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A numerical model of the world ocean is developed to investigate the role of the ocean in the earth's heat balance. Climatological wind stress, temperature, and salinity are imposed as upper boundary conditions. An equilibrium solution is obtained based on an extended numerical integration over the equivalent of 1000 years. Seasonal variations are included. A series of numerical integrations over shorter periods indicate that quantitative aspects, such as the scale depth of the thermocline, are very sensitive to the closure parameterization representing the effect of unresolved scales of motion. The mean depth of the thermocline is found to be in proportion to the global available potential energy. Larger wind driving increases the scale depth of the thermocline, while larger lateral friction or diffusion leads to a shallower thermocline. The model predicts three major meridional cells in the upper thermocline in each hemisphere, corresponding to the three meridional cells of the atmosphere. The tropical and mid-latitude cells are largely wind driven. Thermohaline effects are dominant in the polar meridional cells. Seasonal changes in winds have a profound effect on the meridional circulation in the tropics and cause a flux of surface water from the summer to the winter hemisphere. It is suggested that this mechanism is an important factor in moderating climate by transferring excess heat from the summer hemisphere into the winter hemisphere.