Encroaching seas in the far Pacific are raising the salt level in the wells of the Marshall Islands. Waves threaten to cut one sliver of an island in two. “It’s getting worse,” says Kaminaga Kaminaga, the tiny nation’s climate change coordinator.The rising ocean raises questions, too: What happens if the 61,000 Marshallese must abandon their low-lying atolls? Would they still be a nation? With a U.N. seat? With control of their old fisheries and their undersea minerals? Where would they live, and how would they make a living? Who, precisely, would they and their children become?