| Summary: | Lake‐bottom temperatures have been measured for several years at two lakes with littoral terraces on north‐central Richards Island, a residual pond of the Illisarvik experimental drained lake site, and a taiga lake near Inuvik. The tundra lakes possess distinct thermal regimes: in (1) the deep central pools; (2) shallows where winter ice may reach bottom; and (3) on littoral terraces, where water depth is less than 1 m. In summer, the tundra lakes are uniformly well mixed and reach similar lake‐bottom temperatures at all depths. In winter, conditions vary, depending on the proximity of the ice cover to lake bottom. The annual mean lake‐bottom temperatures have been about 3°C in the deep central pools, 0°C in the shallow pools, and −2°C on the terraces of the tundra lakes. For the taiga lake, where late‐winter ice cover reaches only about half the thickness of the two tundra lakes, annual lake‐bottom temperatures follow the same pattern as in the central pools of the tundra lakes, but the mean temperature is over 5°C. If the thermal regime of the taiga lake is an analogue for tundra conditions following climate warming, then the width of lakes with through taliks on Richards Island may decline by between 20 and 100 m. At equilibrium, about 45% of the lakes and 20% of the surface area of Richards Island may then be underlain by taliks that penetrate permafrost. Copyright © 2005 John Wiley & Sons, Ltd.
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