Thermal and hydrological investigations of degrading permafrost

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The long-term objective of our research program is to understand the response of permafrost terrain to changes in factors that control ground temperatures, particularly changes in surface conditions and climate. Permafrost is ground that remains at or below 0°C for two or more years. The principal factor governing the presence of permafrost is climate, and recent climate warming has led to increases in permafrost temperature throughout the North. The practical consequences of such warming are greatest when the seasonally thawed active layer penetrates into icy ground at the top of permafrost.*******We propose to study the relations between climate and permafrost in western Arctic Canada, and deepening of the active layer. We will emphasize four topics.*******(1) Near Whitehorse, where permafrost is close to 0 °C, ground temperatures do not respond sensitively to climate because of energy needed for thawing ice. We intend to compare adjacent sites with and without permafrost, to determine how much more efficiently sites without permafrost present the climate warming signal, despite seasonal freezing and thawing. We have a 25 year record of ground temperatures to draw upon.*******(2) Near the western Arctic coast, we will examine the effect of slope angle on active-layer thickening. We expect that in flat terrain water liberated from permafrost may remain in place and freeze back, but it may run off from hill slopes. Therefore we expect greater subsidence on hill sides than in flat ground. We expect the association between annual climate and active-layer thickness to vary with slope angle if the top of permafrost changes each year with thawing.*******(3) In the western Arctic, we observe widespread thawing of the ice wedges that bound tundra polygons. These wedges are almost pure ice, and their melting leads to the greatest possible subsidence. The wedges lie below troughs in which snow accumulates, so subsidence may lead to further warming, as the depth of snow and its insulation effect increase. In lowlands water commonly accumulates in the troughs. We wish to determine the rate of trough deepening, its dependence on water and snow depth, and whether it accelerates in the wedges. We will study freeze-back of the troughs, for only once the active layer has refrozen may underlying permafrost cool. We may be able to forecast critical water and snow depths at which trough constituents do not freeze back and ice wedges melt completely.*******(4) Finally, we will study the gradient in permafrost and climate from the western Arctic coast through British Mountains to Old Crow Flats to determine how permafrost-climate relations change due to the influence of the mountains. We suspect that the coldest ground is found where winter inversions develop in mountain valley floors. We wish to determine the effects on permafrost temperatures of the mountains as they block coastal weather from moving inland.******