Atlantic Meridional Overturning Circulation and δ 13 C Variability During the Last Interglacial

• Published in: Paleoceanography and Paleoclimatology
• Main Authors: Kessler, A., Bouttes, N., Roche, Didier M., Ninnemann, U., Galaasen, E., Tjiputra, J.
• Other Authors: Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), 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), Modélisation du climat (CLIM), 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)-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), Vrije Universiteit Amsterdam Amsterdam (VU), 239965 Norges ForskningsrÃ¥d: 254964, We thank the two anonymous referees for their positive and constructive comments, which helped to clarify the manuscript. We also thank the Editor Stephen Barker for the time he dedicated in processing our manuscript and his additional feedback. This work was supported by the Research Council of Norway funded project THRESHOLDS (254964) and ORGANIC (239965) and Bjerknes Centre for Climate Research project BIGCHANGE. We acknowledge the Norwegian Metacenter for Computational Science and Storage Infrastructure (Notur/Norstore) projects nn1002k and ns1002k for providing the computing and storing resources essential for this study. The authors declare no conflict of interest.The model data are available on the Norwegian Research Data Archive server (https://doi.org/10.11582/2019.00037 Kessler,).
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; Greenland; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://hal.archives-ouvertes.fr/hal-02936152; https://hal.archives-ouvertes.fr/hal-02936152/document; https://hal.archives-ouvertes.fr/hal-02936152/file/2019PA003818.pdf; https://doi.org/10.1029/2019PA003818

International audience The Atlantic Meridional Overturning Circulation (AMOC) is thought to be relatively vigorous and stable during Interglacial periods on multimillennial (equilibrium) timescales. However, recent proxy (δ 13 C benthic) reconstructions suggest that higher frequency variability in deep water circulation may have been common during some interglacial periods, including the Last Interglacial (LIG, 130-115 ka). The origin of these isotope variations and their implications for past AMOC remain poorly understood. Using iLOVECLIM, an Earth system model of intermediate complexity (EMIC) allowing the computation of δ 13 C DIC and direct comparison to proxy reconstructions, we perform a transient experiment of the LIG (125-115 ka) forced only by boundary conditions of greenhouse gases and orbital forcings. The model simulates large centennial-scale variations in the interior δ 13 C DIC of the North Atlantic similar in timescale and amplitude to changes resolved by high-resolution reconstructions from the LIG. In the model, these variations are caused by changes in the relative influence of North Atlantic Deep Water (NADW) and southern source water (SSW) and are closely linked to large (∼50%) changes in AMOC strength provoked by saline input and associated deep convection areas south of Greenland. We identify regions within the subpolar North Atlantic with different sensitivity and response to changes in preformed δ 13 C DIC of NADW and to changes in NADW versus SSW influence, which is useful for proxy record interpretation. This could explain the relatively large δ 13 C gradient (∼0.4%0) observed at ∼3 km water depth in the subpolar North Atlantic at the inception of the last glacial.