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Eocene cooling linked to early flow across the Tasmanian Gateway

Eocene cooling linked to early flow across the Tasmanian Gateway
Eocene cooling linked to early flow across the Tasmanian Gateway
The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ?49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.
climate cooling, dinoflagellate cysts, organic palaeothermometry, paleoceanography
0027-8424
9645-9650
Bijl, P.K.
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Bendle, J.A.P.
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Bohaty, S.M.
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Pross, J.
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Schouten, S.
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Tauxe, L.
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Stickley, C.E.
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McKay, R.M.
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Rohl, U.
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Olney, M.
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Sluijs, A.
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Escutia, C.
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Brinkhuis, H.
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Klaus, A.
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Fehr, A.
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Williams, T.
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Carr, S.A.
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Dunbar, R.B.
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Gonzalez, J.J.
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Hayden, T.G.
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Iwai, M.
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Jimenez-Espejo, F.J.
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Katsuki, K.
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Kong, G.S.
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Nakai, M.
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Passchier, S.
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Pekar, S.F.
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Riesselman, C.
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Sakai, T.
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Shrivastava, P.K.
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Sugisaki, S.
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Tuo, S.
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van de Flierdt, T.
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Welsh, K.
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Yamane, M.
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Bijl, P.K.
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Bendle, J.A.P.
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Bohaty, S.M.
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Pross, J.
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Schouten, S.
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Tauxe, L.
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Stickley, C.E.
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McKay, R.M.
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Rohl, U.
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Olney, M.
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Sluijs, A.
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Escutia, C.
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Brinkhuis, H.
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Klaus, A.
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Fehr, A.
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Williams, T.
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Carr, S.A.
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Dunbar, R.B.
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Gonzalez, J.J.
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Hayden, T.G.
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Iwai, M.
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Jimenez-Espejo, F.J.
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Katsuki, K.
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Kong, G.S.
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Nakai, M.
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Passchier, S.
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Pekar, S.F.
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Riesselman, C.
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Sakai, T.
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Shrivastava, P.K.
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Sugisaki, S.
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Tuo, S.
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van de Flierdt, T.
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Welsh, K.
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Yamane, M.
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Bijl, P.K., Bendle, J.A.P., Bohaty, S.M., Pross, J., Schouten, S., Tauxe, L., Stickley, C.E., McKay, R.M., Rohl, U., Olney, M., Sluijs, A., Escutia, C., Brinkhuis, H., Klaus, A., Fehr, A., Williams, T., Carr, S.A., Dunbar, R.B., Gonzalez, J.J., Hayden, T.G., Iwai, M., Jimenez-Espejo, F.J., Katsuki, K., Kong, G.S., Nakai, M., Passchier, S., Pekar, S.F., Riesselman, C., Sakai, T., Shrivastava, P.K., Sugisaki, S., Tuo, S., van de Flierdt, T., Welsh, K. and Yamane, M. (2013) Eocene cooling linked to early flow across the Tasmanian Gateway. Proceedings of the National Academy of Sciences, 110 (24), 9645-9650. (doi:10.1073/pnas.1220872110).

Record type: Article

Abstract

The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52–50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ?49–50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2–4 °C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.

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More information

Published date: 11 June 2013
Keywords: climate cooling, dinoflagellate cysts, organic palaeothermometry, paleoceanography
Organisations: Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 355647
URI: https://eprints.soton.ac.uk/id/eprint/355647
ISSN: 0027-8424
PURE UUID: 2d380203-6c8f-42db-bba9-1acc0464a5ae
ORCID for S.M. Bohaty: ORCID iD orcid.org/0000-0002-1193-7398

Catalogue record

Date deposited: 09 Aug 2013 13:55
Last modified: 06 Jun 2018 12:39

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Contributors

Author: P.K. Bijl
Author: J.A.P. Bendle
Author: S.M. Bohaty ORCID iD
Author: J. Pross
Author: S. Schouten
Author: L. Tauxe
Author: C.E. Stickley
Author: R.M. McKay
Author: U. Rohl
Author: M. Olney
Author: A. Sluijs
Author: C. Escutia
Author: H. Brinkhuis
Author: A. Klaus
Author: A. Fehr
Author: T. Williams
Author: S.A. Carr
Author: R.B. Dunbar
Author: J.J. Gonzalez
Author: T.G. Hayden
Author: M. Iwai
Author: F.J. Jimenez-Espejo
Author: K. Katsuki
Author: G.S. Kong
Author: M. Nakai
Author: S. Passchier
Author: S.F. Pekar
Author: C. Riesselman
Author: T. Sakai
Author: P.K. Shrivastava
Author: S. Sugisaki
Author: S. Tuo
Author: T. van de Flierdt
Author: K. Welsh
Author: M. Yamane

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