EMPIRICAL ORTHOGONAL FUNCTION ANALYSIS OF SATELLITE-DERIVED CURRENTS IN THE TROPICAL ATLANTIC

Abstract

An Empirical Orthogonal Function (EOF) analysis was performed using 22 years of monthly surface currents in order to investigate the main modes of variability of the Tropical Atlantic surface circulation based on satellite data. The EOF1 of the zonal component captures more than 50% of the total variance and represents the central branch of the South Equatorial Current (cSEC). The EOF2 of the zonal component (~8% variance) represents a zonal dipole with a positive signal to the west, and a negative one to the east in the Atlantic Cold Tongue (ACT). The meridional EOF1 (18% variance), with alternating positive and negative structures in the western tropical North Atlantic, representing the high dynamics associated to the North Brazil Current retroflection and its anticyclonic eddies. The meridional EOF2 (~ 12% variance) represents the high variability of the NBC, with stronger intermittent signals propagating from the eastern Atlantic. In the EOF1 of currents speed predominates the cSEC pattern (30%) and the EOF2 (8%) represents the zonal dipole between South Atlantic Warm Pool and the ACT. These dominant modes of surface current variability contribute to the understanding of the ocean-atmosphere interaction processes, zonal and meridional transport variability, and the surface dynamics in the TA. Keywords: EOF Analysis, Remote Sensing, Ocean Currents, Oceanic Dynamics, Tropical Atlantic