Enhanced double-diffusive salt flux from the high-salinity core of Arabian Sea origin waters to the Bay of Bengal

View More View Less
  • 1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India, Current affiliation:National Centre for Polar and Ocean Research, Ministry of Earth Sciences, India
  • 2 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India
  • 3 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India
© Get Permissions
Restricted access

Abstract

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, Summer Monsoon Current carries high salinity water from the AS to the BoB. A time series of microstructure and hydrographic data collected from 4–14 July 2016 in the Southern BoB (8°N, 89°E) showed the presence of subsurface (60–150 m) high-salinity core. The high-salinity core was comprised of relatively warm and saline AS water overlying the relatively cold and fresh BoB water. 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 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 2.8×10−7 kg m−2 s−1; approximately one order of magnitude higher than the flux if salt fingering were neglected.

Corresponding author address: P.N. Vinayachandran, Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560012, India. E-mail: vinay@iisc.ac.in

Abstract

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, Summer Monsoon Current carries high salinity water from the AS to the BoB. A time series of microstructure and hydrographic data collected from 4–14 July 2016 in the Southern BoB (8°N, 89°E) showed the presence of subsurface (60–150 m) high-salinity core. The high-salinity core was comprised of relatively warm and saline AS water overlying the relatively cold and fresh BoB water. 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 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 2.8×10−7 kg m−2 s−1; approximately one order of magnitude higher than the flux if salt fingering were neglected.

Corresponding author address: P.N. Vinayachandran, Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore 560012, India. E-mail: vinay@iisc.ac.in
Save