Spatial and temporal variability of the Brazil current path: Diagnostics from satellite-derived altimetry and a global reanalysis product

Abstract

The Brazil Current (BC) exhibits significant spatial and temporal variability, forming meanders and eddies off Cabo de São Tomé (22°S) and Cabo Frio (24°S) due to baroclinic instability and topographic influences. The BC presents considerable annual and interannual transport variability, affecting its trajectory and cross-sectional attributes. However, the connection between temporal variations in stream structure and its spatial distribution is often overlooked. This study investigates the long-term spatio-temporal variations of the position and structure of the BC between 21°S and 28°S, along the south-southeast Brazilian coast, using 28 years of altimetry and global reanalysis data. Results indicate that the width, depth, core velocity, and position of the BC are sensitive to transport changes, depending on latitude. The current path is more influenced by topographic gradients north of 24°S and less so to the south. At this latitude, the energy exchange between the mean flow and eddies correlates with transport increase, leading to a rise in downstream eddy kinetic energy (EKE) after two months. The BC intensification and path changes are influenced by broader phenomena, including the position and strength of the South Atlantic Subtropical Gyre, the wind stress associated with coastal upwelling (lagged by two months), and El Niño events (lagged by eight months). Rotated Empirical Orthogonal Function analysis at two cross-stream sites near Cabo Frio confirms that variations in strength and transport of the BC are key factors driving velocity variance, along with the growth of eddies due to baroclinic instability and the propagation of continental shelf waves.