Ole Baltazar Andersen (Technical University of Denmark, DTU Space, Denmark); Per Knudsen (Technical University of Denmark, DTU Space, Denmark)

The observations from the Surface Water and Ocean Topography (SWOT) satellite has shown to be revolutionary in spatial resolution and precision. With the introduction of wide-swath altimetry at sample spacing of 250 m by 250 m we are able to get reliable and accurate observations in more complex coastal zones than ever before. Traditional mean sea surface (MSS) reference fields, critical for oceanography, have always relied on conventional nadir-looking satellite altimetry. Even with the introduction of Synthetic Aperture Radar (SAR) altimeters, this lead to most coastal zones in the resulting MSS being degraded due to land-contamination in the underlying observations. Subsequent smoothing or extrapolation might yield acceptable values in low-complexity areas, but have found to be less accurate in more complex areas, such as fjords, archipelagos, lagoons, atolls or similar features.

To utilize the high spatial resolution of SWOT, the new DTU25 MSS utilizes the ocean SWOT product (2 km spacing) in the open ocean, but uses the high-sampling of 250 m spacing in the coastal zones globally, to provide the spacial resolution needed to resolve the most complex coastal features. While providing little benefit in areas with a simple coastline, we see a large effect at coastal features with small enclosed waters, such as atolls with lagoons down to 1 km width. We show a global analysis of the effect of introducing the 250 m data product from SWOT in the MSS models, and subsequent consequences for oceanographic and coastal studies, as well as possible benefits and case-studies for going further inland with higher resolution products from SWOT.