MIXING IN THE BRAZIL MALVINAS CONFLUENCE

Conductivity-temperature-depth profile data from the Western Argentine Basin collected from 1984 to 1989 are used to quantify the cross-front heat and salt transfers associated with the vertical finestructure across the Brazil-Malvinas Confluence. The fluxes are estimated following the statistical model Of JOYCE (Journal of Physical Oceanography, 7, 626-629, 1977). The data indicate that the upper ocean cross-front structure of the large-scale temperature and salinity fields is constant. The medium-scale finestructure intensity is quantified by the variance of the vertical temperature and salinity gradients in the 10-100 m wavelength band. Due to the abundance of intrusions, the upper layer (0-1000 m) variances increase by a factor of four at distances <20 km from the front. Heat and salt flux estimates associated with medium-scale mixing in the upper ocean are of the order 10(-2)-degrees-C m s-1 and 10(-3) m s-1 respectively. These fluxes are an order of magnitude greater than available estimates for other frontal regions. The medium-scale finestructure may therefore play a key role in the dissipation of eddies and intrusive lenses in the region. Heat and salt fluxes between North Atlantic Deep Water and Circumpolar Deep Water are 6.5 x 10(-4)-degrees-C m s-1 and 1.8 x 10(-4) m s-1, and agree with existing estimates. Extrapolation of upper layer Brazil-Malvinas Confluence cross-frontal fluxes to the Subtropical Convergence across the South Atlantic suggests that the medium-scale southward heat flux is about 20% of the oceanic northward heat flux at 30-degrees-S. Similarly, the freshwater flux balances 20% of the excess evaporation north of 30-degrees-S.