Increase in water column denitrification during the last deglaciation; the influence of oxygen demand in the eastern Equatorial Pacific

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doi: 10.5194/bg-7-1-2010
Author(s): Martinez, Philippe; Robinson, Rebecca S.
Author Affiliation(s): Primary:
Université de Bordeaux I, Environnements et Paléoenvironnements Océaniques, Talence, France
University of Rhode Island, United States
Volume Title: Biogeosciences
Source: Biogeosciences, 7(1), p.1-9. Publisher: Copernicus GmbH on behalf of the European Union, Katlenburg-Lindau, International. ISSN: 1726-4170
Note: In English. Published in Biogeosciences Discuss.: 19 May 2009, ; accessed in Feb., 2011; abstract: 60 refs.; illus., incl. sketch maps
Summary: 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.
Year of Publication: 2010
Research Program: ODP Ocean Drilling Program
Key Words: 24 Surficial Geology, Quaternary Geology; Biochemistry; Carbon; Cenozoic; Continental margin; Deglaciation; Denitrification; East Pacific; Equatorial Pacific; Holocene; Late-glacial environment; Leg 202; Marine environment; Nitrates; Nitrogen; North Pacific; Northeast Pacific; Nutrients; ODP Site 1240; ODP Site 1242; Ocean Drilling Program; Ocean circulation; Organic carbon; Oxygen; Pacific Ocean; Paleo-oceanography; Paleocurrents; Panama Basin; Quaternary; Sea water; Southern Ocean; Thermocline; Thermohaline circulation; Upwelling; Winds
Coordinates: N000100 N000100 W0822800 W0822800
N075100 N075100 W0833600 W0833600
Record ID: 2011035491
Copyright Information: GeoRef, Copyright 2020 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany