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Related to pack ice: ice floe, Ice pack therapy
polar sea ice that has lasted through more than two annual cycles of buildup and thaw. It is usually observed in the form of vast ice fields in the Arctic Basin and as shore ice along the northern coasts of Greenland, in the northern straits of the Canadian Arctic Ocean archipelago, and in Antarctica. Hummocks in fields of pack ice are usually smoothed out by recurrent thaws, and as a result the fields tend to be rolling. Extensive pack ice makes passage by ships impossible and presents a serious obstacle to navigation along the pack’s southern margin. Pack ice accounts for 60–90 percent of the ice sheet of the Arctic basin, depending on how far south the pack ice extends.