Offshore Permafrost and Ground Ice, Southern Beaufort Sea, Canada

Abstract

The distribution and origin of offshore permafrost is discussed for the southern Beaufort Sea. Two types of permafrost are identified: permafrost which is in thermal equilibrium with negative sea bottom temperatures, and disequilibrium permafrost, which is not in equilibrium with either positive or negative sea bottom temperatures. The origin of permafrost is considered in terms of the Quaternary period when coastal areas were exposed to cold air temperatures and then submerged. The effect of warm river waters, primarily from the Mackenzie River, is shown to ameliorate coastal water temperatures and may be responsible for a thin active layer at some sites. Water quality and oxygen isotope ratios are given for some samples. The evidence suggests that some relic land permafrost, with ground ice, is present beneath the southern Beaufort Sea. Perforated permafrost should be present, but not extensive thermokarst depressions. By inference, permafrost probably underlies much of the Canadian Arctic waters, although ground ice is likely restricted to a relatively few shallow coastal zones.