The Arctic Ocean, the smallest and shallowest of the world’s five oceans, is melting. Cursed by hostile weather and rough seas, the forbidding, remote and one of the least understood environments in the world is now beginning to open up under the weight of climate change. Navigation, not long ago unthinkable, is increasingly feasible. Large ships are beginning to explore the area in ways that Viking settlers and European merchants could only dream of. Shrinking Arctic sea ice allowed last year a tanker carrying a cargo of liquefied natural gas to travel through the northern sea route for the first time without an icebreaker escort.