Antarctic Ice Sheet

Ice covers much of the polar regions of Earth and is a critical component to the planet's climate. An ice sheet is defined as a mass of ice that is greater than 31,000 mi. (50,000 km) in area, such as those of Antarctica and Greenland. Ice sheets should not be confused with ice caps, which are masses of ice covering less than 31,000 mi. (50,000 km) in area. It is estimated that approximately 90 percent of the Earth's total ice mass is located in the Antarctic Ice Sheet, or 6.4 million cu. mi. (27 million cu. km). The Ross Ice Shelf and the Filchner–Ronne Ice Shelf are the world's largest, both found in Antarctica. Scientists are concerned that increasing temperatures of air and sea will cause significant melting of the world's ice, including the Antarctic Ice Sheet, and cause sea-level rise.

Ice sheets, glaciers, ice caps, permafrost, snow, and sea ice are all components of the Earth's cryosphere (portions of the Earth's surface that are frozen over land or water). In the Southern Hemisphere, the Antarctic Ice Sheet covers approximately 98 percent of the Antarctic continent and is the single largest mass of ice on the planet. Ice sheets form as snow and frost build up in an area, compressing the previously fallen snow into ice. The total area of ice sheets is changed regularly by melting, primarily where the ice comes into contact with water or warmer dry land at its base; and by calving, or the falling off of large pieces of the ice sheet, which become icebergs. The Antarctic Ice Sheet covers the major landmass of the continent in the eastern Antarctic and extends over the ocean in western Antarctica, where the ice sheet is as deep as 2,500 mi. (4,023 km) below sea level.

The Antarctic continent is cold year-round and is as dry as a desert, with little to no annual precipitation. Historically, the Antarctic Ice Sheet has experienced very little melting from the surface. The oldest portions of the Antarctic Ice Sheet are estimated to be 15 million years old. Typically, the seasonal fluctuation that is experienced by the ice sheet is focused on the northern Antarctic peninsula and the northeastern regions of the ice sheet. Most ice from the Antarctic Ice Sheet is lost by calving of glaciers from the protruding ice shelves of the sheet. The total volume of the ice in this region is estimated to be 7.5 million cu. mi. (31 million cu. km).