The RETRO-BMC cruise onboard the R/V Hespérides, April 2017, Brazil-Malvinas Confluence: hydrographic and drifters data [Dataset]

The RETRO-BMC oceanographic cruise was designed to characterize the spatial structures and variability of the Brazil-Malvinas Confluence (BMC) region. The cruise was carried in April 2017 on board the R/V Hespérides, departing from Ushuaia (Argentina) and arriving to Santos (Brazil). There were a total of 33 hydrographic stations, carried out between 13 and 25 April 2017. All stations were offshore from the continental platform and within 42ºS-36ºS and 58ºW-52ºW. Conductivity-temperature-depth (CTD) data were obtained with a SeaBird 911 Plus multi-parametric probe, with redundant salinity and temperature sensors, and additional dissolved oxygen (SBE-43) and fluorescence and turbidity (Wetlabs AFL-NTU-RTD) sensors. Water velocity data was obtained at the stations with a lowered acoustic Doppler current profiler (LADCP) and along the ship’s track with the vessel-mounted ADCP (VADCP). During the entire ship’s track inside the study region, the VADCP gathered velocity data in low-range mode (one velocity profile every 2 min between about 20 and 800 m at 8-m depth bins) and a thermosalinograph gathered salinity and temperature data (every 5 s at a depth of 5 m). The LADCP was attached, together with the CTD, to a 12-liters 24-Niskin-bottle rosette that was used to gather water samples at discrete depths, which were frozen and later analyzed to determine the concentration of inorganic nutrients. In addition, two high-resolution three-dimensional surveys were carried out at the Confluence front with a SeaSoar covering the area between 40.6-39.0°S and 55.6°W-53.8°W. The first transect was completed between the 16 and 17 April, 46 hours covering 620 km, while the second sampled 751 km between the 19 and 21 April 2017, during 52 hours. The SeaSoar was equipped with a SeaBird 911 CTD with the same sensors as in the hydrographic stations, and recorded data in a sawtooth pattern between 5 and 360 m, with a horizontal spacing between apogees of 4 km. Finally, five subsurface drif