Multi-decadal adjustment of the buoyancy and eddy fields in an idealized model of the Southern Ocean

The response of the Southern Ocean (SO) to decadal wind stress variability is heavily influenced by the behavior of both the wind-driven and the eddy-induced meridional overturning circulation (MOC). The relative strength of these two mechanisms affects the net meridional transport of heat, carbon, and other tracers at the latitudes of the Antarctic Circumpolar Current (ACC). In order to better understand the response of the SO density structure, mean flow, and eddy fields to an increase in wind stress, we perform centennial-scale step response experiments in both coarse and eddy-permitting simulations with idealized geometry and forcing. We investigate the mechanisms involved in equilibration, such as the spin-up of subtropical gyres, shifts in the position and intensity of the ACC, the generation of mesoscale eddies, and inter-hemispheric communication. Our results suggest that the adjustment process of the SO density structure occurs on multi-decadal to centennial timescales, such that it may be difficult to detect significant changes in the tilt of isopycnals with the few available decades of hydrographic observation. Our results provide a new interpretation for recent observations and highlight the importance of the interaction between regional SO dynamics and global ocean circulation.