CoAuthors

Christine Provost (Laboratoire LOCEAN-IPSL, Sorbonne Université, (UPMC, Université Paris 6), CNRS, IRD, MNHN, Paris, France); Jean-Michel Lellouche (MERCATOR-OCEAN, Parc Technologique du Canal, Ramonville St. Agne, France); Rio MArie Hélène (ESRIN-ESA European Space Agency, Largo Galileo Galilei, 2 00044 FRASCATI, RM, Italy); Ramiro Ferrari (DCAO/FCEN/UBA, CIMA/CONICET-UBA and UMI IFAECI-3351, Buenos Aires, Argentina); Nathalie Sennéchael (Laboratoire LOCEAN-IPSL, Sorbonne Université, (UPMC, Université Paris 6), CNRS, IRD, MNHN, Paris, France)

Twenty-five years of high-resolution (1/12°) ocean reanalysis provide insights on variations in the Malvinas Current (MC) at 41°S, in the Brazil Current (BC) at 37°S and in their confluence (Brazil-Malvinas Confluence, BMC) from synoptic to interannual time scales. The modelled fields illustrate the contrast between the highly variable baroclinic BC and the rather stable barotropic equivalent MC. The model confirms that the mean MC transport (38.0 Sv  7.4 Sv at 41°S) is larger than the mean BC transport (26.7 Sv  15 Sv at 37°S) and determines the mean latitude of separation of the BC from the slope. An EOF analysis over the 25 years of the reanalysis suggests that changes in the position of the BMC are related to changes in the intensity of the BC at seasonal and semi-annual times scales. At longer time scales, the mean annual position of the Subantarctic (Subtropical) front is highly correlated with the MC (BC) transport time series (correlation coefficient of 0.6 and 0.5 respectively, 90% confidence level). Selected synoptic situations illustrate the model skills in documenting the complex processes of the BMC such as the offshore export of Rio de la Plata Water, the branching of the MC near the Confluence, the rich mesoscale field and the subduction of the MC below the BC with at times large vertical velocities.

Figure caption:
Mean annual position of the STF (a) and SAF (b) defined with model SSH isolines 5 and 30 cm isolines respectively. (c) and (d) annual mean STF and SAF positions on the 2,000 m isobath with MC and BC annual transport superimposed. (e) Mean annual separation distance between the SAF and STF. The red line indicates the mean annual separation averaged over the period 1993-2017.