he edge of Greenland’s ice sheet looked like a big lick of sludgy white frosting spilling over a rise of billion-year-old brown rock. Inside the Twin Otter’s cabin, there were five of us: two pilots, a scientist, an engineer, and me. Farther north, we would have needed another seat for a rifle-armed guard. Here, we were told to just look around for polar-bear tracks on our descent. We had taken off from Greenland’s west coast and soon passed over the ice sheet’s lip. Viewed from directly above, the first 10 miles of ice looked wrinkled, like elephant skin. Its folds...
