The circulation of the Southern Ocean connects ocean basins, links the deep and shallow layers of the ocean, and has a strong influence on global ocean circulation, climate, biogeochemical cycles and the Antarctic Ice Sheet. Processes that act on local and regional scales, which are often mediated by the interaction of the flow with topography, are fundamental in shaping the large-scale, three-dimensional circulation of the Southern Ocean. Recent advances provide insight into the response of the Southern Ocean to future change and the implications for climate, the carbon cycle and sea-level rise.