Researchers say the North Atlantic cold blob pattern points to an earlier and sharper slowdown in AMOC than many climate models had projected, with a shutdown possible by 2100. Stefan Rahmstorf said the change is no longer looking like a low-probability outcome, and that cooling could begin in the late 2030s or 2040s if emissions do not fall very fast.
Rahmstorf on the risk
"The AMOC shutdown is not a low-probability event anymore." Rahmstorf said that during discussion of the new research, adding, "It starts to look likely, maybe even very likely,". He also said the projected cooling in the late 2030s or 2040s "and that actually is a big concern."
Rahmstorf is a physical oceanographer at the Potsdam Institute for Climate Impact Research in Germany, and he said that during his 30-year career studying these ocean currents, he had usually treated the tipping risk as fairly low. The new result changes that reading. The latest work says researchers feel more confident than ever that the AMOC could reach a tipping point by the middle of the century.
Atlantic cold blob pattern
The AMOC is a vast system of currents that carries warm, salty tropical water toward the North Atlantic. That water cools in the northern latitudes, becomes dense, sinks, and then flows back south at deeper depths. Scientists have known for years that the AMOC is weakening, but this research says the slowdown may arrive sooner and hit harder than many climate models had suggested.
Over the last century, the ocean region just south of Greenland and Iceland cooled while much of the world's oceans warmed. Scientists often call that swath the Atlantic cold blob or warming hole. The latest research links the cooling to a declining AMOC rather than only sea surface heat loss, changing winds, or cloud patterns.
People in New England
People in New England, Europe, and other regions around the Atlantic could feel the effects through weather patterns on both sides of the Atlantic. Gerard McCarthy, an oceanographer at Ireland's Maynooth, said, "That cold isn’t a kind of a get-out-of-jail-free card in terms of global warming. Some of the hot extremes can actually be exacerbated by this cold blob in the Atlantic,". The concern is not just the cold patch itself, but what it signals about the circulation that helps move heat around the planet.
Another study in April pointed to a sharp AMOC decline of roughly 50 percent by the end of the century. That leaves the next few decades as the period that matters most for the ocean system's path. If emissions are reduced very fast, the projected cooling risk could ease; if not, the late 2030s and 2040s are where the first changes could show up.
