Pantropical Indo-Atlantic temperature gradient modulates multi-decadal AMOC variability in models and observations

• Published in: npj Climate and Atmospheric Science
• Main Authors: Ferster, Brady, Borchert, Leonard F., Mignot, Juliette, Menary, Matthew, B, Cassou, Christophe, Fedorov, Alexey
• Other Authors: Yale University New Haven, 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)-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)-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)), 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)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Universität Hamburg (UHH), Met Office Hadley Centre (MOHC), United Kingdom Met Office Exeter, Centre Européen de Recherche et de Formation Avancée en Calcul Scientifique (CERFACS), ANR-18-MPGA-0001,ARCHANGE,Changement climatique et Arctique et circulation océanique globale(2018), ANR-20-ERC9-0001,HARMONY,HARMONY : Exploiter la puissance des nouveaux modèles climatiques pour la société(2020)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2023
• Subjects: [SDE]Environmental Sciences; North Atlantic
• Online Access: https://hal.science/hal-04249826; https://hal.science/hal-04249826/document; https://hal.science/hal-04249826/file/s41612-023-00489-x.pdf; https://doi.org/10.1038/s41612-023-00489-x

International audience Abstract Interconnections between ocean basins are recognized as an important driver of climate variability. Recent modeling evidence suggests that the North Atlantic climate can respond to persistent warming of the tropical Indian Ocean sea surface temperature (SST) relative to the rest of the tropics ( rTIO ). Here, we use observational data to demonstrate that multi-decadal changes in pantropical ocean temperature gradients lead to variations of an SST-based proxy of the Atlantic Meridional Overturning Circulation ( AMOC ). The largest contribution to this temperature gradient- AMOC connection comes from gradients between the Indian and Atlantic Oceans. The rTIO index yields the strongest connection of this tropical temperature gradient to the AMOC . Focusing on the internally generated signal in three observational products reveals that an SST-based AMOC proxy index has closely followed low-frequency changes of rTIO temperature with about 26-year lag since 1870. Analyzing the pre-industrial control simulations of 44 CMIP6 climate models shows that the AMOC proxy index lags simulated mid-latitude AMOC variations by 4 ± 4 years. These model simulations reveal the mechanism connecting AMOC variations to pantropical ocean temperature gradients at a 27 ± 2 years lag, matching the observed time lag in 28 out of the 44 analyzed models. rTIO temperature changes affect the North Atlantic climate through atmospheric planetary waves, impacting temperature and salinity in the subpolar North Atlantic, which modifies deep convection and ultimately the AMOC. Through this mechanism, observed internal rTIO variations can serve as a multi-decadal precursor of AMOC changes with important implications for AMOC dynamics and predictability.