Antarctica contains 90% of the world’s ice, and 68% of the world’s fresh water. The ice sheet contains about 30 million km3 which cover 98% of the continent. If it all melted, the sea level world-wide would rise by between 50 and 60 metres.
Ice across the continent
Surprisingly, the thickest ice is located only 400km from the coast, in East Antarctica, where a huge, sub-glacial trench is filled with 4’776m of ice. The average thickness of the ice sheet is 2500-2800m. This enormous weight of ice pushes the continental bedrock of East Antarctica below sea level, so the maximum height of the ice sheet is only about 4000m.
Snow and Ice
The huge mass of the Antarctic ice sheet has accumulated from million of years of Snowfall. Because the air over Antarctica is so cold, it cannot carry much moisture, even as snow, so very little falls in the centre of the continent. Snowfall is higher around the coast and more is carried there from inland by the katabatic winds, so accumulation can be up to 2 m a year.
As snow accumulates in deeper and deeper layer, it gradually turns into ice. Because the accumulation rate is so slow, this very deep ice may be many thousands of years old. The air trapped in the ice can tell scientists about the atmosphere at the time the snow from which it is made fell on the surface.
The Movement of Ice
Although the Antarctic ice sheet may have taken million of years to accumulate, it is not static. Ice is fluid and the ice sheet flows continuously out from the centre to the edges of the continent under the pressure of its own weight, in the same way that icing flows off the cake. The rate of flow varies. It is slowest at the centre and fastest at the edge because the domeshaped ice sheet slopes more steeply at the edge.
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