Advancing mesoscale ocean eddy characterization through combined altimetry and modeling*

Mesoscale ocean eddies, long-lived large-scale coherent vortices, play a crucial role in global heat, salt, and nutrient transport. Accurately characterizing their non-linear evolution from satellite altimetry remains challenging due to limitations in spatial and temporal resolution. Current altimetry-based analyses often assume axial symmetry, simplifying eddy shapes to a few parameters (e.g. amplitude and radius). However, ocean eddies are never symmetric and only appear so as a result of averaging numerous realizations of individual eddies.

We propose a novel approach combining 30 years of historical along-track altimetry data with insights from numerical modeling. Using an Observing System Simulation Experiment (OSSE), the track simulated data are sampled from a synthetic eddy in the eddy-centered reference frame. Various eddy estimation methods, including a parametric model accounting for eddy shape eccentricity and eddy evolution, are explored.

The case study on a selection of isolated eddies from real-world observations reveals any biases (e.g. eddy strength, size, and counts) in the commonly used interpolated mapped product (e.g. AVISO). The proposed approach has the potential to improve the accuracy of inferring eddy properties from sparse along-track data, provide guidance for processing recent 2D high-resolution Surface Water and Ocean Topography (SWOT) data, and enhance both observational strategies and numerical models of ocean dynamics.