A new study analyzing chemical traces in the growth rings of clam shells reinforces growing concerns about the stability of a key North Atlantic Ocean current that helps keep the global climate livable.
The findings, published on Thursday in Science Advances, examined changes in the ocean south of Greenland during the last 150 years and found that the inflow of freshwater has been disrupting the subpolar gyre, which distributes ocean heat, since the 1950s.
The research is another sign that climate heating caused mainly by fossil fuel pollution is pushing the climate toward dangerous tipping points, out of the “safe operating space” for humans, said lead author Beatriz Arellano-Nava, a University of Exeter climate researcher.
A weakening or shutdown of the subpolar gyre and related currents would weaken the northward transport of ocean heat from the tropics to higher latitudes, with different impacts by region. The tropics would experience more extreme heat on land and even worse ocean heatwaves than those already killing billions of marine organisms, from sea stars to sea birds. Sea level rise in most of the tropics would also accelerate from thermal expansion, with warming oceans swelling higher onto shorelines.
Meanwhile, there would likely be regional cooling in the North Atlantic, Arellano-Nava said, and more extremes in Europe: hotter summers, colder winters and worse flooding and droughts, as well as shifts in global precipitation patterns.
The full range of impacts is not well studied, and the intensity would depend on how much the various parts of the current system weaken. A 2024 study raised the stakes, showing that the impacts of a full-scale shutdown of the heat-carrying currents in the North Atlantic could unleash climate chaos in the Northern Hemisphere.