Large Drifter Experiment in the Western Mediterranean Sea reveals Dynamical vs Noise contributions in SWOT-KaRIn Sea Level

The wide-swath altimeter SWOT provides unprecedented two-dimensional sea-level observations, whose ability to capture upper-ocean dynamics requires assessment. The dynamically balanced signal and noise contributions in SWOT-KaRIn Level-3 (L3) sea level products are here originally quantified and contrasted with those from Level-4 (L4) gridded nadir-only products, combining sea level data, 137 trajectories from drifters deployed in the Western Mediterranean, ERA5 winds, and the framework of Demol et al. (2025). The filtered L3-2km product, or interestingly the unfiltered L3-2km product with a 25 km Gaussian filter, offers the best compromise for fine-scale studies, though residual noise still accounts for about one-third of total variance. L4 products contain less balanced signal but are noise-free and better suited for large-scale analyses. SWOT KaRIn adds value mainly at scales smaller than ∼100 km and shorter than ∼10 days. This studies provides a benchmark for global sea-level assessments.