North Atlantic simulations in Coordinated Ocean-ice Reference Experiments phase II (CORE-II). Part II: Inter-annual to decadal variability

• Published in: Ocean Modelling
• Main Authors: Danabasoglu, Gokhan, Yeager, Steve G., Kim, Who M., Behrens, Erik, Bentsen, Mats, Bi, Daohua, Biastoch, Arne, Bleck, Rainer, Böning, Claus W., Bozec, Alexandra, Canuto, Vittorio M., Cassou, Christophe, Chassignet, Eric, Coward, Andrew C., Danilov, Sergey, Diansky, Nikolay, Drange, Helge, Farneti, Riccardo, Fernandez, Elodie, Fogli, Pier Giuseppe, Forget, Gael, Fujii, Yosuke, Griffies, Stephen M., Gusev, Anatoly, Heimbach, Patrick, Howard, Armando, Ilicak, Mehmet, Jung, Thomas, Karspeck, Alicia R., Kelley, Maxwell, Large, William G., Leboissetier, Anthony, Lu, Jianhua, Madec, Gurvan, Marsland, Simon J., Masina, Simona, Navarra, Antonio, Nurser, A.J. George, Pirani, Anna, Romanou, Anastasia, Salas y Mélia, David, Samuels, Bonita L., Scheinert, Markus, Sidorenko, Dmitry, Sun, Shan, Treguier, Anne-Marie, Tsujino, Hiroyuki, Uotila, Petteri, Valcke, Sophie, Voldoire, Aurore, Wang, Qiang, Yashayaev, Igor
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2016
• Subjects: Labrador Sea; North Atlantic; North Atlantic oscillation; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/30679/; https://oceanrep.geomar.de/id/eprint/30679/1/1-s2.0-S1463500315002231-main.pdf; https://doi.org/10.1016/j.ocemod.2015.11.007

Highlights: • Inter-annual to decadal variability in AMOC from CORE-II simulations is presented. • AMOC variability shows three stages, with maximum transports in mid- to late-1990s. • North Atlantic temporal variability features are in good agreement among simulations. • Such agreements suggest variability is dictated by the atmospheric data sets. • Simulations differ in spatial structures of variability due to ocean dynamics. Simulated inter-annual to decadal variability and trends in the North Atlantic for the 1958–2007 period from twenty global ocean – sea-ice coupled models are presented. These simulations are performed as contributions to the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II). The study is Part II of our companion paper (Danabasoglu et al., 2014) which documented the mean states in the North Atlantic from the same models. A major focus of the present study is the representation of Atlantic meridional overturning circulation (AMOC) variability in the participating models. Relationships between AMOC variability and those of some other related variables, such as subpolar mixed layer depths, the North Atlantic Oscillation (NAO), and the Labrador Sea upper-ocean hydrographic properties, are also investigated. In general, AMOC variability shows three distinct stages. During the first stage that lasts until the mid- to late-1970s, AMOC is relatively steady, remaining lower than its long-term (1958–2007) mean. Thereafter, AMOC intensifies with maximum transports achieved in the mid- to late-1990s. This enhancement is then followed by a weakening trend until the end of our integration period. This sequence of low frequency AMOC variability is consistent with previous studies. Regarding strengthening of AMOC between about the mid-1970s and the mid-1990s, our results support a previously identified variability mechanism where AMOC intensification is connected to increased deep water formation in the subpolar North Atlantic, driven by NAO-related surface fluxes. The simulations ...