Dynamics of Atlantic SST anomalies and their interaction with the North Atlantic Oscillation

In this talk, I will present 1D and 2D models of the interaction of the North Atlantic Oscillation (NAO) with its covarying anomalous SST pattern, the so-called Atlantic SST tripole. The 1D model is essentially that developped by Marshall et al. (2000), and governs the evolution of the midlatitude centers of actions of the SST tripole. The 2D model includes explicitely anomalous wind driven currents forced by the NAO, superimposed on a realistic mean circulation. The latter is taken from a regional model of the Atlantic Ocean that assimilates in - situ as well as satellite measurements.

From a close comparison of these model predictions with the observations, I will discuss two major issues:

(i) How important are the effects of Atmosphere - Ocean coupling in the seasonal and pluri-annual evolution of the NAO and the SST tripole?

(ii) What is the relative importance of mean and anomalous advection for the decadal evolution of the SST tripole?