National Institute of Oceanography, India

About: National Institute of Oceanography, India is a facility organization based out in Panjim, Goa, India. It is known for research contribution in the topics: Monsoon & Population. The organization has 4713 authors who have published 6927 publications receiving 174272 citations.

Nitrous oxide in the Arabian Sea

Abstract: Measurements of nitrous oxide (N 2 O) at 16 stations in the Arabian Sea reveal high degrees of surface saturation (186 ± 37%) and consequently large atmospheric fluxes of N 2 O (4.46 ± 2.60 μ mol m −2 day −1 ). Unusually high for a non-upweling period, these values reflect the large vertical gradients of N 2 O just below the mixed layer as the vertical exchange coefficients (0.55 ± 0.32 cm 2 s −1 ) required to sustain the observed fluxes are not very high. Vertical distribution of N 2 O in the Arabian Sea conforms to the trends seen in other oxygen-deficient environments, with minimal values occurring within the secondary nitrite maximum and the maxima in the N 2 O profiles located at the peripheries of this layer. Outside the denitrification zone, only one broad maximum is observed at mid-depth. The mechanisms proposed for the production of N 2 O are re-evaluated in the light of recent data on the nitrogen isotopic composition of N 2 O from the western North Pacific Ocean. It is proposed that a nitrification-denitrification couple represented by the pathway NH 4 + → NO → N 2 O may be a potentially dominant mechanism for N 2 O production in the ocean. This can explain the observed enrichment of 15 N in N 2 O as compared to NO 3 − while nitrification or denitrification alone cannot. Appreciable horizontal (east-west) gradients in N 2 O concentrations are observed at intermediate depths close to the continental margin off the west coast of India suggesting a possible sink of N 2 O within the marginal sediments. The diffusive losses of N 2 O to the denitrifying waters and marginal sediments are estimated as >2 Tg N y −1 . The Arabian Sea as a whole appears to be a net source of N 2 O, suggesting that the gross production of oceanic N 2 O h as been underestimated.