Spatial variations of long-period waves and harbor oscillations around Taiping Island in the South China Sea

Most coral reef islands in the South China Sea are primary influenced by monsoons from the northeast in winter to the southwest in summer. Because the length scale of the islands ranges between O(100 m) and O(1000 m), nearshore waves and currents on the windward and leeward sides are modulated by seasonal wave directions as well as reef morphology. It is well known that long-period swell and infragravity waves play a vital role in dominating hydrodynamics and sediment dynamics on fringing reefs. However, spatial characteristics of long waves on the entire islands have not been well studied. In the present study, a phase-resolving Boussinesq-type wave model, is employed to investigate wave distributions around Taiping Island in the South China Sea during the monsoon. Wave transformations of refraction, diffraction, reflection and nonlinear wave interactions on the complex reef geometry are simulated using a high resolution grid. Model results will display spatial variability of significant wave height, infragravity waves and nearshore currents around the reef platform. The importance of long wave diffraction and resulting wave frequency components at the leeward side of the island will be examined. A small harbor located at the southern island often experiences harbor oscillations during the winter monsoon, even it located at the leeward side. Harbor oscillations forced by periods of wind-wave, swell and infragravity waves will be explored to provide critical indicators for the harbor management.