ice mechanics, and glaciology combined with theory adapted from metallurgy and materials science, a simple constitutive framework is assembled that is capable of capturing most of the observed dynamics. This framework highlights the competition between the role of debris in impeding ice creep and the mitigating effects of unfrozen water at debris-ice interfaces. Abstract Copyright (2014), American Geophysical Union. All Rights Reserved.
15022815 Bockheim, James G. (University of Wisconsin Madison, Department of Soil Science, Madison, WI). Distribution, properties and origin of viscous flow features in the McMurdo dry valleys, Antarctica: Geomorphology, 204, p. 114-122, illus. incl. 5 tables, sketch map, 35 ref., January 1, 2014.
Satellite images and high resolution air photos, coupled with field examinations, were used to examine 24 rock glaciers/debris-covered glaciers and 25 gelifluction sheets, collectively referred to as viscous-flow features, in the McMurdo Dry Valleys, Antarctica. Debris-covered glaciers are the dominant form and are longer (mean length=2.5 km), wider (mean width=0.8 km), and less steep (mean slope=12°) than similar features reported in most arctic and alpine environments. The catchment areas tend to be large, averaging over 9 km2. Most of the debris-covered glaciers are tongue-shaped, and where excavation was possible, the ice core was readily observable. Gelifluction sheets primarily occur at the base of valley sidewalls below talus on slopes ranging from 5 to 30° (average=13°) and contain a very thin active layer (normal range 20 to 40 cm). Both viscous-flow forms occur on the north- and south-facing slopes of the east-west trending valleys and are concentrated in the inland mixed zone and stable upland microclimatic zone; these lobes were not found in the coastal thaw zone. Gelifluction sheets result from the melting of snow high on the valley walls, subsurface flow of meltwater on top of the permafrost, and slow movement downslope. They are readily observable from nonsorted polygons that are stretched into rectangles that are perpendicular to the slope and contain raised polygon rims upslope. The movement of gelifluction sheets can be detected from upturned stones containing carbonate coatings. Rates of horizontal surface flow of the viscous-flow features are comparable to those reported elsewhere in Antarctica and in the alpine and arctic regions of the world. Some of the viscous-flow features appear to be inactive, possibly reflecting the recession of alpine glaciers in high elevation cirques. Abstract Copyright (2014) Elsevier, B.V.
15022830 Wolfe, Stephen A. (Natural Resources Canada, Geological Survey of Canada, Ottawa, ON, Canada); Stevens, Christopher W.; Gaanderse, Adrian J. and Oldenborger, Greg A. Lithalsa distribution, morphology and landscape associations in the Great Slave Lowland, Northwest Territories, Canada: Geomorphology, 204, p. 302-313, illus. incl. 2 tables, sketch maps, 38 ref., January 1, 2014.
Lithalsas are permafrost mounds formed by ice segregation in mineral-rich soil that occur within the zone of discontinuous permafrost. Nearly 1800 lithalsas were mapped using archival aerial photographs within the Great Slave Lowland, Northwest Territories, Canada. These are up to 8 m high and several hundred meters in length and width. One lithalsa, examined by electrical resistivity and boreholes, rises 4 to 6 m above an adjacent peatland, shows clear evidence of ice-segregation at depth and ground heave of between 2.5 and 4.0 m, and is estimated to have formed within the past 700 years. Regionally, lithalsas are typically located adjacent to ponds and streams with mature forms vegetated by deciduous (birch) forest or mixed (birch and spruce) forest with a herb-shrub understory and include circular, crescentic and linear forms. They are abundant within the Lowland region, which contains widespread glaciolacustrine, lacustrine and alluvial fine-grained sediments. The lithalsas are most common within the first few tens of meters above the present level of Great Slave Lake, indicating that many are late Holocene, and some less than 1000 years, in age. A comparison with lithalsas in contemporary environments reveals that comparatively warm but extensive discontinuous permafrost, fine-grained sediments (alluvial, lacustrine, marine or glaciomarine), and available groundwater supply provide the climatic and hydro-geological parameters for the development of lithalsas in permafrost terrain. The identification of lithalsas in this region is important given their sensitivity to climate change and potential hazards to northern infrastructure upon thawing. Abstract Copyright (2014) Elsevier, B.V.
15020790 Zagorski, Jerzy (Ul. Czerniakowska 28a, Warsaw, Poland). Gazohydraty; nowy rodzaj paliw kopalnych [Gas hydrates; a new type of fossil fuel]: Przeglad Geologiczny, 61(8), p. 452-459 (English sum.), illus., 24 ref., 2013.
Unconventional hydrocarbon resources have attracted the attention of petroleum geologists in recent years. Gas hydrates are found in many regions of the world. These accumulations are localized in Arctic regions with permafrost as well as offshore. The first gas hydrate discovery occurred in the Siberian gas field Messoyakha in a permafrost zone and similar accumulations were found in Alaska. Offshore occurrences are located mainly on the continental slopes. Drillings and samples from permafrost and seabeds have provided vast amount of data on the conditions of gas hydrates formation and concentration and allow to better constrain the volume of hydrate-bearing sediments and their gas yield. Resources of hydrocarbons contained in gas hydrate deposits represent a vast energy source potential. Still an essential problem is to elaborate efficient commercial production technology. So far positive developments regard only laboratory or semi-commercial scale.
15026588 Reynaud Schaefer, Carlos Ernesto G. (Universidade Federal de Vicosa, Departamento de Solos, Vicosa, Brazil); Costa Pereira, Thiago Torres; Ker, Joao Carlos; Carreiro Almeida, Ivan Carlos; Bello Simas, Felipe Nogueira; Soares de Oliveira, Fabio; Correa, Guilherme Resende and Vieira, Goncalo. Soils and landforms at Hope Bay, Antarctic Peninsula; formation, classification, distribution, and relationships: Soil Science Society of America Journal, 79(1), p. 175-184, illus. incl. 8 tables, geol. sketch maps, 46 ref., February 2015.
Antarctic soils occur in restricted areas, but few integrated studies on soils and landforms have focused in the Antarctic Peninsula. We studied the representative soils of Hope Bay, emphasizing the processes of quaternary sedimentation, landforms, soil classification, and distribution. Results show that landforms and soils are closely associated in Hope Bay. Ornithogenic soils are associated with Late Pleistocene to Holocene stable ground moraines; these are currently being destroyed by thermokarst erosion around Lake Boekella. Lithic Haploturbels occur chiefly on shallow rocky terrains whereas Typic Haploturbels are found on patterned ground. In Hope Bay, a much colder climate prevails compared with the South Shetlands, and the widespread permafrost close to the surface warrants strong cryoclastic weathering with active and general gelifraction across different lithologies. The shallow occurrence of permafrost in Hope Bay has a strong regulating effect on soils, retarding leaching and soil development processes. Local soils are, in general, shallow and cryoturbic, and the current pedoenvironment on lowland stable areas was subjected to varying phosphatization on previously weathered sedimentary material. The evidence of phosphatization of a formerly larger area appears to be the main driver of pedogenesis at Hope Bay, and nesting activity by penguins on stable surfaces is capable of enhancing weathering and soil formation.
15018603 Jensen, A. E. (Idaho State University, Department of Geosciences, Pocatello, ID); Lohse, K. A.; Crosby, B. T. and Mora, C. I. Variations in soil carbon dioxide efflux across a thaw slump chronosequence in northwestern Alaska: Environmental Research Letters, 9(2), Paper no. 025001, illus. incl. 2 tables, sketch map, 48 ref., January 2014.
Warming of the arctic landscape results in permafrost thaw, which causes ground subsidence or thermokarst. Thermokarst formation on hillslopes leads to the formation of thermal erosion features that dramatically alter soil properties and likely affect soil carbon emissions, but such features have received little study in this regard. In order to assess the magnitude and persistence of altered emissions, we use a space-for-time substitution (thaw slump chronosequence) to quantify and compare peak growing season soil carbon dioxide (CO2) fluxes from undisturbed tundra, active, and stabilized thermal erosion features over two seasons. Measurements of soil temperature and moisture, soil organic matter, and bulk density are used to evaluate the factors controlling soil CO2 emissions from each of the three chronosequence stages. Soil CO2 efflux from the active slump is consistently less than half that observed in the undisturbed tundra or stabilized slump (1.8 versus 5.2 g CO2-C m-2 d-1 in 2011; 0.9 versus 3.2 g CO2-C m-2 d-1 in 2012), despite soil temperatures on the floor of the active slump that are 10-15°C warmer than the tundra and stabilized slump. Environmental factors such as soil temperature and moisture do not exert a strong control on CO2 efflux, rather, local soil physical and chemical properties such as soil organic matter and bulk density, are strongly and inversely related among these chronosequence stages (r2=0.97), and explain ~50% of the variation in soil CO2 efflux. Thus, despite profound soil warming and rapid exposure of buried carbon in the active slump, the low organic matter content, lack of stable vegetation, and large increases in the bulk densities in the uppermost portion of active slump soils (up to ~2.2 g-1 cm-3) appear to limit CO2 efflux from the active slump. Future studies should assess seasonal fluxes across these features and determine whether soil CO2 fluxes from active features with high organic content are similarly low. Copyright 2014 IOP Publishing Ltd
15019721 Koren, Victor (NOAA, National Weather Service); Smith, Michael and Cui, Zhengtao. Physically-based modifications to the Sacramento soil moisture accounting model; Part A, Modeling the effects of frozen ground on the runoff generation process: Journal of Hydrology, 519(Part D), p. 3475-3491, illus. incl. 6 tables, sketch map, 57 ref., November 27, 2014. Includes appendices.
This paper presents the first of two physically-based modifications to a widely-used and well-validated hydrologic precipitation-runoff model. Here, we modify the Sacramento Soil Moisture Accounting (SAC-SMA) model to include a physically-based representation of the effects of freezing and thawing soil on the runoff generation process. This model is called the SAC-SMA Heat Transfer model (SAC-HT). The frozen ground physics are taken from the Noah land surface model which serves as the land surface component of several National Center for Environmental Prediction (NCEP) numerical weather prediction models. SAC-HT requires a boundary condition of the soil temperature at the bottom of the soil column (a climatic annual air temperature is typically used, and parameters derived from readily available soil texture data). A noteworthy feature of SAC-HT is that the frozen ground component needs no parameter calibration. SAC-HT was tested at 11 sites in the U.S. for soil temperature, one site in Russia for soil temperature and soil moisture, eight basins in the upper Midwest for the effects of frozen-ground on streamflow, and one location for frost depth. High correlation coefficients for simulated soil temperature at three depths at 11 stations were achieved. Multi-year simulations of soil moisture and soil temperature agreed very well at the Valdai, Russia test location. In eight basins affected by seasonally frozen soil in the upper Midwest, SAC-HT provided improved streamflow simulations compared to SAC-SMA when both models used a priori parameters. Further improvement was gained through calibration of the non-frozen ground a priori parameters. Frost depth computed by SAC-HT compared well with observed values in the Root River basin in Minnesota. Abstract Copyright (2014) Elsevier, B.V.
15019500 Stecca, G. (Delft University of Technology, Delft, Netherlands); Siviglia, A. and Blom, A. Mathematical analysis of the Saint-Venant-Hirano model for mixed-sediment morphodynamics: Water Resources Research, 50(10), p. 7563-7589, illus., 53 ref., October 2014. Includes appendices.
Sediment of different size are transported in rivers under the action of flow. The first and still most popular sediment continuity model able to deal with mixed sediment is the so-called active layer model proposed by Hirano (1971, 1972). In this paper, we consider the one-dimensional hydromorphodynamic model given by the Saint-Venant equations for free-surface flow coupled with the active layer model. We perform a mathematical analysis of this model, extending the previous analysis by Ribberink (1987), including full unsteadiness and grainsize selectivity of the transported load by explicitly considering multiple sediment fractions. The presence of multiple fractions gives rise to distinct waves traveling in the downstream direction, for which we provide an analytical approximation of propagation velocity under any Froude regime. We finally investigate the role of different waves in advecting morphodynamic changes through the domain. To this aim, we implement an analytical linearized solver to analyze the propagation of small-amplitude perturbations of the bed elevation and grainsize distribution of the active layer as described by the system of governing equations. We find that initial gradients in the grainsize distribution of the active layer are able to trigger significant bed variations, which propagate in the downstream direction at faster pace than the "bed" wave arising from the unisize-sediment Saint-Venant-Exner model. We also verify that multiple "sorting" waves carry multiple associated bed perturbations, traveling at different speeds. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
15022822 Phillips, Jonathan D. (University of Kentucky, Department of Geography, Lexington, KY). State transitions in geomorphic responses to environmental change: Geomorphology, 204, p. 208-216, illus. incl. 4 tables, sketch maps, 60 ref., January 1, 2014.
The fundamental geomorphic responses to environmental change are qualitative changes in system states. This study is concerned with the complexity of state transition models (STM), and synchronization. The latter includes literal and inferential synchronization, the extent to which observations or relationships at one time period can be applied to others. Complexity concerns the extent to which STM structure may tend to amplify effects of change. Three metrics-spectral radius, Laplacian spectral radius, and algebraic connectivity-were applied to several generic geomorphic STMs, and to three real-world examples: the San Antonio River delta, soil transitions in a coastal plain agricultural landscape, and high-latitude thermokarst systems. While the Laplacian spectral radius was of limited use, spectral radius and algebraic complexity provide significant, independent information. The former is more sensitive to the intensity of cycles within the transition graph structure, and to the overall complexity of the STM. Spectral radius is an effective general index of graph complexity, and especially the likelihood of amplification and intensification of changes in environmental boundary conditions, or of the propagation of local disturbances within the system. The spectral radius analyses here illustrate that more information does not necessarily decrease uncertainty, as increased information often results in the expansion of state transition networks from simpler linear sequential and cyclic to more complex structures. Algebraic connectivity applied to landscape-scale STMs provides a measure of the likelihood of complex response, with synchronization inversely related to complex response. Abstract Copyright (2014) Elsevier, B.V.
15023015 Augustowski, Karol (Uniwersytet Pedagogiczny im. Komisji Edukacji Narodowej, Cracow, Poland); Chmielowska, Dorota and Kukulak, Jozef. Geologiczne uwarunkowania dynamiki procesow brzegowych rzek zachodniego Podhala [Geological controls on the dynamics of riverbank retreat in the western Podhale region]: Przeglad Geologiczny, 61(12), p. 755-763 (English sum.), illus. incl. 1 table, 35 ref., 2013.
The western part of Podhale region is drained by the Czarny Dunajec and the Bialy Dunajec rivers, flowing from the Tatra Mts., and streams originating in the region (Cichy Stream, Bystry Stream, Czerwony Stream, Wielki Rogoznik). River banks are cut in the Podhale Flysch or in the alluvium of these rivers overlain with loam deposits of varied origin. This paper investigates the combined effect of weathering, frost processes and mass movements on the banks of the Czarny Dunajec River and its tributaries typified by different substrate material. Bank retreat due to frost processes was measured during multigelation periods using erosion pins. Grain size distribution and cohesion of the substrate were also determined for alluvial and loam deposits. On flysch cutbanks, we determined joint spacing and the density and direction of fractures, and other structural and textural characteristics of the rocks. The results indicate that the rate of bank retreat decreases from the banks cut in sandy loam deposits, through alluvial loam banks (with high clay content), the banks composed of poorly cemented gravels and shaly flysch, to the banks cut in sandstones and highly cemented Neogene gravels. Bank retreat due to frost processes and mass-wasting was more efficient in the cold half-year.
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15026230 Arenson, Lukas U. (BGC Engineering, Vancouver, BC, Canada). Challenges with assessing geohazards related to degrading permafrost [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 252, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Mountain environments are generally very dynamic. Recent changes in climate, however, have affected the rates at which glacial and periglacial environments change. Based on current projections, those changes are expected to be even more dramatic in the future. Ground surface conditions and climatic settings influence the stability and dynamics of slopes in permafrost change. An increase in air temperature modifies the ground thermal regime and the surface energy balance resulting in active layer thickening, ground warming, runoff changes and alterations in frost action cycles. In consequence to these thermal fluxes and their second order impacts to geomorphological processes, the hazard potential for slope instabilities to occur from within such zones changes accordingly. Active layer detachments, thermokarst or increased mass movement frequencies may be unknown because they may not have led to impacts in the past. Under such dynamic conditions it is challenging to quantify the hazard from historic events alone. A typical, quantitative geohazard assessment relies on frequency-magnitude relationships determined from analyzing proxy data or direct observations. Such analyses usually assume stationarity in the available data, which means that no long-term changes occur in the time series. Under currently occurring degrading permafrost conditions, which may be unprecedented, such an assumption must be questioned and alternate approaches in geohazard assessments are required. In this presentation the challenges of geohazard assessments related to degrading permafrost in mountainous environments are highlighted. Based on these challenges a general framework is described. The proposed framework starts with an examination of the effects of changes in climate conditions and how this affects the ground thermal regime. Geohazard probabilities are assessed and compared using current conditions as well as those that may occur in the future. The sensitivity of a geohazard to these projected climatic conditions can then be used as a measure to assess the geohazard's vulnerability to climate change and may offer a systematic tool to evaluate future hazards from the periglacial belt.
15019197 Banville, David (Université Laval, Centre d'Études Nordiques, Quebec City, QC, Canada); Fortier, Richard; Lemieux, Jean-Michel; Molson, John W.; Therrien, René and Ouellet, Michel. Geophysical investigation of a glacial aquifer system in a degrading permafrost environment near Umiujaq, Nunavik, Canada, for 3D hydrogeological modeling purpose [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 67, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
The Center for Northern Studies at Université Laval, in collaboration with the Quebec Ministry of Environment, has implemented a network of groundwater monitoring wells in a 2 km2 catchment basin located in the discontinuous permafrost zone, near the Inuit community of Umiujaq in northern Quebec, Canada. This network provides a unique opportunity to monitor changes in groundwater flow dynamics resulting from permafrost degradation. A 3D geological model is currently being developed for the catchment. This model will be the basis of a 3D hydrogeological model simulating coupled groundwater flow and heat transport in the catchment. These simulations will help assess the future availability and sustainability of groundwater as a source of drinking water for northern communities. The studied catchment lies within a valley draining into Lac Guillaume-Delisle. The groundwater monitoring wells attest the presence of two aquifers: a shallow aquifer in a surficial littoral sand layer and a deep aquifer in glacio-fluvial sediments partly confined by frost-susceptible silty marine sediments. High-resolution aerial photographs, an airborne LiDAR digital elevation model and a map of Quaternary deposits are available to characterize the surface geology. Drilling logs provide subsurface data but it is considered too sparse to build a reliable 3D geological model. Geophysical investigation using seismic refraction, induced polarization and ground penetrating radar was thus undertaken in order to infer the bedrock topography, the extend of ice-rich permafrost and the spatial distribution of aquitard and aquifer materials along several 2D transects across the basin. These geophysical methods are complementary, which increases the reliability of the interpretation. In addition, existing data from drilling logs help constrain inversion of geophysical data. All data is currently analyzed, synthesized and integrated into the SKUA-GOCAD software to build the 3D geological model. This model will be the cornerstone of future hydrogeological simulations intended to assess the impact of climate change on groundwater resources in the presence of degrading permafrost.
15023802 Gruber, Stephan (Carleton University, Geography and Environmental Studies, Ottawa, ON, Canada) and Schmid, Marc-Olivier. Estimating patterns of permafrost occurrence in the Hindu-Kush Himalaya region [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 184, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Climate changes affect glacial and periglacial mountain landscapes. We can observe and measure the loss of surface ice (glaciers) and infer a similarly widespread loss of subsurface ice in permafrost. Investigating the role of permafrost thaw in mountain geomorphic dynamics, however, is difficult as we cannot obtain spatial observations of permafrost occurrence of characteristics. In the Hindu-Kush Himalaya region, our knowledge of permafrost occurrence is so sparse that often, it is difficult to even decide where a detailed investigation may be warranted. The Global Permafrost Zonation Index provides estimates of permafrost extent, i.e. the areal proportion of permafrost. The suitability of its parameterizations and driving data in Asian high mountains, however, is unknown. We performed a first-order evaluation of this data based on the mapping of rock glaciers. These are used, because they are visual indicators of permafrost, and because they can be delineated based on high-resolution remote sensing imagery freely available on Google Earth. For the mapping 4,000 square samples (approx. 30 km2) were randomly distributed over the project region. Every sample was investigated and rock glaciers were mapped by two independent researchers following precise mapping instructions. Samples with insufficient image quality were recorded but not mapped. It is shown that mapping of rock glaciers in Google Earth can be used as first-order evidence for permafrost in mountain areas without ground truth. The minimum elevation of rock glaciers varies between 3,500 and 5,500 m a.s.l. within the region. The Global Permafrost Zonation Index appears to be a reasonable first-order prediction of permafrost in the HKH and based on this, summary statistics and maps are presented.
15026229 Haeberli, Wilfried (University of Zurich, Geography Department, Zurich, Switzerland). Rock/ice avalanches from degrading permafrost into new lakes in deglaciating mountain ranges [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 252, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Continued atmospheric temperature rise in cold mountains causes rapid vanishing of glaciers but much slower degradation and thawing of permafrost. As a consequence, many still existing glacier and permafrost landscapes are now transforming into new landscapes of bare bedrock, loose debris, sparse vegetation, numerous new lakes and steep slopes with slowly degrading/thawing permafrost. In the European Alps, for instance, present glaciers on average loose about 2 km3 per year from their remaining total ice volume of about 80 ± 20 km3. Already in the second half of the century, less ice could be left in surface than in subsurface ice (recently estimated at about 25 km3). Total future lake volume was modeled to increase to a total volume of few km3. Comparable scenarios are likely to take place in many other cold mountain chains. During extended future time periods, the new high-mountain landscapes will be characterized by pronounced disequilibria within their geo- and ecosystems, including long-term stability reduction of steep/icy mountain slopes as a slow and delayed reaction to stress redistribution following de-buttressing by vanishing glaciers and to changes in mechanical strength and hydraulic permeability caused by permafrost degradation and thaw. Many of the new lakes and systems of lakes come into existence in close neighborhood to, or even directly at the foot of, deep-frozen slopes with thermal conditions far out of equilibrium and correspondingly decreasing stability. Such conditions are likely to persist for centuries if not millennia to come. The frequency of high-magnitude rock/ice avalanches seems to rise and the probability of high-magnitude events to reach large water bodies and to cause far-reaching flood waves systematically increases. Options for reduction of long-term risk include adapted spatial planning, early-warning systems, artificial lake-level lowering, and flood retention optimally in connection with multipurpose structures for hydropower production and/or irrigation. A key challenge for scientific research is thereby to define "hot spots" of risk by integrative approaches including process consideration as well as socio-economic vulnerability aspects. This may help deciding where priorities for hazard prevention must be set.
15026231 Hasler, Andreas (University of Fribourg, Department of Geoscience, Fribourg, Switzerland); Geertsema, Marten and Hoelzle, Martin. Permafrost favourability map of British Columbia [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 252, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
A wide variety of very large rock avalanches and an increase of reported rock fall and debris flows from many of the world's cold mountain regions, raise the concern that climate change is reducing slope stability. Permafrost warming and thaw is one of the possible explanations for this observed ongoing change, a hypothesis which is supported by different case-studies and process investigations. To this end, an estimate of potential permafrost distribution and its characteristics is useful for a forensic reanalyses of past events and for predicting where changes in hazard potential may be expected. For British Columbia only extremely coarse mapping of mountain permafrost distribution has been available up till now. Typical empirical-statistical approaches cannot be applied due to sparse ground temperature data over a large and heterogeneous area. To achieve a permafrost estimate we transferred existing permafrost models from comparable mountain ranges to British Columbia: We combined regional spatialized estimates of mean annual air temperature with topography controlled potential solar radiation to obtain an estimate of mean ground temperature throughout BC by applying the empirical relations found in other mid-latitude mountain ranges. Further, an illustrative interpretation key helps to interpret the map in consideration of the locally observable surface conditions. Distributed data from seven field sites are used to demonstrate the model validity and to give a rough estimate of the model uncertainty. The resulting map suggests that a large part of BC's mountain ranges contains permafrost and several recent rock slope failures occurred in permafrost areas.
15026292 Henkemans, Emily (University of Waterloo, Earth Science, Waterloo, ON, Canada); Frape, Shaun; Ruskeeniemi, Timo; Lehtinen, Anne and Claesson Liljedahl, Lillemor. Geochemical characterization of groundwater in an area of continuous permafrost adjacent to the Greenland ice sheet, Kangerlussuaq, West Greenland [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 263, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
In general, knowledge of groundwater chemistry in areas of continuous permafrost in Greenland relies on the study of springs and open pingos, while knowledge of deep groundwater chemistry is limited. Properly instrumented boreholes can provide additional insight into geochemical processes affecting groundwaters in cryogenic environments. As part of the Greenland Analogue Project (GAP), two deep boreholes were drilled and instrumented with sampling systems in the Kangerlussuaq Region of West Greenland. Borehole DH-GAP01 (221 m total length) was drilled at an angle and intercepts a talik beneath a lake less than 2 km from the Greenland ice sheet. Borehole DH-GAP04 (697 m total length) was drilled adjacent to the ice sheet and angled to allow sampling in the bedrock beneath the ice sheet. DH-GAP04 is equipped with three sampling sections installed below the base of the permafrost (350 m below ground surface). Isotopic (d18O, d2H, 3H, d34S-d18OSO4, 87Sr/86Sr, d37Cl and d81Br) and geochemical tools were used to compare the impact of mixing and water-rock interaction to cryogenic processes such as cryogenic concentration and solute exclusion during permafrost formation. Isotopic characterization of fracture minerals, crush and leach and out diffusion were also used to determine water-rock interaction and to obtain estimates of porewater composition to further define these end members. Groundwater in the bedrock beneath the margin of the ice sheet has an isotopic signature (d18O/ d2H) similar to the enriched end of the range of isotopic values observed for regional meltwaters. Recharging glacial meltwaters interact with both bedrock and fracture minerals, evolving from dilute Ca, Na, K-HCO3 type waters to brackish Ca-Na-SO4 waters. Based on the d34S/d18O and 87Sr/86Sr values of the groundwater and fracture fillings, the chemistry is dominated by dissolution of gypsum and other sulphate-bearing mineral phases found as fracture infillings. The extensive presence of gypsum, a highly soluble mineral, below 300 meters in the DH-GAP04 core suggests that the groundwater system below this depth has maintained a degree of stability during, and beyond, the Pleistocene.
15026228 Krautblatter, Michael (Technical University of Munich, Faculty of Civil Geo and Environmental Engineering, Munich, Germany). Permafrost and rock slope stability [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 252, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
An increasing number of rockfalls and rock slope failures from permafrost-affected rock faces have been reported in the last 20 years. However, rock slopes are complex systems with enormous memory effects, very long response times and a high level of spatial complexity on all scales. It is, thus, difficult to reveal systematic patterns of how permafrost rocks react to climate change from the short time scale of field observation. Here, we turn the problem upside down and look at systemic mechanical changes of bedrock with degrading permafrost. Warming frozen bedrock induces fundamental changes in rock- and ice-mechanical properties even well before melting the systems. From a rock mechanical point of view, warming significantly decreases compressive and tensile strength as well as fracture toughness of porous frozen rocks. From an ice-mechanical point of view, warming permafrost affects creep and fracture of ice in fractures and along rock-ice interfaces. We combine these aspects to a rock-ice mechanical model, which can explain anticipated temporal and spatial patterns as well susceptible magnitudes of rock slope failure following climate change. In the laboratory, we have we have started to systematically analyze the mechanical behavior of frozen and thawed rocks to proof the assumptions of the rock-ice mechanical model. Hereby we focus on changes in compressive and tensile strength, elastic properties, p- and s-wave propagation and electrical properties. To approach natural conditions we incorporate effects deriving from anisotropy and scale effects. In the field, we instrumented well-constrained rock instabilities with degrading permafrost to derive high-precision kinematic data and alongside with mechanical data of forcing parameters such cryostatic pressures. Hereby, we can distinguish typical mechanical regimes that we know from laboratory measurements and investigate the effectiveness of different processes incorporated in the rock-ice mechanical model. Here, we develop a simple rock ice-mechanical model that is capable of explaining spatial and temporal patters of rock instability in degrading permafrost rocks and test assumptions in the field and in the lab.
15019196 Lemieux, Jean-Michel (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Fortier, Richard; Molson, John W.; Therrien, René; Ouellet, Michel; Barth, Johannes; Murray, Renaud; Roy-Banville, David and Sottas, Jonathan. Monitoring groundwater flow dynamics in a glacial aquifer system containing degrading and discontinuous permafrost (Umiujaq, Nunavik, Canada) [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 67, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Field investigations have recently been conducted near the Inuit community of Umiujaq (Nunavik, Quebec, Canada), on the eastern shore of Hudson Bay, in order to assess the present and future potential of groundwater as a sustainable source of drinking water in northern communities. The field work combined detailed hydrologic, hydrogeologic, geophysical and thermal investigation methods in a small 2 km2 watershed located in a large valley east of Umiujaq, which drains into the northern end of Lac Guillaume-Delisle. This site lies within the discontinuous permafrost zone where significant permafrost degradation has been observed over the last two decades. The watershed is characterized by the presence of a thick coarse-grained glaciofluvial deposit forming a good aquifer below a thick silty marine unit containing discontinuous ice-rich permafrost. A shallow surficial aquifer lies above the silty unit. An extensive monitoring network has recently been installed in the watershed, including 3 weather stations, 24 groundwater monitoring wells, 9 drive points, 100 soil moisture and temperature probes in the unsaturated zone, 40 surface temperature probes, 3 snowpack thickness measurement stations, 4 heat flux plates and a H-flume at the outlet of the watershed. Twelve thermistance arrays have also been installed in permafrost and non-permafrost areas. Sampling of groundwater in the wells, and surface water in small lakes and at the catchment outlet, was carried out for geochemical analysis (inorganic parameters, stable isotopes of oxygen and hydrogen and radioactive isotopes of carbon, tritium and helium) and for assessment of water quality and origin. In this presentation, the monitoring network will be introduced and a conceptual hydrogeological model of the watershed will be outlined based on a preliminary interpretation of the newly acquired data.
15019437 Osleger, Dillon J. (Montana State University, Department of Earth Sciences-Geology, Bozeman, MT); Montross, Scott N.; Walker, Virginia; Lafrenière, Melissa J. and Lamoureux, Scott F. Spatial dimensions and impacts of permafrost disturbance on microbial community composition in High Arctic ecosystems [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 521, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Climate change is substantially affecting permafrost dynamics, hydrological conditions and landscape stability in High Arctic ecosystems. These changes will correspondingly influence watershed nutrient pathways and availability, mobilization and deposition of sedimentary materials, water quality, that ultimately result in dramatic changes to terrestrial and aquatic ecosystem function and global biogeochemical cycles. To date, inventories of microbial community composition in permafrost landscapes remain poorly defined. This study investigates the microbial community composition of three different Arctic permafrost environments (e.g., streams, thaw ponds, groundwater seeps) on the Sabine Peninsula, Melville Island, Nunavut. Our 16S rRNA gene pyrosequencing results were compared to physiographic and geochemical attributes of the system including: geologic substrate, soil moisture, vegetation, soil type, pH, and major cation and anion concentrations using NMDS (non-metric multidimensional scaling). Chloride and sulfate concentrations and deuterium excess values were used to determine the source of water, solute, and nutrients to streams, thaw ponds, and groundwater seeps. High Arctic ecosystems are an important component of major transitions occurring between Earth-surface environments and a rapidly emerging low-temperature terrestrial biosphere. Permafrost disturbance generates new surface and subsurface pathways for mobilization of solute and nutrients. These landscape scale changes will accelerate biogeochemical fluxes downstream, impact the composition of microbial communities, and ultimately alter the flow of energy and materials through terrestrial and aquatic ecosystems on Earth.
15019444 Pawley, Steven (Alberta Geological Survey, Edmonton, AB, Canada) and Utting, Daniel. Lidar and Landsat based mapping of peatland and permafrost terrain using object-based classification, northeast Alberta [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 522, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Approximately 210,000 km2of Northern Alberta exists within the zone of sporadic discontinuous permafrost, with 26% of the peatlands being estimated to contain perennially frozen ground. Two landform types are associated with permafrost peatlands in Alberta: forest-covered palsa bogs and larger peat plateaus, which form part of a heterogeneous mosaic of uplands, swamps, bogs and fens. The influence of permafrost on ground stability, ecology and surface hydrology, and its sensitivity to disturbance by infrastructure development, makes it an important component of land use and reclamation planning. However, to date, there has been limited mapping at a scale sufficient for these purposes, with previous airphoto-based interpretations providing only a small-scale delineation of the forest-covered permafrost terrain. This research presents results from a methodology and study situated near Fort McMurray, northeast Alberta. The aim of the study was to test the applicability of multispectral (Landsat, SPOT) and LiDAR-derived terrain morphological attributes to classify peatland and permafrost terrain using pixel and object-based image analysis (OBIA) approaches. Multi-resolution segmentation of LiDAR and multispectral data is used to delineate terrain objects. An attribute selection approach is then applied to determine the effectiveness of different spectral and spatial metrics, which are subsequently classified using random forests into upland, peatland, permafrost, and thermokarst terrain classes. Accuracy assessment has demonstrated high classification accuracies (>85%), but when contrasted with pixel-based classification, the OBIA approach produced more spatially coherent results concerning the distribution of localized palsa bogs. These results also demonstrate that near-surface permafrost is significantly more extensive than previously identified in northern Alberta, even at relatively low latitudes (~56.5°).
15019201 Shojae Ghias, Masoumeh (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Therrien, René; Molson, John W. and Lemieux, Jean-Michel. Numerical simulation of coupled groundwater flow and heat transport in a continuous permafrost environment [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 68, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Ongoing field investigations at the Iqaluit airport in Nunavut, Canada, aim at investigating factors that control freezing and thawing cycles of permafrost that in turn cause degradation of existing runways, taxiways, aprons and access roads. Iqaluit is located in the south-eastern part of Baffin Island at the head of Frobisher Bay, at a latitude of 63°45' N. The airport is constructed on a flat terrain located above a succession of glacial deposits and surrounded by hills and rocky plateaus of the Precambrian Shield, in a region of continuous permafrost. Data are currently being collected on soil temperature and movement, surficial geology, snowpack thickness, subsurface hydraulic and thermal properties, as well as water table elevations. The purpose of this work is to identify hydrogeological factors and environmental drivers that have the greatest influence on permafrost degradation at the Iqaluit airport, under future climate scenarios proposed by the IPCC. Based on the current hydrogeological conceptual model at the Iqaluit airport, numerical simulations of coupled groundwater flow and heat transport have been designed to test the impact of plausible combinations of hydrogeological parameters and surface conditions on the temporal and spatial evolution of permafrost degradation. A series of simulations have been designed based on current conditions at the Iqaluit airport, which are assumed to be representative of cold-region paved terrains. The scenarios considered here include: the effect of soil compaction and consolidation on surface material, such as paved roads or natural ground surface, the influence of snow cover, heterogeneity of subsurface glacial deposits including ice lenses, anisotropic hydraulic and thermal properties, and the role of recharge and ground water flow on ground temperature distribution including the relative effect of advective versus conductive heat transport. The results of the various simulations will help enhance the understanding of the interactions between the physical/thermal processes and feedback between frozen ground and different hydrogeological environments, which are of concern for hydrogeological studies in high-latitude areas.
15026288 Walvoord, Michelle A. (U. S. Geological Survey, Denver, CO); Briggs, Martin A.; Day-Lewis, Frederick D.; Jepsen, Steven M.; Lane, John W., Jr.; McKenzie, Jeffrey M.; Minsley, Burke; Striegl, Robert G.; Voss, Clifford I. and Wellman, Tristan P. Permafrost dynamics and changing hydrogeology in a lake-rich landscape [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 262, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Understanding the hydrogeologic control and rate of change of permafrost are critical for assessing climate change impacts in northern ecosystems. Lake-rich lowlands in interior Alaska provide critical habitat for migratory waterfowl, ungulates, and other wildlife. Despite low annual precipitation, the Yukon Flats area in the north central Yukon River Basin of Alaska (USA) supports over 20,000 lakes, due in part to the presence of permafrost. The fate of this lake-rich lowland and, by proxy, similar circumboreal lowland systems under projected climate warming is the focus of a series of recent studies highlighted here. Lake water chemistry analyses of over 200 lakes in the Yukon Flats reveal a large degree of spatial heterogeneity suggestive of a hydrogeologically disconnected system, a conclusion also supported by abrupt spatial changes in lake elevation. Airborne geophysical characterization shows a laterally continuous shallow gravel layer (~25-m thick) that would offer good hydraulic connectivity throughout the lowlands. However, the gravel layer is generally frozen (as permafrost) except beneath surface water bodies; thus inhibiting lateral pathways of groundwater flow under current conditions. Ground-based geophysical characterization provides a high resolution of permafrost distribution and relevant hydrogeologic features at several lake study sites. Relatively recent thaw in the gravel layer appears to be associated with lakes that have experienced change in size (area) over the past several decades, whereas lakes with taliks (unfrozen conduits) that fully penetrate the permafrost layer are more likely to be stable. Multi-scale permafrost characterization provides the basis for numerical models that simulate permafrost dynamics, lake-talik evolution, supra-, intra-, and sub-permafrost groundwater flow, lake-groundwater exchange, active layer dynamics, and permafrost aggradation response to lake recession. Collective field and simulation results provide insight into expected alterations in groundwater flowpaths, water budgets, lake distribution, and lake chemistry in discontinuous permafrost lowlands given continued climate and permafrost change.
15026289 Zhou Min (Peking University, College of Engineering, Beijing, China); Clauson, Kale; Sun Ziyong; Zheng Chunmiao and Zheng, Yan. Spatial and temporal variations in dissolved organic matter compositions of stream water influenced by permafrost melting in a small alpine watershed of Qinghai-Tibetan [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 262, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Climate warming induced permafrost melting in low altitude alpine environment is expected to influence the concentration and characteristics of dissolved organic matter (DOM) in stream water. To what extent such changes can be used to provide warnings for permafrost melting that can benefit from better understanding of spatial and temporal patterns of DOM characteristics. Stream (n=35) and thermokarst pool (n=26) waters collected in July 2012, April, July and Sept of 2013 from a small (area 25 km2), low latitude (99°50' - 99°54' E, 38°12' - 38°17' N) alpine (elevation 2960 - 4820m) watershed, Hulugou, in the NE Qinghai-Tibetan Plateau were analyzed for d18O and dD, concentrations of cations, anions and DOM, and DOM optical properties including specific UV absorbance (SUVA254) and fluorescence index (FI), and 13 DOM components obtained by PARAFAC modeling of fluorescence spectra. In three tributaries and the main stream, concentrations of DOM reached maximum in July of 2012 and 2013, with optical characteristics of DOM suggesting input of DOM with a source similar to thermokarst pool waters and also waters equilibrated with soil (15 ml add to 5 g wet soil) from 0 - 100 cm depth. Concentrations of DOM in one tributary, Red Gully (elevation 3059 - 3248 m) are much higher than in the other two (elevations 3155 - 3622 m and 3184 - 3413 m). Not only were the DOM concentrations of Red Gully water the highest at 4 sampling times (7.2 - 13.3 mg/l), the DOM also displayed the highest SUVA254 (2.3 - 3.2 L mgC-1 m-1), the lowest FI (1.34 - 1.43) and the highest protein components (36%-68%) that would not have been possible without influences of permafrost melting because these characteristics are similar to thermokarst pool waters and that the DOM characteristics of the two other branches are different. The influence of the Red Gully on the main stream DOM through mixing is evident from the stable isotope data and the correlation between SUVA254 and FI. Therefore, changes in concentration and composition of DOM are easily detected in stream water at the lowest altitude of the Hulugou watershed where degradation of permafrost is presumably the most. Seasonality of DOM in stream water is useful to delineate the spatial heterogeneity and the degree of permafrost melting in low attitude alpine environment sensitive to warming.
15023082 Boike, J. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Hubberten, H. W.; Lantuit, H. and Vitanen, L. Changing permafrost in the Arctic and its global effects in the 21st century (PAGE21); a large scale international and integrated project [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33C-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The northern permafrost region contains approximately 50% of the estimated global below-ground organic carbon pool and more than twice as much as is contained in the current atmospheric carbon pool. The sheer size of this carbon pool, together with the large amplitude of predicted arctic climate change implies that there is a high potential for global-scale feedbacks from Arctic climate change if these carbon reservoirs are destabilized. Nonetheless, significant gaps exist in our current state of knowledge that prevent us from producing accurate assessments of the vulnerability of the arctic permafrost to climate change, or of the implications of future climate change for global greenhouse gas (GHG) emissions. In order o close these gaps, the key objectives of PAGE21 are: to improve our understanding of the processes affecting the size of the arctic permafrost carbon and nitrogen pools, to produce, assemble and assess high-quality datasets in order to develop and evaluate representations of permafrost and related processes in global models, to improve these models accordingly, to use these models to reduce the uncertainties in feedbacks from arctic permafrost to global change. The concept of PAGE21 is to directly address these questions through a close interaction between monitoring activities, process studies and modeling on the pertinent temporal and spatial scales. PAGE21 is determined to break down the traditional barriers in permafrost sciences between observational and model-supported site studies and large-scale climate modeling.
15023081 Brown, J. (International Permafrost Association, Woods Hole, MA). The 50th anniversary of the First international conference on Permafrost [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33C-01, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
This year marks the 50th anniversary of the First international conference on Permafrost (ICOP) that was held at Purdue University on 11-15 November 1963. The conference was a historic event in that it brought together for the first time the leading researchers and practitioners from North America and other countries that had diverse interests and activities in the study and applications of perennially frozen ground, cold regions engineering and related laboratory investigations. The 285 registered participants represented engineers, researchers, manufacturers and builders from the USA (231), Canada (42), the USSR (5), Sweden (3) and Argentina, Austria, Great Britain, Japan, Norway, Poland, Switzerland, and West Germany. The conference was organized by the Building Research Advisory Board of the U.S. National Academy of Sciences-National Research Council (NAS-NRC). The carefully edited volume, published in 1966 by the NAS, is considered to be the first multi-national, English-language collection of papers devoted entirely to permafrost topics. The 100 published papers followed closely the actual conference venue and panel discussions: soils and vegetation (9), massive ground ice (10), geomorphology (16), phase equilibrium and transition (8), thermal aspects (8), physico-mechanical properties (7), exploration and site selection (11), sanitary and hydraulic engineering (14), and earthwork and foundations (17). This 1963 Purdue conference essentially broke the "ice" between East and West permafrost researchers and set the stage for the Second ICOP that was held in 1973 in Yakutsk, Siberia, and represented the first large international conference held in the restricted area of Siberia. All subsequent conferences maintained the interdisciplinary principles set forth at Purdue: two more in the United States (Fairbanks 1983, 2008), two in Canada (Edmonton 1978, Yellowknife 1998), and one in Trondheim, Norway (1988), Beijing, China (1993), and Zurich, Switzerland (2003), one more in Russia (Salekhard 2012). Throughout the 50-year history of the International conferences on Permafrost, publication of Proceedings has been the major legacy of each conference. Over the course of the 50 years more than 2000 papers in English were published in the ICOP Proceedings with the assistance of many hundreds of international reviewers. Starting in 2003 (8th ICOP), a second form of publication was initiated that involved Extended Abstracts. Following the formation of the International Permafrost Association (IPA) at the 1983 ICOP, subsequent conferences were under the auspices of the IPA. Starting with the 2008 conference, the Permafrost Young Researchers Network (PYRN) participated in conference activities. The IPA remains the lead organization that represents collectively both the international permafrost science and engineering communities. This first conference, 50 years ago, provided the foundation for the development of an international community of scientists and engineers committed to the advancement of permafrost research and related cold regions design and performance.
15023085 Chadburn, S. (University of Exeter, Exeter, United Kingdom); Burke, E.; Cox, P. and Friedlingstein, P. The effect of arctic mosses on the simulation of permafrost by the JULES land surface model [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C41A-0577, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Thawing permafrost is a potential source of large quantities of carbon, which could lead to significant climate feedbacks in the future, so it is important to include this effect in climate models. JULES (Joint UK Land Environment Simulator) is the land surface model used in the Hadley Centre climate model, as well as a land model in its own right, which will soon be used to quantify the magnitude of carbon release from permafrost thaw. It is therefore imperative that JULES simulates permafrost realistically. It has been shown that the model currently overestimates the permafrost active layer thickness, suggesting that its summer soil temperatures in permafrost regions are too high. One possible reason for this is that the physical properties of organic soil content such as moss and peat are not currently included. This organic matter is abundant at high latitudes and provides thermal insulation to the soil. In this work we include a routine to represent moss cover on the land surface, and find that it significantly improves the modelled soil temperatures. We quantify the effect of this new process on the large-scale representation of permafrost in JULES, including the active layer thickness.
15023089 Dong, X. (, Beijing, China) and Moore, J. Representing permafrost properties and snow density in CoLM [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C41A-0587, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Most land surface models (LSMs) used in climate models do not perform well in modeling the permafrost processes and snow model processes. Due to the complex permafrost distribution characteristics and landscapes of the difference vegetation covered land and snow covered land, the LSMs simulations are even worse. In this study, we revised the permafrost scheme in the original Common Land Model (CoLM) to improve its capability of simulating permafrost processes and snow density processes. We adopted a new frozen soil parameterization scheme, The present version of CoLM includes 10 soil layers of difference thicknesses down to 3.4 m, based on literature and temperature gradient measurements, we extended the model's bottom to a depth below. The simulation is a deep soil column of 25 soil layers. This value is set to 26.3 m deep. What's more, we revised the original snow cover fraction parameterization scheme of CoLM according to the special snow cover distribution characteristics. We revised a snow model including the effects of wind compaction on snow density. We calibrated and validated the modified model against Integrated Global Radiosonde Archive (IGRA) observations from 1986 to 2006. The results indicate that the modified model produced more reasonable simulations of radiation balance components and significantly improved the simulation of soil and snow model content. It also shows an improved capability of reproducing soil temperatures from the top to the bottom of soil layers. The modified CoLM provides a useful tool for understanding and predicting the fate of permafrost under a warming climate.
15023045 Fuchs, M. (Stockholm University, Department for Physical Geography and Quaternary Geology, Stockholm, Sweden). Soil organic carbon inventory and permafrost mapping in Tarfala Valley, northern Sweden; a first estimation of the belowground soil organic carbon storage in a sub-arctic high alpine permafrost environment [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0697, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost regions in the Northern Hemisphere store large amounts of organic carbon and are vulnerable to climate change. Due to a sustained warming of the climate, strongest in the northern high latitudes, permafrost thaws and organic carbon could be released in significant amounts which should not be neglected. This study investigates the soil organic carbon (SOC) storage in the Tarfala Valley (600-2,100 m a.s.l.), northern Sweden, and aims to give a first estimation of the total carbon stock in a sub-arctic high alpine permafrost environment. Further the study describes the actual extent of permafrost in the Tarfala Valley. To achieve these aims, two field studies were carried out, one in summer to collect soil samples and one in winter to measure the bottom temperature of snow (BTS). In addition, the soil samples were analyzed in the laboratory for bulk density, loss on ignition and elemental analyses. The estimated total SOC in the Tarfala catchment area of 31.2 km2 is 23.0 kt C for 0-30 cm and 28.2 kt C for 0-100 cm, which is on average 0.9 kg C m-2 for the upper meter of soil in the study area. Even though the soil organic carbon values are relatively low, these results contribute to the on-going soil organic carbon inventories in the circum-arctic. In Tarfala Valley, permafrost can be considered as continuous at an altitude above 1,561 m a.s.l., discontinuous above 1,218 m a.s.l. and sporadic above 875 m a.s.l. based on a logistic regression model with the altitude as single independent variable. This implies that most of the permafrost affected ground is at an altitude where only sparse or no vegetation is present and only low amounts of organic carbon is stored. In brief, Tarfala Valley cannot be considered as a permafrost carbon hotspot, because this sub-arctic alpine environment does not have the potential to release large amounts of carbon as a result of climate warming and permafrost thawing.
15023029 Hauck, C. (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Delaloye, R.; Roer, I. H.; Hilbich, C.; Hoelzle, M.; Kenner, R.; Kotlarski, S.; Lambiel, C.; Marmy, A.; Müller, J.; Noetzli, J.; Phillips, M.; Rajczak, J.; Salzmann, N.; Schaepman, M. E.; Schar, C.; Staub, B. and Völksch, I. The evolution of mountain permafrost in Switzerland [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C22A-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost, defined as lithospheric material whose temperature remains below 0 °C for two or more consecutive years, occurs in many high-mountain regions of the European Alps. Mountain permafrost in the European Alps is characterized by temperatures only a few degrees below zero and is therefore particularly sensitive to projected climate changes in the 21st century. To evaluate the sensitivity of mountain permafrost to climatic changes and to assess its future evolution, not only climatic variables such as air temperature, radiation and timing and duration of snow cover have to be considered, but also subsurface characteristics such as ground temperature, ice content, porosity or hydraulic properties. In Switzerland, permafrost monitoring started only 1-2 decades ago but currently comprises a large set of meteorological, geophysical, kinematic and ground thermal parameters at a large variety of field sites. Within a large integrating national project (The evolution of mountain permafrost in Switzerland: TEMPS) these data sets are jointly analyzed for the first time by combining observations with model simulations using a dynamic process-oriented soil model capable of addressing frozen terrain. In combination with results from Regional Climate Model ensembles, the project TEMPS aims to create plausible evolution scenarios of mountain permafrost at specific sites and will investigate the interactions between atmosphere and permafrost focusing on the evolution of ground temperature, ice content and related degradation and creep processes. This contribution will show first results concerning (a) new observation techniques in high-mountain permafrost, including thermal, geophysical and kinematic methods, (b) sensitivity studies with the soil model COUP regarding the impact of temperature and precipitation anomalies on different permafrost landforms and (c) strategies for downscaling and debiasing RCM output data for permafrost analysis on the station scale at high altitudes. The results illustrate the difficulties of scale mismatch between spatial models and point observations, as well as the problem of short time series in a climate context, but they highlight also the large potential of bringing together the monitoring and modeling communities, as both can provide key data for each other in the context of anticipated impacts of climate change. First results regarding the permafrost evolution in the Swiss Alps indicate several monitoring stations with permafrost temperatures close to the melting point, with corresponding phase changes observable with e.g. geophysical methods. Simulations suggest increasing air and ground temperatures until the end of the century with a corresponding reduction in snow cover, which does, however, not offset a general warming trend of permafrost temperatures in the simulation models. Nevertheless, the high variability of surface and subsurface materials in the permafrost regions of the European Alps will strongly modulate any general warming trend which might be visible within the coming decades.
15023038 Hayashi, M. (University of Calgary, Department of Geoscience, Calgary, AB, Canada); Rivière, A.; Quinton, W. L.; McKenzie, J. M. and Voss, C. I. Permafrost response to climate change; linking field observation with numerical simulation [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0690, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Scotty Creek basin (152 km2) is located in the Northwest Territories, Canada, within the peat-covered discontinuous permafrost zone with a high density of wetlands. The extensive peat layer (up to 3-4 m thick) is underlain by generally clay-rich glacial sediments. The landcover consists of peat plateaus underlain by permafrost, permafrost-free channel fens, and connected and isolated permafrost-free ombrotrophic flat bogs, occurring as a complex mosaic of patches. The runoff from peat plateaus drains into isolated bogs and a network of connected bogs and fens. During the course of field studies since 1999, stark changes have been observed on the permafrost plateaus, including a deepening of active layer, soil settlement and depression formation, and changes in the lateral and vertical extent of the unsaturated zone. In general, the area of permafrost plateaus is decreasing, and the areas of fens and bog areas are increasing. These changes affect water flow and induce changes in heat transport, which in turn affect the aforementioned changes in permafrost plateaus (i.e. feedback processes). The goal of this study is to understand the feedbacks and their effects on permafrost degradation by used of the field observations and numerical simulations. We use a modified version of the three-dimensional SUTRA model that can simulate groundwater flow and heat transport, including freeze-thaw processes. Numerical simulation of heat transport accounts for the effects of latent heat associated with freezing and thawing, and variable heat capacity, thermal conductivity, and permeability as a function of ice content. The model is used to simulate the plateau-fen-bog complex, where intensive field studies have generated a large amount of data. The SUTRA model does not simulate complex surface processes such as radiative and turbulent heat exchange, snow accumulation and melt, and canopy effects. We use an energy and water transfer model, Northern Ecosystem Soil Temperature (NEST) to calculate the surface conditions and provide the surface boundary conditions for SUTRA. The SUTRA results are then compared to the long-term field and remote sensing data of permafrost degradation. Various hypotheses regarding permafrost degradation are tested: a) tree canopy density, water saturation, soil settlement, and snow cover impact the surface energy budget, b) warmer water flow in fens and connected bogs influences the relative roles of conductive and advective heat transfer, c) the type of mineral soil located below the peat (e.g. silty sand, clay) influences heat transport, water storage and possibly sub-permafrost flow and d) the isolated bogs become connected with each other to form the drainage network. In addition, model simulations are conducted for a small section (3 km2) of the Scotty Creek basin to understand the current permafrost state and predict the degradation in the next twenty years using scenarios generated by a regional climate model.
15023047 Hendricks, A. (University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK); Saito, K.; Bigelow, N. H. and Walsh, J. E. Reconstructed Arctic biome and soil distributions; implications for the late Quaternary permafrost subsystem [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0699, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
As part of a larger project exploring permafrost distribution in the Arctic and Beringia region, we are updating BIOME4 model outputs and pollen maps for 21ka (ka = thousand years ago), 6ka, and 0ka time periods. Vegetation is a key control for permafrost distribution as it can affect the surface conditions controlling permafrost in high latitudes. BIOME4 is a coupled biogeography and biogeochemical model that simulates the global equilibrium distribution of biomes. BIOME4 was initially run with two historical climatologies for the 20th century, one of which is a more current climatology not used in previous BIOME4 runs, to obtain a general "present day" view of the biome distributions. The updated climatology shows advances in the tree line in northern Alaska, but both climatologies generally agree on evergreen and deciduous taiga/montane forest locations. Using PMIP3/CMIP5 global circulation model climate and soil data as well as prescribed carbon dioxide concentrations, we ran the BIOME4 model for each time period. 21ka reconstructions based on the BIOME4 model output show various types of tundra widespread across the region, as far south as 40°N. This differs from present day where modeled tundra is generally limited to northern areas poleward of 70°N, the southernmost extent being ~60°N. However, when compared to real-world data provided by the updated BIOME 6000 global paleovegetation map, preliminary 21ka tundra biomes differ in coverage. The model places shrub tundras in the focus region where we know graminoid or steppe type tundra existed. The discrepancy appears to arise from soil moisture content that was not changed in the BIOME4 runs for the different time periods, implying that soil water content may be very important in obtaining correct biome distributions in the Arctic. In particular, the modeling results suggest that moisture may be a critical feature determining the distribution of shrubby vs. herbaceous tundra. We know from lake level studies that available moisture was much reduced during the 21ka time period.
15023046 Mu, C. (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Zhang, T.; Cao, B.; Wang, Q.; Peng, X. and Cheng, G. Pedogenesis and permafrost carbon over the Eboling Ridge in Heihe River basin, northwestern China [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0698, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Based on field permafrost sampling and laboratory analysis, we found that the average storages of soil organic carbon (SOC), total nitrogen (TN) and soil inorganic carbon (SIC) in permafrost soils were much more than that in the active layer on the Eboling Mountain in the upper reach of Heihe River basin, northwestern China. The objective of this study is to better understand the main soil physicochemical parameters influencing C and N dynamics in permafrost regions of northwestern China. Specifically, we investigated the effect of pedogenesis, cryogenic structure and SIC on SOC, TN and water-soluble organic carbon (WSOC) in the permafrost regions. The preliminary results show that SIC is a significant factor influencing carbon flux between atmosphere and terrestrial ecosystem and the distribution patterns of SOC and N. There are high correlation between SIC, SOC and N in permafrost. SOC and SIC can interact with each other, their small change may radically alter the carbon balance. SIC as a major factor will be crucial for developing large scale models evaluating C and N dynamics. High contents of C and N combined with a low vertical variability in each horizon on the Eboling Mountain can be explained by longer duration of pedogenesis and the influence of permafrost. In permafrost regions, the vertical distribution of soil C and N is also influenced by soil cryogenic structure. The high content of WSOC in deep permafrost soils can be explained by the formation of the ground ice causes the WSOC enrichment followed moisture migration. The average WSOC content in permafrost soils was larger than that in the active layer, suggesting that the labile carbon in permafrost soils has higher quality. SIC can reflect the microbial activity indirectly, due to the good negative relationship between SIC, soil pH and C/N ratios in permafrost. Soil pH values were the important factor influencing the distribution of SIC in deep permafrost soils. SIC in permafrost soils was controlled by acidification and other processes depending on soil pH. Microbial activity may be lower in soils with more acidic pH than in soils at circumneutral and alkaline pH, due to less soluble dissolved organic matter. The effect of geochemical variation in permafrost soils on microbial activity and SOM decomposition rates needs more research. The degradation of permafrost and ground ice melting with permafrost temperature increase on the Eboling Mountain would have severe impact on soil C and available N, which may alter the ecosystems function in arid and semiarid regions. However, in the long term, the growth of vegetation can enhance due to growing season extending, precipitation increasing and temperature increase, which may cause more atmospheric carbon into plants and soils through the photosynthesis. Therefore, the response of permafrost degradation in arid and semi-arid regions to future climate, ecology and landscapes needs more experimental and modeling studies.
15023041 Panda, S. K. (Geophysical Institute, Fairbanks, AK); Marchenko, S. S.; Romanovsky, V. E. and Swanson, D. K. High-resolution near-surface permafrost modeling for the 21st century, Wrangell-St. Elias National Park and Preserve, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0693, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost within most part of Wrangell-St. Elias National Park and Preserve (WRST) is discontinuous and warm i.e. within a few degrees of thawing. It is the physical foundation on which the ecosystems in the park rest. Thawing of permafrost alters this foundation, and can alter ecosystems and landscapes. Nonetheless, the data on permafrost condition and extent within WRST is limited. The current and future permafrost distribution and thickness of active layer can be modeled, given sufficient data about ground properties, vegetation, topography, and climate. We used GIPL 1.0 (Spatially Distributed Model of Permafrost Dynamics in Alaska) model; and downscaled climate forcing from 5 Global Circulation Models (GCM) that work best for Alaska and high-resolution soil landscape and ecotype maps from National Park Service (NPS) as model inputs to develop high-resolution permafrost maps for the recent past (2001-10) and the future decades (2050s and 2090s). The soil landscape and ecotype maps were derived from Landsat TM scenes (Jorgenson et al. 2008). The modeling effort resulted in recent and future permafrost maps of WRST at a spatial resolution of 28.5 m, the best resolution permafrost maps available for any part of Alaska. The model mapped 80% of WRST as underlain by near-surface permafrost during the decade of 2001-10 (Fig. 1) and predicted 50% decrease in the near-surface permafrost extent by 2050s owing to a 2 °C increase in the mean decadal air temperature and slightly higher precipitation. According to the 5 GCM projections, the decadal air temperature will increase by another 2 °C between 2050s and 2090s which will likely cause further increase in the ground temperature and decrease in the permafrost extent. The model predicts a meager 15% of WRST would still remain underlain by near-surface permafrost toward the end of the 21st century. Comparison of the modeled permafrost distribution with in situ observation of permafrost presence/absence at 430 sites showed 95% agreement. Thus, the modeled permafrost distributions are reliable representation of near-surface permafrost extent within WRST. These maps are critical to understand the permafrost condition and to identify the sites vulnerable to thawing. These maps also facilitate informed decision making on resource management.
15023044 Sherstyukov, A. B. (All-Russian Research Institute of Hydrometeorological Information-World Data Center, Obninsk, Russian Federation). Long-term trends and changes of soil temperature of recent decade in the permafrost zone of Russia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0696, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The northern regions of Russia have rich natural resources (oil, gas). In recent years in these areas the engineering structure for oil and gas production and their transportation is increasingly built. Current global warming has a great influence on soil condition in the permafrost zone. This can lead to negative effects on buildings and infrastructure which are built on frozen soils. Changes of the soil state in an area of permafrost demand serious studying. Next steps have been done for research of this problem: Part 1. a) The daily data set of soil temperature under natural surface at depths up to 320 cm at the Russian meteorological stations has been prepared. The earliest year of data set is 1963, the current version is ending in 2011 (660 stations of Russia). Quality control of original data was performed in creating this data set. b) The data set of computed depth of soil seasonal thawing at the Russian meteorological stations till 2011 has been prepared (107 stations with yearly depth of thawing). Part 2. Changes of soils' condition for the last five decades have been researched based on the prepared data sets. The change of mean annual soil temperature at depths has been researched and soil warming in the vast area for 1963-2010 has been shown, the great trends (0.2 divided by 0.4°C/10 years) increase at 320 cm have been found in western and eastern Siberia, and the greatest trends (0,4 divided by 0.5°C/10 years) are found in their south part. This creates favorable conditions for an increase in seasonal thawing depth in a permafrost zone, especially in its south part. The map of average depth of soil seasonal thawing for the same period (1963-2010) was made. It showed that the the greatest depths of thawing 300-400 cm were observed near the border of permafrost and the smallest depths of 50-250 cm predominate in the area of continuous permafrost. Part 3. Global warming of climate was slowed down from the beginning of the XXI century as it is known from publications. Additional researches of soil temperature change in the recent decade showed that positive trends of soil temperature for this decade were changed on negative trends (-0.2 divided by -0.6°C/10 years) in south and southeast western Siberia. The most intensive decrease of soil temperature in this region is observed since 2007. Trends of the thawing depth for permafrost soils were obtained for 2001-2011. Greatest significant positive trends of thawing depth have been obtained in eastern Siberia (3 divided by 5 cm/year). However, spots with significant negative trends are obtained in central Yakutia, and also to the south of Lake Baikal and near the Kolyma River mouth. Conclusions: 1. Using the Russian daily data set of soil temperature at depths up to 320 cm for last 40-50 years, soil warming is shown over the vast territory of Russia. Maximum trends at the 320 cm depth are found in the south part of western and eastern Siberia. 2. One of the impacts of the current climate changes is the general tendency for the increase in the seasonal thawing depth in the vast territory of western and eastern Siberia. 3. In the recent decade the tendency of soil temperature decrease has appeared in the south part of western Siberia near the south border of permafrost also decrease seasonal thawing depth has appeared in some regions. The work was done with the financial support of RFBR (project 11-05-00691).
15023088 Su, X. (Directorate of Environmental and Radiation Protection and Assessment, Canadian Nuclear Safety Commission, Ottawa, ON, Canada); Booshehrian, A. and Wan, R. Numerical simulation of the issues related to uranium mining and tailings management in continuous permafrost zones in Nunavut, Canada [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C41A-0584, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In order to understand the potential environmental effects of a uranium mining and tailings management project in northern Canada, numerical simulations have been conducted on the Kiggavik Project to investigate the issues of permafrost degradation, mine pit floor heave and slope deformation, and potential inflow into the mine pits during mining and tailings disposition. The project includes the development of three open pit mines, the Main Zone, the Centre Zone, and the East Zone at the Kiggavik site, and an open pit mine and an underground mine at the Sissons site. The mined ore will be milled at the Kiggavik site and the mill tailings will be disposed back into the three open pits at Kiggavik. The mining and milling operation of the project will last about 15 to 20 years. Permafrost at the Kiggavik site extends between 220 m to 240 m below ground surface, while permafrost at the Sissons site ranges from 260 m to 280 m below ground surface. The center zone and the east zone will be excavated within permafrost, while the main zone and the open pit at Sissons will penetrate the permafrost layer. A high artesian pressure due to the permafrost constraint was measured at both Kiggavik and Sissons sites, and was found to be higher than the ground surface. The results of numerical simulations on the behavior of the continuous permafrost layer indicate that permafrost degradation around the pits or tailings management facilities is not significant during mine operation. No open talik would form below the excavated area as a result of depositing warm tailings in both East Zone and Centre Zone pits. A thin thawed zone of 3 to 5 m on the side of Centre Zone pit is developed, while the thawed area at the bottom of the pit extends to a depth of 10 to 15 m. For the Main Zone, where the excavation breaks through the permafrost, an open talik would remain following the operation period. The warm tailings would cause a 20 m thick thawed zone along the lower sides of the pit. With regard to the floor heave caused by both excavation and high artesian pressure, a pit bottom vertical deformation ranging from 30 to 50 mm was calculated when the excavation reached 5 m above the permafrost bottom. The wall deformation is between 70 and 100 mm with some tensile stress zones developed along the pit slope. Parametric study conducted on the potential groundwater inflow through a fault zone into the pits under the high artesian pressure reveals that inflow rates are very much dependent on the characteristics of the fault zone which cuts through the open pit/TMF. The numerical results obtained from the simulations provide valued information to assess the potential impact of the mining and the tailings management at Kiggavik to the environment. The deposition of warm tailings back into the excavated open pits would not likely to cause significant impact on permafrost during mine operation. However, additional characterization of the fault zones at the mine locations would be needed to ensure there is no significant inflow into the mining pits and the underground mine opening.
15023040 Woodward, A. (University of Alaska Fairbanks, Resilience & Adaptation Program, Fairbanks, AK) and Kofinas, G. Climate change and thawing permafrost in two Inupiaq communities of Alaska's Arctic; observations, implications, and resilience [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0692, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
For thousands of years the Inupiat of northern Alaska have relied on ecosystems underlain by permafrost for material and cultural resources. As permafrost thaws across the Arctic, these social-ecological systems are changing rapidly. Community-based research and extensive local knowledge of Inupiaq villagers offer unique and valuable contributions to understanding permafrost change and its implications for humans. We partnered with two Inupiaq communities in Alaska's Arctic to investigate current and potential effects of thawing permafrost on social-ecological systems. Anaktuvuk Pass is situated on thaw-stable consolidated gravel in the Brooks Range, while Selawik rests on ice-rich permafrost in Beringia lowland tundra. Using the transdisciplinary approach of resilience theory and mixed geophysical and ethnographic methods, we measured active layer thaw depths and documented local knowledge about climate and permafrost change. Thaw depths were greater overall in Selawik. Residents of both communities reported a variety of changes in surface features, hydrology, weather, flora, and fauna that they attribute to thawing permafrost and/or climate change. Overall, Selawik residents described more numerous and extreme examples of such changes, expressed higher degrees of certainty that change is occurring, and anticipated more significant and negative implications for their way of life than did residents of Anaktuvuk Pass. Of the two villages, Selawik faces greater and more immediate challenges to the resilience of its social-ecological system as permafrost thaws.
15026287 Young, Michael (University of Texas, Austin, Austin, TX); Abolt, Charles J.; Caldwell, Todd G. and Larson, Toti. High-resolution carbon inventory and dynamics in permafrost soils; North Slope, Alaska [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 262, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Perennially frozen soils cover ~17% of the global soil area and are estimated to hold over 1,000 Pg of soil organic carbon (SOC) within their top three meters, making it one of the world's largest stocks of organic carbon. Studies predict varying extents to which ice-wedge polygons serve as carbon sources or sinks. Our goals are to generate a high-resolution data set of SOC stocks that incorporate the effects of cryoturbation and microtopographic land surface features and to use this information to predict mobility of carbon from soils within ice-wedge polygons to wetlands and thermokarst lakes in low-gradient watersheds. The field site is located 50 km south of Deadhorse, Alaska, within wetland tundra that contains extensive ice wedge polygon terrain. The study began in 2012 with high-resolution lidar acquisition (~20 points/m2) in a 480 km2 region, from which individual polygon morphology (e.g., high centered, low centered) could be discerned. In 2013, soil samples were collected from 101 pits within a (100 km2) subarea. Samples were analyzed for TOC, carbon isotopes, and soil texture. In 2014, we further reduced scale to 400 m2 using ground penetrating radar (GPR), cone penetrometry, methane and CO2 gas flux, dissolved and particulate organic carbon (DOC and POC) measurements and laboratory estimates of soil hydraulic and thermal properties. The results of these analyses are used to model carbon transport in aqueous and gaseous (CO2 or CH4) phases. Because this carbon loss may be coupled to direct erosion of ice wedge polygons, we developed a numerical model of soil polygon thermo-erosion, and used it to estimate potential carbon loss as polygons transition from low- to high-centered. GPR results show variability of the active layer thickness and potential flow paths for DOC, and the numerical model highlights the potential for soil erosion as a substantial source of carbon for hydrologic transport. Though results are preliminary, we show the value of coupling soil carbon stocks, hydraulic properties, and fluxes to estimate carbon dynamics.
15019423 Bandara, Sasiri (University of Alberta, Earth and Atmospheric Sciences, Edmonton, AB, Canada) and Froese, Duane. Assessing thermokarst lake history in the Old Crow Basin, northern Yukon, using cryostratigraphy and stable isotope records [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 519, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Thermokarst lakes form following the thaw of ice-rich permafrost and typically drain after 100s to 1000s of years followed by the accumulation of peat, which may lead to the re-aggradation of ice-rich permafrost and a subsequent generation of thaw lakes should disturbance occur. In this study, we investigate the thaw lake cycle through drilling and recovery of permafrost cores from drained thermokarst lake basins in the Old Crow Flats, northern Yukon. Thermokarst lakes and drained thermokarst lake basins are ubiquitous (>3000) in the Old Crow area, but little is known about the environmental dynamics of these basins over Holocene timescales, and whether these lakes follow a "thaw lake cycle". Here, we assess the history of several thermokarst lakes through sampling and analysis of permafrost cores recovered from six drained thaw lakes in the Old Crow Flats. We establish the hydrology and drainage history of these lakes on the basis of pore-ice stable isotope analyses and radiocarbon dates of associated organic materials. The results indicate that only 1 out of the 6 lakes shows evidence of multiple thermokarst cycles. Radiocarbon ages from woody macrofossils show that post-drainage peat accumulation rates are initially rapid, but slow down thereafter. Pore-ice isotopic analyses suggest differing hydrological conditions following lake drainage and peatland development. Specifically, four of our lakes show depletion in d18O over time, reflecting increased contributions from winter precipitation, while one lake shows d18O enrichment over time, indicating predominantly evaporative conditions. The sixth lake shows a relatively constant isotopic history due to largely unchanged near-surface hydrology. These findings suggest variable post-drainage isotopic histories between thermokarst lake basins as a result of spatially varying ecological succession and hydrologic conditions.
15023803 Brardinoni, Francesco (University of Milano-Bicocca, Department of Earth and Environmental Sciences, Milan, Italy); Scotti, Riccardo; Cavalli, Marco and Mair, Volkmar. Landslide and debris-flow sediment flux in glacial and periglacial mountain drainage basins of the eastern Italian Alps [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 184, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
While it is widely recognized that deglaciation and permafrost degradation can induce generalized instability in steep mountain terrain, beyond the documentation of single catastrophic mass-wasting events, there appears to be little empirical work on how the colluvial sediment cascade functions under conditions of increasing atmospheric temperature rise in a formerly glaciated landscape structure. Understanding and quantifying the influence of similar transient conditions on mass-wasting processes holds critical long-term implications on the overall sediment flux reshaping post-LGM landscape evolution, as well as more practical short-term applications on water quality issues, damage control to infrastructure, and reservoir siltation. We present an integrated approach that aims to: (i) document the spatial distribution of mass-wasting activity and sediment production in the Saldur River basin (97 km2); (ii) detect causal linkages between mass-wasting intensity, the potential spatial distribution of discontinuous permafrost, and patterns of glacier retreat; (iii) identify source-to-sink colluvial sedimentary pathways as modulated by the spatial organization of active and relict glacial and periglacial landforms; and (iv) test the reliability of a geomorphometry-based index of sediment connectivity. To these ends, we map rock glaciers, protalus ramparts and moraines, and compile a field- and air photo-based multi-temporal (1959-1969-1982-1997-2000-2006-2008-2011) inventory of colluvial sediment sources. We then combine these data with two historical datasets of debris flow and landslide events (both implemented and maintained by the Autonomous Province of Bolzano) and analyse mass-wasting spatial distribution and intensity in relation to proximity to glacier fronts, intact and relict periglacial landforms, and a permafrost index map (i.e., PermaNET; URL: http://www.permanet-alpinespace.eu/). This work is part of SedAlp (www.sedalp.eu), a project funded through the Alpine Space Programme, and benefits from COST Action ES1306: Connecteur.
15019198 Eckstein, Yoram (P. O. Box 3026, Kent, OH); Savichev, Oleg G. and Pasechnik, Elena Y. Is climate change affecting ground water chemistry in the largest boreal wetland? [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 67, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Boreal wetlands cover approximately 30% of the West Siberian Plain. The Great Vasuygan Mire, Northern Hemisphere's largest contiguous wetlands, occupies low-lying plains in the interfluve of two great Siberian rivers Ob and Irtysh. Most research to date has investigated the peat generating processes and reserves in the West-Siberian Plain wetlands, or the balance of greenhouse gases emissions from the wetlands. Little information exists about temporal changes in the chemical composition of the wetland waters within the Ob-Irtysh interfluve. Although the region's climate is continental with extended cold winters and short hot summers, Western Siberia is experiencing rapid climatic changes. The consequences of these changes include permafrost loss, snow cover reduction, and river flow changes. In this study we investigate whether and how increasing surface air temperatures contributed to changes in the chemical composition of the atmospheric precipitation and water in the mire. We use time-series analysis and multivariate statistics on the hydrochemical data collected between 1994 and 2013 at several sampling sites, to evaluate the statistical significance of the possible correlations between the increasing surface air temperatures and various chemical constituents in the precipitation and the wetland water.
15021446 Kennedy, Kristen (Yukon Geological Survey, Whitehorse, YT, Canada); Lipovsky, Panya and Benkert, Bronwyn. Geoscience mapping for climate change adaptation planning; landscape hazard maps as a tool for communities in Yukon, Canada [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 111, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
The mounting effects of climate change on Northern communities have been widely recognized in both the scientific and traditional knowledge communities. This is of particular concern in Yukon, where there is a high prevalence of warm permafrost and permafrost disappearance has already been documented. In order for Yukon's communities to develop strategies to respond and adapt to the impacts of climate warming on permafrost, it is important to identify and characterize vulnerability and sensitivity to environmental change. Landscape hazard classification maps, which create simplified representations of biophysical vulnerability, have emerged as useful tools in the assessment of landscape-scale vulnerability to climate change. They integrate science into decision-making by amalgamating and classifying geoscience data to create an easily-interpretable ranked representation of current and future hazard potential. Since 2010, the Yukon Geological Survey has been working with the Northern Climate ExChange (part of the Yukon Research Centre at Yukon College) to develop landscape hazards classification maps that identify and characterize existing and potential geologic and landscape-related hazards in Yukon communities (e.g., landslide risk, permafrost stability, flood frequency). To date, we have completed hazard maps for four communities, with an additional four underway. Examples of community-focused geological mapping will be presented, highlighting climate- and development-related hazard assessments and including other biophysical threats such as flooding and forest fires. While hazards mapping is not unique in the North, our approach places emphasis on locally-defined areas of importance identified by decision-makers, practitioners and residents of study communities, including areas identified for future community development or of current hazard-related concern. The creation of a landscape hazards map for Yukon communities represents a direct response to the region's needs, reflecting recognition that careful planning in response to potential future climate change impacts is a wise and resilient approach to sustainability.
15026298 McIntosh, Jennifer C. (University of Arizona, Department of Hydrology and Water Resources, Tucson, AZ); Person, Mark; Hamilton, Stewart; Grasby, Stephen E.; Schlegel, Melissa; Osborn, Stephen G.; Martini, Anna; Zhou, Zheng and Ballentine, Chris. Impacts of Pleistocene glaciation on hydrobiogeochemical processes in sedimentary basins [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 264, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Past and present continental glaciation is an important driver of basinal-scale fluid and solute transport, as well as biogeochemical processes at depth in sedimentary basins. Recent empirical and numerical modeling studies of formation waters from multiple aquifers within the Illinois, Michigan and Appalachian basins illustrate the timing, mechanisms, and magnitude of Pleistocene freshwater circulation. In addition, isotopic and microbial studies of natural gas reservoirs associated with Pleistocene age groundwater demonstrate the importance of freshwater recharge on enhancing biogenic gas generation. Influx of freshwater may have added terminal electron acceptors that actually served to oxidize hydrocarbons and were exhausted prior to methanogenesis. Groundwater flow systems within sedimentary basins are often highly impacted for relatively short periods of time (tens of thousands of years) as the ice sheets advance and retreat across sedimentary basins. Volumetrically significant quantities of relatively fresh groundwater are emplaced episodically during periods of glaciation. However, in some situations, permafrost cover blocks recharge. Because periods of glaciation in the midcontinent region are infrequent, a clear glacial end-member isotopic signature is not always apparent. The current distribution of geochemical tracers is likely the result of many cycles of glaciation. In some settings, overturns in geochemical profiles (e.g. saline water overlaying freshwater) suggest that geochemical conditions are far from equilibrium. Synthesis of ice sheet-permafrost-aquifer interactions in other sedimentary basins worldwide provides further insight into particularly useful natural tracers of the timing and source of freshwater recharge, penetration depths of glacial meltwater, extent of freshwater dilution of basinal brines, and distribution of biogenic gas accumulations. Glaciated sedimentary basins may be future storage sites of anthropogenic waste (e.g. radionuclides and carbon dioxide); thus, it is important to understand how future continental glaciation may alter subsurface hydrologic and biogeochemical conditions. In addition, Pleistocene age groundwater is an important, high quality, fossil water resource in northern latitude regions worldwide.
15023806 Ramsey, Meridith A. (North Dakota State University, Department of Geosciences, Fargo, ND); Lepper, Kenneth; Zamora, Felix J. and Lewis, Adam R. OSL dating of high elevation fan deposits in the Antarctic dry valleys; current results [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 185, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
We have been investigating high elevation alluvial fans, above 1000 m, in the McMurdo Dry Valleys of Antarctica as storehouses for proxy records of climate change. Alluvial deposits at high elevations are small and record occasional sedimentation events indicating brief periods of increased warmth along terrestrial margins of the East Antarctic Ice Sheet. The fans are inactive in the present day based on cross-cutting permafrost wedges and well-developed desert pavements on their surfaces. Thirteen samples from five of these relic alluvial fans, as well as 11 previously collected samples were dated using Optically Stimulated Luminescence (OSL) dating to determine when deposition from aqueous transport occurred, thereby dating brief periods of warming at the glacial margins. Our results suggest clusters of fan activity occurred at 1000-3000 calendar years ago and 8000-10,000 calendar years ago. The OSL ages indicate fan activity also occurred at other times throughout the past 120,000 years, but clustering at these older time periods cannot yet be verified due to the small number of available samples. Possible reasons for increased warmth during the time periods indicated (1-3 ka and 8-10 ka) will be discussed.
15023804 Sailer, Rudolf (University of Innsbruck, Institute of Geography, Innsbruck, Austria); Stötter, Johann; Klug, Christoph and Rieg, Lorenzo. The potential of repeat airborne lidar for the analysis of geomorphodynamic processes in high alpine terrain [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 184, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Airborne lidar offers a wide range of applicability in high alpine geomorphology. In contrast to non-recurring lidar surveys, which deliver base information of the topography and surface characteristics, repeat airborne lidar datasets can be used for the analysis of process induced changes. At the Institute of Geography, University of Innsbruck, Austria, unique datasets with varying repeat cycles and spatial captures are available. Beyond glaciological purposes and due to its high spatial resolution and accuracy these datasets facilitate not only the detection but also the quantification of geomorphodynamic process results over large mountainous regions. Hence, this study is focusing on the ability of airborne lidar data for the quantification of rock falls, debris flows and land slides as well as on permafrost related surface phenomena. Annual lidar surveys of the Rofental region (Otztal, Tyrol) started in 2001 aiming at the generation of geodetic mass balances of Hintereisferner. Due to its high vertical accuracy the lidar data are used for the analysis of dead ice melting, rock falls, fluvial processes and permafrost degradation in the vicinity of Hintereisferner on an annual base from 2001 to 2013. Even processes with very small annual changing rates such as permafrost degradation or fluvial erosion are analysed on the basis of the aforementioned multi-temporal airborne lidar dataset. In addition a bi-temporal lidar survey (2006 and 2010) of a larger area in the Tyrolean Central Alps is used to detect, quantify and analyse gravitative processes. Within this area 189 noteworthy events have been detected. It has to be emphasized that the majority of these events (occurred between 2006 and 2010) are areas where permafrost conditions are likely. Within this region more than 400 rock glaciers are found and the airborne lidar dataset is used to assign an activity index to each of them. The activity index is exclusively based on airborne lidar data, using the volumetric changes and the surface velocities of each rock glacier. We will give a comprehensive overview of the ability of repeat airborne lidar surveys in high alpine terrain, showing the capacities for the quantification of process results and subsequent process analysis like the introduction of a rock glacier activity index or the analysis of gravitative processes.
15023818 Weeks, Don P. (U. S. National Park Service, Water Resources Division, Denver, CO) and Koslow, Melinda. U. S. National Park Service; managing within a landscape of dynamic hydrological systems fueled by a changing climate [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 187, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Rising temperatures associated with climate change will influence many aspects of the hydrological systems in U.S. national parks. Salt water intrusion to coastal freshwater aquifers due to sea-level rise; increase in jökulhlaups in Alaska due to warming; loss of cold-water trout habitat in the U.S. interior West; and increase in coral bleaching in the Caribbean are just a sample of the challenges that park managers are either facing now or will face in the 21st Century. The average annual temperature in the U.S. has increased by 1.3° to 1.9° F since 1895, with most of this increase occurring since 1970. Average annual temperature in the Arctic has risen by almost twice the global rate over the past few decades. Temperatures in the U.S. are expected to continue to rise, further expanding the management challenges. Warmer surface temperatures will increase evaporation from the oceans and inland freshwater systems, which in turn increases globally averaged precipitation. Greater energy in the atmosphere due to warming can strengthen storms and change frequencies and timing, though these changes are difficult to model into the future. Rising temperatures have reduced lake ice, sea ice, glaciers, permafrost, and seasonal snow cover across the U.S. the past few decades. As the average annual temperature increases, sea level also rises due to ocean water expansion as it warms and contributions from melting glaciers and ice sheets. Oceans are also becoming more acidic as they continue to absorb the human-caused carbon dioxide. So how does the U.S. National Park Service manage within these dynamic hydrological systems fueled by a changing climate? How do you identify what climate future to plan for? These are not easy questions to answer and can sometimes be overwhelming. Or, if structured correctly, can stimulate new ways of thinking and planning. Scenario planning is a living process selected by the U.S. National Park Service to plan and manage into the uncertain future of climate change. Through this process, managers and others develop science-based scenarios of the future that incorporate plausible changes in climate and other key variables. These are used as a basis for identifying potential strategies to address future challenges to important resources and values, including the hydrological systems in U.S. national parks.
15020928 Bradley-Cook, Julia I. (Dartmouth University, Department of Ecology and Evolutionary Biology, Hanover, NH); Virginia, Ross A.; Hammond Wagner, C. and Racine, Phoebe E. Soil carbon storage and respiration potential across a landscape age and climate gradient in western Greenland [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B31C-0409, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The soil formation state factors proposed by Hans Jenny (climate, organisms, relief, parent material, time) explain many soil characteristics, yet geological controls on biological carbon cycling are not well represented in regional carbon models. Landscape age, for instance, can directly affect the quantity and quality of soil organic carbon, which are key determinants of the temperature sensitivity of soil organic matter (SOM) to decomposition. Temperature control of SOM decomposition is of particular importance in Arctic soils, which contain nearly half of global belowground organic carbon and have a permafrost thermal regime that straddles the freeze-thaw threshold. We investigated soil carbon storage and respiration potential across a west Greenland transect, and related the landscape carbon patterns to regional variation in climate and landscape age. The four study sites capture a range in: landscape age from 180 years on the inland Little Ice Age moraine near Kangerlussuaq to ~10,000 years at the coastal sites near Sisimiut and Nuuk, mean annual air temperatures from -5.7 to -1.4 °C, and mean annual precipitation from 149 to 752 mm. At each site, we collected surface and mineral samples from nine soil pits within similar vegetation cover and relief classes. We measured total organic carbon and nitrogen though elemental analysis, and incubated soils at 4 °C and field capacity moisture for 175 day to measure carbon dioxide production from which we derived soil respiration potential. We hypothesized that soil carbon storage and respiration potential would be greatest at the sites with the oldest landscape age. Soil carbon content was more than four times greater at the 10,000 year sites (Nuuk = 24.03%, Sisimiut = 17.34%) than the inland sites (Orkendalen = 3.49%, LIA = 0.05%). Carbon quality decreased across the age gradient, as measured by a nearly two-fold increase in C:N ratio from the youngest and driest to the oldest and wettest soils (LIA = 12.2, Nuuk = 22.8). While soil respiration rates were significantly highest in the surface soils at the wettest coastal site, we observed high variation in respiration potential indicating that small-scale variation in carbon quality and other soil properties is high. This study informs our understanding of regional variation of carbon storage and turnover in western Greenland and provides important information for the parameterization of landscape scale models of soil carbon dynamics in the Arctic tundra.
15018645 Cameron-Smith, P. J. (Lawrence Livermore National Laboratory, Livermore, CA); Bhattacharyya, S.; Bergmann, D. J.; Reagan, M. T.; Elliott, S. and Moridis, G. J. The impact of methane clathrate emissions on the Earth system [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract A23D-0278, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Methane is locked in ice-like deposits called clathrates in ocean sediments and underneath permafrost regions. Clathrates are stable under high pressures and low temperatures, so in a warming climate, increases in ocean temperatures could lead to dissociation of the clathrates and release methane into the ocean and subsequently the atmosphere, where methane is both an important greenhouse gas and a key species in atmospheric chemistry. Clathrates in the shallower parts of the Arctic Ocean (around 300m depth) are predicted to be particularly important since clathrates at that depth are expected to start outgassing abruptly in the next few decades. We will present the atmospheric impact of such methane emissions using multi-century steady-state simulations with a version of the Community Earth System Model (CESM) that includes atmospheric chemistry. Our simulations include a plausible release from clathrates in the Arctic that increases global methane emissions above present-day conditions by 22%, as well as a scenario with 10 times those clathrate emissions. The CESM model includes a fully interactive physical ocean, to which we added a fast atmospheric chemistry mechanism that represents methane as a fully interactive tracer (with emissions rather than concentration boundary conditions). The results indicate that such Arctic clathrate emissions (1) increase global methane concentrations by an average of 38%, non-uniformly; (2) increase surface ozone concentrations by around 10% globally, and even more in polluted regions; (3) increase methane lifetime by 13%; (4) increase the interannual variability in surface methane, surface ozone, and methane lifetime, and (5) show modest differences in surface temperature and methane lifetime compared to simulations in which the clathrate emissions are distributed uniformly. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
15023043 Demitroff, M. N. (University of Delaware, Geography, Newark, DE) and Cicali, M. Late Pleistocene wind-action and periglacial phenomena in sandy terrain, New Jersey Pine Barrens [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0695, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Examination of the Pinelands past permafrost environment will add insight to the relatively scant record of the Mid-Atlantic region's periglacial realm, a place where cold, dry, and windy conditions predominated during the recent glacials. This area is especially important to the understanding of mid-latitudinal climate change dynamics in ice-marginal locations--areas greatly affected by diurnal, seasonal, and long-term climate perturbations. We provide examples from a well-preserved pine-forest reserve on coastal plain (39-40° N) that experienced multiple episodes of permafrost aggradation and degradation during the last 200,000 years. While a large number of publications describe an array of relict periglacial phenomena from low-relief areas in Europe's sand belt (UK-Russia), much less is known about the ice-marginal continental mass of North America. High-resolution geodetically corrected airborne LiDAR data enhanced with alternate views through the use of early aerial photo imagery is provided and analyzed to produce bare earth landforms revealing perspective eolian structures. Fieldwork at sand mine operations adjacent to relict dune fields offered sectional views of what lies beneath wind-affected land surfaces. This region was found to have been sparsely vegetated land akin to polar barrens during cold epochs. Coversand is the dominant eolian depositional form, with parabolic dune fields scattered along downwind banks of larger watercourses. Eolian systems interact with the local paleohydrology. Wind-erosional features include ventifacts, blowouts, and, on occasion, yardangs. Sand-filled frost cracks attest to aridity during permafrost aggradation and deep-seasonal frost. These periglacial macrostructures often deform into furrows and sediment-filled pots upon permafrost degradation. The sites are easily accessible providing ample opportunities for frozen ground and climate change studies.
15023042 Levy, J. S. (University of Texas at Austin, Jackson School of Geosciences, Institute for Geophysics, Austin, TX); Fountain, A. G.; Dickson, J. L.; Head, J. W.; Okal, M. H. and Marchant, D. R. Accelerated thermokarst formation in the McMurdo Dry Valleys, Antarctica [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0694, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Thermokarst is a land surface lowered and disrupted by melting ground ice. Thermokarst is a major consequence of climate change in the Arctic, but has been considered to be a minor process in Antarctica. Garwood Valley (78°S, 164°E) is a coastal valley in the McMurdo Dry Valleys (MDV) of Southern Victoria Land, Antarctica and is a natural laboratory in which competing models of Antarctic thermokarst erosion can be tested. Garwood Valley is partially filled with a remnant of the Ross Sea Ice Sheet, a debris-covered ice mass that lodged in the valley during the Pleistocene. Rapid ablation of this buried ice mass via melting and block calving has recently been detected at a large retrogressive thaw feature referred to as the Garwood Valley ice cliff. Curiously, regional air temperatures in the MDV have been declining or stable on decadal timescales. Despite no increase in thawing degree days in Garwood Valley, biannual LiDAR scans show large-scale thermokarst backwasting occurring along the entire face of the ice cliff. Since ground-based data collection began in November 2010 to January, 2012, the ~400 m long ice cliff has backwasted ~1-3 m. Since airborne LiDAR data were first collected in 2001-2002 to January, 2012, backwasting along the ice cliff has ranged from 10-55 m, totaling 44,900 ± 900 m3, or on average, 5,000 ± 100 m3/year. From November 2010 to January 2011, 6,700 ± 130 m3 of ice and capping sediment was removed from the Garwood Valley ice cliff; from January 2011 to January 2012, 11,300 ± 230 m3 of material was removed. These melt and calving rates are comparable to the low end of retrogressive thaw slump erosion in Arctic and alpine environments, and suggest that some coastal MDV ground ice may no longer be stable under current climate conditions. Here, we combine this ground-based and airborne LiDAR data with with timelapse imaging and meteorological data to show that 1) thermokarst formation has accelerated in Garwood Valley; 2) the rate of thermokarst erosion is presently ~10 times the average Holocene rate; and 3) the meteorological variable most strong correlated with thermokarst erosion is increasing annual shortwave radiation. We propose that observed local sky brightening and/or reductions in average cloud cover couple with an albedo feedback (melting of ground ice results in mobilization of overlying sediments, which reduce ice cliff albedo, leading to further ground ice melt) is producing the observed rapid permafrost melting. This suggests that sediment enhancement of insolation-driven melting and ablation of calved blocks may act similarly to expected increases in Antarctic air temperature (presently occurring along the Antarctic Peninsula), and may serve as a leading indicator of imminent landscape change in Antarctica that will generate thermokarst landforms similar to those in Arctic periglacial terrains.
15023087 Liu, L. (University of Washington, Earth and Space Sciences, Seattle, WA); Sletten, R. S.; Hallet, B.; Waddington, E. D. and Wood, S. E. Modeling ground thermal regime of an ancient buried ice body in Beacon Valley, Antarctica using a 1-D heat equation with latent heat effect [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C41A-0583, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
An ancient massive ice body buried under several decimeters of debris in Beacon Valley, Antarctica is believed to be over one million years old, making it older than any known glacier or ice cap. It is fundamentally important as a reservoir of water, proxy for climatic information, and an expression of the periglacial landscape. It is also one of Earth's closest analog for widespread, near-surface ice found in Martian soils and ice-cored landforms. We are interested in understanding controls on how long this ice may persist since our physical model of sublimation suggests it should not be stable. In these models, the soil temperatures and the gradient are important because it determines the direction and magnitude of the vapor flux, and thus sublimation rates. To better understand the heat transfer processes and constrain the rates of processes governing ground ice stability, a model of the thermal behavior of the permafrost is applied to Beacon Valley, Antarctica. It calculates soil temperatures based on a 1-D thermal diffusion equation using a fully implicit finite volume method (FVM). This model is constrained by soil physical properties and boundary conditions of in-situ ground surface temperature measurements (with an average of -23.6°C, a maximum of 20.5°C and a minimum of -54.3°C) and ice-core temperature record at ~30 m. Model results are compared to in-situ temperature measurements at depths of 0.10 m, 0.20 m, 0.30 m, and 0.45 m to assess the model's ability to reproduce the temperature profile for given thermal properties of the debris cover and ice. The model's sensitivity to the thermal diffusivity of the permafrost and the overlaying debris is also examined. Furthermore, we incorporate the role of ice condensation/sublimation which is calculated using our vapor diffusion model in the 1-D thermal diffusion model to assess potential latent heat effects that in turn affect ground ice sublimation rates. In general, the model simulates the ground thermal regime well. Detailed temperature comparison suggests that the 1-D thermal diffusion model results closely approximate the measured temperature at all depths with the average square root of the mean squared error (SRMSE) of 0.15°C; a linear correlation between modeled and measured temperatures yields an average R2 value of 0.9997. Prominent seasonal temperature variations diminish with depth, and it equilibrates to mean annual temperature at about 21.5 m depth. The amount of heat generated/consumed by ice condensation/sublimation is insufficient to significantly impact the thermal regime.
15025238 Throckmorton, H. (Los Alamos National Laboratory, Los Alamos, NM); Perkins, G.; Rearick, M.; Altmann, G. L.; Cohen, Lily R.; Hudak, M.; Gard, M.; Newman, B. D.; Heikoop, J. M. and Wilson, C. J. Isotopic and geochemical signatures of different aged drained thaw lake basins (DTLBs) and drainage channels in Arctic Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B11C-0388, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Arctic tundra contains a vast amount of C stored in permafrost soils, which are highly susceptible to thawing with climate change. Permafrost degradation has implications for land-atmosphere feedbacks through the release of stored C as greenhouse gases (CO2, methane), and runoff of dissolved C. Coastal Arctic topography and geomorphology in particular is highly complex, consisting of irregular polygonal ground features, drainage channel networks, and different aged drained thaw lake basins (DTLBs). Such substantial spatial variability complicates predictions of permafrost degradation with regard to land-atmosphere feedbacks affecting climate and regional ecosystem responses. The DOE Office of Science Biological and Environmental Research Program has funded the Next Generation Ecosystem Experiment (NGEE) Arctic project to assess the release of greenhouse gases from melting Arctic permafrost, with emphasis on regional geomorphology; and to establish a coordinated effort among several research institutions to link field observations with process-based Land models. Results will focus on geochemical and isotopic signatures of waters collected at different depths (surface; from the shallow organic layer; and from the deeper frost table) in Barrow, Alaska in July and September of 2013. Sampling sites were stationed across distinct microtopographic features, including polygonal terrain, different aged DTLBs, and larger drainage channels. The aims of these field campaigns were to assess geochemical and biogeochemical trends and isotopic variability in waters across unique micro-topographic features and with depth, and infer vertical and lateral flows of water and C by collecting field data to validate large-scale regional models. Preliminary results showed some differences with depth and across unique micro-topographic features. Redox indicators (Fe2+ and dissolved oxygen) showed greater reducing conditions with depth, as was expected. In particular, subsurface waters associated with large drainage channels had highly reducing conditions, relative to less distinct, smaller internal drainages. Dissolved inorganic carbon (DIC) concentrations ranged from 0-734 ppm HCO3-, and exhibited a trend of greater concentration with depth for nearly all sites. The 13C DIC isotope signature ranged widely, from -2.2 to -25.1, with the lightest values at the shallow subsurface depth for all sites relative to the surface and deeper subsurface. Additional results will discuss concentrations and isotope signatures of dissolved CH4 (C13 and H2) and organic C at the selected sites; as well as geochemistry (anions and metals).
15023039 Wang, K. (LZU Lanzhou University, Research School of Arid Environment and Climate Change, Lanzhou, China) and Zhang, T. Climatology and changes in the timing and duration of surface soil freeze/thaw status from 1956-2006 over China [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C33A-0691, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
This study investigated the climatology and changes in the surface soil freeze-thaw status across China. We used the observed daily surface soil temperature data from 845 stations over a period from 1956 to 2006. We investigated the spatial and temporal changes in the first and last date of te near surface soil (~5 cm) freezing, duration and number of freezing days, as well as number of freeze/thaw cycles in the near-surface soils. The climatology for each parameter was based on the base period of 1971-2000. The preliminary results showed that the near-surface soil freeze/thaw status was correlated with latitudes and elevations. We found that boundaries of permafrost zones are coincided with regions where the numbers of freezing days were more than 220 days per year. Using the mean number of 15 days of the near surface soil freezing as a criterion, we found that the southern boundary of seasonally frozen ground was about 25°N, and the regions south of 22°N were essentially unfrozen regions. Changes in surface soil freeze/thaw status represented clear temporal trends under the changing climate over China. The number of freezing day and duration of the near-surface soil freezing have decreased by approximately 11 days from 1956 to 2006. The timing of soil freeze/thaw has also changed significantly. There was a trend toward later in the first date of the near-surface soil freezing by about 5 days and earlier in the last date of the near surface soil freezing by 7 days over the period 1956-2006. These changes was accelerated since the 1990s with the linear slope up to -1.4 days per year. Changes in the number of near-surface soil freezing were in a negative correlation with air temperature, i.e., the number of near-surface soil freezing days decreased with increase in air temperature.
15019369 Heinrich, Catherine (St. Lawrence University, Geology, Canton, NY); Stewart, Alexander K. and Hubbard, Trent D. Dendrogeomorphic evidence of frequent mass wasting from reaction wood in black spruce, Northway Jct., Alaskan interior [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 510, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Understanding mass-wasting events along remote transportation corridors such as the Alaska Highway is a crucial infrastructure need. To better understand a problematic road segment near Northway Junction, Alaska we focused on the most intensely deformed area (4.8 hectares) between mileposts 1265-1267, which is dominated by complex, slumping blocks of thawing, perennially frozen, sandy silt. We deliberately sampled 30 Picea mariana, which were tilted and thus visibly affected by mass-wasting processes. Each tree was radially cored (n=60) in the direction of the tilt and at 90° to the first core. Reaction wood and suppression and release events were characterized using microscopic analysis and recorded as modified skeleton plots of event-response phenomena, resulting in a replication-summary plot. Of the 30 trees sampled, 26 contain reaction wood, suppression was present in 24 trees and release was present in 15. Of the trees with reaction wood, the onset of reaction wood occurred in five, area-wide events, occurring in 1966 (5 trees), 1989 (8 trees), 1995 (6 trees), 2006 (7 trees), and 2011 (6 trees), with the 1966 and 1989 events followed by significant growth suppression. Eighty percent of tilting events occurred in areas where the active layer depth was ≤&eq;30 cm. Between 1900-1988 the area was relatively stable with reaction wood accounting for only 5.2 percent of recorded radial growth. Onset of widespread instability occurs in 1989 with reaction wood accounting for 32.7 percent of recorded radial growth from 1989-2013. Highway realignments and patchwork along this section of the highway have occurred in the past 10 years. Patchwork completed in October 2011, for example, can be linked to the onset of reaction wood in 2011 due to mass wasting outside the growing season (late summer 2010-late spring 2011). Further research is needed to correlate climate data with the mass-wasting events, which may provide insight for effective maintenance decisions.
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