ABSTRACT: Modeling the potential hydrothermal response impact of climate change on permafrost of within the South Mackenzie Plain, Northwest Territories, Canada.

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This paper investigates hydrothermal responses of differing landscape components (forested and non-forested upland and wetland sites) with the potential to change a permafrost layer according to local variations in site type,snow pack depth, and daily weather conditions as these have varied from 1963 to 2007, with actual and somewhat increased air temperatures. Observed air temperature was consistently increasing in Fort Simpson area over last 40years. More importantly, average January temperatures increases were more pronounced than the increases in average July temperatures. The Forest Hydrology Model ForHyM was applied to select conditions as these would exist within the South Mackenzie Plain south of Fort Simpson, to discern likely depth and duration of frost penetration into the soil for select upland/wetland conditions, based on daily weather information, from 1963 to 2007. It was found that forested upland soils would experience deep frost and thawing cycles each year, but no permafrost, with two exceptions of two-year durations. In contrast, water-saturated wetland soils with limited drainage would have developed a permafrost layer starting from a hypothetical no-frost condition in 1963. This layer would then deepen over the course of about the next 10 years and become fairly stable thereafter, as long as the year-after-year weather conditions would remain the same. In general, the calculated frost depth varied with site type, and with depth of simulated snow pack and forest litter on the ground: the deeper these layers, the shallower the simulated frost depth. Year-to-year snow depth variations have a particularly strong influence on depth of frost penetration. These results were used to hypothesize likely permafrost distribution patterns within the study area, based on vegetative cover and landforms, local flow patterns, and likely depth-to-water from the soil surface. It was also noted that the hydrological calculations corresponding to the most recent airtemperature changes suggest fairly sudden permafrost losses in areas where the permafrost layer has already thinned to a critically low depth.

Bibliography of Canadian Geomorphology