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|Abstract Submission No.||ABS-2022-05-0310|
|Title of Abstract||Application of Bio-Argo float in understanding denitrification in the northern Indian ocean|
|Organisation||Indian National Centre for Ocean Information Services, Hyderabad|
|Address||101, Vishal Towers (Plot No:1634), Vishal Towers Road , Pragathi Nagar,|
Hyderabad, Telangana, India
|Abstract||N* is a tracer introduced by Gruber and Sarmiento to study the effect of denitrification and nitrogen fixation in the ocean in 1997. It uses phosphate to correct nitrate portion of its distribution due to nitrification reaction. N* describes the combined effect of denitrification and nitrogen fixation or remineralization of the nitrogen-rich organic compound. This process is spatially well separated and can be understood whether the process from the signals are either coming from one or from different processes. N*=N-(16. P) +2.9 μmol/kg Here N* is the nitrate concentration in μmol/kg and P is the concentration of the phosphate in μmol/kg. Distribution of N* has been analyzed for the northern Indian ocean, both the Arabian Sea (AS) and Bay of Bengal (BoB), using data derived from two Bio-Argo floats. The average value of N* at denitrification depths are ~ -12 μmol/kg and ~-5 μmol/kg in AS and BoB, respectively. In concurrence with the previous studies, this study also confirms that AS is a strong denitrification basin, but BoB is not. It is mainly due to the slight difference in oxygen level between the Arabian Sea and the Bay of Bengal: BoB being slightly more oxygenated than AS. Also, we found that N* decreases exponentially in the AS when the oxygen concentration is less than 2 μmol/kg; N* is as low as ~-20 μmol/kg in the core of the AS Oxygen Minimum Zone (OMZ). Along the Oman coast, which is outside the core of OMZ, N* shows large negative values (~-10 μmol/kg). This indicates that the Oman coast is also vulnerable to denitrification. In BoB, N* in the coastal Ocean is considerably low compared to the open ocean which implies coastal BoB is also vulnerable to denitrification in the near future.|