The Ocean Current That Regulates Europe’s Climate Is Weakening, Scientists Just Measured How Fast

A number of tall metal moorings are anchored to the seafloor at four thousand meters off the coast of Abaco, a long, thin island in the Bahamas that most tourists avoid in favor of Nassau. They are covered in sensors that measure temperature, salinity, and pressure, spaced along the wire from the dark crush of the ocean floor to just fifty meters below the surface, much like a Christmas tree is covered in lights. They receive periodic visits from the Royal Research Ship Discovery, whose 55-person crew works nonstop to raise the equipment, download two years’ worth of data, recalibrate, and lower everything back down. It’s laborious, unglamorous, and incredibly significant work.

Since continuous measurements started in 2004, those moorings have been documenting the behavior of the Atlantic Meridional Overturning Circulation, or AMOC as it is known in climate literature, or more colloquially, the ocean conveyor belt that prevents western Europe from looking like Labrador.

Atlantic Meridional Overturning Circulation (AMOC) — Scientific Profile

Every second, the system transports about 17 million cubic meters of warm, salty water northward along the Atlantic’s surface, releasing heat across Iceland, Britain, Norway, and the continental coast before cooling, sinking, and moving southward along the seafloor once more. The mild winters and cool summers that northern Europeans take for granted would not exist without it. It transports 1.2 petawatts of heat, which is the equivalent output of a million power plants.

The most compelling observational evidence that the system is slowing has been found in new measurements released in April 2026. The AMOC is weakening, according to buoy data gathered at four different latitudes in the western Atlantic. not crumbling. Not gone. However, there is a measurable, consistent loss of strength at several points at once. The current data is both sobering and invaluable, according to Dr. Ben Moat, a physical oceanographer at the National Oceanography Centre in Southampton who has spent years aboard ships servicing these moorings. He claims that when the first data was returned in 2005 and 2006, the instruments transformed scientific knowledge of ocean circulation. It’s much less comfortable what they’re saying now.

For some time now, the larger picture has been coming together, and it’s not a happy one. The AMOC may be at its weakest point in over a millennium, according to proxy records, which are ocean sediments that retain chemical indicators of previous climate conditions.

The system seems to be headed toward a tipping point, according to a 2024 Science Advances paper that tracked a crucial measurement known as freshwater transport at the southern boundary of the Atlantic using a physics-based early warning framework. For about 40 years, that signal has been trending negatively. The annual trend in reanalysis products is roughly 1.2 milliSverdrup, which may seem insignificant until you take into account what it signifies: the slow deterioration of the system that keeps European winters mild rather than disastrous.

Whether or not the crossing will occur within the century is still up in the air. A new physics-based model limited by 20 years of actual measurements predicted AMOC weakening of 18 to 43 percent by 2100, according to a Caltech study published in 2025. This was real weakening, but not the dramatic near-collapse that more extreme climate model projections had suggested. The study’s principal investigator, Dave Bonan, was cautious in his wording: “a limited decline, not a catastrophic one, assuming the emissions trajectory doesn’t reach the most punishing scenarios.” Since “limited decline” still refers to a significantly slower current and no one is completely sure where the tipping point is, it’s the kind of finding that is nearly impossible to explain clearly.

There is little question about what occurs at the tipping point. In northwestern Europe, computer simulations of an AMOC collapse result in temperature drops of five to fifteen degrees Celsius, with cooling rates exceeding three degrees per decade in cities like London and Bergen. The simulated Arctic sea ice pack reaches a latitude of fifty degrees north. The monsoon in the Amazon reverses. Without the melting of ice sheets, ocean dynamics alone cause sea levels along the eastern seaboard of North America to rise by more than 70 centimeters. The term “tipping element” has significance for climate modelers who have run these scenarios because it characterizes a system that transitions rather than stabilizes once pushed past a threshold.

Because it’s what really distinguishes this from linear warming, it’s important to briefly understand the mechanism at work, which is the salt-advection feedback. The water must be sufficiently dense to sink when it arrives in order for the AMOC to draw salty, dense water northward. As freshwater from melting Greenland ice pours into the North Atlantic, it dilutes the salinity, lowering the water’s density, slowing the sinking, and weakening the northward pull. This process is already occurring and is accelerating. Less salt is then carried north by a weaker current, further diluting the water and weakening the current. Simple temperature projections fail to capture the self-reinforcing nature of the feedback.

The accumulation of modeling studies and measurement programs over the past ten years gives the impression that the scientific community is in the uncomfortable position of witnessing something happen slowly enough that it doesn’t generate the urgency it probably deserves. According to the National Oceanography Centre, in order to properly evaluate the accuracy of the models forecasting future behavior, at least ten more years of data are required. A reasonable scientific timeline is ten years. Additionally, waiting for confirmation of something that might not be able to be slowed down by then is a long time.