Investigation of Brazil Current rings in the confluence region

TOPEX/Poseidon‐derived along track SHA, climatological temperature, and salinity fields were used within a two‐layer scheme to estimate the depth of the 8°C isotherm in the southwestern Atlantic. These fields were used to monitor the formation and characteristics of the Brazil Current warm‐core anticyclonic rings shed by the first meander trough after poleward excursions of the Brazil Current (BC). Results reveal that 40 warm‐core rings were shed by the BC between January 1993 and October 1998. The observed lifetime ranges between 1 and 4 months, with a mean value of approximately 2 months. At any given time, two to three anticyclonic rings coexisted in the Brazil‐Malvinas confluence region. Most of the rings drifted southward without coalescing with their parent current. Only four rings were identified as being reabsorbed by the BC front after they were shed. No evidence of propagation or absorption of these anticyclones into the eastern limb of the subtropical gyre was observed. These rings have a mean horizontal length scale of 55 km, mean upper‐layer thickness of 260 m, and mean translation speed of 10 km d −1 . Volume anomaly and available potential energy computations showed a mean value of 3.6 × 10 12 m 3 and 2.5 × 10 15 J, respectively. The upper layer transport of the BC was also computed, and a relationship between variations in the southward transport and ring shedding activity was examined. Computation of the heat flux anomaly of the BC rings is estimated to be approximately 0.045 PW per annum. Compilation of these results indicates that warm‐core rings created by meandering boundary current extensions in different regions are generally similar.