The research was led by scientists at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science. Their findings provide some of the strongest direct observational evidence so far that the Atlantic Meridional Overturning Circulation (AMOC) is losing strength. The results could help researchers improve climate models and better understand how ongoing climate change may affect the future.

"A weaker AMOC can shift weather patterns, potentially leading to more extreme storms, changes in rainfall, or colder winters in some regions," said Shane Elipot, a senior author of the study and physical oceanographer at the Rosenstiel School. "It can also influence sea-level rise along coastlines, affecting communities and infrastructure."

Deep Ocean Measurements Reveal Climate Trend

To investigate changes in the AMOC, researchers examined long-term data collected from four ocean monitoring arrays positioned along the western side of the North Atlantic. The monitoring sites ranged from tropical waters to higher latitudes.

The team used instruments anchored to the seafloor that continuously measure pressure, temperature, density, and ocean currents. Researchers applied the same method at each location, using changes in bottom pressure to estimate deep ocean movement below about 1,000 meters. By comparing measurements gathered over time and across multiple regions, the scientists were able to identify long-term changes in the circulation system.

Their observations revealed a steady decline in an important part of the AMOC along the western boundary of the Atlantic, extending from the subtropics to mid-latitudes (about 16.5°N to 42.5°N). Because the slowdown appeared across such a broad area, researchers say it likely reflects a large-scale shift in the Atlantic Ocean rather than a temporary variation.

Why the AMOC Matters

The AMOC is one of the most important systems influencing Earth's climate. It helps move heat through the Atlantic Ocean, shaping temperatures, weather patterns, and sea levels, especially around the North Atlantic region.

Scientists say a weaker AMOC could affect many aspects of global climate, including European winters, hurricane activity, and rainfall patterns in different parts of the world.

Researchers also believe measurements taken along the western edge of the Atlantic could act as an early warning system for long-term climate changes. They compared the monitoring approach to a canary in a coal mine because it may provide an efficient way to detect major shifts in this climate-regulating circulation.

"This research helps scientists better predict how the climate may change in the coming decades -- information that governments, businesses, and communities use to prepare for future environmental conditions," said Elipot .

The study, titled "Meridionally consistent decline in the observed western boundary contribution to the Atlantic Meridional Overturning Circulation," was published in Science Advances.

The research was supported by grants from the U.S. National Science Foundation (OCE-2148723 and OCE-2334091) and UK Natural Environment Research Council grants (NE/Y003551/1 and NE/Y005589/1).