Brazil Current surface circulation and energetics observed from drifting buoys

The southwestern Atlantic mean surface circulation, its associated variability and energetics are studied through the analysis of 13 years of surface drifter data binned onto a 0.5 degrees x 0.5 degrees grid. Special attention is given to the following three main regional features of the domain: the Brazil Current, the Malvinas Current, and the Brazil-Malvinas Confluence. For the western boundary currents, the mean field reveals velocities larger than 45 cm s(-1), associated with high levels of variability (standard deviation of more than 15 cm s(-1)), while the highest values of standard deviation are found in the Brazil-Malvinas Confluence (> 25 cm s(-1)). Conversely, over most of the domain the mean velocities found (20-30 cm s(-1)) and associated standard deviations (< 15 cm s(-1)) are generally lower. High values of kinetic energy of the mean flow per unit mass (265-1000 cm(2) s(-2)) are estimated in the western boundary currents and their extensions. Eddy kinetic energy along the main jet of the western boundary currents is generally lower than the kinetic energy of the mean flow, except for some areas along the Brazil Current path. In contrast, the Brazil-Malvinas Confluence reveals eddy kinetic energy levels comparable or larger (similar to 2500 cm(2) s(-2)) than the mean kinetic energy. Away from the boundary, most of the kinetic energy of the surface circulation is in the eddy field. Furthermore, the analysis of the kinetic energy conversion term suggests the presence of barotropic instabilities along the Brazil Current. Over most of the Brazil Current core, the kinetic energy conversion term points from the mean to eddy kinetic energy.