Is the ocean losing its breath? Insights into ocean oxygenation from Cenozoic 
warm periods

Auderset, Alexandra; Hess , Anya; Moretti, Simone; Sigman, Daniel; Martinez-Garcia, Alfredo

doi:10.5194/egusphere-egu24-17106

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Is the ocean losing its breath? Insights into ocean oxygenation from Cenozoic warm periods

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Martinez-Garcia, Alfredo
Climate Geochemistry, Max Planck Institute for Chemistry, Max Planck Society;

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https://meetingorganizer.copernicus.org/EGU24/EGU24-17106.html
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Citation

Auderset, A., Hess, A., Moretti, S., Sigman, D., & Martinez-Garcia, A. (2024). Is the ocean losing its breath? Insights into ocean oxygenation from Cenozoic warm periods. In EGU General Assembly 2024, Vienna, Austria & Online. doi:10.5194/egusphere-egu24-17106.

Cite as: https://hdl.handle.net/21.11116/0000-000F-2144-F

Abstract

In EGU General Assembly 2024, Vienna, Austria & Online, 14-19 April

The continuous expansion of oxygen-deficient zones (ODZs) poses risks to marine ecosystems and societies dependent on fisheries for income and sustenance. However, the trajectory of this deoxygenation in response to 21st-century climate change remains uncertain. To gain a clearer understanding of future oxygen dynamics and processes leading to deoxygenation, we investigate the response of ODZs during Cenozoic global warming periods in the Miocene and Early Eocene, using a combination of oxygen-sensitive proxies including foraminifer-bound nitrogen isotopes (FB-δ15N) and iodine-to-calcium ratios in planktic foraminifer shells (I/Ca). Our findings reveal contracted, rather than expanded, tropical Pacific ODZs during all studied warm intervals. The increased oxygenation closely aligns with high-latitude warming and reduced meridional sea surface temperature gradients, indicating a climatic driver behind these observed changes. We discuss potential causes for the contraction of ODZs, including (i) diminished wind-driven equatorial upwelling and primary productivity, and/or (ii) increased deep-ocean ventilation. Finally, we compare the behaviour of Pacific vs. Indian Ocean ODZs during the Miocene and investigate potential teleconnections between these two wind-driven ODZs.