The largest ice shelf in the Arctic, a solid feature for 3,000 years, has broken up, scientists in the United States and Canada said Monday. They said the Ward Hunt Ice Shelf, on the north coast of Ellesmere Island in Canada’s Nunavut territory, broke into two main parts, themselves cut through with fissures. A freshwater lake drained into the sea, the researchers reported.
LARGE ICE ISLANDS also calved 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, they said — adding that they did not have the evidence needed to link the melting ice to the steady, planet-wide climate change known as global warming.
Warwick Vincent and Derek Mueller of Laval University in Quebec City, Canada, and Martin Jeffries of the University of Alaska Fairbanks lived at the site, flew over it and used radar satellite imaging for their study.
Writing in the journal Geophysical Research Letters, Vincent’s team said all of the fresh water poured out of the 20 mile (30 km) long Disraeli Fjord.
This in turn has affected communities of freshwater and marine species of plankton and algae, said Mueller, a graduate student who has studied the tiny creatures.
Only 100 years ago the whole northern coast of Ellesmere Island, which is the northernmost land mass of North America, was edged by a continuous ice shelf. About 90 percent of it is now gone, Vincent’s team wrote.
The area has been getting warmer, they said. A similar trend 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,” Mueller said in a telephone interview. “I am not comfortable linking it to global warming. It is difficult to tease out what is due to global warming and what is due to regional warming.”
Records indicate an increase of four-tenths of a degree centigrade every 10 years since 1967. The average July temperature has been 1.3 degrees Celsius or 34 degrees F —just above the freezing point — since 1967.
Climate change has affected ocean temperature, salinity and flow patterns, which also influence the break-up of ice shelves in the Antarctic. “It’s not just as simple as it gets x degrees warmer and the ice melts this much,” Mueller said.
Warmer temperatures weaken the ice, leaving it vulnerable to changed currents and other forces.
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