The Formation of Southern Ocean Gyres

In an inviscid, barotropic ocean, flow is constrained to follow f/h contours. In the North Atlantic, f/h contours are blocked via meridional coastlines to the east and west, which permits the curl imparted by the wind to realise the North Atlantic gyre. The Southern Ocean consists of the composition of the Antarctic Circumpolar Current and a series of sub-polar gyres. Yet, these gyres cannot necessarily be explained by the existence of notable meridional coastlines. We explore the processes that enable Southern Ocean gyres in the absence of meridional walls. We utilise a series of barotropic idealised channel models with varying topographies and find that particular geometries of submarine ridges are key in supporting Southern Ocean gyres. In particular, we find that ridges of a certain steepness are required to block the Antarctic Circumpolar Current and permit gyres. We suggest that the combination of closely-spaced f/h contours and eddy viscosity can block flow, making a meridional ridge the analogue of a continent in terms of gyre dynamics.