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Key Atlantic currents could collapse this…

Environment · November 1, 2026 · The Conversation · 5 min

An Amoc collapse would dramatically alter the world’s climate – often in unexpected ways. Our new study shows how governments should prepare.

<div class="theconversation-article-body"> <figure> <img alt="illustrated satellite image of the north Atlantic" src="https://images.theconversation.com/files/768813/original/file-20261028-62-1txzez.jpg?ixlib=rb-4.1.1&rect=0%2C79%2C1620%2C911&q=45&auto=format&w=754&fit=clip" /> <figcaption> The system of currents that keeps north-western Europe relatively mild is already weakening. (Illustration shows Atlantic surface currents and eddies, with arrows showing the Amoc’s warm northward surface flow and cold southward return flow at depth.) Brenden Jongman / NASA and NOAA data / Amoc pathways added schematically </figcaption> </figure>

<a href="https://theconversation.com/profiles/brenden-jongman-2772417">Brenden Jongman</a>, <a href="https://theconversation.com/institutions/university-of-oxford-1260">University of Oxford</a> and <a href="https://theconversation.com/profiles/jim-hall-2774428">Jim Hall</a>, <a href="https://theconversation.com/institutions/university-of-oxford-1260">University of Oxford</a>

Icelandic government officials <a href="https://www.icelandreview.com/news/iceland-amoc-exercise-atlantic-current-readiness-2026/?srsltid=AYCX9vIZg8G4V1OGJ4ElUd6_QHmY8ee9GqDV9clvToqcrB2WZjSJbHvc">recently met</a> to discuss a dramatic scenario: what if the current that circulates Atlantic waters weakened significantly, or collapsed altogether?

The <a href="https://theconversation.com/topics/amoc-122141">ocean currents are changing</a>, with major implications for climate around the world. Yet our <a href="https://www.nature.com/articles/s41893-026-01961-1">new research</a> suggests most governments are not preparing for this possibility. Of 91 national adaptation plans submitted to the UN climate convention, only two even mention that key Atlantic current, and neither sets out concrete action in response to its possible collapse.

The Atlantic Meridional Overturning Circulation, or Amoc, <a href="https://www.whoi.edu/ocean-learning-hub/ocean-topics/how-the-ocean-works/ocean-circulation/amoc/">is part</a> of the giant conveyor belt of ocean currents that moves warm surface water northward in the Atlantic and sends colder deep water back south. It plays a critical role in regulating the global climate by redistributing heat around the planet, influencing weather patterns and temperatures far beyond the Atlantic basin.

As the climate warms, the Amoc is weakening, and could continue to do so throughout this century. While a full collapse, in which major ocean currents completely reorientate, is unlikely before 2100, <a href="https://www.science.org/doi/10.1126/sciadv.adx4298">a recent study</a> projected a 50% weakening of the Amoc by the end of the century under an intermediate emissions scenario. A collapse would not be unique in geological history. Studies show that the Amoc has undergone dramatic changes before, including <a href="https://www.nature.com/articles/nature02494">a near-complete shutdown</a> around 17,500 years ago, after the coldest period in the last ice age.

A slowdown or collapse would have major implications for temperature and rainfall around the world. In northern Europe, the loss of the heat Amoc transfers northwards from the tropics <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL114611">could lead to</a> winter cold extremes of -20°C in London.

<a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023EF003959">Climate model experiments</a> in which the Amoc is shut down show an average 29% weakening of the West African monsoons and 19% weakening of the Indian summer monsoon, increasing risks of food and water insecurity in regions that rely on monsoon rains. Other studies suggest an increased risk of severe drought in parts of Central America, West Africa and the Amazon region. Fisheries and sea level would also be affected.

<figure class="align-center zoomable"> <a aria-label="Zoomable image" href="https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=1000&fit=clip"><img alt="Big cliffs tower above the sea" src="https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/768819/original/file-20261028-62-8v3iif.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a> <figcaption> The Cliffs of Moher in Ireland, where the Atlantic meets Europe. Warm ocean currents keep north-west Europe relatively mild. tcacidima / shutterstock </figcaption> </figure>

So how can countries prepare for changes in ocean circulation whose timing is highly uncertain? Our research identifies <a href="https://www.nature.com/articles/s41893-026-01961-1">practical steps to incorporate Amoc-related risks</a> into adaptation decision-making.

<h2>Most investments assume only gradual change</h2>

Of the 91 national adaptation plans reported to the UN climate convention so far, only two mention the Amoc. <a href="https://unfccc.int/sites/default/files/resource/Updated-NAP_Brazil_2026_ENG.pdf">Brazil’s plan</a> devotes a dedicated box to warning that its shutdown could push the Atlantic rain belt southwards, tipping the Amazon rainforest towards collapse. <a href="https://unfccc.int/sites/default/files/resource/NAP_Ireland_2025.pdf">Ireland</a> – which relies on the Amoc to sustain its mild climate – mentions that “reliance solely on adaptation may prove insufficient” in case of Amoc collapse, concluding that no national plan can prepare for such tipping points.

Amoc is a particular challenge for adaptation. It represents a very high impact scenario whose likelihood is very difficult to quantify. And yet if the current were to collapse, some parts of the world could experience climate changes in the opposite direction to those they are preparing for, most notably colder winters in north-western Europe.

This is important because many adaptation investments need to be robust to a wide range of potential changes to be effective. Consider a country planning to build a new reservoir to cope with more variable rainfall amounts under climate change. If instead the rainy season becomes shorter and there is less rain overall, the reservoir may seem like a bad investment.

<figure class="align-center zoomable"> <a aria-label="Zoomable image" href="https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=1000&fit=clip"><img alt="Annotated world map" src="https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=600&h=487&fit=crop&dpr=1 600w, https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=30&auto=format&w=600&h=487&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=15&auto=format&w=600&h=487&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=45&auto=format&w=754&h=612&fit=crop&dpr=1 754w, https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=30&auto=format&w=754&h=612&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/768816/original/file-20261028-72-aincrm.jpeg?ixlib=rb-4.1.1&q=15&auto=format&w=754&h=612&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a> <figcaption> The effects of an Amoc slowdown would be felt across the world. <a class="source" href="https://www.nature.com/articles/s41893-026-01961-1/figures/1">Jongman & Hall (2026), Nature Sustainability</a> </figcaption> </figure>

Similarly, in countries that depend on monsoon rains, a weakening or collapse of the Amoc could mean even less rainfall than is projected under climate change. Along Atlantic coastlines, changes in sea level and ocean temperatures could affect how well coastal defences work. Changes in fish stocks could also threaten communities that depend on fishing.

Many investments made now will remain in use for decades. Investments that perform well under moderate Amoc weakening but poorly if the current weakened much more could expose countries to major losses and damages, especially poorer countries with fewer resources to respond to surprises.

<h2>Five ways to prepare for major Amoc weakening</h2>

In our study, we outline five ways policymakers can start preparing now.

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