Variability of Indonesian throughflow within Makassar Strait, 2004–2009

In contrast to earlier measurements, January 2004 through May 2009 Makassar Strait velocities within the main Pacific inflow pathway of the Indonesian throughflow (ITF) are larger with a clear signal of the Asian‐Australian monsoon overriding the relatively weak 2006/2007 El Niño and 2007/2008 La Niña. The Makassar flow is thermocline intensified with maximum along‐channel velocity of −0.8 m/s near 120 m during the southeast monsoon, July to September, decreasing to −0.6 m/s from October to December, during the transition to the northwest monsoon. The temperature variability is highly correlated to ENSO, and the salinity variability reveals low‐salinity surface water inputs to the ITF, possibly from the Java and Sulu seas. Empirical Orthogonal Function (EOF) analysis of the velocity profile reveals that the first mode (45%) is dominated by the intrusions of Kelvin waves from the south, the second mode (30%) reflects ENSO modulation, and the third mode (17%) is associated with regional monsoon winds. The strength of the northward intrusions of Kelvin waves plays an important role in the total transport. The 2004–2009 average seasonal transport varied from −15.5 Sv (Sv = 10 6 m 3 /s) during the northwest monsoon (January to March) to −9.6 Sv during the monsoon transition (October to December). The annual mean transport is southward at 13.3 ± 3.6 Sv, with small year‐to‐year range from 12.5 to 14.0 Sv, substantially higher than measurements from 1997 when El Niño suppressed the transport (9.2 Sv).