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Triple oxygen isotope composition of dissolved O2 in the equatorial Pacific: a tracer of mixing, production, and respiration

Citation

Hendricks, MB and Bender, ML and Barnett, BA and Strutton, P and Chavez, FP, Triple oxygen isotope composition of dissolved O2 in the equatorial Pacific: a tracer of mixing, production, and respiration, Journal of Geophysical Research: Oceans, 110, (C12) Article C12021. ISSN 0148-0227 (2005) [Refereed Article]


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Copyright Statement

Copyright 2005 American Geophysical Union

DOI: doi:10.1029/2004JC002735

Abstract

[1] As a contribution to the study of equatorial Pacific biogeochemistry, we measured the O2/Ar ratio and the triple isotope composition (18O, 17O, and 16O) of O2 along six meridional lines in the equatorial Pacific (8N8S at 95W, 110W, 125W, 140W, 155W, and 170W). O2/Ar ratios and δ18O were close to equilibrium values within the mixed layer and followed the general trend of increasing δ18O with decreasing O2/Ar at greater depths. The 17Δ (≈δ17O0.5δ18O) constrains the fraction of photosynthetic O2; 17Δ was slightly elevated with respect to equilibrium within the mixed layer due to local photosynthetic production. In aphotic zone waters above 250 m depth the average 17Δ values were higher than in the mixed layer. There are four sources of this photosynthetic signal in the dark ocean: production in the euphotic zone prior to subduction in the distant source regions, production below the mixed layer during travel to the equatorial zone, diapycnal mixing with shallower waters bearing photosynthetic O2, and accumulation of photosynthetic O2 produced at very low rates below the 1% light level. Our results also constrain biological production rates within the mixed layer at several locations along 95W and 110W. Our average rate of 14C production (53 34 mmol C m−2 d−1) agreed well with other estimates in the equatorial Pacific, while our average rate of net C production (6.9 6.2 mmol C m−2 d−1) and f ratio (0.12 0.11) were somewhat lower than other estimates. Adding δ18O and 17Δ as tracers to three‐dimensional biogeochemical ocean GCMs and comparing results with observations will extend our understanding of metabolic rates in the study region.

Item Details

Item Type:Refereed Article
Keywords:phytoplankton, tropical pacific, nutrient limitation
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Strutton, P (Professor Peter Strutton)
ID Code:138627
Year Published:2005
Web of Science® Times Cited:56
Deposited By:Oceans and Cryosphere
Deposited On:2020-04-20
Last Modified:2020-05-26
Downloads:4 View Download Statistics

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