A large patch of water in the North Atlantic Ocean, south of Greenland and Iceland, is getting colder while the rest of the ocean heats up. This phenomenon, known as the ‘cold blob’ or ‘warming hole,’ has cooled by nearly 1 degree Celsius since 1900.

What’s Causing the Cold Blob?

Scientists have long debated whether this anomaly is driven by heat loss from the ocean surface due to changes to winds and clouds, or whether it’s a signal of the weakening of a critical system of ocean currents, which transports heat. A new study concludes that it’s the latter, and the finding points to a worrying future.

The Atlantic Meridional Overturning Circulation (AMOC) works like a vast ocean conveyor belt, pulling warm water from the tropics to the Northern Hemisphere, where it cools, sinks, and flows back south. Some scientists warn that the AMOC is heading toward a tipping point, potentially as early as this century, which would mean a future collapse is locked in.

An AMOC shutdown would be a global catastrophe, causing accelerated sea level rise on the US East Coast, plunging Europe into a winter deep freeze, and shifting the monsoon in Africa, driving prolonged droughts. The cold blob has been interpreted by some as a fingerprint of AMOC change, because it’s the region to which the AMOC brings much of its heat.

Study Findings

To better understand what’s happening in this part of the Atlantic, the study scientists combined real-world ocean heat data from instruments and satellites with climate models. They found that cooling in the cold blob was not just happening on the surface but also deep in the ocean, where atmospheric conditions like winds and clouds have a much weaker influence.

All signs point to the influence of the AMOC, the study found. ‘It is changing ocean heat transport’ which is driving the cooling of the cold blob, said Stefan Rahmstorf, a study author and a physics and oceans professor at Potsdam University, Germany.

Original reporting: El Paso News (HLL/CB) — read the source article.