A chunk of ice bigger than the area of Manhattan broke from an ice shelf in Canada's far north and could wreak havoc if it starts to float westward toward oil-drilling regions and shipping lanes next summer, a researcher said on Friday.

 

Global warming could be one cause of the break of the Ayles Ice Shelf at Ellesmere Island, which occurred in the summer of 2005 but was only detected recently by satellite photos, said Luke Copland, assistant professor at the University of Ottawa's geography department.

 

It was the largest such break in nearly three decades, casting an ice floe with an area of 66 square km (25 square miles) adrift in the Arctic Ocean, said Copland, who specializes in the study of glaciers and ice masses. Manhattan has an area of 61 square km (24 square miles).

 

The mass is now 50 square km (19 square miles) in size.

 

"The Arctic is all frozen up for the winter and it's stuck in the sea ice about 50 km (30 miles) off the coast," he said.

 

"The risk is that next summer, as that sea ice melts, this large ice island can then move itself around off the coast and one potential path for it is to make its way westward toward the Beaufort Sea, and the Beaufort Sea is where there is lots of oil and gas exploration, oil rigs and shipping."

 

The break went undetected when it happened due primarily to the remoteness of the northern coast of Ellesmere island, which is only about 800 km (500 miles) from the North Pole.

 

The speed of the crack and drift-off shocked scientists.

 

Satellite images showed the 15-km long (9-mile long) crack, then the ice floating about 1 km (0.6 miles) from the coast within about an hour, Copland said.

 

"You could stand at one edge and not see the other side, and for something that large to move that quickly is quite amazing," he said.

 

Copland said the break was likely due to a combination of low accumulations of sea ice around the mass's edges as high winds blew it away, as well as one of the Arctic's warmest temperatures on record. The region was 3 degrees Celsius (5.4 degrees F) above average in the summer of 2005, he said.

 

Ice shelves in Canada's far north have decreased in size by as much as 90 percent since 1906, and global warming likely played a role in the Ayles break, Copland said.

 

"It's hard to tie one event to climate change, but when you look at the longer-term trend, the bigger picture, we've lost a lot of ice shelves on northern Ellesmere in the past century and this is that continuing," he said. "And this is the biggest one in the last 25 years."