Why is the stability of the Agulhas Current geographically bi-modal?

The Agulhas Current, the largest western boundary current of the southern hemisphere, becomes fully constituted along the eastern coast of South Africa at about 25°S, from where is flows poleward along this coast. South of the continent it retroflects with most of its water being returned to the Indian Ocean in the Agulhas Return Current whereas the rest is injected into the South Atlantic by the shedding of Agulhas Rings at the retroflection point of the current. The flow of the Agulhas Current between its initiation and retroflection points can be divided into two distinct segments by trajectorial characteristics: a northern and a southern Agulhas Current. The path of the northern Current is exceptionally stable, whereas the southern Current meanders in a way more characteristic of western boundary currents. By applying a two-layer, linear, stability theory that specifically considers the effect of a lateral boundary (i.e. the shelf-break) on the stability of an adjacent current flowing parallel to it, we show that the stability of the northern Current is attributable to its proximity to the African land mass, which is located only one tenth of the internal radius of deformation west of the current. By comparison, the southern Current on average flows at a distance of over nine-tenths of the internal radius of deformation from the shelf break, where according to the theory the instability is over twice that of the northern Current.