Coherent water transport across the South Atlantic

TL;DR

This study uses nonlinear dynamical systems theory on satellite data to analyze mesoscale eddies in the South Atlantic, revealing their role in transporting Agulhas leakage with specific coherence and travel characteristics.

Contribution

It introduces a novel application of nonlinear dynamical systems theory to satellite altimetry data for analyzing eddy coherence and transport in the South Atlantic.

Findings

1 to 4 coherent eddies per year detected

Eddies can carry Indian Ocean contents across the South Atlantic

Limited transport of Agulhas leakage northwestward compared to earlier estimates

Abstract

The role of mesoscale eddies in transporting Agulhas leakage is investigated using a recent technique from nonlinear dynamical systems theory applied on geostrophic currents inferred from the over two-decade-long satellite altimetry record. Eddies are found to acquire material coherence away from the Agulhas retroflection, near the Walvis Ridge in the South Atlantic. Yearly, 1 to 4 coherent material eddies are detected with diameters ranging from 40 to 280 km. A total of 23 eddy cores of about 50 km in diameter and with at least 30\pct of their contents traceable into the Indian Ocean were found to travel across the subtropical gyre with minor filamentation. Only 1 eddy core was found to pour its contents on the North Brazil Current. While ability of eddies to carry Agulhas leakage northwestward across the South Atlantic is supported by our analysis, this is more restricted than suggested by earlier ring transport assessments.