Modeling approaches in the investigation of upwelling along the east coast of Peninsular Malaysia: Its driven mechanisms

Numerous processes can cause upwelling, but the processes that cause upwelling along the east coast of Peninsular Malaysia (ECPM) are not well understood. Therefore, the dynamics of upwelling driving processes along the ECPM were investigated in this study. During the southwest monsoon, satellite-derived sea surface temperature (SST) and cruise surveys revealed the presence of upwelling signals, which were indicated by inshore cooler SST and onshore shoaling of the parameters isolines toward the coast and surface. In addition, the satellite-derived SST revealed a prominent feature of cooler water advection from the Java Sea. The Regional Ocean Modelling System (ROMS) was then used to simulate upwelling and the physical characteristics of adjacent waters. The simulation was generally agreed with the available datasets, showing the reliability of the simulated model. A series of simulation-based experiments were carried out to study the various contributions of physical processes to upwelling along the ECPM. The results revealed that wind-driven upwelling processes of Ekman transport were more essential in the generation of upwelling along the ECPM than wind stress curl. The elimination of tides from the model resulted in an intriguing feature in which the salinity along the ECPM decreased significantly, resulting in an increased in density (or salinity) gradient and the ensuing baroclinic pressure gradient force (PGF) in the upper inshore region, which significantly enhanced upwelling along the ECPM, and this is the new finding provided by this study. However, under the real oceanographic conditions, the effects of baroclinic PGF in causing upwelling was expected to be less substantial than the Ekman transport.