Topographic control of Southern Ocean gyres and the Antarctic Circumpolar Current

The large-scale circulation of the Southern Ocean is determined by the underlying topography. The topography of the Southern Ocean is characterised by a series of ridges and basins. This thesis investigates the role of the submarine ridges in the steering of the Antarctic Circumpolar Current and the formation of Southern Ocean gyres. This investigation is carried out through the use of idealised barotropic numerical simulations. Each mechanism has been analysed in terms of both momentum and vorticity. It is shown that the appearance and strength of Southern Ocean gyres are highly dependent on the gradients in topography along their western boundary. Gyres only appear when topographic gradients are sufficiently high along the eastern flank of a meridional ridge. It is also found that the volume transport of the Antarctic Circumpolar Current is dependent on the geometric properties of ridges. The width, meridional asymmetry and meridional alignment of a ridge all affect volume transport.