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Published December 2022 | Published
Journal Article Open

On the Use of Dissolved Oxygen Isotopologues as Biogeochemical Tracers in the Northeast Pacific Ocean

Abstract

The isotopic composition of dissolved oxygen offers a family of potentially unique tracers of respiration and transport in the subsurface ocean. Uncertainties in transport parameters and isotopic fractionation factors, however, have limited the strength of the constraints offered by ¹⁸O/¹⁶O and ¹⁷O/¹⁶O ratios in dissolved oxygen. To improve our understanding of oxygen cycling in the ocean's interior, we investigated the systematics of oxygen isotopologues in the subsurface Pacific using new data and a 2-D isotopologue-enabled isopycnal reaction-transport model. We measured ¹⁸O/¹⁶O and ¹⁷O/¹⁶O, as well as the "clumped" ¹⁸O¹⁸O isotopologue in the northeast Pacific, and compared the results to previously published data. We find evidence that oxygen consumption in the northeast Pacific follows different mass-dependent fractionation exponents from those typically used in oceanographic studies. These fractionation factors imply that an elevated proportion of ¹⁷O compared to ¹⁸O in dissolved oxygen — that is, its triple-oxygen isotope composition — may not uniquely reflect only gross primary productivity and mixing. For all oxygen isotopologues, transport, respiration, and photosynthesis comprise important parts of their respective budgets. Mechanisms of oxygen removal in the subsurface ocean are discussed.

Additional Information

© 2022. American Geophysical Union. We thank D. P. Nicholson for sharing his triple-oxygen data compilation, and L. W. Juranek for sharing her subsurface dataset from the northeast Pacific. In addition, we thank five anonymous reviewers whose comments helped us improve the manuscript. This research was supported by National Science Foundation Grants OCE-1436590, 1533501, and 1559004. Data Availability Statement. The MATLAB code for the two-gyre model can be found on GitHub (https://github.com/liptds). The isotopic data can be found in the Biological and Chemical Oceanography Data Management Office (BCO-DMO) database at https://www.bco-dmo.org/dataset/753594.

Attached Files

Published - JGR_Oceans_-_2022_-_Li_-_On_the_Use_of_Dissolved_Oxygen_Isotopologues_as_Biogeochemical_Tracers_in_the_Northeast_Pacific.pdf

Files

JGR_Oceans_-_2022_-_Li_-_On_the_Use_of_Dissolved_Oxygen_Isotopologues_as_Biogeochemical_Tracers_in_the_Northeast_Pacific.pdf

Additional details

Created:
August 22, 2023
Modified:
October 23, 2023