CGRG Bibliography of Canadian Geomorphology
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Author : Burn, C.R.
Date : 2001.
Title : Tundra lakes and permafrost, Richards Island, western Arctic coast, Canada.
Publication : Annual Scientific Meeting of the Canadian Geophysical Union. May 14-17, 2001, University of Ottawa, Ottawa.
Issue :
Page(s) :
Abstract
Lakes, of average size 33.5 ha, occupy a quarter of the surface area of Richards Island,Northwest Territories. Many of the lakes have prominent shallow littoral terraces, and a central pool deeper than the thickness of winter ice. Near-surface ground temperatures on Richards Island range between -6º and -9ºC, so the relatively warm lake-bottom temperatures cause considerable disturbance to the thermal regime of permafrost. Water and lake-bottom temperatures, the configuration of permafrost, active-layer thickness, and frost heave were measured at a tundra lake between 1992 and 1997. The lake is ovate, 1.6 km long, 800 m wide, and up to 13 m deep. Sandy terraces, covered by less than a metre of water, extend over 100 m from the shore. The terraces are underlain by permafrost, which terminates at their edge in a near-vertical wall. The lake is well mixed in summer, but thermally stratified when ice covered. The annual mean temperature measured at lake bottom in the central pool ranged between 1.5º and 4.6ºC, depending on depth, and between -0.2º and -5ºC on the terraces, due to differences in snow cover. In consequence, the temperature of permafrost at 7 m depth in the terraces also varied, from -2º near shore to -5ºC in mid-terrace. The active layer in the terraces was uniformly 1.4 m deep. Pore-water expulsion during freezing of the active layer led to growth of frost blisters in the subaqueous sediments. A geothermal model of talik configuration indicates that there is no permafrost beneath the central pool of the lake. The model suggests that, at equilibrium, 30 to 40% of the lakes on Richards Island have taliks that penetrate permafrost.
Bibliography of Canadian Geomorphology