The Deep 3D Overturning Circulation in the Southern Ocean from ARGO Floats

The Southern Ocean fundamentally influences the Earth's climate through it's strong control over the Meridional Overturning Circulation. However, due to its complex dynamics and a lack of observations, the Southern Ocean overturning is poorly understood. Here we combine velocity and hydrographic data from drifting ARGO floats to estimate the overturning in the Southern Ocean and present detailed maps showing the strong regional variability of the overturning. We find that despite fluxes being strongly localised, alternating northward and southward fluxes effectively cancel, leaving a small residual that contributes to the total overturning. We show that regional variability of meridional fluxes has an influence on the dynamics of the large-scale overturning, finding that the mean geostrophic currents and eddy-PV fluxes that contribute to the total overturning both arise from flow/topography interaction. We conclude by noting that the influence of topography and `local' dynamics is vital for understanding the Southern Ocean overturning.