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Nitrous oxide in the western Bay of Bengal

DRS at CSIR-National Institute of Oceanography

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Title Nitrous oxide in the western Bay of Bengal
 
Creator Naqvi, S.W.A.
Jayakumar, D.A.
Nair, M.
DileepKumar, M.
George, M.D.
 
Subject Chemistry and Biogeochemistry
nitrous oxide
nutrients
saturation
thermocline
euphotic zone
vertical profiles
ISW, Bengal Bay
 
Description Extensive observations on nitrous oxide (N@d2@@O) in the atmosphere and waters of the western Bay of Bengal during March-April 1991 yield surface saturations and atmospheric fluxes ranging from 89.3 to 213.9% (mean 125.2%), and from 0.10 to 10.67 ~kmol (N@d2@@O)/m@u2@@/d (mean 0.65 ~kmol/m@u2@@'d), respectively. The overall N@d2@@O flux from the Bay of Bengal is estimated to be 0.027-0.077 Tg N/yr which is substantially lower than that computed for the Arabian Sea (0.19-0.28 Tg N/yr). Lower surface saturations and consequently smaller air-sea fluxes in the Bay of Bengal may result from strong stratification caused by the immense river runoff. The computed vertical exchange coefficient (0.16 cm@u2@@/s) at the top of the thermocline is about 1/3 of the corresponding value (0.55 cm@u2@@/s) in the Arabian Sea. The associated smaller nutrient fluxes to the euphotic zone may be significantly responsible for the lower productivity of the Bay of Bengal. As expected, marked accumulation of N@d2@@O occurs in subsurface layers of the Bay of Bengal with the total inventory of excess nitrous oxide (~nN@2@@O) estimated as ~5.4 Tg N. Since the Bay of Bengal is not an active water-column denitritification site, there appears to be no loss of N@d@@O through bacterial reduction. Vertical profiles of N@d2@@O are characterized by a pronounced maximum at ~ 200-300 m which intensifies northward. The N@d2@@O distribution seems to be influenced by the subsurface circulation. The relationship between ~nNd2@@O and the apparent oxygen utilization (AOU) is linear in three ranges: at AOU < 150 ~kM, from AOU ~- 150 ~kM to the N@d2@@O maximum (depth ~- 300 m), and at depths >~ 1000 m. Within the depth range ~ 300-1000 m, however, ~nN@d2@@O and AOU are not significantly correlated due to large changes in N@d2@@O concentrations associated with small varitions in the ambient oxygen levels
 
Date 1994-12-23T10:06:28Z
2017-09-30T01:55:44Z
1994-12-23T10:06:28Z
2017-09-30T01:55:44Z
1994
 
Type Journal Article
 
Identifier Marine Chemistry, vol.47(3-4); 1994; 269-278
0304-4203
http://drs.nio.org/drs/handle/2264/7402
 
Language en
 
Relation Mar Chem
SCI
 
Publisher Elsevier