Multi-centennial variability of the AMOC over the Holocene: A new reconstruction based on multiple proxy-derived SST records

• Published in: Global and Planetary Change
• Main Authors: Ayache, Mohamed, Swingedouw, Didier, Mary, Yannick, Eynaud, Frédérique, Colin, Christophe
• Other Authors: Environnements et Paléoenvironnements OCéaniques (EPOC), Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1 (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-École Pratique des Hautes Études (EPHE), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2018
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; North Atlantic
• Online Access: https://hal.science/hal-01901183; https://doi.org/10.1016/j.gloplacha.2018.08.016

International audience The Meridional Overturning Circulation (AMOC) is believed to have played a key role in climate variability over the Holocene, but the reconstruction of its variations remains limited by inconsistencies among different proxy records used. To circumvent this issue, we propose a new statistical method to reconstruct the AMOC variations based on multiple sources of information, i.e. 22 proxy records of annual Sea Surface Temperature (SST) compiled in the North Atlantic and covering the Holocene (HAMOC database). Our approach consists of isolating the main variability modes hidden in the Atlantic Ocean through principal component analysis (PCA) and then evaluating their link with the AMOC. To estimate the skill of our method, we use a pseudo-proxy approach applied to observational SST data covering the period 1870–2010, as well as simulations from a comprehensive climate model (IPSL-CM5A-LR) where the AMOC variations are known. In instrumental observations and most of the model simulations, the first mode of SST variations from the PCA analysis over the North Atlantic can be related with the external radiative forcing, while the second mode is reminiscent of the AMOC variability and of its signature on SST. When computed over the Holocene period using the HAMOC database, the first mode is indeed well correlated with the insolation changes, marked by a general cooling of the Northern Atlantic from 9 thousand years ago (ka). The second mode, that we consider here as a reconstruction of standardized AMOC variations following the pseudo-proxy analysis in the model simulations and in the observations, is in general agreement with a few independent reconstructions of the deep branch of the AMOC recorded in the North Atlantic. Based on this new AMOC index reconstruction, we highlight that the Early Holocene may have been associated with an AMOC enhancement, followed by a general weakening trend from around 6–7 ka up to 2 ka, in line with the major hydro-dynamical re-organization which occurred in ...