Eastern Atlantic deep-water circulation and carbon storage inferred from neodymium and carbon isotopic compositions over the past 1.1 million years

• Published in: Quaternary Science Reviews
• Main Authors: Kazuyo, Tachikawa, Rapuc, William, Vidal, Laurence, Dubois-Dauphin, Quentin, Westerhold, Thomas, Guihou, Abel, Bickert, Torsten, Pérez-Asensio, José, Deschamps, Pierre, Skonieczny, Charlotte
• Other Authors: Centre Européen de Recherche et d'Enseignement des Géosciences de l'Environnement (CEREGE), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Collège de France (CdF (institution))-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Environnements, Dynamiques et Territoires de Montagne (EDYTEM), Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS), Center for Marine Environmental Sciences Bremen (MARUM), Universität Bremen, Géosciences Paris Saclay (GEOPS), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Southern Ocean; Ice Sheet; North Atlantic; Sea ice
• Online Access: https://hal.science/hal-03152875; https://hal.science/hal-03152875/document; https://hal.science/hal-03152875/file/Tachikawa21QSR_copy.pdf; https://doi.org/10.1016/j.quascirev.2020.106752

International audience The Mid-Pleistocene transition (MPT; 1200 to 800 thousand years, kyr) is marked by the shift from 41-kyr to 100-kyr interglacial-glacial cyclicity without substantial change in the astronomical forcing. This change in climate response relied on internal feedback processes including interaction between ice sheet/sea ice, ocean circulation and the carbon cycle. It was suggested that a major perturbation of global oceanic carbon chemistry occurred at around 900 ka (Marine Isotope Stage, MIS, 24-22) although the mechanism responsible for the change is still to be elucidated. To investigate the link between the Atlantic Meridional Overturning Circulation (AMOC) and oceanic carbon storage for the past 1100 kyr, we combined neodymium isotopic composition (Nd-143/Nd-144 or epsilon(Nd)) recorded in foraminiferal authigenic fractions with epibenthic foraminiferal delta C-13 and delta O-13 from two cores in the North- and South-east Atlantic Ocean. Glacial/interglacial eNd amplitude is smaller before the 900-ka event than after the event. The 900-ka event is marked by increase in seawater epsilon(Nd) at both sites. These observations are consistent with previous studies, suggesting basin-wide epsilon(Nd) changes. Combined with existing data, these new results reveal a persistent meridional gradient of seawater epsilon(Nd) in the Atlantic Ocean over the past 1100 kyr. By comparing the reconstructions with numerical modelling results, we propose that weaker AMOC and changes in Nd sources to the North Atlantic were the main reasons for the observed eNd shift at the 900-ka event in relation to the evolution of the Northern hemisphere cryosphere. The influence of enhanced Southern Ocean overturning circulation on eNd values was estimated to be minor. Seawater epsilon(Nd) and benthic delta C-13 relationship for the whole study period indicates the presence of carbon-rich glacial deep water (>3000 m) in the North and the South Atlantic, in particular at MIS 22 and 24. This suggests that, in addition to ...