The large, looping Atlantic Ocean current that keeps northwestern Europe fairly warm and influences sea levels along the U.S. coast is a key component of the Earth’s climate system. But because of global warming, it may be more likely to substantially slow down — or even collapse — than previously thought, according to two new studies.

Sunrise over the Atlantic Ocean, where the Atlantic Meridional Overturning Circulation transports warm, salty water from the tropics toward the pole.
Credit: Curtis Keester/flickr

If that current, called the Atlantic Meridional Overturning Circulation, were to slow down substantially, it could lead to chillier weather in northern and western Europe, starve economically important fisheries and cause waters to rise along the U.S. coast, leading to more so-called “sunny day” flooding and storm surge when hurricanes come ashore. It could also shift tropical rain belts, causing major disruptions to regional climate in Central and South America.

The new studies factor in elements that have been missing from previous projections of how likely the collapse of the current is. One study factors in the melting of the Greenland Ice Sheet, which is adding a pulse of freshwater into the North Atlantic, but is difficult to incorporate into current climate models. The other attempts to correct a bias in climate models that underestimates how unstable the AMOC really is.