Solitary Waves Impinging on an Isolated Tropical Reef: Arrival Patterns and Wave Transformation Under Shoaling

Large nonlinear internal solitary waves (NLIWs) are known to transit west northwest across the northeastern South China Sea from generation sites around the two-ridge system in the Luzon Strait. The waves are important because their energy flux and dissipation are several orders of magnitude larger than the surrounding ocean. The wave transit has been well studied up to about the 100 m isobath but observations in shallower water have been scarce. Using oceanographic moorings and an innovative distributed temperature sensing optical cable, the NLIW transformations were observed from 2000 to 2 m on the flanks of Dongsha Atoll (Pratas Reef). Possible outcomes included reflection, refraction around the island, wave breaking, and penetration into shallow water. Upslope penetration depended on incident wave amplitude and direction as well as the local stratification.