A view of the Brazil-Malvinas confluence, March 2015

Shelf Water Export at the Brazil-Malvinas Confluence Evidenced From Combined in situ and Satellite Observations

“…The hydrographic cruise that took place in April-May 2016 in the Uruguayan EEZ provided an unprecedented dataset to In this work, we focused on cross-shelf exchanges as they have important consequences for carbon export, water masses transformations, and marine biodiversity. Previous studies provide evidence that, regionally, shelf water export is closely related to the confluence position (e.g., Matano et al, 2014;Berden et al, 2020;Orúe-Echevarría et al, 2021; Figure 11A). This control is somehow expected since the Brazil and Malvinas currents generate a barotropic pressure gradient that extends into the shelf controlling the outer shelf circulation (Palma et al, 2008;Matano et al, 2010).…”

“…Another useful approximation to study shelf water export processes are high-resolution numerical models, as they reproduce the shelf-water export, especially when the confluence and the separation of the Brazil Current from the shelf break are along the same front (Berden et al, 2020;Orúe-Echevarría et al, 2021), but probably also to better simulate the impact of mesoscale eddies, like those observed during the 2016 cruise (Figure 11). Recent numerical simulations highlight the role of along-shelf winds in modulating the magnitude of alongshelf transports and the resulting shelf-open ocean exchanges (Berden et al, in press).…”

“…The data display evidence of intrusions of SASW and STSW at several vertical levels within the relatively warm and salty TW and SACW. Large amplitude thermohaline intrusions observed in this region are ubiquitous of the confluence region (e.g., Piola and Georgi, 1982;Bianchi et al, 1993;Orúe-Echevarría et al, 2021), and are indicative of intense isopycnal mixing between the adjacent water masses with contrasting thermohaline properties (Figure 5B). Water masses found at deeper depths were those characteristics of the region: UCDW, NADW, LCDW, and AABW, respectively (Maamaatuaiahutapu et al, 1992(Maamaatuaiahutapu et al, , 1994Provost et al, 1995;Valla et al, 2018; Table 2 and Figure 5B).…”

“…Between 36.5 and 38.8 • S, the ocean area over the slope is characterized by high eddy kinetic energy with changes in current speed and direction (Figure 1A). Satellite-derived salinity, in situ observations, and modeling studies suggest that this region is also where most of the cross-shelf exchanges in the Southwestern Atlantic take place (Guerrero et al, 2014;Matano et al, 2014;Franco et al, 2018;Berden et al, 2020;Orúe-Echevarría et al, 2021).…”

Mixing and Overturning Across the Brazil‐Malvinas Confluence

“…The ensuing convergence generates an intense and extensive frontal zone, characterized by marked thermohaline contrasts and a complex vertical structure implicating diverse water masses (Provost et al., 1995). Retroflection and meandering of the BMC as it separates from the western boundary lead to the development of a highly‐energetic, multi‐scale eddy environment, rich in mesoscale and submesoscale structures (Bianchi et al., 1993; Legeckis & Gordon, 1982; Lentini et al., 2002, 2006; Orúe‐Echevarría, Castellanos, et al., 2019; Orúe‐Echevarría et al., 2021; Orúe‐Echevarría, Pelegr, et al., 2019; Provost et al., 1999). The action of such vigorous, convoluted flow field on the cross‐BMC thermohaline gradients primes the area for strong water mass modifications and meridional transports (Bianchi et al., 1993, 2002; Gordon, 1989).…”