ABSTRACT: The behaviour of a polar ice dammed lake, Ellesmere Island, NWT

CGRG Bibliography of Canadian Geomorphology
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Abstract

Most of the literature on ice-dammed lakes deals with lakes associated with temperate glaciers. However, recent observations indicate that there may be many lakes associated with cold or polar ice. Preliminary reconnaissance suggested that a small, deep, isothermal lake ponded against the western margin of the Ellesmere Ice Cap on Ellesmere Island in Canada might be an important source of sudden inputs of water into the main river system of the area. Sudden, partial drainage of this lake was observed in three successive years, 1973 through 1975. Glacier outburst floods (jokulhlaups) occurred in each of these years, with the 1973 event being the most severe. The water balance of the lake and the characteristics of the ice dam, monitored in 1974, indicated that barrier flotation was the key factor in the initiation of the jokulhlaups. There did not appear to be any leakage through the ice dam prior to the jokulhlaups, which began with a violent and forceful extrusion of water at high pressure at the outlet. The annual drainage events were separate events, with drainage initiated at progressively lower levels each year. Both the total volume of water discharged and the maximum rates of discharge were smaller with each successive year. The discharge rate decreased rapidly after the first few days of the drainage event. Barrier lifting and disturbance due to flotation of the shelf ice, resulting from rising lake levels during the first part of the summer season, appeared to be the trigger mechanism initiating lake drainage. The decreasing magnitude of the jokulhlaups and the fall in maximum lake levels over the 3 year period suggest that a series of annual drainage events might be succeeded by a period of nondrainage or lake recharge

Bibliography of Canadian Geomorphology