Permafrost hydrology in changing climatic conditions: seasonal variability of stable isotope composition in rivers in discontinuous permafrost

Role of changing climatic conditions on permafrost degradation and hydrology was investigated in the transition zone between the tundra and forest ecotones at the boundary of continuous and discontinuous permafrost of the lower Yenisei River. Three watersheds of various sizes were chosen to represent the characteristics of the regional landscape conditions. Samples of river flow, precipitation, snow cover, and permafrost ground ice were collected over the watersheds to determine isotopic composition of potential sources of water in a river flow over a two year period. Increases in air temperature over the last forty years have resulted in permafrost degradation and a decrease in the seasonal frost which is evident from soil temperature measurements, permafrost and active-layer monitoring, and analysis of satellite imagery. The lowering of the permafrost table has led to an increased storage capacity of permafrost affected soils and a higher contribution of ground water to river discharge during winter months. A progressive decrease in the thickness of the layer of seasonal freezing allows more water storage and pathways for water during the winter low period making winter discharge dependent on the timing and amount of late summer precipitation. There is a substantial seasonal variability of stable isotopic composition of river flow. Spring flooding corresponds to the isotopic composition of snow cover prior to the snowmelt. Isotopic composition of river flow during the summer period follows the variability of precipitation in smaller creeks, while the water flow of larger watersheds is influenced by the secondary evaporation of water temporarily stored in thermokarst lakes and bogs. Late summer precipitation determines the isotopic composition of texture ice within the active layer in tundra landscapes and the seasonal freezing layer in forested landscapes as well as the composition of the water flow during winter months

Analysis of the origin of Aufeis feed-water on the arctic slope of Alaska

The origin of water feeding large aufeis fields (overflow river ice) on the Arctic Slope of Alaska is analyzed. Field measurements of two large aufeis fields on the eastern Arctic Slope were taken during July of 1978 and 1979. Measurements of aufeis extent and distribution were made using LANDSAT Multispectral Scanner Subsystem (MSS) satellite data from 1973 through 1979. In addition, ice cores were analyzed in the laboratory. Results of the field and laboratory studies indicate that the water derived from aufeis melt water has a chemical composition different from the adjacent upstream river water. Large aufeis fields are found in association with springs and faults thus indicating a subterranean origin of the feed water. In addition, the maximum extent of large aufeis fields was not found to follow meteorological patterns which would only be expected if the origin of the feed water were local. It is concluded that extent of large aufeis in a given river channel on the Arctic Slope is controlled by discharge from reservoirs of groundwater. It seems probable that precipitation passes into limestone aquifers in the Brooks Range, through an interconnecting system of subterranean fractures in calcareous rocks and ultimately discharges into alluvial sediments on the coastal plain to form aufeis. It is speculated that only small aufeis patches are affected by local meteorological parameters in the months just prior to aufeis formation

Water Body Distributions Across Scales: A Remote Sensing Based Comparison of Three Arctic Tundra Wetlands

Water bodies are ubiquitous features in Arctic wetlands. Ponds, i.e., waters with a surface area smaller than 104 m2, have been recognized as hotspots of biological activity and greenhouse gas emissions but are not well inventoried. This study aimed to identify common characteristics of three Arctic wetlands including water body size and abundance for different spatial resolutions, and the potential of Landsat-5 TM satellite data to show the subpixel fraction of water cover (SWC) via the surface albedo. Water bodies were mapped using optical and radar satellite data with resolutions of 4mor better, Landsat-5 TM at 30mand the MODIS water mask (MOD44W) at 250m resolution. Study sites showed similar properties regarding water body distributions and scaling issues. Abundance-size distributions showed a curved pattern on a log-log scale with a flattened lower tail and an upper tail that appeared Paretian. Ponds represented 95% of the total water body number. Total number of water bodies decreased with coarser spatial resolutions. However, clusters of small water bodies were merged into single larger water bodies leading to local overestimation of water surface area. To assess the uncertainty of coarse-scale products, both surface water fraction and the water body size distribution should therefore be considered. Using Landsat surface albedo to estimate SWC across different terrain types including polygonal terrain and drained thermokarst basins proved to be a robust approach. However, the albedo–SWC relationship is site specific and needs to be tested in other Arctic regions. These findings present a baseline to better represent small water bodies of Arctic wet tundra environments in regional as well as global ecosystem and climate models

Remote sensing of snow and ice: A review of the research in the United States 1975 - 1978

Research work in the United States from 1975-1978 in the field of remote sensing of snow and ice is reviewed. Topics covered include snowcover mapping, snowmelt runoff forecasting, demonstration projects, snow water equivalent and free water content determination, glaciers, river and lake ice, and sea ice. A bibliography of 200 references is included

Summer CO2 evasion from streams and rivers in the Kolyma River basin, north-east Siberia

Inland water systems are generally supersaturated in carbon dioxide (CO2) and are increasingly recognized as playing an important role in the global carbon cycle. The Arctic may be particularly important in this respect, given the abundance of inland waters and carbon contained in Arctic soils; however, a lack of trace gas measurements from small streams in the Arctic currently limits this understanding.We investigated the spatial variability of CO2 evasion during the summer low-flow period from streams and rivers in the northern portion of the Kolyma River basin in north-eastern Siberia. To this end, partial pressure of carbon dioxide (pCO2) and gas exchange velocities (k) were measured at a diverse set of streams and rivers to calculate CO2 evasion fluxes. We combined these CO2 evasion estimates with satellite remote sensing and geographic information system techniques to calculate total areal CO2 emissions. Our results show that small streams are substantial sources of atmospheric CO2 owing to high pCO2 and k, despite being a small portion of total inland water surface area. In contrast, large rivers were generally near equilibrium with atmospheric CO2. Extrapolating our findings across the Panteleikha-Ambolikha sub-watersheds demonstrated that small streams play a major role in CO2 evasion, accounting for 86% of the total summer CO2 emissions from inland waters within these two sub-watersheds. Further expansion of these regional CO2 emission estimates across time and space will be critical to accurately quantify and understand the role of Arctic streams and rivers in the global carbon budget

Remote sensing of recent changes in permafrost-influenced wetlands

Changes in thermokarst lakes have been identified across many high-latitude ecosystems at different spatial and temporal scales. With the declassification of the Landsat archive in 2008, it is now possible to conduct a near-complete yearly time series of homogenous geospatial imagery to assess the trends seen in thermokarst lake surface area. By implementing an automated land- cover classification algorithm, this study examined the dynamics of lake surface area over different spatial and temporal scales in the Tuktoyaktuk Peninsula, Northwest Territories, Canada. Due to the presence of a statistically significant structural temporal break between the years 1997 and 1998, lake areal trends were estimated at two temporal scales, a longer term scale (1985 to 2011) and its component shorter scales (1985 to 1997 and 1998 to 2011). Large lakes saw the greatest changes both in lake areal increase and decreases at all temporal scales, and was suggested to drive the overall changes in surface area. In addition, regional differences were observed in the spatial distribution of individual lake area trends. On the broad scale, a latitudinal divide bifurcated the peninsula into two regions of approximately equal area, where the northern region exhibited general trends of lake areal decline, while the southern region exhibited general trends of lake areal increase. Within these regions, meso- and local hot and cold spots were identified, some that exhibited trends in concordance with local surroundings, while others represented local spatial heterogeneity in areal trends. The spatiotemporal trends in lake area were suggested to be influenced at varying scales by atmospheric and climate variables, and by ground characteristics such as coincident permafrost and surficial geology. As the Arctic continues to warm, a continued observation of thermokarst lake evolution over both broad landscapes and localised regions will be increasingly valuable to future studies that investigate the resulting transformation of the Arctic permafrost region

Surface water dynamics of shallow lakes following wildfire in boreal Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2013Wildfire is ubiquitous to interior Alaska and is the primary large-scale disturbance regime affecting thawing permafrost and ecosystem processes in boreal forests. Since surface and near surface hydrology is strongly affected by permafrost occurrence, and wildfire can consume insulating organic layers that partially control the thickness of the active layer overlying permafrost, changes in the active layer thickness following fire may mark a distinct change in surface hydrology. In this study, we examined surface area dynamics of lakes following wildfire in four regions of Interior Alaska during a 25-year period from 1984 - 2009. We compared the surface water dynamics of lakes in burned areas relative to lakes in adjacent unburned (control) areas. Lake area changes in the short-term (0-5 years), mid-term (5-10 years), and long-term (>10 years) were analyzed. Burn severity, as a function of radiant surface temperature change, was also explored. Surface water changes were greatest during the short-term (0-5 years) period following fire, where burn lakes increased 10% and control lakes decreased -8% (P=0.061). Over the 5-10 year post-fire period, there was no significant difference in lake dynamics within burned areas relative to control unburned areas. On average, there was an 18 percent decrease in surface water within burned areas over the >10 year post fire time period, while unburned control lakes averaged a 1 percent decline in surface water. The long term declining trend within burned areas may have been due to talik expansion and/or increased evapotranspiration with revegetation of broadleaf plants. Fire had the greatest effect on radiant surface temperature within two years of a fire, where radiant temperatures increased 3-7°C in the most severely impacted areas. Temperature differences between burn and control areas remained less than 1°C as vegetation reestablished. There was no correlation between radiant temperature change and decreasing lake area change. Conversely, there was a trend between lake area differences increasing in size and increases in temperature. While fire displayed the greatest effect on lake area in the short-term, a combination of fire, climate, and site-specific conditions dominate long-term lake area dynamics in Alaska boreal forest

Quarterly literature review of the remote sensing of natural resources

The Technology Application Center reviewed abstracted literature sources, and selected document data and data gathering techniques which were performed or obtained remotely from space, aircraft or groundbased stations. All of the documentation was related to remote sensing sensors or the remote sensing of the natural resources. Sensors were primarily those operating within the 10 to the minus 8 power to 1 meter wavelength band. Included are NASA Tech Briefs, ARAC Industrial Applications Reports, U.S. Navy Technical Reports, U.S. Patent reports, and other technical articles and reports

Contemporary (1951–2001) Evolution of Lakes in the Old Crow Basin, Northern Yukon, Canada: Remote Sensing, Numerical Modeling, and Stable Isotope Analysis

This study reports on changes in the distribution, surface area, and modern water balance of lakes and ponds located in the Old Crow Basin, northern Yukon, over a 50-year period (1951–2001), using aerial photographs, satellite imagery, a numerical lake model, and stable O-H isotope analysis. Results from the analysis of historical air photos (1951 and 1972) and a Landsat-7 Enhanced Thematic Mapper (ETM+) image (2001) show an overall decrease (-3.5%) in lake surface area between 1951 and 2001. Large lakes typically decreased in extent over the study period, whereas ponds generally increased. Between 1951 and 1972, approximately 70% of the lakes increased in extent; however, between 1972 and 2001, 45% decreased in extent. These figures are corroborated by a numerical lake water balance simulation (P-E index) and stable O-H isotope analysis indicating that most lakes experienced a water deficit over the period 1988–2001. These observed trends towards a reduction in lake surface area are mainly attributable to a warmer and drier climate. The modern decrease in lake levels corresponds well to changes in regional atmospheric teleconnection patterns (Arctic and Pacific Decadal oscillations). In 1977, the climate in the region switched from a predominantly cool and moist regime, associated with the increase in lake surface area, to a hot and dry one, thus resulting in the observed decrease in lake surface area. Although some lakes may have drained catastrophically by stream erosion or bank overflow, it is not possible to determine with certainty which lakes experienced such catastrophic drainage, since an interval of two decades separates the two air photo mosaics, and the satellite image was obtained almost30 years after the second mosaic of air photos.La présente étude fait état des changements caractérisant la répartition, l’étendue et le bilan hydrique contemporain des lacs et des étangs situés dans le bassin Old Crow, dans le nord du Yukon, sur une période de 50 ans (1951–2001). L’étude s’est appuyée sur des photographies aériennes, l’imagerie satellitaire, un modèle numérique des lacs et l’analyse des isotopes stables O-H. D’après les résultats de l’analyse des photos aériennes historiques (1951 et 1972) et d’une image par capteur ETM+ (Enhanced Thematic Mapper) de Landsat-7 (2001), il y a eu rétrécissement général ( 3,5 %) de la surface des lacs entre 1951 et 2001. D’un point de vue général, l’étendue des grands lacs a diminué au cours de la période visée par l’étude, tandis que celle des étangs a augmenté. Entre 1951 et 1972, l’étendue d’environ 70 % des lacs s’est accrue, mais entre 1972 et 2001, l’étendue de 45 % des lacs a diminué. Ces données ont été corroborées au moyen de la simulation numérique du bilan hydrique des lacs (indice P-E) et de l’analyse des isotopes stables O-H, qui ont laissé entrevoir que la plupart des lacs ont enregistré un déficit en eau au cours de la période allant de 1988 à 2001. Les tendances de réduction de la surface des lacs qui ont été observées sont principalement attribuables à un climat plus chaud et plus sec. La diminution contemporaine du niveau des lacs correspond bien aux changements caractérisant les modèles régionaux de téléconnexion atmosphérique (oscillations décadaires arctiques et pacifiques). En 1977, le climat de la région est passé d’un régime à prédominance fraîche et humide (associé à l’augmentation de la surface des lacs de la région) à un régime chaud et sec, ce qui s’est traduit par la diminution de la surface des lacs qui a été observée. Bien que certains lacs puissent avoir été drainés de manière catastrophique en raison de l’érosion des cours d’eau ou du débordement des rives, il est impossible de déterminer avec certitude quels lacs ont été la cible d’un assèchement si catastrophique puisqu’un intervalle de deux décennies sépare les deux mosaïques de photographies aériennes, et que l’image satellitaire a été obtenue presque une trentaine d’années après la deuxième mosaïque de photo aérienne