The role of subpolar deep water formation and Nordic Seas overflows in simulated multidecadal variability of the Atlantic meridional overturning circulation

• Published in: Ocean Science
• Main Authors: Lohmann, Katja, Jungclaus, Johann H., Matei, Daniela, Mignot, Juliette, Menary, Matthew, B, Langehaug, H. R., Ba, Jin, Gao, Yongqi, Otterå, Odd Helge, Park, Wonsun, Lorenz, Stephan J.
• Other Authors: Max Planck Institute for Meteorology (MPI-M), Max-Planck-Gesellschaft, Processus de la variabilité climatique tropicale et impacts (PARVATI), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-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)-Université Paris Diderot - Paris 7 (UPD7)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), United Kingdom Met Office Exeter, Nansen Environmental and Remote Sensing Center Bergen (NERSC), Bjerknes Centre for Climate Research (BCCR), Department of Biological Sciences Bergen (BIO / UiB), University of Bergen (UiB)-University of Bergen (UiB), Helmholtz Centre for Ocean Research Kiel (GEOMAR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2014
• Subjects: [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph]; Denmark Strait; Iceland; Nordic Seas
• Online Access: https://hal.science/hal-01135681; https://hal.science/hal-01135681/document; https://hal.science/hal-01135681/file/os-10-227-2014.pdf; https://doi.org/10.5194/os-10-227-2014

International audience We investigate the respective role of variations insubpolar deep water formation and Nordic Seas overflows forthe decadal to multidecadal variability of the Atlantic merid-ional overturning circulation (AMOC). This is partly doneby analysing long (order of 1000 years) control simulationswith five coupled climate models. For all models, the max-imum influence of variations in subpolar deep water forma-tion is found at about 45◦N, while the maximum influenceof variations in Nordic Seas overflows is rather found at 55to 60◦N. Regarding the two overflow branches, the influenceof variations in the Denmark Strait overflow is, for all mod-els, substantially larger than that of variations in the over-flow across the Iceland–Scotland Ridge. The latter might,however, be underestimated, as the models in general do notrealistically simulate the flow path of the Iceland–Scotlandoverflow water south of the Iceland–Scotland Ridge. The in-fluence of variations in subpolar deep water formation is,on multimodel average, larger than that of variations in theDenmark Strait overflow. This is true both at 45◦N, wherethe maximum standard deviation of decadal to multidecadalAMOC variability is located for all but one model, and atthe more classical latitude of 30◦N. At 30◦N, variations in subpolar deep water formation and Denmark Strait overflowexplain, on multimodel average, about half and one-third re-spectively of the decadal to multidecadal AMOC variance.Apart from analysing multimodel control simulations, wehave performed sensitivity experiments with one of the mod-els, in which we suppress the variability of either subpolardeep water formation or Nordic Seas overflows. The sensitiv-ity experiments indicate that variations in subpolar deep wa-ter formation and Nordic Seas overflows are not completelyindependent. We further conclude from these experimentsthat the decadal to multidecadal AMOC variability north ofabout 50◦N is mainly related to variations in Nordic Seasoverflows. At 45◦N and south of this ...