SWOT was successfully launched in December 2022, with the main goal of observing ocean surface topography in two dimensions with an effective resolution down to 15-30 km wavelengths. This study evaluates the nature of the small scale features detected by the KaRIn instrument and examines the extent to which these observations can be used to investigate physical–biogeochemical interactions at these scales. Because the spatial distribution of surface chlorophyll is strongly influenced by advection, and surface topography is directly linked to geostrophic velocities, small scale patterns observed by SWOT are expected to be consistent with the fine scale structures in the surface chlorophyll field.

We analysed spatial correlations between SWOT Sea Surface Height (Level 3 product) and satellite derived surface chlorophyll concentration (CMEMS GlobColour). For comparison, we also assessed correlations between chlorophyll and DUACS multi satellite altimetry maps to highlight the added value of SWOT relative to existing mesoscale resolving products. Correlation coefficients between SSH (SWOT and DUACS) and chlorophyll were computed over 120 km segments along the SWOT swath. Initial results show that large scale meridional gradients dominate the correlation patterns. To isolate mesoscale and submesoscale variability, both SSH and chlorophyll fields were band pass filtered to retain spatial scales between 15 and 100 km.

For the unfiltered fields, SWOT and DUACS exhibit broadly similar correlation magnitudes and spatial structures. Strong negative correlations occur in upwelling systems and western boundary currents, while positive correlations dominate the subtropical southern Indian and Pacific Oceans. In contrast, the band pass filtered comparison reveals a marked degradation in DUACS performance, whereas SWOT maintains higher correlation values and similar spatial patterns. An exception is the equatorial band, where DUACS shows stronger correlations. Examination of the SSH fields indicates that SWOT’s small scale signals in this region are largely unbalanced (e.g., internal waves), and therefore not associated with surface currents or with the distribution of surface chlorophyll.

These findings demonstrate that SWOT provides new and robust capabilities for investigating physical–biogeochemical interactions at 15–100 km scales across the global ocean.