'This is a collapse of the ice cover.'

Ice cover on the Arctic Ocean reached its lowest level on record this summer and climate experts say an ice-free North Pole within the next 20 to 30 years is all but inevitable.

Satellite images show ice over the Arctic Ocean melted to such an extent this summer that the Northwest Passage is nearly ice-free. And a huge swath of sea stretching from Alaska to central Russia is completely free of ice.

Tom Agnew, a research meteorologist with Environment Canada in Toronto, said this year's ice cap is smaller than the previous record low set in 2005.

"This year, it's now about 20 per cent below what it was at the record low in 2005 and it's still going down," he said. "So this is a collapse of the ice cover essentially."

What's more, Agnew said even the best efforts to rein in the emissions of greenhouse gases that are causing climate change are unlikely to stop the melting.

"It doesn't matter what we do right now," he said. "We're committed to this warming."

The rapidly shrinking ice pack raises a host of potential complications for everyone from Inuit hunters to military planners.

Thawing ice shortens hunting seasons and makes travelling on sea ice more risky. Species adapted to the frigid Arctic climate will struggle, while southern species could gradually flood north.

"Traditional lifestyles which require hunting and fishing off the ice will become more and more difficult and more and more dangerous," Agnew said.

Meanwhile, the potential opening of the Northwest Passage presents a nightmare scenario for the federal government in Ottawa, which has been trying desperately to assert Canadian sovereignty over the passage, which it claims as internal waters.

But almost no other country recognizes that claim and Canada faces the possibility of increased shipping traffic through the vast and sparsely populated Arctic archipelago. Such traffic would be difficult to police, and threats like oil spills and smugglers would be difficult to contain.

But Christopher Wright, a consultant to the ports and shipping industry based in Digby, Nova Scotia, said it's unlikely the Northwest Passage, ice or no ice, will become a major highway for shipping traffic.

Wright said the traditional Northwest Passage route that runs from the eastern mouth of the Parry Channel, heads south through Peel Sound then runs south of Victoria Island, can only be traversed by ships that sit less than 10 metres deep in the water. A northern route over Banks Island that can handle larger ships is still locked in ice for most of the summer.

An ice-free Northwest Passage "will make sense for selected cargoes and selected routes, but it's very unlikely to start a free-for-all with shipping," Wright said.

Captain Stéphane Julien of the Canadian Coast Guard ship Amundsen, currently on an 15-month, 50,000-kilometre scientific mission that will take the boat from Labrador to Inuvik and from Sanikiluaq to 81 degrees north off the coast of Ellesmere Island, said sea ice thickness in the Arctic varies from year to year.

Julien said ice in the Foxe Basin this year appears to be average, while the waters of the Northwest Passage and the western Arctic are "easier and easier to sail every year."

The Amundsen is capable of crashing through ice up to 15 feet thick, and with more than 20 years experience Julien said he can feel the difference with summer ice these days. It feels rotten, he said, like melting ice in springtime.

"It seems like it's less hard," he said.

Wright said the melting Northwest Passage might be easier to navigate for smaller vessels, like cruise ships and boats hauling cargo to and from Arctic mine sites. But bulk shippers need reliable routes and would likely choose the Northeast Passage over Russia, which features deeper water and a shorter distance between Eastern Europe and Asia.

And as satellite pictures show, that passage is now completely ice-free during summer.