Abstract: Thanks to the INSTANT (international Nusantara stratification and transport) and MITF (monitoring the Indonesian throughflow) programs, more data became available for studying the Indonesian throughflow (ITF) through the Makassar Strait. The ITF in the Makassar Strait shows a broad range of activities, from tidal, intraseasonal, seasonal, to annual time scales. The maximum velocity in the Makassar Strait is thermocline intensified, at -1.0 m•s^-1 during the southeast monsoon and -0.8 m•s^-1 during the northwest monsoon. The interannual variability of the ITF has a positive correlation with NINO 3.4, leading NINO 3.4 by 1~2 months, while the ITF in the upper 150 m has a negative correlation with the dipole model index (DMI), but the ITF below 200 m has a positive correlation with the DMI, lagging DMI by 1~2 months. Empirical orthogonal function (EOF) analysis of seasonal variability reveals that the first two dominant modes account for 97% of the total variance, namely, the first and second modes accounted for 65% and 32% of the total variance, respectively. EOF of the interannual variability shows that the first mode accounts for 51% of the total variance, and the second, for 39%. The second mode of the seasonal variability and the first mode of the interannual variability are dominated by the intrusions of Kelvin waves from the tropical Indian Ocean. The first mode of the seasonal variability and the second mode of the interannual variability reflect ENSO modulation of Rossby waves from the tropical Pacific Ocean.

Key words: Indonesian throughflow, Makassar Strait, interannual variability