New York - A 50-square-kilometre chunk of the Canadian Arctic ice shelf has broken off and is floating freely in the Arctic Ocean, the Globe and Mail newspaper reported Wednesday.

The ice from the northern coast of Ellesmere Island about 800 kilometres south of the North Pole broke off in early August. It could be up to 4,500 years old and 40-metres thick, making its disappearance more worrisome than the sea ice that typically forms ice bergs, researchers said.

Researcher Derek Mueller of Trent University in Peterborough, Ontario, said 214 square kilometres of shelf ice has been lost this summer likely as a result of global warming.

"You just can't have ice shelves in a warm climate," Mueller told the newspaper. "You can't link any one event to climate change, but we can certainly link patterns."

Ellesmere Island is Canada's third largest and most northern island. A century ago, it was completely covered in 70-metre thick, up to 4,500-year-old ice. By 1990, the ice was reduced to six separate sheets.

The most recent piece of ice to break off was part of the Markham Ice Shelf. In July, a part of the Ward Hunt Ice Shelf broke off.