ice sheet is a series of interconnected ice caps, and has been built up from snowfalls, highest near the coast, over a period of hundreds of thousands of years. Much of the interior receives less than than half the annual rainfall of the world's desert
s (about 50mm). The accumulated snow
is balanced by ice drainage towards the coast, mostly via large glaciers that may move at hundreds of metres per year. The snow does not melt, but is rather compressed into ice by later snowfalls. The ice cap thins as it moves northward to warmer conditions, and forms crevasses as flow quickens and buckles over underlying rock. Crevasse
s rarely exceed 100mm in depth.
Antarctica has two distinct ice sheets: Greater East and Lesser West. Greater East includes the South Geographic Pole. The average ice thickness is 2.4-8 km, but can get as thick as 4.8 in Australia's territory. Their weight is less now than it was during more heavily glaciated periods.
The Australian Antarctic Territory includes the Lambert Glacier, one of the largest in the world, which feeds the Amery Ice Shelf. All of the snow that falls within the interior of the Lambert basin, which drains up to eight percent of the total Antarctic ice sheet area, is discharged to the sea via the Lambert Glacier. Because this region is particularly susceptible to change, it is a valuable subject for the study of ice flow processes. It has been determined that more snow is falling in the interior than is being discharged. Ice cores extracted by glaciologists reveal parameters such as precipitation, atmospheric temperature, volcanic events, chemistry and biologic activity.
The ice sheet and surrounding sea ice have a profound influence on the weather, esp. that of the Southern Hemisphere. Research in this area establishes if the ice sheet is growing and shrinking, and what its reaction would be to any future climate change, to determine the impact on global sea level.