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[1] The baroclinic structure of the Brazil Current(BC)-Intermediate Western Boundary Current (IWBC) at 22°-23°S was investigated. A reanalysis of the pioneer velocity profile measurements of the TRANSCOBRA Experiment [Evans and Signorini, 1985] revealed that the BC-IWBC system is about 75-80% baroclinic. Mapped velocity structure showed flow reversal at about 450 m, an IWBC thickness of 1200 m and core velocities exceeding 0.30 m s À1 . Total (baroclinic) transports for BC (southwestwards) and IWBC (northeastwards) were 5.6 (4.2) Sv and 3.6 (4.1) Sv, respectively. The strong baroclinic character of the BC-IWBC system and the lack of direct velocity observations in the area yielded us to propose the use of the cross-shelf version of the Princeton Ocean Model to generate absolute baroclinic velocities from hydrographic data. These velocities presented a similar reversal depth, and the transports of about 6 -7 Sv for both BC-IWBC were also comparable to values reported in the literature.

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[1] We use four current meter moorings and quasi-synoptic hydrographic observations in conjunction with a one-dimensional quasi-geostrophic linear stability model to investigate downstream changes in the Brazil Current (BC) System between 22 S and 28 S. The data set depict the downstream thickening of the BC. Its vertical extension increases from 350 m at 22.7 S to 850 m at 27.9 S. Most of this deepening occurs between 25.5 S and 27.9 S and is linked to the bifurcation of the South Equatorial Current at intermediate depths (Santos bifurcation), which adds the Antarctic Intermediate Water flow to the BC. Geostrophic estimates suggest that the BC transport is increased by at least 4.3 Sv ($70%) to the south of that bifurcation. Moreover, the Santos bifurcation is associated with a substantial increase in the barotropic component of the BC System. On average, the water column average kinetic energy (IKE) is 70% baroclinic to the north and 54% barotropic to the south of the bifurcation. Additionally, the BC shows conspicuous mesoscale activity off southeast Brazil. The water column average eddy kinetic energy accounts for 30-60% of the IKE. Instabilities of the mean flow may give rise to these mesoscale fluctuations. Indeed, the linear stability analysis suggests that the BC System is baroclinically unstable between 22 S and 28 S. In particular, the model predicts southwestward-propagating fastest growing waves ($190 km) from 25.5 S to 27.9 S and quasi-standing most unstable modes ($230 km) at 22.7 S. These modes have vertical structures roughly consistent with the observed eddy field.

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