Southern Ocean CO2 release at the peak warmth of the Cenozoic

Southern Ocean CO2 release at the peak warmth of the Cenozoic | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Southern Ocean CO 2 release at the peak warmth of the Cenozoic Simone Moretti, François Fripiat, Mathis Hain, Valeria Luciani, and 10 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6622599/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract The Early Eocene Climatic Optimum (EECO) was an interval in Earth’s history when reconstructed temperatures and atmospheric CO2 concentrations were among the highest of the Cenozoic Era (i.e., the last 66 million years). The causes of the high CO2 levels remain unclear. The Southern Ocean, a major “leak” in the global ocean’s biological carbon pump that has been implicated in the CO2 changes over recent ice age cycles, may also have played a role earlier in the Cenozoic. Here, we report foraminifera-bound δ15N measurements that show higher surface nitrate concentrations in the Southern Ocean during peak EECO. The associated venting of CO2 from the deep ocean to the atmosphere would have been amplified by the low seawater pH buffering capacity of the Eocene. Previously proposed low silicate rock weatherability during the Eocene may have weakened the “weathering thermostat”, allowing the reconstructed change in biological pump efficiency in the Southern Ocean to explain at least half of the atmospheric CO2 increase observed during the EECO. Earth and environmental sciences/Biogeochemistry Earth and environmental sciences/Ocean sciences Full Text Additional Declarations There is NO Competing Interest. Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6622599","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":520088451,"identity":"58fa465c-833f-411f-aa59-d4e7f5154595","order_by":0,"name":"Simone 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