Abstract
Declining atmospheric CO2 concentrations are considered the primary driver for the Cenozoic Greenhouse-Icehouse transition, ~34 million years ago. A role for tectonically opening Southern Ocean gateways, initiating the onset of a thermally isolating Antarctic Circumpolar Current, has been disputed as ocean models have not reproduced expected heat transport to the Antarctic coast. Here we use high-resolution ocean simulations with detailed paleobathymetry to demonstrate that tectonics did play a fundamental role in reorganising Southern Ocean circulation patterns and heat transport, consistent with available proxy data. When at least one gateway (Tasmanian or Drake) is shallow (300 m), gyres transport warm waters towards Antarctica. When the second gateway subsides below 300 m, these gyres weaken and cause a dramatic cooling (average of 2–4 °C, up to 5 °C) of Antarctic surface waters whilst the ACC remains weak. Our results demonstrate that tectonic changes are crucial for Southern Ocean climate change and should be carefully considered in constraining long-term climate sensitivity to CO2.
| Original language | English |
|---|---|
| Article number | 6465 |
| Pages (from-to) | 1-8 |
| Journal | Nature Communications |
| Volume | 12 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Dec 2021 |
Bibliographical note
Funding Information:This research was undertaken with support from Australian Research Council Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001), Discovery Project 180102280, and computational resources from the Australian National Computational Infrastructure. We thank Dave Hutchinson for providing the forcing input data for our model. D.R.M. is supported by the ORCHESTRA project (NE/ N018095/1). K.H.’s research has been funded by the Deutsche Forschungsgemeinschaft (DFG) under the project GO724/15-1 and institutional resources from the Research Program PACES-II, Workpackage 3.2, of the Alfred Wegener Institute (AWI). The European Research Council under the European Community’s Seventh Framework Program provided funding by ERC Starting Grant OceaNice #802835 to P.K.B.; J.H.L. was supported by the Rough Ocean project (number 302743) from the Norwegian Research Council. D.R.M., K.H. and J.H.L. received a “Visiting Scholarship” from the University of Tasmania. We thank Max Nikurashin and Eivind Straume for constructive discussions and comments.
Publisher Copyright:
© 2021, The Author(s).
Funding
This research was undertaken with support from Australian Research Council Special Research Initiative for Antarctic Gateway Partnership (Project ID SR140300001), Discovery Project 180102280, and computational resources from the Australian National Computational Infrastructure. We thank Dave Hutchinson for providing the forcing input data for our model. D.R.M. is supported by the ORCHESTRA project (NE/ N018095/1). K.H.’s research has been funded by the Deutsche Forschungsgemeinschaft (DFG) under the project GO724/15-1 and institutional resources from the Research Program PACES-II, Workpackage 3.2, of the Alfred Wegener Institute (AWI). The European Research Council under the European Community’s Seventh Framework Program provided funding by ERC Starting Grant OceaNice #802835 to P.K.B.; J.H.L. was supported by the Rough Ocean project (number 302743) from the Norwegian Research Council. D.R.M., K.H. and J.H.L. received a “Visiting Scholarship” from the University of Tasmania. We thank Max Nikurashin and Eivind Straume for constructive discussions and comments.
