The largest ice shelf in the Arctic has broken up, scientists in the United States and Canada have said.
They said the Ward Hunt ice shelf, on the north coast ofEllesmere Island in Canada's Nunavut territory and a solid feature for 3,000 years, broke into two main parts, themselves cut through with fissures.
A freshwater lake drained into the sea, the researchers reported.
Large ice islands also broke off from the shelf, and some are large enough to be dangerous to shipping and to drilling platforms in the Beaufort Sea.
Local warming of the climate is to blame, scientists said, adding they did not have the evidence needed to link the melting ice to the steady, planet-wide climate change known as global warming.
Only 100 years ago, the whole northern coast of EllesmereIsland, which is the northernmost land mass of North America, was edged by a continuous ice shelf. About 90 per cent of it is now gone, according to researchers.
The area has been getting warmer, they said. A similartrend in the Antarctic has caused the break-up of huge ice shelves there.
"There's a regional trend in warming that cycles back 150 years," Mr Derek Mueller of Laval University in Quebec City, Canada, said. "I am not comfortable linking it to global warming."
Records indicate an increase of four-tenths of a degreecentigrade every 10 years since 1967. The average Julytemperature has been 1.3 degrees since 1967.