Freeze-thaw cycles at Resolute, N.W.T.

Abstract
Research workers in many fields have been interested in freezethaw cycles in the active layer. They are a phenomenon, however, on which few quantitative data exist, particularly for far northern regions. This paper presents soil-temperature data from Resolute, N.W.T ., for 1960, based on continuous Speedomax records from five levels: air, ground surface, and at depths of 2.S , 10 and 20 cm. The number of cycles is surprisingly small. On the ground, for example, where most were recorded, there were only 23 in the range 28° to 32° F, 18 in the range 28° to 34° F, and 7 in the range 25° to 35° F . Most occurred in May and June. At depths of 2.5 cm and below, only the annual cycle was recorded. However, crossings of the freezing line of short duration and small amplitude were more numerous; with 194 occurring in the standard screen, and 170 on the ground surface during the summer. On one day alone the temperature crossed the freezing line 13 times on the ground surface. Problems in assessing the significance of cycles are discussed, and it is concluded that assumptions still widely held that they are a vigorous process in arctic regions are in need of revision. Probably it is impossible to define their parameters. The effectiveness of fluctuations across the freezing line depends, among other things, on thermal conductivity and water content of the soil, and on speed of changes in temperature and their duration. Each situation is likely a special case, and without universal application.

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