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Article: Plio-Pleistocene denitrification in the eastern tropical North Pacific: Intensification at 2.1 Ma

TitlePlio-Pleistocene denitrification in the eastern tropical North Pacific: Intensification at 2.1 Ma
Authors
KeywordsEtnp Denitrification
Nitrogen Isotopes
Ocean Biogeochemistry
Plio-Pleistocene
Upper Ocean Circulation
Issue Date2008
Citation
Geochemistry, Geophysics, Geosystems, 2008, v. 9 n. 11 How to Cite?
AbstractGlobal climate has changed substantially over the past ̃4 million years (Ma) toward, on average, colder conditions and higher amplitude oscillation between glacial and interglacial periods. Corresponding changes in marine biogeochemistry could have linked oceanic circulation changes to the global carbon cycle, but remain poorly understood. We report a high-resolution, 4-Ma-long δ15N record from Ocean Drilling Program Site 1012 on the California margin, which monitors denitrification intensity in one of the principal Oxygen Minimum Zones (OMZs) of the open ocean. The δ15N record demonstrates that eastern tropical North Pacific (ETNP) denitrification was weak for much of the late Pliocene. Though there was no apparent change associated with Northern Hemisphere glaciation (NHG) at ̃2.7 Ma, denitrification strengthened substantially (by ̃2% in δ15N) at ̃2.1 (Ma). Since 2.1 Ma, intense denitrification in the ETNP occurred during interglacial periods and was generally very climate-sensitive. We infer that two oceanic changes, the shoaling of the thermocline in the eastern Pacific (and thus the strengthened Walker circulation) and the development of a modern-like frontal system in high-latitude southern ocean around ̃2.1 Ma provided favorable conditions for intensification of ETNP denitrification that was also likely mirrored south of the equator. Intermediate water circulation changes likely created the poorly ventilated zones susceptible to the suboxic condition required by denitrification. 2.1 Ma thus marks a critical point for the reorganization of the ocean's nitrogen cycle in which open ocean denitrification became a significant loss term during interglacial phases of climate. Given linkage between the ocean's N and C cycle, ETNP denitrification changes probably contributed to Plio-Pleistocene climatic changes. © 2008 by the American Geophysical Union.
Persistent Identifierhttp://hdl.handle.net/10722/151293
ISSN
2015 Impact Factor: 2.993
2015 SCImago Journal Rankings: 2.439
ISI Accession Number ID
Funding AgencyGrant Number
National Science FoundationOCE 0351599
OCE 0623487
0318371
Funding Information:

We thank the Ocean Drilling Program for providing samples and the National Science Foundation for supporting this research (OCE 0351599 and OCE 0623487 to TDH; 0318371 to MAA). We also thank two anonymous reviewers for their constructive and thorough review and A. C. Ravelo and L. E. Lisiecki for providing their data. ZL thanks K. T. Lawrence and L. C. Cleaveland for discussions and T. Wu and R. Singh for technical assistance.

References

 

DC FieldValueLanguage
dc.contributor.authorLiu, Zen_US
dc.contributor.authorAltabet, MAen_US
dc.contributor.authorHerbert, TDen_US
dc.date.accessioned2012-06-26T06:20:12Z-
dc.date.available2012-06-26T06:20:12Z-
dc.date.issued2008en_US
dc.identifier.citationGeochemistry, Geophysics, Geosystems, 2008, v. 9 n. 11en_US
dc.identifier.issn1525-2027en_US
dc.identifier.urihttp://hdl.handle.net/10722/151293-
dc.description.abstractGlobal climate has changed substantially over the past ̃4 million years (Ma) toward, on average, colder conditions and higher amplitude oscillation between glacial and interglacial periods. Corresponding changes in marine biogeochemistry could have linked oceanic circulation changes to the global carbon cycle, but remain poorly understood. We report a high-resolution, 4-Ma-long δ15N record from Ocean Drilling Program Site 1012 on the California margin, which monitors denitrification intensity in one of the principal Oxygen Minimum Zones (OMZs) of the open ocean. The δ15N record demonstrates that eastern tropical North Pacific (ETNP) denitrification was weak for much of the late Pliocene. Though there was no apparent change associated with Northern Hemisphere glaciation (NHG) at ̃2.7 Ma, denitrification strengthened substantially (by ̃2% in δ15N) at ̃2.1 (Ma). Since 2.1 Ma, intense denitrification in the ETNP occurred during interglacial periods and was generally very climate-sensitive. We infer that two oceanic changes, the shoaling of the thermocline in the eastern Pacific (and thus the strengthened Walker circulation) and the development of a modern-like frontal system in high-latitude southern ocean around ̃2.1 Ma provided favorable conditions for intensification of ETNP denitrification that was also likely mirrored south of the equator. Intermediate water circulation changes likely created the poorly ventilated zones susceptible to the suboxic condition required by denitrification. 2.1 Ma thus marks a critical point for the reorganization of the ocean's nitrogen cycle in which open ocean denitrification became a significant loss term during interglacial phases of climate. Given linkage between the ocean's N and C cycle, ETNP denitrification changes probably contributed to Plio-Pleistocene climatic changes. © 2008 by the American Geophysical Union.en_US
dc.languageengen_US
dc.relation.ispartofGeochemistry, Geophysics, Geosystemsen_US
dc.subjectEtnp Denitrificationen_US
dc.subjectNitrogen Isotopesen_US
dc.subjectOcean Biogeochemistryen_US
dc.subjectPlio-Pleistoceneen_US
dc.subjectUpper Ocean Circulationen_US
dc.titlePlio-Pleistocene denitrification in the eastern tropical North Pacific: Intensification at 2.1 Maen_US
dc.typeArticleen_US
dc.identifier.emailLiu, Z:zhliu@hku.hken_US
dc.identifier.authorityLiu, Z=rp00750en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1029/2008GC002044en_US
dc.identifier.scopuseid_2-s2.0-70350417793en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-70350417793&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume9en_US
dc.identifier.issue11en_US
dc.identifier.eissn1525-2027-
dc.identifier.isiWOS:000261142600001-
dc.publisher.placeUnited Statesen_US
dc.identifier.scopusauthoridLiu, Z=16177844800en_US
dc.identifier.scopusauthoridAltabet, MA=7003622651en_US
dc.identifier.scopusauthoridHerbert, TD=7005866440en_US

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