AN OCEAN DYNAMICAL THERMOSTAT

The role of ocean dynamics in the regulation of tropical sea surface t emperatures (SSTs) is investigated using the Zebiak-Cane coupled ocean -atmosphere model. The model is forced with a uniform heating, or cool ing, varying between +/-40 W m(-2) into the ocean surface. a new clima tological SST pattern is established for which the area-averaged tempe rature change is smaller in magnitude than the imposed forcing. The fo rcing is balanced almost equally by a change in the heat flux out of t he ocean and by vertical advection of heat in the ocean through anomal ous equatorial ocean upwelling. The generation of anomalous upwelling is identified here as a possible mechanism capable of regulating tropi cal SSTs. This ocean dynamical thermostat mechanism has a seasonally v arying efficiency that causes amplification (weakening) of the seasona l cycle for the heating (cooling). The interannual variability also ch anges under the imposed forcing. These results suggest that the role o f ocean dynamics should be included in any discussion of the regulatio n of the tropical climate.