Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release

• Published in: Nature Communications
• Main Authors: Gottschalk, Julia, Michel, Élisabeth, Thöle, Lena M., Studer, Anja S., Hasenfratz, Adam P., Schmid, Nicole, Butzin, Martin, Mazaud, Alain, Martínez-García, Alfredo, Szidat, Sönke, Jaccard, Samuel L.
• Other Authors: University of Bern, Columbia University New York, Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Utrecht University Utrecht, Climate Geochemistry Department Mainz, Max Planck Institute for Chemistry (MPIC), Max-Planck-Gesellschaft-Max-Planck-Gesellschaft, University of Basel (Unibas), Geological Institute ETH Zürich, Department of Earth Sciences Swiss Federal Institute of Technology - ETH Zürich (D-ERDW), Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich)- Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich), Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung (AWI), Oeschger Centre for Climate Change Research (OCCR), Institute of Earth Sciences Lausanne, Université de Lausanne = University of Lausanne (UNIL), Deutsche Forschungsgemeinschaft, DFG: GO 2294/2-1 Vetenskapsrådet, VR: VR-349-2012-6278 Max-Planck-Gesellschaft, MPG Bundesministerium für Bildung und Forschung, BMBF: 01LP1919A Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, SNF Deutsche Forschungsgemeinschaft, DFG, J.G. and S.L.J. (grants PP00P2_144811 and 200021_163003), A.S.S. (grant PBEZP2_145695), and A.M.-G. (grant PZ00P2_142424) acknowledge funding from the Swiss National Science Foundation. J.G. was also supported by a Global Research Fellowship from the German Research Foundation (DFG grant GO 2294/2-1), and a promotion grant from the Intermediate Staff Association of the University of Bern. A.M. and E.M. acknowledge financial support from the French Ministry of Research and Higher Education, the Swedish Research Council (grant VR-349-2012-6278), and the French National Institute of Sciences of the Universe at the French National Centre for Scientific Research. A.M.-G. further acknowledges funding from the Max Planck Society. M.B. is supported by the German Federal Ministry of Education and Research (BMBF), a Research for Sustainability initiative (FONA, www.fona.de) through the PalMod project (grant number: 01LP1919A). We thank the French Polar Institute Paul-Émile Victor, the captains and the crew of RV Marion Dufresne during the Indien-Sud cruises for their help retrieving sediment core MD12-3396CQ. We also thank the staff of the Laboratoire de Mesure du Carbone-14 of the ARTEMIS French National AMS facility, the Laboratory for Radiocarbon Analysis at the University of Bern (especially Michael Battaglia and Gary Salazar), Christopher Bronk Ramsey, Gulay Isguder, Fabien Dewilde, Derek Vance and Corey Archer for technical support. We are indebted to Sophie Hines, Ning Zhao, Jerry McManus, Jimin Yu, Andy Hogg, Veronica Tamsitt, Spencer Jones, Danny Sigman, and Wally Broecker for insightful discussions.
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDV]Life Sciences [q-bio]; Indian; Kerguelen; Kerguelen Island; Southern Ocean
• Online Access: https://hal.archives-ouvertes.fr/hal-03109190; https://hal.archives-ouvertes.fr/hal-03109190/document; https://hal.archives-ouvertes.fr/hal-03109190/file/s41467-020-20034-1.pdf; https://doi.org/10.1038/s41467-020-20034-1

International audience Past changes in ocean 14C disequilibria have been suggested to reflect the Southern Ocean control on global exogenic carbon cycling. Yet, the volumetric extent of the glacial carbon pool and the deglacial mechanisms contributing to release remineralized carbon, particularly from regions with enhanced mixing today, remain insufficiently constrained. Here, we reconstruct the deglacial ventilation history of the South Indian upwelling hotspot near Kerguelen Island, using high-resolution 14C-dating of smaller-than-conventional foraminiferal samples and multi-proxy deep-ocean oxygen estimates. We find marked regional differences in Southern Ocean overturning with distinct South Indian fingerprints on (early de-)glacial atmospheric CO2 change. The dissipation of this heterogeneity commenced 14.6 kyr ago, signaling the onset of modern-like, strong South Indian Ocean upwelling, likely promoted by rejuvenated Atlantic overturning. Our findings highlight the South Indian Ocean’s capacity to influence atmospheric CO2 levels and amplify the impacts of inter-hemispheric climate variability on global carbon cycling within centuries and millennia.