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This vast system of ocean currents, which includes the Gulf Stream, plays an essential role in regulating the global climate, particularly by transporting heat from the tropics to the North Atlantic.
Current climate models show very divergent results regarding the future evolution of this ocean circulation. On average, they predict a slowdown of about 32% by the end of the century in an intermediate emission scenario. However, these estimates remain very uncertain.
To refine these projections, the researchers applied four different methods to constrain climate models using real observations of the climate system. The most effective approach combines a large number of observed variables (temperature, salinity, etc.) using an advanced statistical method called regularized linear regression, which is still rarely used in climate science.
AMOC weakened by 51%!
Their analysis leads to a notable conclusion: the slowdown of the AMOC could reach about 51% by 2100, with significantly reduced uncertainty. This represents a weakening about 60% greater than that suggested by the average of climate models.
According to the researchers, this difference is largely explained by correcting a bias present in the models regarding surface salinity in the South Atlantic. However, several recent studies indicate that this region plays a key role in the stability of the AMOC and could be linked to the existence of a potential tipping point in the ocean system.
These new results therefore suggest that the future weakening of this major current could be greater than expected, with possible consequences for regional and global climate, particularly on temperatures in Europe, precipitation patterns, and sea level.
For scientists, better quantifying this risk is crucial: a more precise estimate of the AMOC slowdown will help improve adaptation strategies to climate change and more effectively anticipate its impacts.