Interaction of Mesoscale Variability with Large-Scale Waves in the Argentine Basin

Abstract

Abstract The Argentine Basin of the South Atlantic Ocean is a region of complicated ocean dynamics involving a wide range of spatial and temporal scales. Previous studies reported the existence of a basin mode of topographic barotropic Rossby waves with a period close to 25 days in the region. Using observations of sea level anomalies from satellite altimeter measurements, the present study provides evidence of interaction between the large-scale 25-day waves and the energetic mesoscale variability of the region. The amplitude of the 25-day waves is highly intermittent with dominant periods in the range of 110–150 days. Within this period band, the wave amplitude is coherent with the energy level of the mesoscale variability: when the mesoscale energy level goes down, the wave amplitude goes up, and vice versa, suggesting an exchange of energy between the two scales. This coherence is linked to the first three empirical orthogonal functions (EOFs) of the sea level anomalies. The spatial patterns of these EOFs are characterized by eddies and meanders associated with the Brazil–Malvinas Confluence. The findings of the study suggest a mechanism of energy exchange at work between the mesoscale variability and the large-scale waves in the Argentine Basin.