Buffering effect and its related ocean dynamics in the Indonesian throughflow region

Analysis of results from a high-resolution general circulation model confirms the existence of a “buffering” effect in the Indo-Australian Basin in which the upper ocean receives an excess of water from February to June and releases it during the rest of the year. A similar, but significantly weaker, phenomenon exists in the Indonesian seas. The buffering mostly results from geostrophic convergence, with the directly wind-driven Ekman divergence playing a role only within the Indonesian seas. Upward phase propagation, or equivalently, downward energy propagation, is revealed, indicating the prominent influence of remotely forced Kelvin waves originating in the equatorial Indian Ocean. The model demonstrates that these Kelvin waves penetrate as far eastward as the Ombai Strait along the southern Indonesian coastal waveguide, and that they have a notable influence on the upper-ocean convergence/divergence in the Indo-Australian Basin. Some of the semiannual signal turns northward through the Lombok and Ombai Straits to impact the circulation and thermal structure within the Indonesian seas.