An assessment of Antarctic Circumpolar Current and Southern Ocean meridional overturning circulation during 1958–2007 in a suite of interannual CORE-II simulations

• Published in: Ocean Modelling
• Main Authors: Farneti, Riccardo, Downes, Stephanie M., Griffies, Stephen M., Marsland, Simon J., Behrens, Erik, Bentsen, Mats, Bi, Daohua, Biastoch, Arne, Böning, Claus W., Bozec, Alexandra, Canuto, Vittorio M., Chassignet, Eric, Danabasoglu, Gokhan, Danilov, Sergey, Diansky, Nikolay, Drange, Helge, Fogli, Pier Giuseppe, Gusev, Anatoly, Hallberg, Robert W., Howard, Armando, Ilicak, Mehmet, Jung, Thomas, Kelley, Maxwell, Large, William G., Leboissetier, Anthony, Long, Matthew, Lu, Jianhua, Masina, Simona, Mishra, Akhilesh, Navarra, Antonio, George Nurser, A.J., Patara, Lavinia, Samuels, Bonita L., Sidorenko, Dmitry, Tsujino, Hiroyuki, Uotila, Petteri, Wang, Qiang, Yeager, Steve G.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2015
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/30383/; https://oceanrep.geomar.de/id/eprint/30383/1/1-s2.0-S1463500315001183-main.pdf; https://doi.org/10.1016/j.ocemod.2015.07.009

Highlights: • We focus on ACC and Southern Ocean MOC during 1958–2007 in 17 CORE-II forced models. • Most CORE-II simulations are close to eddy saturation. • Most CORE-II simulations are far from showing signs of eddy compensation. • Constant in time or space k results in poor representation of mesoscale eddy effects. • MOC has larger sensitivity than ACC transport even in eddy saturated state. Abstract: In the framework of the second phase of the Coordinated Ocean-ice Reference Experiments (CORE-II), we present an analysis of the representation of the Antarctic Circumpolar Current (ACC) and Southern Ocean meridional overturning circulation (MOC) in a suite of seventeen global ocean–sea ice models. We focus on the mean, variability and trends of both the ACC and MOC over the 1958–2007 period, and discuss their relationship with the surface forcing. We aim to quantify the degree of eddy saturation and eddy compensation in the models participating in CORE-II, and compare our results with available observations, previous fine-resolution numerical studies and theoretical constraints. Most models show weak ACC transport sensitivity to changes in forcing during the past five decades, and they can be considered to be in an eddy saturated regime. Larger contrasts arise when considering MOC trends, with a majority of models exhibiting significant strengthening of the MOC during the late 20th and early 21st century. Only a few models show a relatively small sensitivity to forcing changes, responding with an intensified eddy-induced circulation that provides some degree of eddy compensation, while still showing considerable decadal trends. Both ACC and MOC interannual variabilities are largely controlled by the Southern Annular Mode (SAM). Based on these results, models are clustered into two groups. Models with constant or two-dimensional (horizontal) specification of the eddy-induced advection coefficient κ show larger ocean interior decadal trends, larger ACC transport decadal trends and no eddy compensation in the MOC. ...