A new study disputes a long-held fear that climate change will lead to a quick, total collapse of the Atlantic Meridional Overturning Circulation (AMOC), the ocean current that brings warmth to northwestern Europe.
Scientists from the UK’s Met Office and University of Exeter examined 34 models showing future planetary warming, with emissions growing as much as fourfold, and said the AMOC did not completely collapse under any of them.
The research, published in the journal Nature on Wednesday, found that even if the melting of the Greenland ice sheet adds high amounts of freshwater to the North Atlantic, it will only weaken the ocean current. The system would be sustained by Southern Ocean winds, which continue to pull deep water to the surface, maintaining the current and preventing total collapse this century.
“Climate change is still happening. The AMOC is very likely to weaken. And so we need to reduce our greenhouse gas emissions,” said Jonathan Baker, a scientist at the Met Office and the paper’s lead author, in an interview with Bloomberg Green. “But it’s reassuring that the AMOC is unlikely to collapse this century because that would have really devastating impacts, especially an abrupt collapse.”
Previously researchers had suggested a sudden tipping point could be reached where the AMOC completely shuts down as soon as midcentury. This would lead to a swift change to the European climate, making temperatures across the continent between 5C and 15C lower than they currently are, and would leave little time to adapt.
The AMOC is driven by cold, dense salty water sinking in the North Atlantic and moving southwards, where it is pulled back to the surface and warms. The warm water then moves north again, becoming cooler as it goes.
The AMOC is very likely to weaken if more melting ice adds freshwater to the North Atlantic ocean, the study finds, as this would make the water lighter and less likely to sink. Studies have noted that a weaker AMOC leads to higher sea level rises, especially on the US East Coast, changes in rainfall patterns and a reduction in ocean carbon storage. Some scientists think this has already started to happen.
The new analysis in Nature “provides a counterbalance” for recent studies that have suggested the AMOC is more likely to shut down than previously thought, said Joel Hirschi, associate head of marine systems modeling at the UK’s National Oceanography Centre, who was not involved in the research.
The study’s co-author Geoff Vallis, a professor at the University of Exeter, said the finding “does not in any way mean that global warming is not a severe problem for society and our planet.”
“I think it very unlikely that my house will burn down in the coming years; however, I still buy insurance to guard against that risk,” he said.
Photograph: Snow-covered rooftops of houses in Crowborough, UK, in March 2023. A complete collapse in the Atlantic Meridional Overturning Circulation would make temperatures in Europe much colder. Photo credit: Carlos Jasso/Bloomberg
Topics Europe