A study published Monday concluded that melting ice in Greenland caused by climate change could cause the Atlantic Meridional Overturning Circulation (AMOC) to collapse as soon as 2025, ushering in dramatic consequences for the planet.
The AMOC brings warm water north and east from the Caribbean, while delivering colder Arctic water south. If it were to suddenly shut down, scientists believe North America would experience weather changes such as more severe hurricanes and northern Europe would get a lot colder.
But you’re not likely to see igloos in London very soon. While climatologists say the collapse of the AMOC is a real threat, and that the new study raises a legitimate alarm that we may pass a key climate change tipping point sooner than previously thought, there’s a lot we still don’t know about exactly when it might happen.
“I think the authors in this case are on to something real,” Michael Mann, a University of Pennsylvania climate scientist, told Axios. “We could be talking decades rather than a century.”
WHY THE AMOC IS SO IMPORTANT: The AMOC is part of what the National Oceanic and Atmospheric Administration calls “the global ocean conveyor belt.” That keeps northern Europe several degrees warmer than it would otherwise be at that latitude — Paris is farther north than notoriously frigid-in-winter Montreal, for example.
WHY IT’S AT RISK: In recent years, studies have shown that the current is at its weakest in 1,000 years. Although scientists are not certain why, several studies have attributed that weakening to an influx of fresh water from the melting of Arctic sea ice, including the Greenland ice sheet, and increasing precipitation — both of which are results of global warming. The AMOC is driven by heavier cold water sinking, which raises warm water to the surface, but since fresh water is lighter than salt water, it has reduced the tendency of colder water near the surface to sink.
WHAT THE NEW STUDY FOUND: Researchers used sea surface temperature data dating back to 1870 to estimate AMOC current strength over time. Projecting forward from the gradual weakening of the system, they estimated it will collapse between 2025 and 2095, with the most likely date being around midcentury.