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

Julia Gottschalk (1, 2) , Elisabeth Michel (3, 4) , Lena M. Thöle (1, 5) , Anja S. Studer (6, 7) , Adam P. Hasenfratz (1, 8) , Nicole Schmid (1) , Martin Butzin (9) , Alain Mazaud (3, 10) , Alfredo Martínez-García (6) , Sönke Szidat (11) , Samuel L. Jaccard (1, 12)

1 UNIBE - Universität Bern / University of Bern
2 Columbia University [New York]
3 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
4 PALEOCEAN - Paléocéanographie
5 Universiteit Utrecht / Utrecht University [Utrecht]
6 Climate Geochemistry Department [Mainz]
7 Unibas - Université de Bâle = University of Basel = Basel Universität
8 Geological Institute [ETH Zürich]
9 AWI - Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine
10 CLIMAG - Climat et Magnétisme
11 OCCR - Oeschger Centre for Climate Change Research
12 Institute of Earth Sciences [Lausanne]

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.

Domaines: Sciences du Vivant [q-bio]

Julia Gottschalk, Elisabeth Michel, Lena M. Thöle, Anja S. Studer, Adam P. Hasenfratz, et al.. Glacial heterogeneity in Southern Ocean carbon storage abated by fast South Indian deglacial carbon release. Nature Communications, 2020, 11 (1), ⟨10.1038/s41467-020-20034-1⟩. ⟨hal-03109190⟩