THE INDONESIAN THROUGHFLOW AND THE GLOBAL CLIMATE SYSTEM

The role of the Indonesian Throughflow in the global climate system is investigated with a coupled ocean atmosphere model by contrasting sim ulations with realistic throughflow and closed Indonesian passages. Th e Indonesian Throughflow affects the oceanic circulation and thermocli ne depth around Australia and in the Indian Ocean as described in prev ious studies and explained by Sverdrup transports. An open throughflow thereby increases surface temperatures in the eastern Indian ocean, r educes temperatures in the equatorial Pacific, and shifts the warm poo l and centers of deep convection in the atmosphere to the west. This c ontrol on sea surface temperature and deep convection affects atmosphe ric pressure in the entire Tropics and, via atmospheric teleconnection s. in the midlatitudes. As a result, surface wind stress in the entire Tropics changes and meridional and zonal gradients of the tropical th ermocline and associated currents increase in the Pacific and decrease in the Indian Ocean. The response includes an acceleration of the equ atorial undercurrent in the Pacific. and a deceleration in the Indian Ocean. Thus the Indonesian Throughflow exerts significant control over the global climate in general and the tropical climate in particular. Changes of surface fluxes in the Pacific warm pool region are consist ent with the notion that shading by clouds, rather than increases of e vaporation, limit highest surface temperatures in the open ocean of th e western Pacific. In the marginal seas of the Pacific and in the Indi an Ocean no such relationship is found. The feedback of the throughflo w transport and its wind forcing is negative and suggests that this in terplay cannot excite growing solution or lead to self-sustained oscil lations of the ocean-atmosphere system.