Internal structure and environmental significance of a perennial snowbank, Melville Island, NWT

Abstract

A perennial snowbank located in the continuous permafrost zone was cored to obtain details of its internal structure and history. In spring the snowbank is up to 10 m thick and composed of deep snow accumulated during the previous winter, overlying ice developed by basal ice accretion over many years. The perennial ice exhibits a layered structure with alternating clear and milky banks and contains randomly oriented, variably shaped bubbles. Horizons of aeolian and mudflow deposits occur at irregular intervals and correspond to periods of aggradation and thaw truncation of the snowbank. Tritium concentrations in a core from the deepest portion of the snowbank indicate that the basal 2 m of ice pre-dates 1957. Other layers of ice likely represent precipitation that fell between 1958 and 1962, between 1968 and 1976, and after 1983. Ice developed during the 1963 atmospheric tritium peak is no longer present. Energy balance measurements indicate that potential climatic warming is unlikely to eliminate the perennial portion of the snowbank unless accompanied by substantially less snow drifting at the site. -from Authors