The Southern Ocean, which stretches from Antarctic ice-shelf cavities to the northern fringe of the Antarctic Circumpolar Current, is a key region for water mass formation and for the uptake, storage and lateral exchanges of heat, carbon and nutrients. At present, the Southern Ocean acts as a sink of anthropogenic carbon and heat and as a source of natural carbon, but its role in future climate conditions remains uncertain. Processes on the Antarctic continental shelf also need to be better understood in order to assess the ocean’s role in Antarctic ice loss and the resulting meltwater impact on sea level. To reduce these uncertainties, it is critical to investigate the mechanisms underlying Southern Ocean's internal variability and its response to external forcing. Recent advances in observational technology, data coverage, circulation theories, and numerical models are providing a deeper insight into the three-dimensional patterns of Southern Ocean change. This session will discuss the current state of knowledge and novel findings concerning Southern Ocean circulation, water mass formation and pathways, mixing and mesoscale dynamics, ocean-ice-atmosphere interactions, sea ice changes, inflow of warm water to ice shelf cavities, and biological productivity, as well as the heat, nutrient and carbon budgets. This includes work on all spatial scales (from local to basin-scale to circumpolar) and temporal scales (past, present and future). We particularly invite cross-disciplinary topics involving physical and biological oceanography, glaciology, or biogeochemistry.