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A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific : evidence of a deepening thermocline?

Kienast, M. and Lehmann, M. F. and Timmermann, A. and Galbraith, E. and Bolliet, T. and Holboum, A. and Normandeau, C. and Laj, C.. (2008) A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific : evidence of a deepening thermocline? Geophysical research letters, Vol. 35, no. 23 , 5 S..

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Official URL: http://edoc.unibas.ch/dok/A5249290

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Abstract

Sedimentary delta N-15 records from the oligotrophic western equatorial Pacific (WEP) off Mindanao show that late Holocene sedimentary delta N-15 is substantially lower than that of the early Holocene, following a gradual <3 parts per thousand decrease that occurred between 7 and 3 kyrs ago. Analyses of modem day nitrate isotope profiles from the same region indicate the sensitivity of the WEP N pools towards (1) the advection of N-15-enriched nitrate from the Eastern Equatorial Pacific (EEP) by the North Equatorial Current (NEC) and the Mindanao Current in subsurface waters and, (2) at shallow depths, the input of new and N-15-depleted nitrate through N, fixation. We suggest that the Holocene decrease in sedimentary delta N-15 reflects a diminished relative input of N-15-enriched nitrate to the surface biota, either through an increase of regional nitrogen fixation, a change in nitrate consumption along the advective path of nitrate supply, or a decrease in the vertical Supply Of N-15-enriched nitrate from the NEC. The latter mechanism is consistent with a Holocene deepening of the WEP nitracline/thermocline. Citation: Kienast, M., M. F. Lehmann, A. Timmermann, E. Galbraith, T. Bolliet, A. Holboum, C. Normandeau, and C. Laj (2008), A mid-Holocene transition in the nitrogen dynamics of the western equatorial Pacific: Evidence of a deepening thermocline?, Geophys. Res. Lett,, 35, L23610, doi: 10.1029/2008GL035464.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geowissenschaften > Geochemie Stoffkreisläufe (Lehmann)
UniBasel Contributors:Lehmann, Moritz F
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:American Geophysical Union
ISSN:0094-8276
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:22 Mar 2012 14:30
Deposited On:22 Mar 2012 14:15

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