Seasonal variation of sea surface current in the Gulf of Thailand

In this study, the seasonal variations in the surface water currents within the Gulf of Thailand were revealed through the use of (i) temperature and salinity data derived from the world ocean database, (ii) the monthly dynamic heights anomaly (DHA) from TOPEX/Poseidon and (iii) the ERS-2 altimetry data, during 1995-2001. The mean dynamic height (MDH) and mean geostrophic current were derived from the climatological temperature and salinity data, while the DHA data was derived from the MDH and their geostrophic currents. The mean geostrophic current showed a strong southwestward flow of the South China Sea water along the gulf entrance. Counterclockwise eddies in the inner gulf and the western side of the gulf entrance were associated with upwelling in the area. Seasonal geostrophic currents showed a basin-wide counterclockwise circulation during the southwest monsoon season and a clockwise circulation during the northeast monsoon season. Upwelling was en- hanced during the southwest monsoon season. The circulation patterns varied seasonally probably due to the variation in wind regimes. Finally, the congregation, spawning, and migration routes of the short-bodied mackerel were found to conform to the upwelling and surface circulation in the gulf.