Three Agulhas rings observed during the Benguela Current experiment

A field program to study the circulation of the Benguela Current and its ex tension into the southeastern Atlantic Ocean has completed the survey and i nstrument deployment phase. We report here new observations of three Agulha s rings north and west of Cape Town, South Africa. Three mesoscale anticycl onic rings initially identified by means of TOPEX/POSEIDON altimetry were s urveyed with expendable bathythermographs, conductivity-temperature-depth-o xygen profiles, direct current measurements from a lowered acoustic Doppler current profiler, a hull-mounted acoustic Doppler current profiler, and sa tellite-tracked surface drifters. Characteristics of the rings are presente d, and their origins are discussed. Two are typical Agulhas rings surveyed at different times after their generation; the third Agulhas ring has an an omalous water mass structure whose most likely origin is the Subtropical Fr ont.