INDONESIAN THROUGHFLOW IN A COUPLED GENERAL-CIRCULATION MODEL

The Indonesian throughflow is analyzed in an extended simulation with a coupled ocean-atmosphere model. The model, developed by the Max-Plan ck-Institut fur Meteorologie, Hamburg, Germany, combines an atmospheri c general circulation model at T42 resolution (2.8 degrees latitude by 2.8 degrees longitude) and a primitive equation ocean model with zona l resolution of 2.8 degrees and a meridional resolution of 0.5 degrees in the tropics and is coupled without flux correction equatorward of a latitude of 60 degrees. The onset and strength of the monsoon in the Indonesian waters agree well with climatology, and many aspects of th e observed temperature fields in the eastern Indian Ocean and Timer Se as are found in simulation. Differences between simulation and observa tions of temperature occur in mean and seasonal cycles in the far west ern Pacific. The annual cycles of sea level along the coast of Sumatra and lava are simulated satisfactorily. The simulated throughflow tran sports on average 13.8 Sv (10(6)m(3)s(-1)) from the Pacific to the Ind ian Ocean. The vertically averaged (barotropic) component of the throu ghflow has a seasonal range of 13.1 Sv and is weakest in February and strongest in July. In contrast, deviations from the vertical average o f the throughflow (baroclinic) are strongest in March and September. T he average and seasonal cycle of the barotropic component of the throu ghflow are forced by winds over the Pacific and along the western coas ts of Australia and South America, as described by the island rule. Fo r closed Torres Strait, the contribution of the average bottom pressur e torque is small, and friction closes the vorticity balance. For annu al timescales, baroclinic flows affect the throughflow transport throu gh the bottom pressure torque. The annual cycle of the baroclinic comp onent of the throughflow is forced predominantly by winds over the Ind onesian Seas. The throughflow exports 0.9 PW of heat from the Pacific into the Indian Ocean and is an important heat sink for the western Pa cific. The throughflow is a major heat source for the Indian Ocean and is associated with reversal of the divergence of the meridional trans port of heat south of 10 degrees S that is balanced by heat fluxes fro m the ocean to the atmosphere.