## 3 Results  
### Time-Mean Eddy Propagation  
The intensity of eddy variability in the South Atlantic is demonstrated by the standard deviation of SSH (Figure 1). The most energetic regions are associated with the Agulhas Retroflection, the Agulhas Return Current, and the Brazil-Malvinas Confluence. Elevated eddy energy is also observed along the ACC, especially near the Drake Passage and between 30-40\({}^{\circ}\)E. The time-mean speed and direction of the horizontal movement of SSH patterns associated with transient eddy variability estimated with the OF are displayed in Figure 3. Like the space-time correlation analysis, the OF provides a description of the transient eddy propagation velocity in the Eulerian frame of reference. The method reveals the relatively swift propagation of eddies along the Agulhas Current flowing along the southeastern coast of Africa with velocities of 5-7 km/day. Upon reaching the Agulhas Retroflection, the eddy motion becomes weak, and no eddies tend to follow the eastward Agulhas Return Current. Once new eddies are formed by the Agulhas Retroflection (around 20\({}^{\circ}\)E, 40\({}^{\circ}\)S), they start propagating westward-northwestward with a speed of 4-5 km/day. There is no significant northward eddy propagation along the relatively weak Benguela Current that flows along the southwestern coast of Africa. Nevertheless, eddies are generated near the eastern boundary and propagate westward as Rossby waves in a vast region north of 35\({}^{\circ}\)S. This region represents the northern part of the South Atlantic subtropical gyre. The mesoscale variability towards the equator becomes weak (Figure 1), and westward-propagating signals have smaller amplitudes compared to signals at higher latitudes. The speeds of westward propagation increase from 2-3 km/day at 33-35\({}^{\circ}\)S to 5-7 km/day at 10-15\({}^{\circ}\)S (Figure 3). There is a remarkable transition between the coherent basin-wide westward propagation north of 33\({}^{\circ}\)S and the region south of this latitude and to the east of the Argentine Basin with a very weak westward flow. This meridional contrast is apparently the result of the mean-flow effect on eddy propagation. As illustrated by the contours of the mean dynamic topography (Figure 1), the latitude of 33\({}^{\circ}\)S divides the subtropical gyre in two parts: the northern part with the general northwestern direction of the surface flow and the southern part with the eastward direction of surface currents. This means that the mean flow reinforces the westward propagation north of 33\({}^{\circ}\)S and compensates for the westward propagation south of this latitude. Near the western boundary, there is a well-defined band of southwestward velocities of up to 5 km/day between 25\({}^{\circ}\)S and 40\({}^{\circ}\)S associated with the Brazil Current. Further south, along the Argentine coast, the northward-flowing Malvinas Current is also a pathway of eddy movement, with eddy propagation velocities reaching 7 km/day. The bottom topography plays an important role in constraining the eddy motion, especially in the Southern Ocean where stratification is weak and the vertical extent of eddies can reach the bottom (e.g., [23]). The Argentine Basin represents another good example of eddy propagation steered by the bottom topography (Figure 4). The Southern Ocean eddies enter the basin from the Scotia Sea, mainly through channels in the North Scotia Ridge,  
Figure 3: The time–mean vectors of eddy propagation velocity obtained with the optical flow method. The color shading indicates the absolute speed in km per day. and follow the continental shelf break. At about 40\({}^{\circ}\)S, eddies carried by the northward Malvinas Current collide with those carried by the southward Brazil Current. This process forms the highly energetic Brazil-Malvinas Confluence--the region with the high standard deviation of SSH (Figure 1) but very slow eddy propagation (Figures 3 and 4).