Ocean currents in the North Atlantic. Warmer colors indicate higher temperatures. NASA

A vast system of Atlantic currents that delivers warmth to northern Europe is at risk of collapse, according to a growing body of research. The latest study to warn of its demise finds there is at least a 10 percent chance that a collapse may already be “locked in.”

The Atlantic Meridional Overturning Circulation, or AMOC, ferries warm water from the tropics to northern Europe. As the water cools, it becomes more dense and drops to the ocean depths, where it flows south, back toward the tropics. But as oceans warm, those waters are not so cool, or so dense, as they once were, causing the system of ocean circulation to slow down.…