Global Range: Wide general distribution in seasonally and permanently ice-covered waters of Northern Hemisphere; Arctic Ocean and several adjoining seas and freshwater lakes. Local abundance varies with winter ice conditions. In North America, ranges seasonally into North Atlantic as far south as Labrador and Newfoundland, Hudson and James bays, and Bering Sea (usually to Nunivak Island or Bristol Bay); in winter and spring, ranges as far south as the limit of sea ice. See Reeves et al. (1992) for information on distribution in Eastern Hemisphere.