Variability of Indonesian throughflow within Makassar Strait, 2004-2009

Abstract

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 =106 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). © 2012. American Geophysical Union. All Rights Reserved.