Large-amplitude Rossby lee waves are observed in the Southern Ocean of an ocean general circulation model. These waves result in a reduced ability of an associated coupled ocean-atmosphere general circulation model to model the observed sea ice distribution around Antarctica. To understand this behavior, Rossby lee waves within a meridionally sheared eastward directed ocean current are investigated theoretically. It is found that shearing the current results in a significant asymmetry in the lee wave field, the amplitude of which increases linearly downstream. In the regions where the meridional gradient of the shear exceeds β but is of opposite sign, there are no Rossby lee waves. Waves are trapped to the region where β dominates. Investigation of the ocean general circulation model shows that the meridional shear does not exceed β. However, the meridional gradient of Ertel's potential vorticity, a more appropriate quantity in a continuously stratified ocean general circulation model, is negative as required. ¿ 1999 American Geophysical Union <