Time‐space variability of the local dynamics of the Malvinas‐Brazil confluence as revealed by inverted echo sounders

Two inverted echo sounders have been deployed for approximately 8 months in the region of the confluence of western boundary currents in the South Atlantic (37°58.7′S, 51°56.4′W, and 37°29.3′S, 53°49.3′S). The confluence of the subtropical Brazil Current with the sub‐Antarctic Malvinas Current creates a strong, sharp thermohaline front. From the time series obtained with the sounders, two parameters are obtained and analyzed: dynamic height from the surface relative to 800 m and the position of the front. The time series of dynamic height indicates the presence of a cold intrusion during November, the southward extension of the Brazil Current and northward extension of the Malvinas Current during January, and a simultaneous warming of the area at both moored locations (0.04 dyn m/month) from March through June. From the dynamic height time series, mean geostrophic velocities are calculated. The mean value from mid‐December through mid‐June is −14 cm/s, representative of an average southward transport of 10 × 10 6 m 3 /s. The maximum southward transport, 23 × 10 6 m 3 /s, is during January. The front oscillates around its mean position with a period of about 1 month and an amplitude that varies from 10 to 50 km. The velocity of the displacement reaches values up to 10 km/d. Atmospherically forced oscillations are detected in the records. A 21‐day oscillation in the time series, obtained with the instrument located on the slope of the continental shelf, is associated with a coastally trapped wind forced response.