The Atlantic Meridional Overturning Circulation (AMOC), the current system that transports warm, salty water from the Gulf of Mexico northward, significantly moderating the climate of Western Europe, is noticeably weakening. A recent study, featuring direct measurements taken at four distinct ocean locations, provides the most compelling evidence yet for this trend. The findings were published in the journal Science Advances.
This system functions like a natural conveyor belt: warm surface water proceeds north, cools down, increases in density, sinks to the ocean floor, and then flows back south along the eastern edge of the Atlantic basin. It is precisely this mechanism that makes Western Europe considerably warmer than locations in Canada or Russia situated at comparable latitudes. Previous evidence suggested the system had already diminished by approximately 15 percent since 1950, but until this investigation, direct observational data was insufficient for definitive conclusions.
This new research is primarily based on data collected by the RAPID-MOCHA array of sensors, operational since 2004, spanning from the Bahamas across to the Canary Islands. Scientists meticulously measured water temperature, salinity, current velocity, and water pressure across the Atlantic. Their calculations indicate a reduction in the water flow within the system of roughly 90,000 cubic meters per second annually—a rate of decline faster than previously documented. Between 2004 and 2023, the circulation has weakened by an additional estimated 10 percent.
“The Atlantic circulation is slowing down at the western boundary, and by using data gathered across multiple latitudes from the sensor array throughout the basin, we confirm that this signal observed at the western boundary aligns with the data from the wider North Atlantic,” states Qianqian Xing of the University of Miami, the lead author of the study. In addition to the primary sensor line, the team analyzed pressure readings from three moored buoys situated along the western Atlantic rim—near the West Indies, the eastern coast of the USA, and Nova Scotia. Signs of deceleration were even more pronounced at these locations, with lower margins of error, lending greater robustness to the results.
The researchers attribute the slowdown to the melting of the Greenland ice sheet, positing that the influx of freshwater dilutes the dense, salty water, hindering its ability to sink effectively and thus disrupting the entire circulation mechanism. Stefan Rahmstorf, a scientist at the Potsdam Institute for Climate Impact Research who was not involved in the research, describes this as “the most convincing direct observational evidence to date” of the circulation’s weakening. Should this trend persist and the system eventually halt, it could precipitate severe consequences, including sharply colder winters in Europe and disruptions to monsoon patterns in Asia and Africa.
About the Author
