But the northern route, which runs through the McClure Strait in a straight shot from Baffin Bay west of Greenland to the Beaufort Sea north of Alaska, is another story. "Everyone wants the McClure route because it's quicker, it saves money," he says.
The McClure route opened last year, and once before that, in 1998. The European Space Agency reported that the strait opened up this year—open water was visible from space—although it wasn't safe for ship crossings.
"You could in principle navigate through it [this year], avoiding ice floes, and looking for the narrow opening, but the wind can move the ice around within hours so it can be a bit tricky," says Christian Melsheimer, a researcher at the Institute of Environmental Physics at the University of Bremen in Germany, whose research group produces daily maps of sea ice. "Some interpret this as 'the passage is open'; some would rather wait until the ice concentration is near zero percent across the whole passage."
The minimum sea ice cover in the Canadian Arctic Archipelago shrunk by 6.6 percent and the hazardous multiyear ice by 8.6 percent each decade between 1979 and last year. So the amount of sea ice in the region is indeed decreasing, just not in the right way for the Northwest Passage to become a viable alternative to the Panama Canal anytime soon.
"Obviously, if the climate is warming then you would have less first-year ice," says Kubat. "But, based on our analysis of our work, there is ice [in the passage], and with some melt of first-year ice you have more multiyear ice in the shipping lanes."
Climate models predict that even as sea ice disappears from the Arctic Ocean in the summer, the northern part of the Canadian Arctic Archipelago will remain a stronghold for multiyear ice. That means hard, ship-wrecking multiyear ice in all the channels of the Northwest Passage.
"Even in 2040, when there is no more summer ice in the Arctic, the archipelago will still be clogged with ice," Tremblay says.
As a result, ships may be able to sail plumb across the Arctic Ocean to Eurasia before they can navigate the Northwest Passage to ply the waters along North America's Arctic coast safely. But by that time any gains from a shipping shortcut will have been dramatically offset by potential losses elsewhere in the Northern Hemisphere due to the effects of climate change. "There are certainly some positive benefits at least in the short term economically," says Walt Meier, a research scientist at the National Snow and Ice Data Center in Boulder, Colo., "but the negative impacts, I think, ultimately outweigh that."
The U.S. Southwest, for instance, will dry up; ocean circulation, jet streams and storm tracks will probably all change, he says. "There definitely will be impacts on all the U.S. and Europe and Asia," Meier notes, "and at least [on] all of the Northern Hemisphere due to the loss of summer sea ice in the Arctic."