Intraseasonal variations of surface and subsurface currents off Java as simulated in a high‐resolution ocean general circulation model

Abstract

A high‐resolution ocean general circulation model (OGCM) is used to explore dynamics of intraseasonal variability in surface and subsurface currents off Java. The results indicate that the surface current, the so‐called South Java Coastal Current (SJCC), is dominated by variations with a period of 90 days. In the subsurface current, which is referred to as the South Java Coastal Undercurrent (SJCU), 60‐day variations are the most prominent feature. A normal mode analysis demonstrates that the first baroclinic mode is the leading mode, which accounts for 70% of the total variance, whereas the second baroclinic mode explains 24% of the total variance. The 90‐day variations in the SJCC captured mostly by the first baroclinic mode are found to be primarily driven by winds. Those are associated with propagation of the first baroclinic Kelvin waves generated in the central equatorial Indian Ocean. On the other hand, the 60‐day variations in the SJCU enhanced by wind forcing over the eastern equatorial Indian Ocean off Sumatra are mostly captured by the second baroclinic mode.