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Understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation, species habitat, biogeochemical cycling, and biodiversity. Recent field studies in interior Alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation. This study assesses the hydrologic control exerted by permafrost, elucidates modes of regional groundwater flow for various spatial permafrost patterns, and evaluates potential hydrologic consequences of permafrost degradation. The Yukon Flats Basin (YFB), a large (118,340 km super(2)) subbasin within the Yukon River Basin, provides the basis for this investigation....
The data from nine permafrost thermal monitoring sites at widely separated locations across northern Canada were examined individually, spatially, and temporally. Three sites are in Nunavut (Alert, Iqaluit, and Baker Lake), two in the Northwest Territories (Table Mountain and Wrigley), and four in the Yukon Territory (Wolf Creek, Sixty Mile, Alpine Burwash, and Red Creek). The sites have between one and five boreholes that are instrumented to between 3 and 60 m with records of varying durations. Most of the boreholes are co-located with weather stations recording air temperatures and snow depths. A comprehensive analysis of each site is presented assessing the relations between climate and permafrost temperatures,...
The boundary between forest and tundra in mountainous areas, alpine treeline, is expected to advance as climate warming continues and change is likely to be pronounced in northern latitudes. I studied the white spruce ( Picea glauca (Moench) Voss) treeline in the Kluane region of southwest Yukon, Canada, with the objectives of: (i) characterizing its responses to past climate change, and (ii) assessing the influence of different environmental variables on spruce growth and treeline dynamics. Four investigations were conducted, each employing fundamentally different methodologies and occupying distinct levels within a hierarchical, scale-based, analytical framework. At the landscape scale, I mapped spruce distribution...
The impact to the permafrost during and after wildfire was studied using 11 boreal forest fire sites including two controlled burns. Heat transfer by conduction to the permafrost was not significant during fire. Immediately following fire, ground thermal conductivity may increase 10-fold and the surface albedo can decrease by 50% depending on the extent of burning of the surficial organic soil. The thickness of the remaining organic layer strongly affects permafrost degradation and aggradation. If the organic layer thickness was not reduced during the burn, then the active layer (the layer of soil above permafrost that annually freezes and thaws) did not change after the burn in spite of the surface albedo decrease....
Over the past 50 years, Alaska has experienced a warming climate with longer growing seasons, increased potential evapotranspiration, and permafrost warming. Research from the Seward Peninsula and Kenai Peninsula has demonstrated a substantial landscape-level trend in the reduction of surface water and number of closed-basin ponds. We investigated whether this drying trend occurred at nine other regions throughout Alaska. One study region was from the Arctic Coastal Plain where deep permafrost occurs continuously across the landscape. The other eight study regions were from the boreal forest regions where discontinuous permafrost occurs. Mean annual precipitation across the study regions ranged from 100 to over...
Permanent electrode arrays were set up at ten monitoring sites from Whitehorse, Yukon, to Fort St. John, British Columbia, in order to gain a clearer perspective of the effectiveness of electrical resistivity tomography (ERT) monitoring over an annual cycle of freezing and thawing. This research forms part of a longer-term project that is attempting to use ERT to examine changes in permafrost resulting from climate change. Inter-site and intra-site variability were examined by installing and maintaining data-loggers to monitor active layer and shallow permafrost temperatures, air temperatures, and snow depths at each site from August 2010-August 2011. Additional site information was collected on each ERT survey...
To determine the influence of fire and thermokarst in a boreal landscape, we investigated peat cores within and adjacent to a permafrost collapse feature on the Tanana River Floodplain of Interior Alaska. Radioisotope dating, diatom assemblages, plant macrofossils, charcoal fragments, and carbon and nitrogen content of the peat profile indicate approximately 600 years of vegetation succession with a transition from a terrestrial forest to a sedge-dominated wetland over 100 years ago, and to a Sphagnum-dominated peatland in approximately 1970. The shift from sedge to Sphagnum, and a decrease in the detrended tree-ring width index of black spruce trees adjacent to the collapse coincided with an increase in the growing...
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Near-surface air temperature inversions are a common element of northern environments. Seasonal and inter-annual variations of low-level inversion characteristics were examined using 47 years of twice-daily radiosonde data from Whitehorse airport (1956-2003). Nocturnal low-level inversion events occurred throughout the year in 68% of the 0400h PST radiosonde ascents. Afternoon (1600h PST) inversion events, in contrast, were primarily a winter phenomena, limited to 24% of the readings between October and March, and were deepest and strongest during the winter months. Shorter, weaker, lower magnitude inversions appeared progressively more frequently during the 1974-2003 warming at Whitehorse. The impact (1956-2003)...
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...
To accurately represent subsurface flow in a hydrologic model of permafrost terrain during spring thaw, an understanding of soil thaw and soil thaw rates is required. Research was conducted on an organic-covered hillslope in Granger Basin, Yukon Territory, to quantify relationships between net radiation, snowmelt and soil thaw energy. The infiltration and freezing of meltwater into the soil may contribute to pre-thaw warming. When this energy (1.82 MJ·m -2 ·d-1 ) is taken into account, the daily mean contribution to soil thaw from net radiation is approximately 9%. Measured and estimated soil thaw depths compared well (R2 = 0.75) when energy was distributed across the hillslope. This research contributes to the...
The influence of permafrost growth and thaw on the evolution of ice-rich lowland terrain in the Koyukuk-Innoko region of interior Alaska is fundamental but poorly understood. To elucidate this influence, the cryostratigraphy and properties of perennially frozen sediments from three areas in this region are described and interpreted in terms of permafrost history. The upper part of the late Quaternary sediments at the Koyukuk and Innoko Flats comprise frozen organic soils up to 4.5 m thick underlain by ice-rich silt characterised by layered and reticulate cryostructures. The volume of visible segregated ice in silt locally reaches 50 per cent, with ice lenses up to 10 cm thick. A conceptual model of terrain evolution...
Increased attention directed at the permafrost region has been prompted by resource development and climate change. This review surveys advances in permafrost hydrology since 2000. Data shortage and data quality remain serious concerns. Yet, there has been much progress in understanding fundamental hydrologic processes operating in a wide range of environments, from steep mountainous catchments, to the Precambrian Shield with moderate relief, to the low-gradient terrain of plains, plateaus and wetlands. Much of the recent research has focused on surface water, although springs and groundwater contribution to streamflow have also been studied. A compendium of water-balance research from 39 high-latitude catchments...
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Old Crow Flats is a 5600 km2 glaciolacustrine plain that straddles the forest-tundra ecotone in northern Yukon. Continuous taiga corridors occur in the entrenched river valleys, where annual mean ground temperatures (Tg) at the depth of zero annual amplitude at two locations were ?3.1 and ?4.0ºC in 2013. On the Flats, the vegetation cover is patchy, and Tg varied between ?5.1 and ?2.6ºC. Annual mean near-surface permafrost temperatures (Tps) measured on the Flats between 2008 and 2011 in patches of taiga, tall shrubs and low shrubs were correlated with local snow depth. Snow depth was controlled by vegetation height if the snow supply was not limited, for example, where low shrubs and large lakes dominate the landscape....
map background search result map search result map Vegetation-Permafrost Relations within the Forest-Tundra Ecotone near Old Crow, Northern Yukon, Canada Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a boreal-rich fen Characteristics of low-level temperature inversions, Whitehorse Yukon Territory: 1956--2003 Emissions of methane from northern peatlands: a review of management impacts and implications for future management options Seasonal ice and hydrologic controls on dissolved organic carbon and nitrogen concentrations in a boreal-rich fen Characteristics of low-level temperature inversions, Whitehorse Yukon Territory: 1956--2003 Emissions of methane from northern peatlands: a review of management impacts and implications for future management options Vegetation-Permafrost Relations within the Forest-Tundra Ecotone near Old Crow, Northern Yukon, Canada