Interannual variation of the Indonesian throughflow in the Timor Passage as revealed in SODA: 1958 – 2008

Temporal variability of the Indonesian Throughflow (ITF) in the Timor Passage was evaluated with special focus on its interannual variation. The ITF transport was estimated as a latitudinal averaged of an along strait currents in the Timor Passage based on the output of Simple Ocean Data Assimilation (SODA) experiment from 1958 – 2008. A Complex Empirical Orthogonal Function (CEOF), then, was applied to the interannual estimated ITF transport to extract the dominant mode of variability. The result has shown that the leading CEOF mode was explaining 67.2% of the total interannual variation. The reconstructed first CEOF time series shows strong positive anomalies (towards the Pacific Ocean) during 1962 – 1969, 1972 – 1978, 1997 – 1999, 2002 – 2005 and 2007. The transport was reversed (towards the Indian Ocean) during other periods. The upper layer transport above ∼200m depth is significantly correlated with the zonal wind stress in the western equatorial Pacific Ocean, with the transport lagging the winds by about 10 months. The middle layer transport between about 200 – 600m depth is significantly influenced by the zonal wind from the eastern equatorial Indian Ocean in which the zonal winds lag the ITF by about 5 months. In addition, the deeper layer transport below about 600m depth shows significant zero lag correlation with the zonal wind stress in the western equatorial Pacific Ocean, though the impact of the equatorial Indian Ocean zonal wind stress is not negligible.