Two Studies Report AMOC Slowdown Evidence from Models and Observations

Two new studies published this month provide updated evidence that the Atlantic Meridional Overturning Circulation (AMOC) is weakening significantly. One study, released Thursday in the journal Science Advances, combined climate models with real-world ocean temperature and salinity data to project that the AMOC will slow by more than 50% by the end of the century, a decline 60% stronger than the average estimated by all climate models.

The second study, published last week by University of Miami scientists, analyzed data from four moorings along the western boundary of the North Atlantic Ocean.

These moorings have continuously measured water temperature, salinity, and ocean current velocity since 2004. The study found evidence of AMOC weakening at all four latitudes over the past two decades. Pessimistic climate models showing strong AMOC weakening are unfortunately the realistic ones, and the potential for the AMOC to pass a tipping point as early as the middle of this century heightens fears.

The AMOC’s weakening could even be more pronounced because meltwater from Greenland is not included in the climate models. The observation of weakening at all four locations is significant. The western boundary of the Atlantic Ocean is the canary in a coal mine for AMOC changes, and the real-world data helps validate climate model predictions.

The weakening is already occurring and is underestimated by current projections, increasing the risk of an AMOC tipping point. The AMOC, which transports heat, salt, and freshwater through the ocean, has been continuously monitored since 2004. Its last known collapse occurred roughly 12,000 years ago.