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Proxy-Model Comparison for the Eocene-Oligocene Transition in Southern High Latitudes
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  • Emily Tibbett,
  • Natalie J Burls,
  • David Hutchinson,
  • Sarah J Feakins
Emily Tibbett
University of Southern California

Corresponding Author:ejtibbett@gmail.com

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Natalie J Burls
George Mason University
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David Hutchinson
University of New South Wales
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Sarah J Feakins
University of Southern California
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The Eocene-Oligocene Transition (EOT) marks the shift from the greenhouse to icehouse conditions at 34 Ma, when a permanent ice sheet developed on Antarctica. Here we compile published proxy temperature records on and around Antarctica for timeslices defined for the late Eocene (40-34Ma) and early Oligocene (34-30 Ma) bracketing the EOT. Compiled proxy records for mean annual sea surface temperature (SST) cool by on average 1°C and land surface mean air temperature (MAT) by 2°C between the timeslices. Proxy data were compared to climate model simulations for each time interval. We use previous climate model simulations representing pre- and post- EOT, typically forced with a halving of pCO2 – that results in a larger than expected cooling based on proxies for temperature. We scaled the model outputs to identify the magnitude of pCO2 change needed to drive a commensurate change in temperature to best fit the temperature proxies. Relative to a post-EOT pCO2 level of 560 ppmv, this temperature scaling approach indicates a 27% decrease in pCO2, consistent with carbon dioxide proxy reconstructions. These proxy-model intercomparisons show that pCO2 is the primary driver of declining temperatures across the EOT, and the magnitude of that forcing was likely consistent with the 200 ppmv estimate from the latest pCO2 proxy compilations.
15 Dec 2022Submitted to ESS Open Archive
16 Dec 2022Published in ESS Open Archive