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| Titel |
Icehouse–greenhouse variations in marine denitrification |
| VerfasserIn |
T. J. Algeo, P. A. Meyers, R. S. Robinson, H. Rowe, G. Q. Jiang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 4 ; Nr. 11, no. 4 (2014-02-27), S.1273-1295 |
| Datensatznummer |
250117253
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| Publikation (Nr.) |
 copernicus.org/bg-11-1273-2014.pdf |
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| Zusammenfassung |
| Long-term secular variation in the isotopic composition of seawater fixed
nitrogen (N) is poorly known. Here, we document variation in the N-isotopic
composition of marine sediments (δ15Nsed) since 660 Ma
(million years ago) in order to understand major changes in the marine N
cycle through time and their relationship to first-order climate variation.
During the Phanerozoic, greenhouse climate modes were characterized by low
δ15Nsed (∼−2 to +2‰) and icehouse
climate modes by high δ15Nsed (∼+4 to
+8‰). Shifts toward higher δ15Nsed occurred
rapidly during the early stages of icehouse modes, prior to the development
of major continental glaciation, suggesting a potentially important role for
the marine N cycle in long-term climate change. Reservoir box modeling of the
marine N cycle demonstrates that secular variation in
δ15Nsed was likely due to changes in the dominant locus
of denitrification, with a shift in favor of sedimentary denitrification
during greenhouse modes owing to higher eustatic (global sea-level)
elevations and greater on-shelf burial of organic matter, and a shift in
favor of water-column denitrification during icehouse modes owing to lower
eustatic elevations, enhanced organic carbon sinking fluxes, and expanded
oceanic oxygen-minimum zones. The results of this study provide new insights
into operation of the marine N cycle, its relationship to the global carbon
cycle, and its potential role in modulating climate change at
multimillion-year timescales. |
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