The death of Agulhas rings and the emergence of a modified Brazil Current

Florida State University, Tallahassee FL

Investigators

Abstract

The western South Atlantic circulation is strongly affected by rings and western boundary currents. It has been surmised that the drift of the Confluence Zone is in large part due to variations in the transports of the upstream currents approaching the confluence from the north and south (i.e., the Brazil and Malvinas currents). The project investigates the influence that Agulhas rings may have on the Brazil Current variability. Although Agulhas rings lose much of their strength and energy as they cross the entire South Atlantic, they are so large and energetic to begin with that they are still very important to the energy balance when they reach the Brazil Current and blend into it. The absorption of Agulhas rings upstream by the Brazil Current is a nonlinear process and the main goal is to determine the influence of Agulhas rings on the temporal variation of the Brazil Current using a combination of analytical models and process-oriented numerical simulations. Intellectual merit: New observations using satellite data vividly illustrate the importance of the above eddy-current interaction problem. The problem received limited attention in the past primarily because it is a very difficult nonlinear problem. Dr. Nof's previous work on the very same subject has shown that it is not a simple matter to determine whether the rings would strengthen or weaken the Brazil Current. He and collaborators have now developed analytical and numerical techniques, which should, for the first time, enable us to give the answer to the above question. Broader impacts: The study would benefit society by (i) the education of a new Ph.D., and (ii) providing a continuous series of lectures and demonstrations to unprivileged kids at the Florida Sheriffs Youth Branch in Live Oak.