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

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  • 1 Centre for Atmospheric and Oceanic Sciences, Indian Institute of Science, Bangalore, India
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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, 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°N, 89°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 × 10−7 kg m−2 s−1, approximately one order of magnitude higher than the flux if salt fingering was neglected.

Current affiliation: National Centre for Polar and Ocean Research, Ministry of Earth Sciences, India.

Supplemental information related to this paper is available at the Journals Online website: https://doi.org/10.1175/JPO-D-20-0192.s1.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: P. N. Vinayachandran, 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, 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°N, 89°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 × 10−7 kg m−2 s−1, approximately one order of magnitude higher than the flux if salt fingering was neglected.

Current affiliation: National Centre for Polar and Ocean Research, Ministry of Earth Sciences, India.

Supplemental information related to this paper is available at the Journals Online website: https://doi.org/10.1175/JPO-D-20-0192.s1.

© 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: P. N. Vinayachandran, vinay@iisc.ac.in

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