2008-07-29 23:12:40 GMT 2008-07-30 07:12:40 (Beijing Time) Xinhua English
OTTAWA, July 29 (Xinhua) -- The continuous fragmentation of the largest remaining ice shelf in the Arctic over the past years is a one-way change brought about by rising earth temperatures, a Canadian scientist said Tuesday.
The fracture of a four-square-kilometer chunk of ice from the ice shelf last week marks the continuation of a process that has been years in the making, said Derek Mueller, a polar scientist and research fellow at Trent University in Ontario.
Mueller said the changes in the shelf, which surrounds Ward Hunt Island off the north coast of Ellesmere, provide further evidence the planet, and in particular the North, is warming due to climate change.
An expedition by U.S. explorer Robert Peary in 1906 put the size of the Ellesmere Island Ice Shelf at just under 9,000 square kilometers. The ice shelf has since broken up into smaller pieces, the largest of which is the Ward Hunt Island Shelf. The total area of all of these pieces is now less than 900 square kilometers.
Mueller said if year-to-year warming was not occurring, Arctic researchers would have been able to detect some renewal of ice during the winter months, either through thickening of the ice or the spread of the shelves. But researchers have not seen any sign of renewal, he said.
Mueller was part of the team of polar researchers that first discovered in 2002 a large central crack in the ice shelf, which had occurred between 2000 and 2002. An expedition alongside Canadian Rangers on a patrol around Ellesmere Island in April 2008 found an 18-kilometer crack along the shelf, a further sign that fragmentation was likely.
Ice shelf integrity was lost in 2002 and this is a one-way change, he said.