ADJUSTMENT OF THE NORTH ATLANTIC THERMOHALINE CIRCULATION TO THE ATMOSPHERIC FORCING IN A GLOBAL AIR-SEA COUPLED MODEL

Interannual scale adjust ment of the thermohaline circulation(THC) to the forcing of the North Atlantic Oscillation(NAO) is examined by using the out put of the recently finished 300 years integration of the Bergen Climate Model(BCM).The results show that a positive phase NAO and thereby an intensified westerlies enhances the net heat flux loss of the Labrador Sea, in conjunction with the positive salinity anomaly over there, water at the surface then becomes denser, and deep convection occurs.Three months after the NAO reaches its maximum state, the Labrador Sea convection reaches its largest depth.Response of the North Atlantic thermohaline circulation to the Labrador Sea convection lags 3 years in the model.The oceanic pole ward heat transport has a maximum simult aneous correlation with the THC.In addition, feedback of the convection on the atmosphere in the model is detected.One to four months after the convection reaches its largest depth, the convective heat release leads to a warmer surfaceair over the Labrador Sea.