Photo by Jakob Owens
Scientists have published some of the strongest direct observational evidence to date that the Atlantic Meridional Overturning Circulation, the vast system of ocean currents that regulates climate across Europe and the North Atlantic, has been weakening for nearly two decades, with new modelling suggesting the slowdown could be far more severe by the end of the century than previously projected.
The study, led by researchers at the University of Miami Rosenstiel School of Marine, Atmospheric and Earth Science and published in Science Advances, examined data from four ocean monitoring arrays along the western boundary of the North Atlantic, spanning tropical to mid-latitudes. Using seafloor-anchored instruments that continuously record pressure, temperature, density and ocean currents, the team identified a consistent decline in deep ocean flow across a broad geographic sweep, from approximately 16.5°N to 42.5°N, that researchers say reflects a basin-wide shift rather than short-term variation.
A canary in a coal mine
The breadth of the observed slowdown is what distinguishes this study from previous work. Because the weakening appeared consistently across all four monitoring sites, the authors argue it represents meaningful, large-scale change in the circulation system. Previous climate model projections had estimated an average AMOC slowdown of around 32 per cent by the end of the century. The new study, however, estimates the system could slow by 51 per cent by 2100 under a mid-range greenhouse gas emissions scenario – a substantially more alarming trajectory.
Shane Elipot, senior author and physical oceanographer at the Rosenstiel School, said the implications extended well beyond oceanography: “A weaker AMOC can shift weather patterns, potentially leading to more extreme storms, changes in rainfall, or colder winters in some regions. It can also influence sea-level rise along coastlines, affecting communities and infrastructure.”
The researchers say the western boundary monitoring approach could serve as an early warning system, “a canary in a coal mine”, for broader climate shifts. “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,” Elipot added.
Why AMOC matters
The AMOC acts as a vast conveyor belt, drawing warm surface water northward from the tropics and returning cold, dense water southward at depth. It is the primary mechanism that keeps north-west Europe significantly warmer than its latitude would otherwise suggest. Driven by differences in the temperature and salinity of seawater, it is vulnerable to freshwater influx from Greenland’s shrinking ice sheet, which dilutes surface salinity and reduces the density difference that drives the circulation.
An AMOC collapse could bring harsher winters across northern Europe, droughts in South Asia and the Sahel, and higher sea levels along the North American coastline. A 2026 paper published in Communications Earth & Environment found that a near-complete shutdown would increase atmospheric CO₂ by 47–83 parts per million, adding around 0.2°C of additional warming, with scientists warning of cascading effects on other climate tipping elements.
The political salience of the issue is growing. In November 2025, Iceland designated the risk of an AMOC shutdown a national security threat. In 2024, more than 40 researchers signed an open letter to the Nordic Council of Ministers warning of a “serious risk” of collapse.
Observational evidence catching up with models
The study is significant because it is based on direct measurements rather than proxy indicators or modelling. Previous high-profile warnings relied on sea surface temperature patterns as indirect signals of circulation change. The University of Miami team’s use of bottom pressure measurements at four western boundary sites provides a more direct window into the overturning system itself, and the consistency of the signal across all four locations gives the findings unusual weight.
The research was co-funded by the UK Natural Environment Research Council, underscoring the direct relevance of AMOC science to UK climate and coastal policy.