Deep in the Atlantic Ocean, four mooring stations have been measuring ocean currents for over twenty years. Scientists have now discovered something worrying: the Atlantic Meridional Overturning Circulation, or AMOC, is weakening at every single station.
In April 2026, two new studies were published in Science Advances. The first study, led by Valentin Portmann from Inria's Bordeaux Sud-Ouest center in France, used new methods to improve climate predictions. His team projects that the AMOC will weaken by about 51% by 2100. This is much worse than previous estimates of 32%.
The second study, led by Qianjiang Xing from the University of Miami, looked at twenty years of direct measurements. The data showed that the deep ocean flow is slowing down everywhere researchers examined, from the Caribbean to Canada.
The main reason appears to be melting ice from Greenland. As the ice sheet melts, fresh water flows into the Atlantic Ocean, making the water less salty. This prevents the normal cooling and sinking process that drives the AMOC.
Scientists warn that if the AMOC stops completely, it could change European weather patterns, raise sea levels along the US East Coast, and alter tropical rainfall. For decades, scientists thought this was a distant problem. Now, expert Stefan Rahmstorf estimates there is more than a 50 percent chance of reaching a critical tipping point soon.