Research Objectives
To determine the role in the coupled ocean-atmosphere system of oceanic transport from the Pacific to the Indian Ocean through the Indonesian Seas.
Computational Approach
A sophisticated climate model that couples general circulation models of the ocean and atmosphere was integrated with both open and closed Indonesian passages. Climate and Indonesian throughflow simulated by the first integrations compare favorable with observations. Effects of the Indonesian Throughflow on the earth's climate are determined by contrasting this climate state with the simulation obtained after closure of the oceanic passages between Australia and Asia.
Accomplishments
The Indonesian throughflow affects the circulation and thermocline depth around Australia and in the Indian Ocean. It shifts the western Pacific/eastern Indian Ocean warm pool and centers of deep atmospheric convection to the west by increasing surface temperatures in the eastern Indian Ocean and reducing temperatures in the equatorial Pacific. This control on sea surface temperature and deep convection affects atmospheric pressure in the entire tropics and, via atmospheric teleconnections, in the mid latitudes. As a result, surface wind stresses in the entire tropics change and meridional and zonal gradients of the tropical thermocline and associated currents increase in the Pacific and decrease in the Indian Ocean. The response includes an acceleration of the equatorial 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. Results also indicate that feedbacks of the throughflow transport and its wind forcing are negative, and suggests that this interplay can not excite growing solution or lead to self sustained oscillations of the ocean-atmosphere system.
Significance
In addition to increasing the understanding of the oceanic transport through the only low latitude connection of the world's oceans, this research serves the continuing effort of evaluation and improving climate models that play a pivotal role in the prediction of natural climate variability and of anthropogenic climate changes.
Publications
Schneider, N. 1997. The Indonesian throughflow and the global climate system. J. Climate, in press.
Schneider, N., T. Barnett. 1997. Indonesian throughflow in a coupled general circulation model. J. Geophys. Res. 102:12341-12358.
Schneider, N., T. Barnett, M. Latif and T. Stockdale. 1996. Warm pool physics in a coupled GCM. J. Climate 9:219-239.
Changes of the surface wind stress (arrows) due to closure of the Indonesian throughflow.
Changes of the stress that are significantly beyond the natural climate variability are color
coded, where the color corresponds to changes of the wind stress magnitude in N/m*m.