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Ice Shelves in Antarctica

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Ice is less dense than water and because near the coast ice sheets generally rest on a bed below sea level, there comes a point where it begins to float. It floats in hydrostatic equilibrium and either it stays attached to the ice sheet as an ice shelf, or breaks away as an iceberg. Being afloat, ice shelves experience no friction under them, so they tend to flow even more rapidly than ice streams, up to 3 km per year. Much of Antarctica is fringed by ice shelves. Ross and Ronne-Filchner ice shelves each have areas greater than the British Isles.

Ice cliffs of the Brunt Ice Shelf near Mobster creek
Ice cliffs of the Brunt Ice Shelf near Mobster creek

Across the base of ice shelves, sea water and ice come into contact. Where this sea water is warm enough, the ice shelf will melt, adding cold fresh water to the sea. This diluted seawater eventually helps to form a water mass called Antarctic Bottom Water which is present in many of the deepest parts of the ocean.

Eventually, ice breaks off the ice shelves to form icebergs. We will see shortly that ice shelves may be sensitive indicators of climate change.