Author(s): S. P. Blachut
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Abstract: As part of a program of glacio-hydrological investigations (1972-1975) on a high Arctic ice cap, Ellesmere Island, Canada, a catastrophically draining ice-dammed lake was studied in detail. Monitoring of the thermal regime of the 200 m deep ice-covered lake was carried out as a possible aid in the investigation of lake drainage mechanisms. Lake water temperature profiles were recorded using a thermistor cable and a resistance bridge throughout the summer season, 1974, and at a variety of depths and locations throughout the lake. The results indicate near isothermal conditions for the entire depth of the lake, and no apparent spatial or temporal trends. Temperatures were consistently between 0.0 and 1.0C, with only minor variations along the entire depth profiles. The most significant source of temperature variation was proximity to the large floating glacier ice tongue which bordered one margin of the lake. The uniform low temperatures are a function of the adjacent ice cap, low influent water temperatures, the short and cool high Arctic summer season and the presence and persistence of the lake ice cover. The characteristics of this lake fit into Hutchinson's (1957) category of a true polar or amictic lake in his lake thermal classification scheme. This category is described as having a temperature of less than 4°c year-round, essentially isothermal profiles, no thermocline development, and a lake ice cover persisting the entire summer season in most years. Examples of amictic lakes have been noted in Antarctica, Greenland and Axel Heiberg Island, but are considered to be uncommon features. The Canadian high Arctic contains a high density of ice-dammed lakes associated with the ice caps of Ellesmere, Axel Heiberg, Devon and Baffin Islands. A high proportion of these lakes is postulated to belong to the amictic category, making them more common phenomena than suggested by Hutchinson and others.
Year: 1978