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Antarctica contains more than 90% of the world's ice. This ice is present as ice sheets, ice shelves and sea ice.
Antarctica contains more than 90% of the world’s ice. The ice comes in different forms:
What data might scientists be able to gather from ice and what do you think this data would be used for?
The Antarctic ice sheet is a layer of ice on the continent formed from thousands of years of snowfall that has been compressed as new snow has been deposited on top. It is the largest single mass of ice on Earth covering 99% of the continent, an area of 14 million km2, to a maximum depth of 4700m. Around 90% of the Earth’s fresh water is held in the ice sheet.
The Antarctic ice sheet is made up of two sheets that merge into one:
An ice shelf is a floating extension of the ice sheet formed on land as the sheet flows downhill onto the sea. They are made of fresh water.
How do you think scientists measure the movement of ice?
The Ross Ice Shelf is one of the largest in the world, covering an area nearly twice the size of New Zealand. The Ross Ice Shelf varies in thickness from over 1000m where it is fed by glacial ice from the ice sheet to less than 100m at the ice front.
Sea ice is formed on the ocean surface when the water temperature falls to –2 degrees Celsius. It still contains some salt (about 1% compared with the 3.5% of sea water). As ice is less dense than water it floats on the surface forming a layer up to several metres thick.
Each winter sea ice forms, although some parts do not melt the following summer. Sea ice begins to form in the Ross Sea in March/April and usually breaks up by mid-summer to leave open water again, except where pockets of fast ice remain in bays and inlets.
Sea ice is not the same as icebergs. Icebergs break off the edges of ice shelves and so are made of fresh water.
The ice sheet that covers almost all of Antarctica is made up of two ice sheets that merge into one. The East Antarctic ice sheet is the larger of the two. Image: NASA (edited).
The Ross Ice Shelf is one of the largest in the world. It is a floating extension of the West Antarctic Ice Sheet and is 100m thick at its leading edge. Image: Josh Landis, NSF.
Sea ice viewed from the window of a C17 aircraft from a height of 9500m. Sea ice is formed on the ocean surface when the water temperature falls to -2°C. Image: LEARNZ.
An ice shelf is formed when the ice sheet flows downhill into the sea. The ice shelf is made of fresh water. Can you see where the ice shelf meets the sea ice? Image: LEARNZ.
Icebergs break off the edges of ice shelves and so are made of fresh water. Icebergs move with the wind and ocean currents.