A giant ice shelf the size of 11,000 football fields has snapped free from Canada's Arctic, leaving behind a trail of floating icy boulders.

Scientists said the mass of ice broke clear 16 months ago from the coast of Ellesmere Island, in Canada's remote north.

However, no one witnessed the dramatic spectacle, which took place bout 800 kilometres south of the North Pole.

Scientists using satellite images later noticed that it became a newly formed ice island in just an hour.

Laval University's Warwick Vincent, who studies Arctic conditions, travelled to the new ice island and couldn't believe what he saw.

"It was extraordinary," Vincent said Thursday. "This is a piece of Canadian geography that no longer exists."

Vincent said in 10 years of working in the region, he has never seen such a dramatic loss of sea ice.

The collapse was so powerful that earthquake monitors 250 kilometres away picked up tremors from it.

Scientists said it is the largest event of its kind in 30 years. They point their fingers at climate change as a major contributing factor.

"We think this incident is consistent with global climate change," Vincent said, adding that the remaining ice shelves are 90 per cent smaller than when they were first discovered in 1906.

"We aren't able to connect all of the dots . . . but unusually warm temperatures definitely played a major role."

Laurie Weir, who monitors ice conditions for the Canadian Ice Service, was looking over satellite images when she noticed that the shelf had split and separated.

Weir contacted Luke Copland, head of the new global ice lab at the University of Ottawa, who began an investigation into what actually took place.

Using U.S. and Canadian satellite images and data from seismic monitors, Copland discovered the ice shelf collapsed in the early afternoon of Aug. 13, 2005.

"These ice shelves can break up really quickly, perhaps more quickly than we thought they could do in the past," he said.

"Within an hour we could see this entire ice chunk just disconnect and float away."

Within days, the floating ice shelf had drifted a few kilometres offshore. It travelled west for 50 kilometres until it finally froze into the sea ice in the early winter.

Derek Mueller, a polar researcher with Vincent's team, saw that Ellesmere's Ward Hunt Ice Shelf had cracked in half in 2002. He also noticed that sea ice, which creates a buffer zone around ice shelves, was approaching lower and lower levels.

"These ice shelves get weaker and weaker as the temperature rises," he said.

"And the summer of 2005 had a combination of high temperatures and strong winds that probably blew the sea ice away, making this ice shelf much more vulnerable."

The Ayles Ice Shelf, roughly 66 square kilometres in area, was one of six major ice shelves remaining in Canada's Arctic. They are packed with ancient ice that dates back more than 3,000 years.

"We're seeing the tragic loss of unique features of the Canadian landscape," Vincent said, adding the global climate is crossing an unprecedented threshold.

"There are microscopic organisms and entire ecosystems associated with this ice, so we're losing a part of Canada's natural richness."

Meanwhile, the spring thaw brings another concern as the warming temperatures could release the ice shelf from its Arctic grip. Prevailing winds could then send the ice island southwards, deep into the Beaufort Sea.

"Over the next few years this ice island could drift into populated shipping routes," Weir said.

"There's significant oil and gas development in this region as well, so we'll have to keep monitoring its location over the next few years."

With files from The Canadian Press