Scientists 'stunned' by Arctic ice behaviour

The giant Ayles Ice Island south of the North Pole has broken in two, one of several "remarkable" occurrences in a year that has seen a record-shattering retreat of the Arctic ice.

"We have people here in the ice service with over 40 years experience and they're all stunned," says Doug Bancroft, director of the Canadian Ice Service, of the extraordinary behaviour of Arctic ice this summer.

"They've never seen anything like this."

The break-up of the ice island last month was just one of several highlights of a summer season that also saw the Northwest Passage open up for the second year in a row.

There has been the occasional summer in the past where the passage was almost ice-free in late summer, making it possible to navigate the fabled passage in a small vessel, says Bancroft.

But to see it happen two years in a row is unprecedented in four decades of record-keeping, he says.

Just two per cent of the 2,300-kilometre-long passage had sea ice at the peak of the ice retreat in mid-September this year, compared to the normal 14 per cent, Bancroft says.

"Normally you'd encounter ice for 400 kilometres of that, this year there was only 20 kilometres," he said.

The Ayles Ice Island, a Manhattan-sized chunk of ice that cracked off an ancient ice shelf at the north end of Ellesmere Island in 2005, also had an incredible summer. After spending more than a year struck in the pack ice at the north end of Ellesmere, the giant slab started moving and sailed into a channel that is normally blocked by ice year-round. The island, which hit a top speed of 10 nautical miles a day, cracked in half in early September and the two pieces are now on opposite sides of a small island in the Arctic archipelago. They are now about 360 nautical miles from where they originated, says Bancroft.

The ice service uses satellites and a beacon to follow the islands, which have now headed into a "graveyard" of multi-year ice far from shipping lanes and oil, gas and mining operations. Bancroft is, however, reluctant to say they won't break loose and become a potential menace in future.

"2007 was such an usual summer in so many respects that people aren't making forecasts about the fate and evolution of very large chunks of ice such as this," says Bancroft, noting how the Arctic ice is changing - and melting - much faster than climate models predicted.

"If you look at what happened in the last three years, it closely resembles the absolutely worst-case scenario, but about 20, 25 years ahead of schedule," he says, referring to models created by international teams of scientists to predict the impact of global warming on the north. They had forecast the Arctic could be free of summer ice as early as 2050.

On Monday the U.S. National Snow and Ice Data Center issued a seasonal wrap-up that said the Arctic sea ice hit the lowest level in 2007 since satellite measurements began in 1979. The average sea ice extent for the month of September was 4.28 million square kilometres, the lowest September on record, shattering the previous record for the month, set in 2005, by 23 per cent. At the end of the melt season, September 2007 sea ice was 39 per cent below the long-term average from 1979 to 2000.

"The sea ice cover is in a downward spiral and may have passed the point of no return," Mark Serreze, a senior scientist at the U.S. centre said in the statement that warned the Arctic could be ice-free in summer by 2030.

Bancroft agrees that the ice "may" have passed the point of no return, stressing that no one really knows for sure.

But he says there is no question the ice has supported the Arctic ecosystem for millennia is "rapidly" changing.

"There is a sense of urgency here," says Bancroft, noting that research teams from around the world are focused on the Arctic as part of the International Polar Year and working to get a better read on the ice and its ecosystem.