Oceanic heat transport and its seasonal variations are determined with a diagnostically calculated seasonal velocity and an observed seasonal temperature. The heat transport of the Indonesian Throughflow varies greatly from 0.82 to 1.62 PW (1 PW=1015 W). The northward heat transport through the South Atlantic is similar to the heat transport of the Agulhas Leakage, but the phases of these variations are opposite to each other. Hence the South Atlantic circulation alone produces a southward heat transport during boreal winter, and the heat from the Indian Ocean maintains a northward heat flux in the South Atlantic. The meridional heat transport in the global ocean varies with an almost annual cycle, and a large amount of heat is transported toward the winter pole (7.0 PW northward and 3.1 PW southward) in the tropical ocean by the surface Ekman current. Although the meridional heat transport has large variations, the nonlinear contribution to the annual mean is very small in the present model. The nonlinear heat transport is mainly produced by seasonal variations of the surface temperature and the Ekman current. Hence further studies with a fine grid model to resolve the seasonal variation of the western boundary currents will be required to properly address the nonlinearity of the heat transport. ¿ 1998 American Geophysical Union