We report on a numerical investigation of three-dimensional circulation in the Southern Ocean over a domain extending from Antarctica to -36 degrees latitude and from the sea surface to a depth of 500 metres. The high latitude Southern Ocean is a region low in measurements but important for climatic and biological applications. Our investigation is based upon velocity data simulated by a state-of-the-art 1/4 degree resolution global ocean model. We construct an approximate transfer operator from the velocity data and identify dominant coherent circulation structures from eigenmodes of the transfer operator.