The Ocean’s ‘Conveyor Belt’ Is Starting to Wobble
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Global Warming Brings Mammoth Atlantic Current toward a Tipping Point
The Atlantic Ocean has a circulation system powerful enough to shape the climate of entire continents—and scientists say it is weakening.
The Atlantic Meridional Overturning Circulation (AMOC), of which the Gulf Stream is a part, carries warm surface water northward and sends colder, denser water back toward the south through a deep-ocean pathway. Global warming—especially that aspect that’s melting the Greenland ice sheet—is believed to be disrupting the physical forces that keep this vast system moving.
The stakes are global, according to computer models cited in a 2026 study. A weaker AMOC could alter European temperatures, shift rainfall and monsoon patterns, disrupt marine ecosystems and fisheries, reduce agricultural productivity, and accelerate sea-level rise along the US East Coast.
Scientists disagree about how quickly the circulation could weaken and whether it will actually collapse this century. For example, researchers at Utrecht University in the Netherlands said in an August 2026 study that the AMOC “stayed strong” and could “shift with the climate” under certain circumstances.
But scientists increasingly agree on one point: The AMOC is changing, and understanding where that change could lead has become an urgent climate question.
The AMOC’s massive and complex pattern of circulation, part of a network of colossal ocean currents around the world, is propelled by a combination of physical properties such as water density, temperature, wind, salinity, and depth. They work together to generate the movement of ocean water over the planet. The process is difficult to measure, but its significance is global.
Even some slowing of the current could have a tremendous impact on global climate, the natural environment, and human society.
Like so many other powerful natural forces, however, it is vulnerable to the effects of human behavior. Scientists have been measuring the AMOC for more than 20 years. While they all do not agree on methods, models, or measurements, a consensus is clear: The AMOC is showing signs of slowing and even possibly shutting down someday.
And the culprit is widely known: increased global temperatures. If or when the AMOC will shut down cannot be said for certain, but even some slowing of the current could have a tremendous impact on global climate, the natural environment, and human society.
What is the AMOC?
The current is a dynamic interaction of salinity and temperature that stretches from the warm tropical waters near the Equator all the way to the subpolar, North Atlantic waters off the coasts of Greenland and Iceland. The process is fueled by basic laws of physics and chemistry.
Dr. Susan Lozier, a professor in Earth and atmospheric sciences at the Georgia Institute of Technology, explained that “to understand the AMOC, you have to understand density.” Specifically, salty water is denser than fresh water. And cold water is denser than warm water. Both sink when encountering fresher or warmer water.
Because of these qualities, “water becomes stratified,” Lozier said. The salinity and temperature differential “creates a convection.”
In the north, cold, salty water sinks, forming what is known as the North Atlantic Deep Water. This draws warm surface water northward all the way from the Tropics and the South Atlantic. While those waters are slowly moving northward, the cold, deep water travels southward underneath. In the north, the warm water eventually becomes cold and sinks, while the cold, deep water warms and rises in the south. This fuels a continuous circulation or convection of currents in the ocean, which has been functioning for millennia.
Glaciers in Greenland, Iceland, and the Arctic are melting at breakneck speed, pouring fresh water into the ocean.
Now, however, as the global climate gradually warms, the same principles of density that propel the AMOC are working against it. Rising temperatures are warming the North Atlantic waters. Warmer waters do not sink. Additionally, glaciers in Greenland, Iceland, and the Arctic are melting at breakneck speed, pouring fresh water into the ocean. Fresh water is less dense than seawater, so it also does not sink.
When the northern waters sink more slowly, the convection that draws water from the south is slowed. So, this confluence of increasing warmth and decreasing salinity is robbing the AMOC of the physics that enable it to circulate.
The Consequences
The AMOC drives water and atmospheric temperatures, which in turn impact climate, natural ecosystems, and human society and habitation globally. If the AMOC slows down or stops, these systems could be irreparably damaged, and the effects could be long lasting.
Peter Ditlevsen is a professor at the Niels Bohr Institute at the University of Copenhagen, Denmark, where he studies the physics of ice, climate, and Earth. He explained the correlation between oceanic and atmospheric conditions: “The top 6 meters of the ocean have a direct effect on the Earth’s atmosphere,” he said. More specifically, “ocean temperatures set atmospheric temperatures.”
This, he noted, is because the top layer of the ocean holds as much thermal energy (heat) as the entire Earth’s atmosphere. The ocean absorbs heat from the atmosphere and releases it back into the atmosphere very slowly.
This dynamic dictates climate, and it has implications of continental proportions. As the AMOC travels north bringing warm surface waters to the higher latitudes, warm air travels with it, creating the climate on land along the way.
For example, the AMOC is responsible for the relatively mild climate of European countries along the Atlantic. Without the AMOC, these areas would be much colder. “Scandinavia would be more like Alaska,” Ditlevsen explained. It is important to note that Scandinavia and Alaska sit at approximately the same latitude, but their climates are very different. Alaska has much harsher and colder winters. This difference is attributable to the AMOC.
If the AMOC were to slow down or stop, these warm waters and the warm air they bring would slacken or cease, and temperatures on the European continent would drop precipitously.
The consequences of this could be catastrophic. “We really don’t want this to happen,” says Stefan Rahmstorf in a May 2026 interview with YaleEnvironment360. Rahmstorf is a professor of the physics of the ocean at the Potsdam Institute for Climate Impact Research in Germany. In the interview, he discussed data suggesting the AMOC experienced a similar slowdown after the last Ice Age, which ended 12,000 years ago. All the melting ice dumped huge quantities of fresh water into the ocean, which had the same effect on the AMOC that scientists are now predicting is likely to happen again.
The last time the AMOC slowed down, it put much of Europe back into Ice Age–like conditions.
The last time the AMOC slowed down, it put much of Europe back into Ice Age–like conditions. “The effects are among the most drastic we have seen in the paleorecord,” Rahmstorf said.
The impact of similar conditions in modern times would be wide ranging, and colder temperatures would only be the least of it.
A widening difference in temperatures between the regions of the Equator and the Arctic North would result in much more dramatic storms and climate instability. Shorter growing seasons and dryer conditions would drastically reduce agricultural output, leading to food scarcity in Europe. The disruption of ocean current circulation would affect marine life, causing fisheries to collapse. A shift in monsoon patterns normally fed by the AMOC would cause drought and water insecurity in Africa and Asia. As the AMOC stalled, warm water backing up in the Atlantic would accelerate sea-level rise on the eastern coastline of the United States, possibly requiring millions of people to relocate.
The ‘Cold Blob’ and the ‘Tipping Point’
All of this might sound apocalyptic to skeptics. But the data is compelling.
In 2015, Rahmstorf and several of his colleagues shared the findings of their research in an article entitled “Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation,” published in the journal Nature Climate Change. The article described the presence of a “conspicuous region of cooling in the northern Atlantic,” what many now call the “cold blob.” Rahmstorf and his colleagues described how the evidence suggests this cooling may be due to a slackening in the AMOC over the 20th century and particularly after 1970.
Other efforts are underway to study the problem. Shane Elipot is an associate professor in the Department of Ocean Sciences, University of Miami. A physical oceanographer, he uses observational and modeled data to study the AMOC. “All models are pointing to a weakening of the AMOC,” he said.
Elipot is a leading researcher on the project known as the Meridional Overturning Circulation and HeatFlux Array (MOCHA). The project gathers data from meters and sensors anchored to an array of moorings in the mid-Atlantic.
According to Elipot, the measurements gathered by MOCHA and its partner research organizations show a 10% decrease in the AMOC over 20 years.
“The good news is that the overturning [AMOC] is unlikely to collapse before 2100,” she said. However, that should not lead to complacency.
Lozier, of Georgia Tech, is a leading scientist in one of those research partners. She discussed her project’s findings in a 2024 TED Talk. In it, she reassured viewers. “The good news is that the overturning [AMOC] is unlikely to collapse before 2100,” she said. However, that should not lead to complacency.
The questions of when and if the AMOC will collapse revolve around the so-called “tipping point.” This is the point at which the collapse of the AMOC has begun, and from which there is no turning back.
Ditlevsen describes it like the Wile E. Coyote character in the Looney Tunes Road Runner cartoons, who runs off the cliff but doesn’t realize it until he looks down. “We could be on the way already,” he says.
Others are less dramatic.
According to Elipot, “a collapse of the AMOC is not as certain” as is its slowing. On the subject of an actual tipping point, Elipot adds, “that is open to research.”
When it comes to the AMOC, researchers generally agree there is a pattern and a problem that merits our attention. The consequences of dismissing it could be catastrophic, if not for us, then for future generations. Ditlevsen notes that “the medicine is the same as it is for global warming,” which is to reduce global CO2 emissions. Of the AMOC collapse, he says, “there is still a chance to reverse it.”
*Rick Laezman is a freelance writer in Los Angeles, California. He has a passion for energy efficiency and innovation. He has covered renewable power and other related subjects for over 10 years.
The author conducted interviews with Dr. Shane Elipot, Dr. Susan Lozier, and Dr. Peter Ditlevsen.
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