Small scale features of sound velocity structure in the northern Arabian sea during February-May 1974

Abstract

Microstructure of sound velocity in the upper 500 m of the northern Arabian Sea based on STD (salinity-temperature-depth profiler) data is presented. Relatively warm and saline waters of the Persian Gulf intruding into the Arabian Sea at intermediate depths (200-400 m), influence the sound velocity structure and cause formation of an upper sound channel in the northern Arabian Sea. The Persian Gulf waters spread as tongues at 1 or 2 more levels (up to a limited extent), besides the prominent one characterised by temperature inversion and salinity maximum, causing significant perturbations in sound velocity. As the distance from the source region increases, the Persian Gulf water loses its identity and does not affect the sound velocity structure. In the upper 50 m, the sound velocity structure changes significantly from spring to summer during which period a seasonal thermocline forms due to intense surface heating. The studies indicate a seasonal variation in the flow paths of the Persian Gulf water and consequent changes in the sound velocity structure.