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Environment

FACTBOX: Antarctica's vanishing ice shelves

(Reuters) - The Antarctic Peninsula’s vast Wilkins Ice Shelf is poised to become the 10th floating shelf on the frozen continent to recede or vanish into the ocean.

A Reuters visit to the Wilkins with the British Antarctic Survey, making the first plane landing in the area, showed it was held in place only by a 40 km (25-mile) long strip of ice that has shrunk to about 500 meters (1,600 ft) wide at its narrowest point and could collapse at any time.

Fifty years ago, the strip was more than 100 km wide. The shelf is still about the size of Jamaica.

Following are facts about ice shelves.

-- Ice shelves are extensions of land-based ice sheets that float on the sea. They can be several hundred meters thick and are found mainly in bays around Antarctica, with some in the Arctic. Antarctica’s biggest, the Ross Ice Shelf, is the size of France.

-- Scientists worry that that the collapse of ice shelves could prompt glaciers inland to start sliding faster toward the sea, raising sea levels. Antarctica holds enough fresh water to raise sea levels by 57 meters (187 ft), so even a limited melt would have big consequences.

-- Since 1950, ten ice shelves on the Peninsula, which snakes up toward South America, have contracted or collapsed.

-- The British Antarctic Survey reckons that 25,000 sq km (10,000 sq mile) of ice shelves have been lost in total -- an area the size of Macedonia, Rwanda or the U.S. state of Vermont.

-- Ice shelves that have broken up since 1950 are the Larsen A, Larsen B and Larsen C, Prince Gustav, Muller, Jones, Wordie, George VI north, George VI south and the Wilkins.

-- Among the most dramatic collapses was that of the Larsen A within a few weeks in 1995, when satellite images abruptly showed the bay dotted with icebergs. The Larsen B also abruptly collapsed in 2002.

-- For Reuters latest environment blogs click on: blogs.reuters.com/environment/

Editing by Andrew Roche

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