Thermal frontal zone along the east coast of Peninsular Malaysia

Abstract

Monthly satellite-derived sea surface temperature (SST) climatology was used to investigate the thermal frontal zone along the east coast of Peninsular Malaysia (ECPM) during both northeast and southwest monsoons. In addition, in situ hydrographic observations were conducted to investigate the vertical structure of thermohaline fronts during the southwest monsoon and inter-monsoon period. During the northeast monsoon, the locations of the front is determined by the speed of the southward flowing western boundary current, located near South Vietnam, which causes the tongue of cooler water, flooding into the ECPM. As the speed of southward flowing western boundary current increases, the cooler water tongue moves closer to the ECPM. On the other hand, as current speed decreases, the distinctive cooler water tongue recedes from the ECPM. During the southwest monsoon, the presence of a cooler water patch is observed in the SST climatology data and limited field data exhibit upwelling features (i.e. the presence of isotherm and isohaline shoaling towards the coast and surface). Analysis of European Centre for Medium-range Forecast (ECMWF) wind data show the presence of positive wind stress curl in the region, indicating a driving mechanism for upwelling. Additionally, analyses of onshore and offshore SST differences suggest that significant atmospheric forcing during different monsoon periods are responsible for the seasonal evolution of SST patterns.