Satellite altimetry and current-meter velocities in the Malvinas Current at 41°S: comparisons and modes of variations

ARTANA, CAMILA; CHRISTINE PROVOST; FERRARI, RAMIRO; PIOLA, ALBERTO R.; MARTIN SARACENO

Congreso; Ocean Surface Topography Science Team (OSTST) Meeting; 2017

Ocean Surface Topography Science Team

Three year-­long current-­meter arrays were deployed in the Malvinas Current at 41°S below a satellite altimeter track at about 10 years intervals. Surface geostrophic velocities (SGV) derived from satellite altimetric data products from CMEMS are compared with the velocities at theupper current-­meter (300 m). Multi-­satellite gridded SGV compare better with in situ observations than along-­track SGV. In spite of the proximity of the moorings to the complex Brazil-­Malvinas Confluence (BMC) region, satellite SGV are significantly correlated with the 20-­day low-­passed in situ velocities (0.85 for along-­isobaths velocities, 0.8 for cross-­isobaths velocities). The recent in situ measurement period (2014-­2015) stands out in the altimetry record with a long-­lasting (4 months) high level of eddy kinetic energy at the mooring site and a southernmost location of the Subantarctic Front (SAF). The first two modes of variations of sea level anomaly (SLA) over the BMC remarkably match the first two modes of the low-­passed in situ velocities. The first mode is associated with a latitudinal migration of the SAF, and the second with alongitudinal displacement of the Brazil Current overshoot. The two modes dominate the 24-­year long record of SLA in the BMC, with energy peaks at the annual and semi-­annual periods for the first mode and at 3 to 5 months for the second mode. The SLA over the Southwest Atlanticwere regressed onto the two confluence modes of SLA variations and showed remarkable standing wave-­train like structures in the Argentine Basin.