When a Russian submarine embarked on a secret mission during the summer of 2007, it might as well have been the 15th century. Its task was bizarrely medieval—to plant Russia's flag on newly discovered territory. But this wasn't some terra incognita; the tricolor landed on exposed seabed in the Arctic Ocean, where melting ice had provided new access to highly sought oil and mineral deposits. The rest of the world did a double take. Is that how the game is really played?

Of course it isn't. The flag claimed as much for Russia as the flag planted on the moon in 1969 claimed for the U.S.—nothing, really. But the gesture wasn't entirely empty. Its real significance materialized in the debate that it started, one about how to divvy up the globe's truly last frontier.

Scientists have declared that both of the world's ice caps are in perilous states; the Arctic is more vulnerable than the Antarctic because of added climate volatility at the top of the planet. The intuitive victims are the polar bear, and further down the line, the world's grandchildren. Those, certainly, are the victims who have received the most attention.

But in his new book, After the Ice, Alun Anderson makes the insightful case that consequences cast too far into the future ignore geopolitical factors of today. Water where ice once stood changes global trade routes and national-security calculations, especially between countries like the U.S and Russia, whose icy relationship used to be separated by the expanse of the great Pacific. Just this summer, for example, the sea above Russia opened to international commercial shipping as the ice melted.

Figuring out who controls the top of the world isn't easy. The U.N.-sanctioned Law of the Sea offers a hazy view of how the land is divvied up, relying on geologic data not easily interpreted. Continental shelves usually indicate the edges of coastal nations, but even the term "edge" is subject to sliding definitions of where a country's "natural prolongation" actually ends. The sprinkling of islands belonging to Canada and Greenland complicate the equation, and governments won't trust ostensibly neutral third parties to disburse the immensely valuable natural resources buried under the surface.

Anderson's key insight isn't his call to action (we should prevent further melting to save the planet, etc.); it's his astute observation that we haven't thought much about how to manage human activities in the region: oil rigs that bleed petroleum may be too distant for clean-up assistance; cruise ships perusing iceberg-filled seas may not be reachable in time by rescue vessels. The solution isn't as simple as plunking down new naval bases as a safety net for new commerce and military activity. The climate and seclusion of the Arctic simply make any large-scale development impossible.

Still, the Arctic's future isn't all gloom. First, new shipping routes are cheaper and, in some instances, more energy-efficient than old ones. (Insurers have been slow to warm up to allowing ships carrying expensive goods to pass through potentially dangerous waters, but a handful of successful voyages may change that.) Second, in a nod to hopelessly depressed environmentalists, Anderson does a calculus of biological productivity. Yes, melting ice may ultimately kill the polar bear and Arctic walrus. But new quantities of water and sun will contribute to more diverse and productive parts of the ocean. Neither of which are terms heard lately from ocean advocates.