Dominated by the Antarctic Circumpolar Current (ACC), the vast Southern Ocean can influence large-scale surface climate features on various time scales. Its climatic relevance stems in part from being the region where most of the transformation of the World Ocean’s water masses occurs. In climate change experiments that simulate greenhouse gas-induced warming, Southern Ocean air-sea heat fluxes and three-dimensional circulation patterns make it a region where much of the future oceanic heat uptake occurs, though the magnitude of that heat storage is one of the larger sources of uncertainty associated with the transient climate response in such model projections. These links are explored here in a coupled model context by analyzing a suite of experiments associated with the Intergovernmental Panel on Climate Change’s Fourth Assessment Report. The potential impacts of the predicted change in Southern Ocean sea-ice extent, concentration and seasonality, water masses, ocean circulation and frontal positions on heat, carbon and marine ecosystems are examined.