Untangling the Relationship Between AMOC Variability and North Atlantic Upper‐Ocean Temperature and Salinity

Abstract

AbstractThe relationship between Atlantic meridional overturning circulation (AMOC) variability and high‐latitude North Atlantic buoyancy changes is complicated by the latter both driving, and responding to, AMOC changes. A maximum covariance analysis applied to a 1,201‐year preindustrial control simulation reveals two leading modes that separate these two distinct roles of North Atlantic temperature and salinity as related to AMOC variability. A linear combination of the two modes accounts for most of the variation of a widely used AMOC index. The same analysis applied to another control simulation known to possess two distinct regimes of AMOC variability—oscillatory and red‐noise—suggests that the North Atlantic buoyancy‐forced AMOC variability is present in both regimes but is weaker in the latter, and moreover there is pronounced multidecadal/centennial AMOC behavior in the latter regime that is unrelated to North Atlantic buoyancy forcing.