North Atlantic surface ocean warming and salinization in response to middle Eocene greenhouse warming

Robin van der Ploeg; Margot J Cramwinckel; Ilja J Kocken; Thomas J Leutert; Steven M Bohaty; Chris D Fokkema; Pincelli M Hull; A Nele Meckler; Jack J Middelburg; Inigo A Müller; Donald E Penman; Francien Peterse; Gert-Jan Reichart; Philip F Sexton; Maximilian Vahlenkamp; David De Vleeschouwer; Paul A Wilson; Martin Ziegler; Appy Sluijs

doi:10.1126/sciadv.abq0110

North Atlantic surface ocean warming and salinization in response to middle Eocene greenhouse warming

Sci Adv. 2023 Jan 25;9(4):eabq0110. doi: 10.1126/sciadv.abq0110. Epub 2023 Jan 25.

Authors

Robin van der Ploeg¹, Margot J Cramwinckel¹, Ilja J Kocken¹, Thomas J Leutert², Steven M Bohaty³, Chris D Fokkema¹, Pincelli M Hull⁴, A Nele Meckler², Jack J Middelburg¹, Inigo A Müller¹, Donald E Penman⁵, Francien Peterse¹, Gert-Jan Reichart^{1

6}, Philip F Sexton⁷, Maximilian Vahlenkamp⁸, David De Vleeschouwer^{8

9}, Paul A Wilson³, Martin Ziegler¹, Appy Sluijs¹

Affiliations

¹ Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands.
² Bjerknes Centre for Climate Research and Department of Earth Science, University of Bergen, Bergen, Norway.
³ University of Southampton, Waterfront Campus, National Oceanography Centre, Southampton, UK.
⁴ Department of Geology and Geophysics, Yale University, New Haven, CT, USA.
⁵ Department of Geosciences, Utah State University, Logan, UT, USA.
⁶ NIOZ Royal Netherlands Institute for Sea Research and Utrecht University, Den Burg, Texel, Netherlands.
⁷ School of Environment, Earth & Ecosystem Sciences, The Open University, Milton Keynes, UK.
⁸ MARUM - Center for Marine and Environmental Sciences, University of Bremen, Bremen, Germany.
⁹ Institute of Geology and Paleontology, University of Münster, Münster, Germany.

Abstract

Quantitative reconstructions of hydrological change during ancient greenhouse warming events provide valuable insight into warmer-than-modern hydrological cycles but are limited by paleoclimate proxy uncertainties. We present sea surface temperature (SST) records and seawater oxygen isotope (δ¹⁸O_sw) estimates for the Middle Eocene Climatic Optimum (MECO), using coupled carbonate clumped isotope (Δ₄₇) and oxygen isotope (δ¹⁸O_c) data of well-preserved planktonic foraminifera from the North Atlantic Newfoundland Drifts. These indicate a transient ~3°C warming across the MECO, with absolute temperatures generally in accordance with trace element (Mg/Ca)-based SSTs but lower than biomarker-based SSTs for the same interval. We find a transient ~0.5‰ shift toward higher δ¹⁸O_sw, which implies increased salinity in the North Atlantic subtropical gyre and potentially a poleward expansion of its northern boundary in response to greenhouse warming. These observations provide constraints on dynamic ocean response to warming events, which are consistent with theory and model simulations predicting an enhanced hydrological cycle under global warming.