Enhanced Double-Diffusive Salt Flux from the High-Salinity Core of Arabian Sea Origin Waters to the Bay of Bengal

The inflow of high-saline water from the Arabian Sea (AS) into the Bay of Bengal (BoB) and its subsequent mixing with the relatively fresh BoB water is vital for the north Indian Ocean salt budget. During June-September, the Summer Monsoon Current carries high-salinity water from the AS to the BoB. A time series of microstructure and hydrographic data collected from 4 to 14 July 2016 in the southern BoB (8 degrees N, 89 degrees E) showed the presence of a subsurface (60-150 m) high-salinity core. The high-salinity core was composed of relatively warm and saline AS water overlying the relatively cold and fresh BoB water. The lower part of the high-salinity core showed double-diffusive salt fingering instability. Salt fingering staircases with varying thickness (up to 10 m) in the temperature and salinity profiles were also observed at the base of a high-salinity core at approximately 75-150-m depth. The average downward diapycnal salt flux out of the high-salinity core due to the effect of salt fingering was 2.8 x 10(-7) kg m(-2) s(-1), approximately one order of magnitude higher than the flux if salt fingering was neglected.

Automated summary

During the summer monsoon, high-salinity water from the Arabian Sea flows into the Bay of Bengal, forming a warm and salty layer of Arabian Sea water overlying the relatively cold and fresh Bay of Bengal water. The lower part of the high-salinity core exhibits double-diffusive salt fingering instability.