The dynamics of the marine nitrogen cycle across the last deglaciation

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Author(s) Eugster, O., Gruber, N., Deutsch, C., Jaccard, S. L., Payne, M. R.
Publication Type Journal Items, Publication Status: Published
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Title The dynamics of the marine nitrogen cycle across the last deglaciation
Author(s) Eugster, O.
Gruber, N.
Deutsch, C.
Jaccard, S. L.
Payne, M. R.
Journal or Series Title Paleoceanography
Volume Number 28
Issue Number 1
Start Page 116
End Page 129
ISSN 0883-8305
1944-9186
Publisher American Geophysical Union
Publication Place Washington, DC, USA
Publication Date 2013
Abstract We use a geochemical box model to investigate the changes in marine N-fixation and denitrification required to match the observed sedimentary delta N-15 changes between similar to 30 kyr B.P. and the late Holocene. This is achieved by optimizing a set of seven parameters that describe the strengths of three ocean-internal N feedbacks and the response of the oceanic N cycle to four external forcings. Scenarios that best match the delta N-15 constraints indicate a strong transient decrease in N-fixation in the early deglacial in response to the decrease in iron input by dust. Around 15 kyr B.P., N-fixation rebounds primarily in response to an abrupt increase in water column denitrification caused by an expansion of anoxia. Benthic denitrification is not well constrained by our model but tends to increase in sync with water column denitrification. As a result of the transient imbalance between N-fixation and denitrification, we infer a glacial-to-interglacial decrease in the marine N inventory of between 15 and 50%. The model diagnoses this reduction in order to simultaneously fit the data from all ocean basins, requiring it to reduce the degree by which water column denitrification in the oxygen minimum zones is influencing the delta N-15 of nitrate of the whole ocean (dilution effect). Our optimal solution suggests a glacial N cycle that operated at nearly the same rates as that in pre-industrial times, but sensitivity cases with substantially lower rates fit the data only marginally worse. An important caveat of our study is the assumption of an unchanging ocean circulation. An initial sensitivity experiment shows that this affects primarily the magnitude of the change in the N inventory, while the diagnosed deglacial dynamics with global marine N-fixation taking a dip before the onset of denitrification remains a robust result.
DOI 10.1002/palo.20020
Additional Notes Published online 23 March 2013
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03775
03731
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NEBIS System Number 000035190
Source Database ID WOS-000317838200011
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@article{gstr2013,
  author = "Eugster, O. and Gruber, N. and Deutsch, C. and Jaccard, S. L. and Payne, M. R.",
  title = "{T}he dynamics of the marine nitrogen cycle across the last deglaciation",
  journal = "Paleoceanography",
  year = 2013,
  volume = "28",
  number = "1",
  pages = "116--129",
}


E-Citations record created: Mon, 27 May 2013, 11:23:51 CET