The Southern Hemisphere oceans absorb the majority of the excess heat stored in the climate system due to anthropogenic greenhouse gas emissions. Here, we identify the dominant oceanic processes and associated atmospheric forcings which determine this heat uptake and redistribution in the Southern Hemisphere oceans. The Southern Hemisphere ocean warming centred at middle latitudes is a robust feature in the recent decade-long Argo observations, the longer historical observations over several decades, the CMIP5 historical simulations and projections for the 21^st Century. The enhanced mid-latitude ocean warming between 35°S and 50°S is located near the boundary between subtropical and subpolar gyres. For those models with climatological gyre boundary located more northward, the latitudes of largest warming are also biased more northward and there are larger poleward displacements of the gyre boundary in future projections. The largest surface heat flux into the ocean mainly occurs south of the enhanced ocean warming band, and about two thirds of the surface heat uptake south of 50°S is transferred northward by the ocean. The equatorward and downward subductions of the Southern Ocean surface warming and freshening signals result in spiciness signatures on density surfaces and deepening of the isopycnals as well. Under a theoretical framework by Bindoff and McDougall (1994), we associate the Southern Hemisphere ocean temperature and salinity changes with three distinctive processes, i.e., pure warming, pure freshening, and pure heave, which generally correspond to surface heat flux, freshwater flux, and wind forcing, respectively. Our analysis reveals how the Southern Hemisphere oceans absorb and redistribute the excess heat from anthropogenic warming, which plays a key role in the global energy budget and also influences regional sea-level rise.