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Recent warming at high-latitudes has accelerated permafrost thaw in northern peatlands, and thaw can have profound effects on local hydrology and ecosystem carbon balance. To assess the impact of permafrost thaw on soil organic carbon (OC) dynamics, we measured soil hydrologic and thermal dynamics and soil OC stocks across a collapse-scar bog chronosequence in interior Alaska. We observed dramatic changes in the distribution of soil water associated with thawing of ice-rich frozen peat. The impoundment of warm water in collapse-scar bogs initiated talik formation and the lateral expansion of bogs over time. On average, Permafrost Plateaus stored 137 ± 37 kg C m^sup -2^, whereas OC storage in Young Bogs and Old Bogs...
We employed an integrated approach that combined remote sensing techniques with field measurements to predict the presence/absence of near-surface permafrost in a section of the Alaska Highway corridor. We investigated the correlative relationships among vegetation type, topography, moss thickness, tussock condition and near-surface permafrost in the study area. Analysis of moss thickness and active-layer depth in low-lying plains (slope <8?) showed an inverse relationship in different vegetation classes. The maximum likelihood classification of remotely sensed data mapped 80% of the study area as covered with vegetation. We developed an empirical-statistical (Binary Logistic Regression) model to establish the statistical...
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....
Many northern lake-rich regions are undergoing pronounced hydrological change, yet inadequate knowledge of the drivers of these landscape-scale responses hampers our ability to predict future conditions. We address this challenge in the thermokarst landscape of Old Crow Flats (OCF) using a combination of remote sensing imagery and monitoring of stable isotope compositions of lake waters over three thaw seasons (2007?2009). Quantitative analysis confirmed that the hydrological behavior of lakes is strongly influenced by catchment vegetation and physiography. Catchments of snowmelt-dominated lakes, typically located in southern peripheral areas of OCF, encompass high proportions of woodland/forest and tall shrub vegetation...
Upland soils formed in three different parent materials in the Lewes Plateau of the Central Yukon were studied: till from the McConnell (MIS 2) and penultimate (MIS 4 or 6) glaciations, and weathered bedrock beyond the penultimate limit Soils at penultimate and McConnell sites have solum thicknesses of 50-75 cm and <50 cm respectively but other field and chemical observations did not identify differences in weathering patterns between age groups. The two groups have distinctive clay mineral assemblages, with smectite present in the youngest deposits. These results contrast with reconnaissance studies conducted in the 1970s and 1980s on low-elevation soils in the Klondike Plateau. My study shows that field criteria...
Wildfire 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...
Permafrost soils are large reservoirs of potentially labile carbon (C). Understanding the dynamics of C release from these soils requires us to account for the impact of wildfires, which are increasing in frequency as the climate changes. Boreal wildfires contribute to global emission of greenhouse gases (GHG[mdash]CO2, CH4 and N2O) and indirectly result in the thawing of near-surface permafrost. In this study, we aimed to define the impact of fire on soil microbial communities and metabolic potential for GHG fluxes in samples collected up to 1[thinsp]m depth from an upland black spruce forest near Nome Creek, Alaska. We measured geochemistry, GHG fluxes, potential soil enzyme activities and microbial community...
Syngenetic permafrost forms when alluvial, aeolian and/or colluvial sediment accumulates under cold-climate conditions. Observations from within the CRREL permafrost tunnel near Fairbanks, Alaska, indicate that layered, lenticular-layered and micro-lenticular cryogenic structures are characteristic of this type of permafrost. In contrast, reticulate cryogenic structures indicate local thaw modification. During the growth of syngenetic permafrost, episodes of thermokarst erosion may operate preferentially along ice wedges leading to the development of gullies and tunnels in the near-surface sediments. The local thaw unconformities that result are inferred by the recognition of thermokarst-cave ice (pool ice), and...
This study is the first known attempt in North America to use the basal temperature of snow (BTS) method to predict the distribution of mountain permafrost. The study site, Wolf Creek Research Basin, Yukon Territory (60°30'N, 135°13'W), is a 195 km 2 basin ranging in elevation from 650-2100 m with a mean annual air temperature of about -4°C at 1235 m a.s.l. A modeled BTS surface, based on 394 measured BTS values and with elevation and potential incoming solar radiation as independent variables, was created within a GIS environment with an r2 value similar to European results. The distribution of permafrost within the basin was identified from pits and boreholes. A subsequent logistic regression was used to compare...
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...
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...
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...
Northern peatlands in boreal and subarctic regions store about 500 Gt of carbon (C). Understanding the fate of this large C pool under a warmer climate is important, as temperatures in northern latitudes have increased quicker than the global averages over the past 100 years. Both regional climate (e.g., temperature and precipitation) and local factors (e.g., topography) influence peatland response to climate changes. To better understand peatland response to climate changes, paleoecological techniques were used to study the C accumulation and paleohydrololgy of peatlands in different Alaskan climate regions. In addition, local-scale factors were studied through comparison of two nearby peatlands in different surficial...