Atlantic Ocean Current on Track for 51% Collapse by 2100 — Far Worse Than Previous Estimates

The Atlantic Meridional Overturning Circulation, the vast ocean current system that keeps Western Europe temperate and regulates climate across the Northern Hemisphere, is on course to weaken by approximately 51 percent by the year 2100 — far more than previous models had projected and potentially enough to trigger catastrophic climate disruptions that could last centuries, according to a new study published in the journal Science Advances. The research, led by French oceanographer Valentin Portmann and colleagues, used an innovative statistical approach that combined real-world ocean observations with the outputs of climate models, and found that earlier projections had systematically underestimated the threat by roughly 60 percent.

The AMOC is essentially a global conveyor belt of ocean water that moves warm, salty water northward from the tropics toward the North Atlantic, releases its heat into the atmosphere — warming Europe and the American East Coast — and then sinks as the cooled water becomes denser, flowing south along the ocean floor. The system is driven by differences in water temperature and salinity, and climate scientists have known for years that rising temperatures from greenhouse gas emissions are disrupting this delicate balance by melting Arctic ice, adding fresh water to the North Atlantic, and reducing the density contrast that drives the circulation. What the new study establishes is the magnitude of the disruption: a 43 to 59 percent weakening by century's end, with the central estimate landing at 51 percent relative to pre-industrial circulation levels.

The consequences of such a weakening would be severe and geographically broad. Northern Europe, which relies on the AMOC to deliver warmth far beyond what its latitude would otherwise allow — London sits at the same latitude as parts of Canada but has a far milder climate — could experience dramatic temperature drops, particularly in winter. Southern Europe and North Africa could face prolonged droughts as storm tracks shift. The U.S. East Coast, including cities like New York, Boston, and Miami, would experience accelerated sea level rise because the AMOC currently holds water away from the coast; as it weakens, that water returns. The study estimated that food production in the most affected regions could fall by more than 50 percent for staple crops like wheat and maize. Additionally, the researchers calculated that a collapsing AMOC could release stored oceanic carbon equivalent to 47 to 83 additional parts per million of atmospheric CO2, adding approximately 0.2 degrees Celsius of additional warming on top of baseline projections.

A separate study published concurrently in Nature Communications Earth & Environment confirmed these findings using different methods, adding weight to the conclusion that previous IPCC assessment reports had significantly underestimated AMOC collapse risk. The new consensus estimate puts collapse probability at more than 50 percent under current emissions trajectories — up from the roughly 5 percent risk estimated in some earlier analyses. Direct observational monitoring of the AMOC, which has been conducted at four deep-ocean measurement sites since 2004, confirms a consistent two-decade downward trend in the circulation's strength. Scientists note that ocean systems can cross tipping points abruptly, meaning the transition from a weakening AMOC to a near-collapse state could happen far faster than the gradual model projections suggest.

The Portmann team's methodological innovation was the use of ridge-regularized linear regression — a technique that avoids overfitting by introducing a penalty for overly complex models — to integrate multiple observational signals simultaneously: sea surface temperature and sea surface salinity data from across the North Atlantic basin. Previous models had used these signals separately or relied predominantly on model simulations with limited observational grounding. By anchoring the analysis more firmly in observed data, the researchers reduced prediction error by 79 percent compared to standard approaches. "Nations need to prepare now," one oceanographer told the journal's editors. "The changes we're projecting are not reversible on human timescales. The window for meaningful action is shrinking."