High-resolution altimetric sea level anomaly from Jason2, Saral/AltiKA and Sentinel3 to SWOT: A spectral regional analysis in the New Caledonia region

Le résumé fourni par la source

The Surface Water and Ocean Topography (SWOT) wide-swath satellite altimetry mission represents a major advance over conventional nadir-pointing altimetry in resolving small-scale ocean dynamics. However, we demonstrate the potential of conventional altimeters such as Jason, Saral/AltiKa, S3a in observing small-scale ocean dynamics by using High-Resolution (HR) sea surface height products instead of classical Low-Resolution product. We analyse SSH wavenumber spectra around New Caledonia in the southwestern tropical Pacific – an important study site in the context of SWOT. This region is characterized by complex ocean dynamics, featuring high mesoscale activity and internal tides. The comparison of SWOT SSH spectrum with Saral/Altika and S3a HR SSH spectra shows a good consistency between both altimetric measurements for small scales down to 20 km wavelength. Spectra exhibit mesoscale spectral slopes extending down to 60 km wavelength, highlighting the dominant SQG (Surface Quasi-Geostrophic) dynamics in the surface layers, particularly present in winter while QG (Quasi-Geostrophic) dynamics prevail in summer. A second k-2 spectral slope emerges at smaller scales down to 30 km wavelength in accordance with SSH slope of the Garret and Munk spectrum. The spectral signatures of internal tides are visible over a broad range of wavelengths up to 150 km in summer when submesoscale activity is less energetic. This study highlights the value of these HR along track data for documenting fine scale dynamics over a long time period and raises the question of their assimilation in operational systems in conjunction with SWOT data or once the SWOT mission has been completed.

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