Antarctic ice pack

Antarctic sea ice is the sea ice of the Southern Ocean. It extends far north in winter and retreats almost to the coastline each summer. Sea ice freezes from seawater, and is usually less than a few meters thick. It should not be confused with the ice shelves, which are formed by glaciers flowing out into the sea and floating free of the bottom (these can be up to a kilometer thick). There are two subdivisions of sea ice: fast ice, which is attached to land; and ice floes, which are not.