SWOT Sheds Light on Seiche Oscillations Within Atoll Islands

Abstract This study investigates the occurrence of surface elevation oscillations, known as seiches, at the atoll scale. We show that the innovative Ka‐band Radar Interferometer (KaRIn) onboard the Surface Water Ocean Topography (SWOT) satellite makes it possible to visualize seiche‐like structures within lagoons of French Polynesia. This ability to capture two‐dimensional sea surface undulations of low amplitude (on the order of a few centimeters) in relatively small water bodies (less than 80 km in length) is unprecedented in satellite altimetry, and opens new avenues of research into these events and their contribution to coastal erosion and flooding. Our study combines sea surface height observations from SWOT with in situ measurements conducted in the Raroia lagoon and theoretical calculations based on an eigenvalue model. These three complementary approaches—satellite remote sensing, in situ data, and theoretical modeling—allow us to investigate both the spatial and spectral properties of seiches in atoll islands.