(Roughly) Daily“It is by the deep, hidden currents that the oceans are made one”*…
The global conveyor belt, shown in part here, circulates cool subsurface water and warm surface water throughout the world. The Atlantic Meridional Overturning Circulation is part of this complex system of global ocean currents. This illustration is captured from a short video produced by NOAA Science on a Sphere.A significant part of the earth’s climate infrastructure is under threat. New research suggests the Atlantic Meridional Overturning Circulation (or AMOC) could weaken by half this century with wide ranging consequences for weather, food, and sea levels across the world. Alison Smart and Charlotte Venner unpack the past and ponder the future of this critical ocean current…
London, England, and Quebec City, Canada sit at roughly the same latitude (51°N and 47°N, respectively) but have vastly different climates. Historically, Quebec City had 99 freezing days in an average year—weather you might expect from its relative proximity to the Arctic—but London only experienced three freezing days in an average year, despite being slightly further north. This difference is largely due to an ocean current called the Atlantic Meridional Overturning Circulation (AMOC), which distributes warmth from the Tropics via the Atlantic Ocean.
Now, impacts from climate change are weakening the AMOC, and it could collapse entirely in the near future. AMOC collapse would rapidly make regions of the Northern Hemisphere with historically mild weather colder and harsher, while triggering irreversible changes in the global climate.
The AMOC is both the product of a stable climate and a factor in maintaining weather patterns around the planet. To plan for future scenarios, we need to first understand how the AMOC works and what might happen if it collapses…
[Smart and Venner explain the AMOC and outline the ways in which it shapes the climate of regions around the world…]
… Even minor weakening of the AMOC can significantly impact local climates, as has happened several times in the past 12,000 years. A “Little Ice Age” occurred in Europe in the Middle Ages, likely connected to a disruption in the AMOC. Just a slight slowdown in the AMOC could make Europe colder overall, disrupt global precipitation patterns from South America to India, and worsen drought in Africa.
The more freshwater pours into the ocean, and the more ocean temperatures rise, the weaker the AMOC becomes—until, at some threshold, it could stop moving altogether.
It is possible that the AMOC will collapse entirely if warming continues. There is no agreed-upon global average temperature at which collapse becomes certain, but there are signals we can track and historical examples we can examine to predict the likelihood of collapse…
… The consequences of total AMOC collapse would be far-reaching, severe, and irreversible on timescales relevant to humans. AMOC collapse would cool parts of the Northern Hemisphere and warm parts of the Southern Hemisphere by multiple degrees Celsius and drastically alter weather around the world.
In Europe, winter temperatures would drop, cold snaps could increase, and winter storms would intensify. A 2025 research letter found that, even if global warming reached 2°C, AMOC collapse would make Europe colder than it is today, creating extreme winters in Northwestern Europe in which record cold might reach -20°C (-4°F) in London and -50°C (-58°F) in Scandinavia. Even milder cold days would increase, with approximately 150 to 180 frost days per year in Utrecht, Netherlands, compared to a historic average of about 53. Precipitation would likely shift and decrease, potentially drying out some parts of Europe and making others wetter.
Around the world, other climates would change, likely in less extreme ways.
- North America. The East Coast of North America would likely experience rapid sea level rise as the gravitational pull of the AMOC weakens, as well as cooler conditions, with some parts of Eastern Canada and the North Atlantic coast cooling by several degrees Celsius, erratic storms, weather variability, and more intense hurricanes.
- Tropics & South America. Without the AMOC, the ITCZ would shift south, potentially leading to drying in the Northern Tropics and parts of the Amazon and wetter conditions in the Southern Tropics.
- Africa. Because of the shift in the ITCZ, West Africa and the Sahel would be much drier, experiencing severe and frequent drought and reduced rainy seasons. The Sahel could possibly transition from a semi-arid climate to hot dry desert.
- Asia. Because of the shift in the ITCZ, weakened and more erratic monsoons in Asia would lead to increased drought and a higher risk of extreme precipitation events.
These changes may occur rapidly, create climate risks, and cause systemic disruption in affected regions. The collapse of the AMOC would also be a tipping point in the global climate, meaning that the changes would likely be difficult, if not impossible, to reverse on human timescales.
Once the AMOC passes a critical threshold of weakening, called a tipping point, it would continue to weaken until it collapses. AMOC collapse could also create systemic impacts that activate other tipping points as well as feedback loops that could generate further warming.
For example, if AMOC collapse contributed to changes like a permanent dieback of the Amazon Rainforest or increased ice loss, those changes would generate their own warming effect on Earth’s climate. A 2026 paper suggests that AMOC collapse would result in substantial carbon release from oceans and add around 0.2°C in additional atmospheric warming.
Reducing greenhouse gas emissions may slow warming enough to reduce weakening and delay collapse. If collapse begins, it is unlikely we could stop it. There is no feasible technological way to reengineer ocean currents…
A bracing, but important read: “A complete guide to the Atlantic Meridional Overturning Circulation (AMOC).”
See also: “What would happen if the Atlantic Meridional Overturning Circulation (AMOC) collapses? How likely is it?”
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As we put on our sailin’ shoes, we might send interconnected birthday greetings to Andrew Sharrett; he was born on this date in 1946. An archaeologist, his application of world-systems theory to questions of change on large, often global, scale made him one of the most influential archaeologists of the late 20th/early 21st centuries. Sharrett is best known for his theory of the secondary products revolution; but his work touched on a broad range of fundamental human developmental issues: global migration and colonization, the spread of agriculture, the development of metallurgy and urbanism, and the development of new forms of consumption, to name a few. All of those dynamics were, as Sharrett observed, shaped in significant ways by the climatic conditions in which they unfolded.
#AMOC #AndrewSharrett #Archaeology #AtlanticMeridionalOverturningCirculation #climate #climateChange #culture #environment #history #oceanCurrents #oceans #socialAnthropology
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