Upwelling along the Java-Sumatra Indian Ocean coasts is a response to regional winds associated with the monsoon climate. The upwelling center with low sea surface temperature migrates westward and toward the equator during the southeast monsoon (June to October). The migration path depends on the seasonal evolution of alongshore winds and latitudinal changes in the Coriolis parameter. Upwelling is eventually terminated due to the reversal of winds associated with the onset of the northwest monsoon and impingement of Indian Ocean equatorial Kelvin waves. Significant interannual variability of the Java-Sumatra upwelling is linked to ENSO through the Indonesian throughflow (ITF) and by anomalous easterly wind. During El Ni¿o episodes, the Java-Sumatra upwelling extends in both time (into November) and space (closer to the equator). During El Nino (La Ni¿a), the ITF carries colder (warmer) water shallowing (deepening) thermocline depth and enhancing (reducing) upwelling strength. ¿ 2001 American Geophysical Union