SENSITIVITY OF THE NORTH-ATLANTIC TO SURFACE FORCING IN AN OCEAN GENERAL-CIRCULATION MODEL

The sensitivity of the circulation and surface properties of the North Atlantic to different forms of surface forcing is investigated using a Bryan and Cox type model. Forcing taking the form of heat and freshw ater fluxes calculated using hulk aerodynamic formulae (with an effect ive salt Aux representing freshwater forcing) failed to simulate the l ow salinity region in the Labrador Sea and north of the Gulf Stream. B y contrast, the use of this form of surface forcing, but with direct f reshwater forcing and transport instead of the more commonly used salt flux, reproduces the low salinity in these regions and gives a circul ation in good agreement with that obtained using the robust diagnostic mode. Since coupled climate models currently use an artificial salt f lux form for the freshwater fluxes between ocean and atmosphere, the p oor performance of this surface forcing reported here has significant implications for climate prediction.