The largest ice shelf in the Arctic, a solid feature for 3,000 years, has broken up, report U.S. and Canadian scientists. A team led by Professor Warwick Vincent of Laval University in Quebec City, Canada, lived at the site, flew over it and used radar satellite imaging for their study, published in the journal Geophysical Research Letters. The researchers report that 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. 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. Vincent and colleagues also report that all of the fresh water poured out of the 30 km long Disraeli Fjord and this has, in turn, affected communities of freshwater and marine species of plankton and algae.
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% of it is now gone, write Vincent and colleagues, who say the local area has been getting warmer. The researchers say they do not have the evidence needed to link the melting ice to the steady, planet-wide climate change known as global warming. 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,” said team member, Derek Mueller. “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 Celsius every 10 years since 1967. The average July temperature has been 1.3°C – 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.