Detailed description of coastal eddy alongshore propagation with SWOT high-resolution altimetry

Coastal mesoscale eddies, which are essential for the redistribution of heat, nutrients, and momentum, often propagate along the coastline. Monitoring the propagation of these coastal eddies requires high spatio-temporal resolution, which has made their observation particularly challenging using conventional gridded altimetry. The initial fast-sampling phase of the Surface Water and Ocean Topography (SWOT) wide-swath mission offers an unprecedented opportunity to resolve these features at fine spatio-temporal scales. This study analyzes the alongshore propagation of a coastal anticyclonic eddy in the Algerian Basin, comparing the capability of SWOT with that of conventional altimetry. SWOT measurements better capture the eddy’s structure, deformation and trajectory, particularly during its interaction with coastal topography, leading to refined estimates of the eddy’s alongshore propagation speed. These results confirm SWOT’s added value in observing coastal mesoscale dynamics, and highlight new opportunities for understanding the interaction between small mesoscale eddies and coastal topography.