Variability of N* in the North Indian Ocean

Distribution of N* has been analyzed for the north Indian ocean, both the Arabian Sea (AS) and Bay of Bengal (BoB) using the data derived from two bio Argo floats. The average value of N* at denitrification depth is ~ -12mol/kg in AS and ~-5 mol/kg in BoB. In concurrence with the previous studies, this study also confirms that AS is a strong denitrification basin whereas the denitrification is not seen in the BoB. It is mainly due to the slight difference in oxygen level between Arabian Sea and Bay of Bengal. Oxygen level in BoB is higher than the Arabian Sea. Also, we found that N* decreases exponentially in the AS when the oxygen concentration is less than 2mol/kg. N* reaches up to -20mol/kg in the box taken in the open ocean in the AS, which is a denitrification zone. Outside the denitrification zone , which is along the Oman coast also N* shows the large negative value (-10mol/kg ). This indicates that Oman coast is also vulnerable to denitrification. In BoB, N* in the coastal box is reducing considerably compared to the open ocean which implies a far possibility of denitrification in this region in the near future.