Only a few years ago, even large commercial vessels wouldn't take on the ice-bound Northwest Passage linking the Atlantic and Pacific via the Canadian north — but climate change has changed all that.

Now, a group of hearty adventurers hopes to be the first to row the 1,900-mile route this summer.

"Several people have kayaked it [a section at a time] over several years. But no one has ever done this under human power in a single season. Not even close," Kevin Vallely, who is heading up the rowing team, told The Globe and Mail on Wednesday.

Vallely has completed his last shakedown cruise and plans to set off at the beginning of July from Inuvik in northern Canada with three crew mates in a custom-built, 23-foot rowboat. They expect to take 75 days to reach their eastern destination, the town of Pond Inlet. Along the way they're bracing for encounters with dangerous ice, storms and polar bears, not to mention the psychological challenge of four men in a small boat in those difficult circumstances.

"We have guns" as a precaution against polar bears, Vallely tells The Globe and Mail. "But we'll have rubber bullets and bear bangers ... we don't want to kill a bear."

The newspaper says Vallely, "who has done numerous wilderness treks over the past 20 years, said if your physical conditioning is just right, body fitness peaks during a long journey and then slowly deteriorates."

" 'Obviously you have to train enough that you don't get injured [by the exertion of the expedition]. But you don't want to train too much, because if you go into it Tour de France fit, in a couple of weeks you would be fried,' he said. 'So you go into it fit, but not crazy fit, and you build up and you get really strong about half-way through. And then you slowly start to fall apart. By the end you want to be tired, happy to be done, but not completely baked.' "

As we reported back in March, computer simulations of various climate change models indicate that Arctic ice will be so thin by the middle of the century that commercial shipping from North America to Russia or Asia via the Arctic could become routine.

In recent years, Arctic sea ice has shrunk to its smallest extent on record, opening up the Northwest Passage. A solo sailor in a 27-foot fiberglass sailboat was one of 18 private yachts to sail the route last year.

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