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North Atlantic temperature change across the Eocene-Oligocene Transition
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  • Ilja Japhir Kocken,
  • Peter Dirk Nooteboom,
  • Kasper van der Veen,
  • Inigo A Müller,
  • Anna Nele Meckler,
  • Martin Ziegler
Ilja Japhir Kocken
Utrecht University

Corresponding Author:[email protected]

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Peter Dirk Nooteboom
Institute of Marine and Atmospheric Research Utrecht
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Kasper van der Veen
Utrecht University
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Inigo A Müller
Université de Genève
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Anna Nele Meckler
University of Bergen
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Martin Ziegler
Utrecht University
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The Eocene–Oligocene transition (~34 Ma), is marked by the rapid development of a semi-permanent Antarctic ice-sheet, as indicated by ice-rafted debris. Proxy reconstructions indicate a drop in atmospheric CO₂ and global cooling. How these changes affected sea surface temperatures in the North Atlantic and ocean water stratification remains poorly constrained. In this study, we apply clumped-isotope thermometry to well-preserved planktic foraminifera, that are associated with mixed-layer and thermocline dwelling depths from the drift sediments at IODP Site 1411, Newfoundland, across four intervals bracketing the EOT. The mixed-layer dwelling foraminifera record a cooling of 2.2 ± 2.4 °C (mean ± 95% CI) across the EOT. While the cooling amplitude is similar to previous SST reconstructions, absolute temperatures (Eocene 20.0 ± 2.7 °C, Oligocene 18.0 ± 2.1 °C) appear colder than what is expected for this location based on previously reconstructed SSTs for the northernmost Atlantic. We discuss seasonal bias, recording depth, and appropriate consideration of paleolatitudes, all of which complicate the comparison between SST reconstructions and model output. Thermocline dwelling foraminifera record a larger cooling across the EOT (Eocene 19.0 ± 3.4 °C, Oligocene 14.0 ± 3.1 °C, cooling of 5.2 ± 3.2 °C), than foraminifera from the mixed layer, consistent with an increase in ocean stratification which may be related to the onset or intensification of the Atlantic meridional overturning circulation.