Sensitivity of the Atlantic meridional overturning circulation to model resolution in CMIP6 HighResMIP simulations and implications for future changes

• Published in: Journal of Advances in Modeling Earth Systems
• Main Authors: Roberts, Malcolm J., Jackson, Laura C., Roberts, Christopher D., Meccia, Virna, Docquier, David, Koenigk, Torben, Ortega Montilla, Pablo, Moreno‐Chamarro, Eduardo, Bellucci, Alessio, Coward, Andrew, Drijfhout, Sybren, Exarchou, Eleftheria, Gutjahr, Oliver, Hewitt, Helene, Iovino, Doroteaciro, Lohmann, Katja, Putrasahan, Dian Putrasahan, Schiemann, Reinhard, Seddon, Jon, Terray, Laurent, Xu, Xiaobiao, Zhang, Qiuying, Chang, Ping, Yeager, Stephen G., Castruccio, Frederic S., Zhang, Shaoqing, Wu, Lixin
• Other Authors: Barcelona Supercomputing Center
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2020
• Subjects: Àrees temàtiques de la UPC::Enginyeria agroalimentària::Ciències de la terra i de la vida::Climatologia i meteorologia; Ocean circulation; Northern Hemisphere; Climatic changes; Oceanic circulation; AMOC; Model resolution; Atlantic; Future projection; Northern Hemisphere climate; Multimodel; Simulació per ordinador; Climatologia; Canvis climàtics; North Atlantic
• Online Access: http://hdl.handle.net/2117/328534; https://doi.org/10.1029/2019MS002014

A multimodel, multiresolution ensemble using Coupled Model Intercomparison Project Phase 6 (CMIP6) High Resolution Model Intercomparison Project (HighResMIP) coupled experiments is used to assess the performance of key aspects of the North Atlantic circulation. The Atlantic Meridional Overturning Circulation (AMOC), and related heat transport, tends to become stronger as ocean model resolution is enhanced, better agreeing with observations at 26.5°N. However, for most models the circulation remains too shallow compared to observations and has a smaller temperature contrast between the northward and southward limbs of the AMOC. These biases cause the northward heat transport to be systematically too low for a given overturning strength. The higher‐resolution models also tend to have too much deep mixing in the subpolar gyre. In the period 2015–2050 the overturning circulation tends to decline more rapidly in the higher‐resolution models, which is related to both the mean state and to the subpolar gyre contribution to deep water formation. The main part of the decline comes from the Florida Current component of the circulation. Such large declines in AMOC are not seen in the models with resolutions more typically used for climate studies, suggesting an enhanced risk for Northern Hemisphere climate change. However, only a small number of different ocean models are included in the study. M. J. R., C. D. R., V. M., D. D., T. K., P. O., E. M.‐C., A. B., S. D., E. E., O. G., D. I., K. L., D. P., R. S., J. S., and L. T. acknowledge PRIMAVERA funding received from the European Commission under Grant Agreement 641727 of the Horizon 2020 research program. M. R., L. C. J., and H. H. were supported by the Met Office Hadley Centre Climate Programme funded by BEIS and Defra (GA01101). R. S. acknowledges funding from the National Environmental Research Council (NERC). A. C. acknowledges funding from the ACSIS project that is supported by the Natural Environment Research Council (Grant NE/N018044/1). XX acknowledges funding ...