The dominant mechanisms of variability in Atlantic ocean heat transport ina coupled ocean-atmosphere GCM

The variability of the Atlantic meridional ocean heat transport (OHT) has b een diagnosed from a simulation of a coupled ocean-atmosphere general circu lation model (GCM), and the mechanisms responsible for this variability hav e been elucidated. Interannual variability is dominated by windstress-drive n Ekman fluctuations, which account for 50.3% of the OHT variance. By contr ast, decadal and multidecadal variability in Atlantic OHT is dominated by a mixed thermohaline/gyre mode driven by variations in buoyancy fluxes and w indstress curl. It accounts for 55.6% of low pass filtered OHT variance. Th e North Atlantic Oscillation (NAO) has a significant role in both the inter annual mode and the low frequency mode, but it is not the only important dr iver. A notable feature of both modes is significant changes in the tropica l atmosphere and ocean. We highlight a number of potential mechanisms invol ved in the tropical-extratropical teleconnections.