THE ROLE OF OCEAN-ATMOSPHERE INTERACTIONS IN TROPICAL COOLING DURING THE LAST GLACIAL MAXIMUM

A simulation with a coupled atmosphere-ocean general circulation model configured for the Last Glacial Maximum delivered a tropical climate that is much cooler than that produced by atmosphere-only models. The main reason is a decrease in tropical sea surface temperatures, up to 6 degrees C in the western tropical Pacific, which occurs because of t wo processes. The trade winds induce equatorial upwelling and zonal ad vection of cold water that further intensify the trade winds, and an e xchange of water occurs between the tropical and extratropical Pacific in which the poleward surface flow is balanced by equatorward flow of cold water in the thermocline. Simulated tropical temperature depress ions are of the same magnitude as those that have been proposed from r ecent proxy data.