A probabilistic estimate of global marine N-fixation and denitrification

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Author(s) Eugster, Olivier, Gruber, Nicolas
Publication Type Journal Items, Publication Status: Published
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Title A probabilistic estimate of global marine N-fixation and denitrification
Author(s) Eugster, Olivier
Gruber, Nicolas
Description 15 p.
Journal or Series Title Global Biogeochemical Cycles
Volume Number 26
Issue Number 4
Start Page GB4013
ISSN 0886-6236
1944-9224
Publisher American Geophysical Union
Publication Place Washington, DC
Publication Date 2012-12
Abstract We determine the global rates of marine N-fixation and denitrification and their associated uncertainties by combining marine geochemical and physical data with a new two-dimensional box model that separates the Atlantic from the IndoPacific basins. The uncertainties are estimated using a probabilistic approach on the basis of a suite of 2500 circulation configurations of this box model. N-fixation and denitrification are diagnosed in an inverse manner for each of these configurations using N*, P*, and the stable nitrogen isotope composition of nitrate as data constraints. Our approach yields a median water column denitrification rate of 52 TgN yr(-1) (39 to 66 TgN yr(-1), 5th to 95th percentile) and a median benthic denitrification rate of 93 TgN yr(-1) (68 to 122 TgN yr(-1)). The resulting benthic-to-water column denitrification ratio of 1.8 confirms that the isotopic signature of water column denitrification has a limited influence on the global mean stable isotopic value of nitrate due to the dilution of the waters with a denitrification signal with the remainder of the ocean's nitrate pool. On the basis of two different approaches, we diagnose a global N-fixation rate of between 94 TgN yr(-1) and 175 TgN yr(-1), with a best estimate of 131 TgN yr(-1) and 134 TgN yr(-1), respectively. Most of the N-fixation occurs in the IndoPacific suggesting a relative close spatial coupling between sources and sinks in the ocean. Our N-fixation and denitrification estimates plus updated estimates of atmospheric deposition and riverine input yield a pre-industrial marine N cycle that is balanced to within 3 TgN yr(-1) (-38 to 40 TgN yr(-1)). Our budget implies a median residence time for fixed N of 4,200 yr (3,500 to 5,000 yr).
DOI 10.1029/2012GB004300
Additional Notes Published online 28 November 2012
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
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NEBIS System Number 000041178
Source Database ID WOS-000311842000001
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@article{gstr2012,
  author = "Eugster, Olivier and Gruber, Nicolas",
  title = "{A} probabilistic estimate of global marine {N}-fixation and denitrification",
  journal = "Global Biogeochemical Cycles",
  year = 2012,
  volume = "26",
  number = "4",
  pages = "GB4013--",
  month = dec,
}


E-Citations record created: Mon, 07 Jan 2013, 09:53:18 CET