In a second study, images captured by Envisat, the European Space Agency's (ESA) environmental satellite, show that the Wilkins Ice Shelf is at risk of partly breaking away from the Antarctic Peninsula as the ice bridge that connects it to Charcot and Latady Islands looks set to collapse.

New rifts are quickly expanding along the ice bridge, resulting in a large block of ice breaking away, the ESA said in a statement, adding that last year saw the ice loss of about 1800 sq km from Wilkins, or about 14 percent of its size.

In another study published in the journal Geophysical Letters, the U.S. National Oceanic and Atmospheric Administration reported that ice is melting much more rapidly than expected in the Arctic as well, based on new computer analyses and recent ice measurements.

Clinton also formally announced that at the treaty conference the United States would be proposing mandatory limits on the size of Antarctic cruise ships and the number of passengers they bring ashore.

"We have submitted a resolution that would place limits on landings from ships carrying large number of tourists. We have also proposed new requirements for lifeboats on tour ships to make sure they can keep passengers alive until rescue comes."

Tourism to the Antarctic region has increased five-fold since the early 1990s as tens of thousands of people cruise during the Southern Hemisphere's summer to see shrinking icebergs and wildlife.

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Editor:Yang Jie