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Budgetary and biogeochemical implications of N sub(2)O isotope signatures in the Arabian Sea

DRS at CSIR-National Institute of Oceanography

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Title Budgetary and biogeochemical implications of N sub(2)O isotope signatures in the Arabian Sea
 
Creator Naqvi, S.W.A.
Yoshinari, T.
Jayakumar, D.A.
Altabet, M.A.
Narvekar, P.V.
Devols, A.H.
Brandes, J.A.
Codispoti, L.A.
 
Subject biogeochemistry
nitrous oxide
isotopes
nitrification
vertical profiles
 
Description Nitrous oxide (N sub(2)O) is an important greenhouse gas that also plays a role in the chemistry of stratospheric ozone depletion, but its atmospheric budget has yet to be well-quantified sup(1-5). However, multi-isotope characterization of N sub(2)O emitted from various natural sources is a potentially powerful tool for providing the much-needed constraints. It is generally believed that production of isotopically light (low sup(15)N/ sup(14)N and sup(18)O/ sup(16)O ratios) N sub(2)O occurs in the upper ocean through nitrification process, and that the flux of this N sub(2)O from sea to air isotopically counters the flux of heavy N sub(2)O from the stratosphere to the troposphere sup(1,2). But eastern-boundary ocean-upwelling zones, which contain oxygen-depleted waters and are sites of intense N sub(2)O efflux sup(6-10), have not been adequately studied. We show here, using new isotope data, that in spite of huge denitrification-related enrichments of sup(15)N and sup(18)O in N sub(2)O at mid-depths in the Arabian Sea, N sub(2)O emitted from upwelled waters is only slightly enriched in sup(18)O, and moderately depleted in sup(15)N, relative to air. These opposing isotopic signatures and modest departures from the isotopic composition of tropospheric N sub(2)O indicate that air-sea exchange cannot-given the heavy isotopic signature of N sub(2)O derived from the stratosphere-allow the troposheric budget of N sub(2)O to be closed without invoking hitherto-unknown N sub(2)O sources and sinks. Our oceanic data cannot be explained through either nitrification or denitrification alone, such that a coupling between the two processes may be an important mechanism of N sub(2)O production
 
Date 2009-01-11T11:53:53Z
2009-01-11T11:53:53Z
1998
 
Type Journal Article
 
Identifier Nature, Vol.394; 462-464p.
http://drs.nio.org/drs/handle/2264/1909
 
Language en
 
Rights Copyright [1998]. All efforts have been made to respect the copyright to the best of our knowledge. Inadvertent omissions, if brought to our notice, stand for correction and withdrawal of document from this repository.
 
Publisher Macmillan