Upwelling characteristics during El Nino 2015 in Maluku Sea

Abstract

Investigation of upwelling characteristics in Banggai-Maluku Sea (BMS) during super El Nino 2015 event and its interannual variation related to ENSO used validated INDESO model output and satellite imagery datasets between 2008 and 2015. The result shows the upwelling episode occurs during the Southeast Monsoon period from June to October, and its maximum in September. It is mainly forced by fully developed southerly monsoon winds, dragging surface water northward similar to the wind direction since the effect of Coriolis vanishes near the equator. Warm surface water in the center upwelling is replaced by upwelled colder water from about 60 m, which evolves from southern to northern region then curving to northeastern due to the boundary of Sulawesi mainland. Upwelling characteristics in 2015 event is indicated by drastic changes in ocean-atmosphere variables, such as increased northward meridional winds/infrared heat flux/transport volume, decreased sensible heat flux/mixed layer depth, upwelled 26°C isotherm from 60 m depth to surface, and blooming surface chlorophyll-a. Between 2008 and 2015, upwelling intensity in 2015 was the most powerful (index: -5.35), in contrast to upwelling intensity during 2010 strong La Nina event (+0.27). Hence, ENSO influences significantly on fluctuation of upwelling intensity in BMS.