WINNIPEG–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 But David Barber says the thick, multi-year frozen sheets crucial to the northern ecosystem have been replaced by thin "rotten" ice that can't support weight of the bears. "It caught us all by surprise because we were expecting there to be multi-year sea ice. The whole world thought it was multi-year sea ice," said Barber, who just returned from an expedition to the Beaufort Sea.

"Unfortunately, what we found was that the multi-year (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 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 multi-year ice floe broke up into pieces," Barber said. "This floe was 16 km 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.

Multi-year sea ice used to cover 90 per cent of the Arctic basin, Barber said. It now covers 19 per cent. Where it used to be up to 10 metres thick, it's now 2 metres at most.

The findings, soon to be published in the journal Geophysical Research Letters, come 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 images the experts relied on were misleading because the rotten ice looks sturdy on the surface and has a similar superficial temperature, Barber explained.

"The satellites give us only part of the story. The multi-year ice is disappearing and it's almost all gone now from the northern hemisphere."

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