Disentangling internal and external contributions to Atlantic multidecadal variability over the past millennium

• Published in: Geophysical Research Letters
• Main Authors: Fang, Shih-Wei, Khodri, Myriam, Timmreck, Claudia, Zanchettin, Davide, Jungclaus, Johann
• Other Authors: Max-Planck-Institut für Meteorologie (MPI-M), Max-Planck-Gesellschaft, Océan et variabilité du climat (VARCLIM), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-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)-École polytechnique (X), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Institut Polytechnique de Paris (IP Paris)-Institut Polytechnique de Paris (IP Paris)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), University of Ca’ Foscari Venice, Italy, ANR-17-EURE-0006,IPSL-CGS,IPSL Climate graduate school(2017)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; North Atlantic
• Online Access: https://hal.science/hal-03530833; https://hal.science/hal-03530833v1/document; https://hal.science/hal-03530833v1/file/Geophysical%20Research%20Letters%20-%202021%20-%20Fang%20-%20Disentangling%20Internal%20and%20External%20Contributions%20to%20Atlantic%20Multidecadal.pdf; https://doi.org/10.1029/2021gl095990

International audience The Atlantic multidecadal variability (AMV) modulates the North Atlantic surface ocean variability and affects decadal climates over the globe; its underlying mechanisms remain, however, under debate. In this study, we use a multi-model ensemble of transient past-millennium (850–1849) and unperturbed preindustrial control simulations contributing to the paleoclimate modeling intercomparison project—phase 4 (PMIP4) to decompose the AMV signal into the internal AMV and the external signal. The internal component of AMV exhibits no robust behavior across simulations during periods of major forcing such as strong volcanic eruptions, whereas the external forced temperature responds to volcanic eruptions with an immediate radiative cooling followed, in some simulations, by a sequence of damped multidecadal oscillations. The internal component tightly relates with the Atlantic meridional overturning circulation (AMOC) and dominates the fluctuations of AMV; whereas the external signal has limited impacts on AMOC and explains ∼25% of the AMV variance over the past millennium.