The Brazil Current mesoscale eddies: Altimetry-based characterization and tracking

Abstract

The Brazil Current (BC) has been reported as eddy-dominated, with recurrent formation of eddies and meanders along the margin. In this study, we characterize the variability of mesoscale eddies associated with this western boundary current from its origin site to the southern end of the South Brazil Bight (∼15°S – ∼28°S). We apply an eddy detection method on a 27-year multi-satellite altimetry product. We offer a first quantitative estimate of the eddy dominance along the BC path. On average, there are no major differences in the eddy parameters between cyclones and anticyclones. However, north of the 20∘S, the eddies are larger and slower in swirling speed, whereas the opposite patterns occur with the eddies south of 20∘S. Although there is no notable seasonality in the eddy formation in general, there is a tendency to form cyclones in the vicinity of capes and bights of the southeastern Brazilian shelfbreak. In contrast, there is a scattered horizontal distribution of anticyclone formation for most of the BC domain throughout the seasons. The Vitória, Cape São Tomé and Cape Frio Eddies account for ∼30% of the total cyclones in the analysis. The Vitória Eddy (VE) tends to be more often generated in austral autumn, the season of lowest kinetic energy and volume transport of the BC. The Cape São Tomé Eddy (CSTE) and Cape Frio Eddy (CFE) are more energetic in the seasons of the BC’s highest volume transport (austral spring and summer). Despite most of the eddies being described as quasi-stationary in the current literature, our analysis of the eddy trajectories showed that the VE, CFE and CSTE can detach and migrate off of the mean BC axis. We estimate that ∼30% of the CFE events pinch off and migrate southwestward. The CSTE and CFE presented the highest growth rates (0.08 and 0.07 day−1 , respectively) of the recurrent eddies. These results provide a first robust characterization of the BC mesoscale eddies.