Clément Vic (LOPS, France); Sophie Cravatte (IRD, New Caledonia); Lionel Gourdeau (LEGOS, France)

The Surface Water Ocean Topography (SWOT) satellite altimetry mission provides sea surface height (SSH) at unprecedented spatial scales encompassing mesoscale to submesoscale dynamics as well as internal gravity waves motion. While SWOT offers new opportunities to study energy redistribution, momentum transfer, and nonlinear scale interactions, a key challenge lies in accurately disentangling the SSH signal to attribute variability to different dynamical regimes. In 2023, an extensive in-situ experiment was conducted in the southwestern tropical Pacific focusing on the deployment and recovery of mooring lines in an internal tide generation and propagation hotspot located beneath both SWOT swaths during the fast-sampling phase. The region's strong mesoscale and submesoscale activity, combined with energetic internal tides, makes it an ideal site to separate near-geostrophic (balanced) and wave-driven (unbalanced) motions. Using a time-filtering technique, we decompose the moored observations into distinct dynamical flow regimes. Our results reveal the coexistence of mesoscale dynamics and semidiurnal internal tides, the latter associated with vertical isopycnal displacements of up to 150 m and steric SSH variations of up to 20 cm. Steric SSH estimated from the moorings shows good agreement with the daily-aliased SWOT SSH. These mooring observations provide crucial insight into the vertical structure of fine-scale ocean dynamics and how they manifest at the surface, helping to unravel the complex signals captured by SWOT.