Analysis of Upwelling Event in Western Maluku Sea in 2015

Abstract

Maluku Sea is a secondary entry portal Indonesian Through flow (ITF) with less intensive study. It is connected with Tomini Gulf and Seram-Banda Sea. In the western MS, previous study reported surface features of seasonal upwelling from satellite data. This study aims to further analyze generating force of upwelling and to fully describe oceanic-atmospheric changes before-during-after upwelling event in 2015. The INDESO model output and satellite imagery were used in this study. It is shown that seasonal upwelling in MS is characterized by increased meridional wind stress and northward transport volume, increased sensible heat flux, decreased infrared heat flux, SST cooling, and surface chlorophyll-a blooming. Here, upwelling is generated by southerly monsoon winds, which are fully developed during the Southeast Monsoon period. Since the study area is closed to the equator, the effect of Coriolis may be neglected. In addition, the region between Banggai and Taliabu is relatively opened to Banda Sea. Thus, the strong southerly winds directly drag surface water masses northward and then upwelled colder water occurs in southern region. Upwelling area then evolves towards northeast due to island boundary and is enhanced by recirculation of Maluku ITF. Evolution of mixed layer depth due to upwelling appears in the upper 60 m, which transports water mass northward from June to its peak in September, and decays in October.