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 in 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. A raft of research suggests this system is weakening as human-driven global warming melts ice and causes a surge of freshwater into the ocean, disrupting the AMOC’s delicate balance of heat and salinity.

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. To better unravel 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.

Implications of the Cold Blob

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. While uncertainties remain, the study bolsters evidence of a link between the cold blob and a weakening AMOC.

Original reporting: KRDO (Colorado Springs metro) — read the source article.