Surprise! The North Atlantic Current is Stable – Watts Up With That?

Essay by Eric Worrall

Another nail in the coffin of climate models? A study published in Nature suggests there is no evidence for a decline in AMOC over the last 60 years.

AMOC study: Critical ocean current has not declined in the last 60 years

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In the Atlantic Ocean, a system of connected currents – the AMOC – moves water throughout the world’s oceans powered by a combination of winds and ocean density. It not only distributes the ocean’s heat, moisture, and nutrients, but regulates the Earth’s climate and weather too.

As the climate is continuously changing and the atmosphere is warming, many scientists fear that fresh water from melting polar ice sheets could significantly disrupt – or even collapse – the AMOC. While a decline of the AMOC would have grave consequences, a collapse would be truly catastrophic, as Oceanographic reported back in October 2024.

As studies about the AMOC’s long term future are still uncertain, a team of scientists from Woods Hole Oceanographic Institution (WHOI) took a closer look at the past to help inform the AMOC’s likely future.

In a new paper published in Nature Communications, scientists made a surprising announcement: The AMOC has not declined in the last 60 years, indicating that it is currently more stable than expected.

“Our paper says that the Atlantic overturning has not declined yet,” Nicholas P. Foukal, study author, adjunct scientist in Physical Oceanography at WHOI and assistant professor at the University of Georgia, said. “That doesn’t say anything about its future, but it doesn’t appear the anticipated changes have occurred yet.”

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Read more: https://oceanographicmagazine.com/news/new-study-argues-amoc-has-not-declined-in-the-last-60-years/

The abstract of the study;

Atlantic overturning inferred from air-seaheatfluxes indicates no decline sincethe 1960s

Jens Terhaar1,4,5, Linus Vogt 1,2 & Nicholas P. Foukal 1,3

Received: 2 July 2024
Accepted: 6 December 2024
Published online: 15 January 2025

The Atlantic Meridional Overturning Circulation (AMOC) is crucial for globalocean carbon and heat uptake, and controls the climate around the NorthAtlantic. Despite its importance, quantifying the AMOC’s past changes andassessing its vulnerability to climate change remains highly uncertain.Understanding past AMOC changes has relied on proxies, most notably seasurface temperature anomalies over the subpolar North Atlantic. Here, we use24 Earth System Models from the Coupled Model Intercomparison ProjectPhase 6 (CMIP6) to demonstrate that these temperature anomalies cannotrobustly reconstruct the AMOC. Instead, wefind that air-sea heatfluxanomalies north of any given latitude in the North Atlantic between 26.5°N and50°N are tightly linked to the AMOC anomaly at that latitude on decadal andcentennial timescales. On these timescales, air-sea heatflux anomalies arestrongly linked to AMOC-driven northward heatflux anomalies through theconservation of energy. On annual timescales, however, air-sea heatfluxanomalies are mostly altered by atmospheric variability and less by AMOCanomalies. Based on the here identified relationship and observation-based estimates of the past air-sea heatflux in the North Atlantic from reanalysis products, the decadal averaged AMOC at 26.5°N has not weakened from 1963 to 2017 although substantial variability exists at all latitudes.

Read more: https://www.nature.com/articles/s41467-024-55297-5.epdf

Michael Mann appears to be a fan of imminent AMOC collapse theories;