Satellite altimetry and current-meter velocities in the Malvinas Current at 41°S: comparisons and modes of variations
Event: 2017 Ocean Surface Topography Science Team Meeting
Session: Science II: Large Scale Ocean Circulation Variability and Change
Presentation type: Type Poster
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 are compared with the in situ velocities at the upper 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 a longitudinal 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 Atlantic were regressed onto the two confluence modes of SLA variations and showed remarkable standing wave-train like structures in the Argentine Basin.