The Arctic Ocean's formidable natural barriers have deterred most human activity for millennia. But with the ocean expected to be ice-free in summer by 2030, the Arctic is now squarely in the geopolitical spotlight, as powers near and far rush to secure their positions in an emerging competition. By some estimates, the Arctic contains 30 percent of the world's undiscovered natural gas and 13 percent of its oil reserves. What's more, the receding ice could soon provide access to minerals, fish and other resources. At the same time, potential shipping routes will become available. Entering the fray is China, albeit from a position of weakness. Unlike the five Arctic states, China's lack of a coastline on the ocean deprives it of a legal basis to articulate claims for access to the region, as well as the ability to project power alone. At the same time, the Arctic's strategic value -- and...