As the Ocean Warms, a ‘Cold Blob’ in the Atlantic Has Puzzled Scientists. It Might Be a Warning Sign About a Key Current System

A patch of water south of Greenland and Iceland has cooled by nearly 1.8 degrees Fahrenheit since 1900. A new study suggests that it shows a crucial system of ocean currents is weakening, which could alter Earth’s climate

Michele Debczak | Correspondent

June 30, 2026 12:17 p.m.

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

The ocean has been heating up over the past century, largely due to human activity that produces heat-trapping greenhouse gases. But strangely, a patch of the Atlantic Ocean south of Greenland and Iceland has been trending in the opposite direction.

While this may sound like good news for our warming planet, the “cold blob” could be a sign of a more concerning pattern with far-reaching effects.

In a study published on May 28 in the journal Geophysical Research Letters, a team of scientists used observations dating back to 1870 to analyze the mysterious phenomenon. Their findings suggest that the cold blob may have resulted from broader changes taking place throughout a crucial system of currents in the Atlantic Ocean, which could drastically alter the Earth’s climate.

Worldwide, the sea surface temperatures have risen by an average of about 1.8 degrees Fahrenheit since 1900, but the cold blob has chilled by almost that amount during that period. Some scientists suspect that the cooling patch of water is an isolated event caused by interactions with the local atmosphere. In 2022, a team reported that increased westerly winds were removing heat from the ocean surface there.

Other researchers, however, say that it’s a sign that the Atlantic Meridional Overturning Circulation, or AMOC, is weakening. The AMOC is a system of currents of varying depths that spans the entire Atlantic Ocean. This “global conveyor belt” is responsible for carrying warm water to the North Atlantic and cold water to the south. Past research suggests that the AMOC is slowing due to climate change, and, if it continues, it could cause sea level rise on the U.S. East Coast, cool Europe and disrupt precipitation patterns in parts of South America, Africa and India, among other alterations.

In the new study, researchers analyzed the cold blob and climate using weather observations from satellites, buoys and ships. Their work hints that the blob’s cooler temperatures extend deep below the surface, so rather than losing its heat to the atmosphere, it’s possible that the AMOC isn’t delivering much warm water to the area in the first place.

Winds and other local atmospheric influences explain only a “modest fraction” of the cold blob, study co-author Stefan Rahmstorf, a physical oceanographer at the Potsdam Institute for Climate Impact Research in Germany, tells New Scientist’s Alec Luhn. “Even if, in some modeling approaches, it seems possible that the cold blob is caused by the atmosphere, in fact, the data show it is caused by the ocean.”

“The region to the south of Greenland is highly sensitive to AMOC change,” Wei Liu, a climate scientist at the University of California, Riverside who was not involved in the study, tells USA Today’s Janet Loehrke.

Because of that, some scientists worry that it could be an early warning sign of the system’s eventual collapse. As Ben Noll reports for the Washington Post, that would have catastrophic effects in parts of Northern Europe, potentially plunging Iceland into winters that reach minus 50 degrees Fahrenheit. This proposal is controversial, however, and many experts say that fears of a total AMOC collapse happening anytime soon are overblown. But that doesn’t mean the cold blob isn’t a cause for concern.

“Even without a collapse, a weakening of the AMOC could have serious climate impacts,” says ocean scientist Jonathan Baker of the Met Office, the U.K.’s weather service, who was not involved in the study, to Yale Environment 360’s Nicola Jones. The current system also carries nutrients and affects the ocean’s salinity levels, which means that any changes could also spell trouble for the marine ecosystems that depend on it.

Michele Debczak | Read More

Michele Debczak is a writer and editor based in Brooklyn, New York. She appears in seasons four through six of History Channel’s “The Food That Built America,” and her work has been featured in Mental Floss, IndieWire, Eater and Vice.