Sensitivity of AMOC Fingerprints Under Future Anthropogenic Warming

Detecting the response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic warming can only be made with fingerprints indirectly because of the lack of sufficiently long direct measurements. However, whether the relationship between the AMOC and its fingerprints is stationary is rarely examined. This study uses coupled and ocean‐alone model simulations to investigate the sensitivity of two typical AMOC fingerprints under future anthropogenic warming. We found a lower sensitivity of the North Atlantic warming hole fingerprint in future warming scenarios associated with the differing vulnerability of deep‐water origins to external forcing and climate feedback. In contrast, the remote South Atlantic salinity pile‐up fingerprint is relatively insensitive to variations in AMOC sources, and its sensitivity to the AMOC is slightly enhanced by an intensified hydrological cycle. Our study implies that fingerprints outside the northern deep convection region may become more suitable in representing the response of AMOC to future warming. Plain Language Summary The Atlantic meridional overturning circulation (AMOC) is an important component of the Earth's climate system. Due to the lack of sufficiently long direct measurements, the response of the AMOC to global warming has to be inferred from the AMOC fingerprints. Here we show that the sensitivity of AMOC fingerprints can be nonstationary under continuous warming scenario. It raises concerns when reconstructing AMOC change using these fingerprints in the context of climate change. Possible reasons for variations in sensitivity are further investigated. For the subpolar SST fingerprint, its sensitivity to AMOC change will be reduced as a result of differing responses of multiple deep‐water sources to global warming. The fingerprint outside the subpolar North Atlantic is less influenced by the variation in AMOC sources and can more faithfully represent the AMOC change in a warming climate. Key Points Relationship between Atlantic meridional overturning circulation (AMOC) fingerprints and AMOC can be nonstationary in a changing climate Warming hole shows reduced sensitivity to AMOC in a warmer climate while the sensitivity of salinity pile‐up is slightly strengthened Differing vulnerability of AMOC sources and changed hydrological cycle influence the sensitivity of the two fingerprints, respectively