Assessing Dynamical Contributions to SWOT Sea Surface Height in an Internal Tide Hotspot

Abstract

The Surface Water and Ocean Topography (SWOT) mission has revealed high‐frequency sea surface height anomaly (SSHA) variability associated with internal gravity waves, yet comparison with in situ observations remains limited. Here, we analyze a mooring array beneath the swaths of SWOT Cal/Val south of New Caledonia, an internal tide (IT) hotspot in the southwestern tropical Pacific. SWOT agrees closely with mooring‐derived SSHA, exhibiting three times larger variance than gridded SSHA from nadir altimetry. This excess variance is mainly driven by coherent ITs, explicitly extracted from SWOT swaths, with amplitudes exceeding 10 cm. Comparison with mooring‐based estimates demonstrates centimeter‐level accuracy in the retrieved IT signal. SWOT‐derived ITs reveal substantial errors in empirical IT atlases, routinely used to correct SWOT. Particularly, absolute (relative) errors in SSHA‐derived current velocities exceed 15 cm s−1 ${\mathrm{s}}^{-1}$ (80%) in 10% of cases during SWOT Cal/Val, calling for improved methods to separate wave‐like and balanced motions.