When the sea starts to freeze, it turns sluggish, “almost like you would be operating in oil,” says Eero Lehtovaara. An imposing but genial Finn with a gray goatee, Lehtovaara heads public affairs for the marine division of Swiss industrial giant ABB Group. He’s also a veteran ship captain. We’re chatting at an ABB plant near the Helsinki dockyards, where the company assembles propulsion pods — picture huge, futuristic outboard motors — for ships that specialize in breaking up ice. “I’ve spent more time in ice on ships than I would like to even remember,” Lehtovaara says.

Only once, however, did he witness the sea solidifying in real time. He was standing watch 25 years ago on a ship sailing from the UK to Oulu, a port on Finland’s northwestern coast. It was near midnight on Christmas Eve, and he’d just called his wife before taking his position on the bridge. The ship was cruising at 13 knots a little north of Gotland, the Swedish island that guards the central Baltic Sea. Outside, under a clear starry sky, the temperature was below 0F. Just then the water turned listless, the waves died out, and Lehtovaara lost sight of what he calls “the contour of the sea.”