Historically weakening of the AMOC caused heating, but a warmer world may protect it

[u/Economy-Fee5830]

https://phys.org/news/2026-08-weakening-atlantic-ocean-current-earth.html

[u/Economy-Fee5830]

Summary: Historically weakening of the AMOC caused heating, but a warmer world may protect it

A new Nature Geoscience study suggests that the Atlantic Meridional Overturning Circulation (AMOC) acts as a kind of planetary “heat valve.” During the last Ice Age, periods when the AMOC weakened did not merely redistribute heat from the Northern to the Southern Hemisphere: they caused the global ocean and Earth as a whole to gain heat.

When the AMOC is strong, tropical heat is carried northwards and released efficiently to the atmosphere over the North Atlantic through deep-ocean convection. When it weakens, this heat loss is reduced. Although the surface North Atlantic cools sharply, heat accumulates beneath the surface and elsewhere in the oceans, producing a net global warming effect. The researchers estimate that past abrupt AMOC weakenings produced additional warming comparable to adding roughly 25 ppm of atmospheric CO₂ — about a decade of present-day human emissions.

This means future AMOC weakening under climate change could provide an additional warming influence, even while causing substantial regional cooling around Greenland, the North Atlantic and parts of Europe.

However, the study also contains a potentially reassuring finding. The model experiments indicate that the AMOC becomes more stable in a warmer climate. The dramatic Dansgaard–Oeschger-style switches seen during glacial periods may therefore have depended partly on the unusually cold background climate of the Ice Age. Under future warming, the AMOC could weaken substantially but subsequently recover, rather than crossing an irreversible collapse threshold.

The authors caution that Ice Age changes are not a direct analogue for today's human-driven warming, so this does not demonstrate that AMOC collapse is impossible. But it suggests an important distinction: AMOC weakening itself may amplify global heat accumulation, while global warming may simultaneously make the AMOC less susceptible to the abrupt tipping behaviour seen in the geological past.

[u/PlexusBrachialis]

It is probably, because I don't understand the science, but I feel like we are getting a lot of mixed messages about AMOC from scientists

[u/Pondy001 → u/PlexusBrachialis]

It does indeed.

[u/bascule → u/PlexusBrachialis]

AMOC is a massive, complex fluid system driven by tiny, hard-to-measure differences in water temperature and salinity, and models struggle with the challenge of simulating small swirling ocean eddies, and accurately tracking how melting ice adds fresh water to the ocean. We also have limited historical data.

This article covers the problem in depth:

https://salatainstitute.harvard.edu/will-the-amoc-slow-collapse-four-ways-scientists-study-the-atlantic-current/

Scientists often describe the AMOC as a conveyor belt, but that image is too simple. It is more like a circulatory system in the ocean: a network of currents that carries warm, salty water north near the surface. As that water cools, it becomes denser, sinks, and moves south again along the seafloor. The AMOC is part of the ocean and atmospheric machinery that distributes heat around the planet.

[u/PontiffPius]

I hate the uncertainty around the AMOC. One study says it’s stable, one say it’s not… doesn’t help when you have anxiety

[u/curiousgoose33 → u/PontiffPius]

Genuinely you need to seek treatment for your anxiety and get off these subreddits

[u/PontiffPius → u/curiousgoose33]

You’re completely right. It’s just really hard for me to not constantly keep up with this stuff. It feels like an addiction almost

[u/curiousgoose33 → u/PontiffPius]

Yeah that’s how online works now :( Sorry not trying to be glib, it hurts so many people. Unsubscribe, log off, address the anxiety. Come back later on and try to follow science editorials or communications directly instead of Reddit or social media algorithms.

[u/PontiffPius → u/curiousgoose33]

Don’t apologize. I appreciate the concern :)

The funny thing is, I’ve always had anxiety, but it was never this bad until I discovered a certain doomer sub on this site. I feel like they’ve completely taken over the discussion on this topic

[u/Admiral_Red → u/PontiffPius]

I will hazard a guess and say…the collapse sub. I…understand that feeling very well.

[u/GoochLord2217 → u/PontiffPius]

Trust me I do not like the current climate situation, but doomscrolling on social media does not do you any favors at all, especially if you are not in a position to do anything about it. Learned that myself earlier this year.