A giant ice shelf broke free from Canada's remote Arctic 16 months ago, but no one was on hand to witness the creation of 55-million-square-foot, free-floating island of ice.

Later, scientists using satellite images realized the mass of ice broke clear from the coast of Ellesmer Island, about 497 miles (800 kilometers) south of the North Pole.

Laurie Weir, who monitors ice conditions for the Canadian Ice Service, was poring over satellite images in 2005 when she saw the Ayles Ice Shelf had split and separated. Weir notified Luke Copland, head of the new global ice lab at the University of Ottawa, who decided to find out what happened.

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

"What surprised us was how quickly it happened," Copland said. "It's pretty alarming. Even 10 years ago scientists assumed that when global warming changes occur that it would happen gradually so that perhaps we expected these ice shelves just to melt away quite slowly, but the big surprise is that for one they are going, but secondly that when they do go, they just go suddenly, it's all at once, in a span of an hour."

Within days, the floating ice shelf had drifted a few miles (kilometers) offshore. It traveled west for 31 miles (50 km) until it finally froze into the sea ice in the early winter.

Warwick Vincent of Laval University, who studies Arctic conditions, traveled to the newly formed ice island and could not believe his eyes.

"This is a dramatic and disturbing event. It shows that we are loosing remarkable features of the Canadian North that have been in place for many thousands of years," Vincent explained on Thursday. "We are crossing climate thresholds, and these may signal the onset of accelerated change ahead."

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

The collapse of the ice shelf was so shattering that earthquake monitors 155 miles (250 km) away recorded the event. The 41-square-mile (66 sq km) ice shelf was one of six major ice shelves remaining in Canada's Arctic.

Scientists say it is the largest event of its kind in Canada in 30 years and 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, "percent 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."

Derek Mueller, a polar researcher with Vincent's team, said the ice shelves get weaker and weaker as the temperature rises. He visited Ellesmere's Ward Hunt Ice Shelf in 2002 and noticed it had cracked in half.

"We're losing our ice shelves and this a feature of the landscape that is in danger of disappearing altogether from Canada," Mueller said. "In the global perspective Antarctica has many ice shelves bigger than this one, but then there is the idea that these are indicators of climate change."

The spring thaw may bring 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 explained. "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."

Source:Xinhua/Agencies