Time-series measurements of temperature and salinity profiles were made every two hours at 74¿30'E, 9¿13'N in the southeastern Arabian Sea (SEAS) during 22-March--7-April and 23-May--7-June 2003 as part of the Arabian Sea Monsoon Experiment (ARMEX). The observations show that a 20 m thick barrier layer (BL) exists during March--April owing to a surface layer of low-salinity waters advected earlier during December--January from the Bay of Bengal. The BL is almost annihilated by 7 April owing to upwelling. The relic BL that survives is annihilated later in May by upwelling, and by the inflow of high-salinity waters from the north and by mixing due to stronger winds, which deepen the mixed layer. We present evidence from satellite data and arguments based on existing theories to show that both the upwelling and the advection of high-salinity waters are remotely forced.