A Russian tanker carrying liquified natural gas has passed through the Bering Strait in the middle of winter without an icebreaker escort, an unprecedented event that may hint at the future of the region as climate change alters global commerce. The tanker is traversing the northern coast of Siberia, called the North Sea Route, in the middle of January. Historically, shipping through the North Sea Route has been blocked by thick winter sea ice, which makes the route impassable to all but specialized icebreakers. But climate change has altered that equation. After Russia's unusually warm summer, much of the route is still open water, and most of the ice is thin and spread out.