Enhanced Carbonate Counter Pump and upwelling strengths in the Indian sector of the Southern Ocean during MIS 11

• Published in: Quaternary Science Reviews
• Main Authors: Brandon, Margaux, Duchamp-Alphonse, Stéphanie, Michel, Elisabeth, Landais, Amaelle, Isguder, Gulay, Richard, Patricia, Pige, Nicolas, Bassinot, Franck, Jaccard, Samuel L., Bartolini, Annachiara
• Other Authors: Université Paris Cité (UPCité), Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement (LGL-TPE), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Université de Lausanne = University of Lausanne (UNIL), Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), ANR-11-IDEX-0003,IPS,Idex Paris-Saclay(2011)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2022
• Subjects: Southern Ocean; Marine Isotope Stage 11; Coccolith; Planktonic foraminifera; Geochemistry; Carbonate Counter Pump; Upwelling; Atmospheric CO 2 concentration; [SDU]Sciences of the Universe [physics]
• Online Access: https://insu.hal.science/insu-03710162; https://insu.hal.science/insu-03710162/document; https://insu.hal.science/insu-03710162/file/99969.pdf; https://doi.org/10.1016/j.quascirev.2022.107556

International audience While numerous studies have highlighted the central role of Southern Ocean (SO) dynamics in modulating rapid increases in atmospheric CO 2 concentrations during deglaciations, fewer studies have yet focused on the impact of the Biological Carbon Pump - and more specifically the Carbonate Counter Pump (CCP) - in contributing to increase the CO 2 concentration in oceanic surface waters and thus, in the atmosphere. Here, we present micropaleontological (coccolith, planktonic foraminifera) and geochemical (CaCO 3 , Ca XRF , δ 13 C N. pachyderma ) constraints from sediment core MD04-2718 retrieved in the Polar Front Zone of the Indian Ocean covering the time interval spanning Marine Isotope Stage (MIS) 12 to MIS 10 (440,000-360,000 years). We compare our results with published records from the SO to reconstruct past changes in CCP and upwelling dynamics and understand their leverage on the ocean-atmosphere portioning of CO 2 . We demonstrate that the sharp increase in atmospheric pCO 2 during Termination V was likely associated with enhanced deep-water ventilation in the SO, that promoted the release of previously sequestered CO 2 to the ocean surface as the westerly wind belt and the frontal system migrated southwards. Enhanced CCP is observed later, during MIS 11, and is likely the consequence of higher sea surface temperature and higher nutrient availability due to the reinvigoration of SO upwelling leading to increased coccolith (and to a lesser degree, planktonic foraminifera) production and export. The low eccentricity signal recorded during MIS 11 might have additionally strengthened the CCP, exerting a specific control on Gephyrocapsa morphotypes. In addition to the strong global biological productivity and higher carbon storage on land, these synergistic mechanisms may have permitted to shape the distinctive 30 ka-long pCO 2 plateau characteristic of MIS 11.