One of Canada's top northern researchers says the permanent Arctic sea ice that is home to the world's polar bears and usually survives the summer has all but disappeared.
Experts around the world believed the ice was recovering because satellite images showed it expanding. But David Barber says the thick, multiyear frozen sheets crucial to the northern ecosystem have been replaced by thin "rotten" ice which can't support the weight of the bears.
"It caught us all by surprise because we were expecting there to be multiyear sea ice - the whole world thought it was multiyear sea ice," said Dr. Barber, who just returned from an expedition to the Beaufort Sea.
"Unfortunately what we found was that the multiyear [ice]has all but disappeared. What's left is this remnant, rotten ice."
Permanent ice, which is normally up to 10 metres thick, was easily pierced by the research ship, said Dr. Barber, who holds the Canada research chair in Arctic science at the University of Manitoba.
The team finally reached what it thought was stable ice, only to watch a crack appear just as researchers were preparing to descend onto the floe.
"As I watched, over the course of five minutes, the entire multiyear ice floe broke up into pieces," Dr. Barber said. "This floe was 10 miles across. Something that's twice the size of Winnipeg, it just broke up right in front of our eyes."
The ice is unable to withstand battering waves and storms because global warming is rapidly melting it at a rate of 70,000 square kilometres each year, he said.
Multiyear sea ice used to cover 90 per cent of the Arctic basin, Dr. Barber said. It now covers roughly 19 per cent. Where it used to be up to 10 metres thick, it's now two metres at most.
The findings, which are soon to be published in the journal Geophysical Research Letters, comes as a shock to experts worldwide. Although northern sea ice hit a record low in 2007, researchers believed it was recovering because of what they were seeing on satellite images.
But the satellites the experts relied on were misleading because the rotten ice looked sturdy on the surface and has a similar superficial temperature, Dr. Barber explained.
"The satellites give us only part of the story. The multiyear ice is disappearing and it's almost all gone now from the northern hemisphere."
The deterioration has far-reaching consequences for the North and its iconic mammal. Polar bears that rely on the permanent ice to survive the summer have fewer and fewer places of refuge, Dr. Barber said.
"Polar bears are being restricted to a small fringe of where this multiyear sea ice is. As we went further and further north, we saw less and less polar bears because this ice wasn't even strong enough for the polar bears to stand on."
The lack of sea ice may be good news to some who want to see the North opened to industry. Without thick ice blocking the way, ships can more easily gain access to the Arctic's natural resources.
"We were doing almost the same speed we'd do in open water through what we thought was multiyear sea ice," Dr. Barber said. "Transportation and all the issues of navigation across the pole all become very real when you no longer have any multiyear sea ice."
But opening the Arctic to international shipping could have an impact on the ecosystem if freighters bring with them new contaminants and species, he added.
Dr. Barber said the sea ice is virtually beyond repair and it would take years of cold weather to restore the Arctic to its former state.
"I think we're on our way to an Arctic ice cover that will be seasonal and not perennial."