Abstract

On 13 August 1978, a lake on the western Arctic coast was artificially drained, in a multidisciplinary experiment on the growth of permafrost on the unfrozen bottom of the drained lake. A bowl-shaped talik (unfrozen basin) with a maximum depth of about 32 m underlay the lake bottom prior to drainage. In the first winter after drainage, downward freezing started on the exposed lake bottom and upward freezing from permafrost beneath the talik. After drainage, the soft lake-bottom sediments hardened from water loss and freeze–thaw consolidation. Gradual thinning of the active layer at many sites was accompanied by ground uplift and the growth of aggradational ice. Downward and upward freezing has resulted in solute rejection, freezing-point depressions, pore-water expulsion from the freezing of the saturated lake-bottom sands, and convective heat transfer from groundwater flow in an open hydrologie system. The increasingly saline intrapermafrost groundwater, flowing at an increasingly negative temperature because of a freezing-point depression, has accelerated the rate of permafrost growth in the interpermafrost zone in the direction of flow. The experiment has demonstrated that the growth of permafrost at the drained lake site, and at other sites with groundwater flow, requires a three-dimensional conductive–convective heat transfer approach.

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