Seasonal / Interannual Variations of the Indonesian Throughflow and the eastern Indian Ocean
Yukio Masumoto
Department of Earth and Planetary Physics, Graduate School of Science, University of Tokyo Also at Frontier Research System for Global Change, Institute for Global Change Research
Seasonal and interannual variations of the Indonesian throughflow and the eastern Indian Ocean are investigated by use of an Indo-Pacific OGCM forced by wind stresses derived from ERS satellites.
First, the model was driven for 5 years by the climatological monthly winds averaged from July 1992 to June 1997. The simulated throughflow transport has a value of 4.3Sv, with maximum (minimum) transport of 8.7Sv (0.5Sv) in September (February). After the climatological seasonal run, an interannual integration was continued with the monthly mean wind stress from July 1992 through June 1997. During the first half of the integration, the throughflow gradually increases and reaches a maximum transport of 22.8Sv to the Indian Ocean in August 1995.
The throughflow weakens after August 1995 and changes its direction toward the Pacific Ocean in June 1997 with the magnitude of 4.9Sv. While the simple “Island Rule” can be used to estimate the mean throughflow transport, the most of the interannual and intraseasonal variability in the throughflow are not well captured by the rule.
In the eastern Indian Ocean, a large anomaly of the low sea surface height off the coast of Sumatra is developed in 1994, which is consistent with TOPEX / Poseidon altimeter observation. Associated with this anomaly are the very weak Wyrtki Jets in the eastern equatorial Indian Ocean and the strong northwestward wind stresses over the region. The Indonesian throughflow, however, does not show a significant variation associated with this phenomena.