Meeting Documents

Three Atmospheric Patterns Dominate Decadal North Atlantic Meridional Overturning Circulation Variability (Invited)

Abstract

Variability in the Atlantic Meridional Overturning Circulation (AMOC) arises from interacting processes with multiple time scales, with dominant processes dependent on both the latitude and timescale of interest. Here, we identify dominant atmospheric modes of wind stress and heat fluxes responsible for driving decadal AMOC variability using a novel approach combining dynamical and statistical attribution (dynamics-weighted principal component, or DPC analysis). Using a one-degree configuration of the MITgcm and the ECCOv4-r4 ocean state estimate, we find that for both the subpolar (55°N) and subtropical (25°N) AMOC, the most effective mode of heat flux forcing closely resembles the North Atlantic Oscillation, which acts to drive meridionally coherent AMOC anomalies via propagating western boundary density anomalies. The optimal wind stress patterns rearrange the ocean buoyancy field and provide evidence for variations in the intensity and position of the jet stream in modulating decadal AMOC strength. We demonstrate by modifying historical fluxes in ECCOv4-r4 that most decadal AMOC variability can be explained by these leading patterns.