Giant sheets of ice totaling almost 20 square km broke off an ice shelf in the Canadian Arctic last week and more could follow later this year, scientists said yesterday. Temperatures in large parts of the Arctic have risen faster than the global average in recent decades, a development experts say is linked to global warming. The ice broke away from the shelf on Ward Hunt Island, just off giant Ellesmere Island in one of the northernmost parts of Canada. It was the largest fracture of its kind since the nearby Ayles ice shelf -- 25 square miles -- broke away in 2005.

Scientists had already identified deep cracks in the Ward Hunt shelf, which measures around 155 square miles. It is one of five along Ellesmere Island in the northern Arctic. ?Because the break-off occurred between two large parallel cracks they're thinking more could go this summer before the freeze sets in,? said Trudy Wohlleben of the Canadian Ice Service. Ellesmere Island was once home to a single enormous ice shelf totaling around 3,500 square miles. All that is left today are five much smaller shelves that together cover just under 400 square miles. ?The break-off is consistent with other changes we've seen in the area, such as the reduction in the amount of sea ice, the retreat of the glaciers and the break-up of other ice shelves,? Wohlleben said. She said a likely reason for the shelf breaking away was a strong wind from the south.

Warwick Vincent, director of the Centre for Northern Studies at Laval University in Quebec, said much of the remaining Ward Hunt ice shelf is now in a vulnerable state. ?It underscores the fact that each year we're now crossing new thresholds in environmental change in the High Arctic, and our concern in the longer term is that these may signal the onset of serious change at all latitudes, much further to the south, for example.?

Derek Mueller, an Arctic ice shelf specialist at Trent University in Ontario, said he was concerned by the rapidity of changes over the last few years. ?It's a bit of a wake-up call for those people who aren't yet affected by climate change that there are places on earth that are, and the same could be true for them (these people) if you fast-forward a decade or two or three.?