The El Niño Southern Oscillation (ENSO) effects on the sea level of the Java Sea are studied using the time lag analysis and the HYbrid Coordinate Ocean Model (HYCOM). The time lag analysis results show that the time lags among wind, Southern Oscillation Index (SOI) and sea level changes are 0 to 2 month lag. The HYCOM-estimated sea levels are validated using tide gauge sea levels. Due to the shallowness of the Java Sea, the wind-induced mixed layer is easily reaches to the bottom. The HYCOM-estimated volume transport is compared with European Remote Sensing (ERS) satellite wind vectors. The HYCOM results show that the ENSO effects on the sea level greater than the wind effect.
Jakarta, Semarang and Surabaya, which are located along the northern coast of the Java Island, are easily affected by the sea level change of the Java Sea. This condition is worsened by the land subsidence along the North Jakarta, and Semarang since 1980s (Hirose et al., 2001). Subsidence level in Jakarta measured by using JERS-1 SAR (Synthetic Aperture Radar) was around 10 cm from 1993 to 1995 and 6 cm from 1995 to 1998. The Java Sea is a shallow body of sea and has average depths of around 40 to 50 meters. A map showing the location of the Java Sea has been depicted in Fig. 1. The Java Sea is bordered by the Kalimantan Island on the north, the Java Island on the south, the Sumatra Island on the west, the southern Makassar Strait on the east, the Karimata Strait on the northwest, and the Sunda Strait on the southwest. Past observation (Gordon et al., 2003) and ocean model results (Sofian et al., 2006a) show that the northwest monsoon wind drives the Java Sea low-salinity surface water move to the southern Makassar Strait during the northwest monsoon from October to March.
