The majority of mesoscale eddies in the ocean have been shown to be highly nonlinear. This is important, because as such they are capable of trapping water in their interior as they propagate. By transporting momentum, heat, mass and the chemical constituents of seawater, they can contribute to water mass distributions and ocean biology. Here, we use satellite observations of sea surface height and sea surface temperature to specifically focus on the influence of eddies on the distribution of fronts in Eastern Boundary Currents. Previous studies have shown that the area near the coast with high frontal activity broadens during the upwelling season, and several mechanisms have been suggested to explain that phenomena. Satellite observations and idealized numerical model simulations are used to demonstrate that nonlinear eddies play an important role in that process. Model simulations are further used to investigate the influence of the coupling between eddies and winds on upwelling and SST frontal variability in Eastern Boundary Currents.