Oceanic nutrient rise and the late Miocene inception of Pacific oxygen-deficient zones
Creators
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1.
Boston College
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2.
Max Planck Institute for Chemistry
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3.
Princeton University
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4.
National Taiwan University
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5.
ETH Zurich
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6.
University of Toronto
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7.
Texas A&M University
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8.
University of Western Australia
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9.
California Institute of Technology
Abstract
The modern Pacific Ocean hosts the largest oxygen-deficient zones (ODZs), where oxygen concentrations are so low that nitrate is used to respire organic matter. The history of the ODZs may offer key insights into ocean deoxygenation under future global warming. In a 12-My record from the southeastern Pacific, we observe a >10‰ increase in foraminifera-bound nitrogen isotopes (¹⁵N/¹⁴N) since the late Miocene (8 to 9 Mya), indicating large ODZs expansion. Coinciding with this change, we find a major increase in the nutrient content of the ocean, reconstructed from phosphorus and iron measurements of hydrothermal sediments at the same site. Whereas global warming studies cast seawater oxygen concentrations as mainly dependent on climate and ocean circulation, our findings indicate that modern ODZs are underpinned by historically high concentrations of seawater phosphate.
Copyright and License
© 2022 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY).
Acknowledgement
We thank the International Ocean Discovery Program, the Oregon State University Core Repository, and D. C. Lund (University of Connecticut) for providing the samples used in this study. We also thank G. R. Rossman for assistance with the Fe and P content analyses. This work was funded by Boston College (to X.T.W.), the Simons Foundation (to X.T.W.), the David and Lucile Packard Foundation (to W.W.F.), the US NSF (to D.M.S.), the Australian Research Council (to B.R.), and the ACS Petroleum Research Fund (to Y.G.Z.).
Data Availability
All study data are included in the article and/or supporting information.
Files
pnas.2204986119.pdf
Additional details
Identifiers
- ISSN
- 1091-6490
- PMCID
- PMC9659387
Funding
- Boston College
- Simons Foundation
- 497534
- David and Lucile Packard Foundation
- National Science Foundation
- Australian Research Council
- American Chemical Society
- Petroleum Research Fund