A semiannual Indian Ocean forced Kelvin wave observed in the Indonesian seas in May 1997

Recent observations within the Indonesian exit passages and internal seas h ighly resolve the arrival and passage of a semiannual Kelvin wave. In mid-M ay 1997, surface and subsurface currents were to the southeast at a mooring located south of Java in the South Java Current, while local wind forcing was northwestward. Subsequent northward fluctuations in the geostrophic cur rent through Lombok Strait and in observed currents from two moorings locat ed in Makassar Strait are commensurate with the speed and passage of a Kelv in wave through the region. The Kelvin wave was due to westerly wind forcin g in the remote equatorial Indian Ocean during the semiannual April/May mon soon transition period. This was confirmed through a simple remote wind-for ced analytical Kelvin wave model of velocity at the South Java Current moor ing location and sea level in Lombok Strait and also in the numerical gener al circulation model of Murtugudde et al. [1998]. Warm temperature anomalie s measured at the south Java mooring and within Makassar Strait an associat ed with the passage of the Kelvin wave. Salinity anomalies measured at the south Java mooring are consistent with an Indian Ocean source. The observed passage of the Kelvin wave during May 1997 unambiguously demonstrates for the first time that equatorial Indian Ocean remote wind forcing may on occa sions influence the internal Indonesian seas.