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| Titel |
Increase in water column denitrification during the last deglaciation: the influence of oxygen demand in the eastern equatorial Pacific |
| VerfasserIn |
P. Martinez, R. S. Robinson |
| 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 ; 7, no. 1 ; Nr. 7, no. 1 (2010-01-04), S.1-9 |
| Datensatznummer |
250004360
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| Publikation (Nr.) |
 copernicus.org/bg-7-1-2010.pdf |
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| Zusammenfassung |
| Here we present organic export production and nitrogen
isotope results spanning the last 30 000 years from a core recovered off
Costa Rica (Ocean Drilling Program (ODP) Site 1242) on the leading edge of
the oxygen minimum zone of the Eastern Tropical North Pacific. Marine export
production reveals glacial-interglacial variations with low organic matter
(total organic carbon and total nitrogen) contents during warm intervals,
twice more during cold episodes and double peaked maximum during the
deglaciation, between ~15.5–18.5 and 11–13 ka B.P. When this new
export production record is compared with four nearby cores from within the
Eastern Pacific along the Equatorial divergence, good agreement between all
the cores is observed. The major feature is a maximum of export during the
early deglaciation. As for export production, water-column denitrification,
represented by sedimentary δ15N records, along the Eastern
tropical North and South Pacific between 15° N and 36° S is also
coherent over the last deglaciation. Each of the nitrogen isotope profiles
indicate that denitrification increased abruptly at 19 ka B.P to a maximum
during the early deglaciation, confirming a typical Antarctic timing. It is
proposed that the increase in export production and then in subsurface
oxygen demand lead to an intensification of water-column denitrification
within the oxygen minimum zones in the easternmost Pacific at the time of
the last deglaciation. The triggering mechanism would have been primarily
linked to an increase in preformed nutrients contents feeding the Equatorial
Undercurrent driven by the resumption of overturning in the Southern Ocean
and the return of nutrients from the deep ocean to the sea-surface. An
increase in equatorial wind-driven upwelling of sub-surface nutrient-rich
waters could have played the role of an amplifier. |
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