Likely accelerated weakening of Atlantic overturning circulation emerges in optimal salinity fingerprint

An optimal salinity fingerprint is proposed to detect the long-term Atlantic meridional overturning circulation (AMOC) response to anthropogenic forcing. A real-word application suggests a likely accelerated weakening of the AMOC in recent decades. The long-term response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic forcing has been difficult to detect from the short direct measurements available due to strong interdecadal variability. Here, we present observational and modeling evidence for a likely accelerated weakening of the AMOC since the 1980s under the combined forcing of anthropogenic greenhouse gases and aerosols. This likely accelerated AMOC weakening signal can be detected in the AMOC fingerprint of salinity pileup remotely in the South Atlantic, but not in the classic warming hole fingerprint locally in the North Atlantic, because the latter is contaminated by the noise of interdecadal variability. Our optimal salinity fingerprint retains much of the signal of the long-term AMOC trend response to anthropogenic forcing, while dynamically filtering out shorter climate variability. Given the ongoing anthropogenic forcing, our study indicates a potential further acceleration of AMOC weakening with associated climate impacts in the coming decades.

Automated summary

An optimal salinity fingerprint is proposed to detect the long-term Atlantic meridional overturning circulation (AMOC) response to anthropogenic forcing. A real-word application suggests a likely accelerated weakening of the AMOC in recent decades. Our study provides observational and modeling evidence for a likely accelerated weakening of the AMOC since the 1980s under the combined forcing of anthropogenic greenhouse gases and aerosols. This finding has significant implications for understanding the future climate impacts associated with AMOC weakening.