The Antarctic ice sheet is one of the two polar ice caps of the Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth. The total ice mass on the Earth covers an area of almost 14 million square km and contains 30 million cubic km of ice. Around 90% of that, or 27 million cubic km, is located in Antarctica. That is, approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to 70 m of water in the world's oceans. In East Antarctica, the ice sheet rests on a major land mass, but in West Antarctica the bed can extend to more than 2,500 m below sea level. The land would be seabed if the ice sheet were not there. British Antarctic Survey: The Antarctic Ice Sheet and Rising Sea Levels
Ice enters the sheet through precipitation, and typically leaves the sheet by calving of coastal icebergs that melt once in the ocean. .
An analysis of NASA satellite data from 1979-1999 has shown that areas of Antarctica where ice is increasing outnumbers areas of decreasing ice roughly 2:1. . This was significant because there is a large amount of ice in the area and climate models predicting global warming also predict that some of the most severe events from warming should occur in Antarctica. The general trend shows that a warming climate in the southern hemisphere would transport more moisture to Antarctica causing the interior ice sheets to grow, while calving events along the coast will increase, causing these areas to shrink . More recent satellite data suggests that the total amount of ice in Antarctica has begun decreasing in the past few years .
It is a common misconception that the melting of floating ice shelves will not raise sea levels. Because ice shelves are made of fresh water, they will be less dense, i.e, have greater volume than sea water even when melted. The volume of the (melted) water contained in the ice shelf is about 3% greater than the volume of the sea water needed to displace the ice shelf. So as it melts that additional 3% will increase sea level slightly.
