The contribution of ocean dynamics on the variability of European winter temperatures in a long coupled model simulation

Abstract

A large part of the interannual variability of the European winter air temperature is caused by anomalies of the atmospheric circulation and the associated advection of air masses. However, part of the temperature variability cannot be linearly explained by such processes. Here, a long control simulation with a coupled atmosphere-ocean climate model is analyzed with the goal of decomposing the European temperature anomalies in an atmospheric-circulation-dependent part and a residual. The thermohaline circulation, closely connected in the model to the intensity of the Gulf Stream, lags the evolution of the temperature residuals by several years and does not seem to exert any control on their evolution. The variability of the oceanic convection in the northern North Atlantic on the other hand correlates with the temperature residual evolution at lags close to zero. It is hypothesised that oceanic convection produces a sea-surface temperature fingerprint that leads to the European temperature residuals.