|Northeast Passage / Northern Sea Route|
It seems that sailing ships across the top of the world has become viable, for a couple months of the year anyway. The linked article is all about the military buildup in the Arctic, but the map is from the Economist which has a paywall. Wikipedia has a similar map that also shows the Northwest Passage. I'm not sure anyone is using that yet.
P.S. As Bruce points out, ice breakers are kind of crucial to traveling this route. I've put up several posts about ice breakers, and half of those posts are about the Russians.