title: Equatorial heat accumulation as a long-term trigger of permanent Antarctic ice sheets during the Cenozoic.
abstract: Growth of the first permanent Antarctic ice sheets at the Eocene-Oligocene Transition (EOT), ∼33.7 million years ago, indicates a major climate shift within long-term Cenozoic cooling. The driving mechanisms that set the stage for this glaciation event are not well constrained, however, owing to large uncertainties in temperature reconstructions during the Eocene, especially at lower latitudes. To address this deficiency, we used recent developments in coccolith biogeochemistry to reconstruct equatorial Atlantic sea surface temperature (SST) and atmospheric pCO2values from pelagic sequences preceding and spanning the EOT. We found significantly more variability in equatorial SSTs than previously reported, with pronounced cooling from the Early to Middle Eocene and subsequent warming during the Late Eocene. Thus, we show that the Antarctic glaciation at the Eocene-Oligocene boundary was preceded by a period of heat accumulation in the low latitudes, likely focused in a progressively contracting South Atlantic gyre, which contributed to cooling high-latitude austral regions. This prominent redistribution of heat corresponds to the emplacement of a strong meridional temperature gradient that typifies icehouse climate conditions. Our equatorial coccolith-derived geochemical record thus highlights an important period of global climatic and oceanic upheaval, which began 4 million years before the EOT and, superimposed on a long-term pCO2decline, drove the Earth system toward a glacial tipping point in the Cenozoic.
authors.affiliation: Institut des Sciences de la Terre de Paris (UMR UPMC/CNRS 7193 ISTeP), Université Pierre et Marie Curie, CNRS, Sorbonne Universités, 75252 Paris Cedex 05, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Tremblin
authors.affiliation: Department of Earth Sciences, University of Oxford, Oxford OX1 3AN, United Kingdom.
authors.forename: Michaël
authors.identifier: 0000-0003-1427-1891
authors.initials: M
authors.lastname: Hermoso
authors.affiliation: Institut des Sciences de la Terre de Paris (UMR UPMC/CNRS 7193 ISTeP), Université Pierre et Marie Curie, CNRS, Sorbonne Universités, 75252 Paris Cedex 05, France; Fabrice.Minoletti@upmc.fr.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Minoletti
keywords: Atlantic equatorial SSTs; Cenozoic pCO2; Eocene−Oligocene climate transition; coccolith-based proxies; meridional temperature gradient