Confluence of factors make it unsustainable.

There are many types of ships that might take advantage of ice-free waters in the future: naval vessels, cruise ships, container ships, scientific vessels, and transport ships to offshore drilling platforms.

These ships would have to contend with myriad challenges in an increasingly ice-free Arctic. One of the most prominent is the fact that ice in the Arctic will vary drastically year to year. “Regardless of which climate change scenario path we’re on, interannual variability remained very high for a long period,” said Lynch, who led the latest PNAS study.

Although 83 of more than 500,000 trips were shorter and 45 saved sailing time in Wang’s sustainability analysis, only 20 were economically feasible. “We definitely think that’s a surprising result, because people always talk about the Arctic as having great potential for shipping.”

Complications don’t stop there: It’s difficult to get Arctic satellite navigation coverage, the ice is hard to forecast, emergency operations are challenging, and shipping has various restrictions under the Polar Code, which limits the sizes of vehicles allowed. Wang has worried about the effects of invasive species on the fragile Arctic environment, too.