Observations of near-seabed currents induced by very large internal solitary waves over a sand dune field in the South China Sea

Internal waves are known to generate currents sufficient to suspend seabed sediment. Presented here are first-ever measurements of the near-seabed currents over a sand dune field in the South China Sea (SCS) during the passage of internal solitary waves (ISW) in June 2014 aboard the R/V Ocean Research V (OR5). Horizontal currents were observed to exceed 100 cm/s, reaching as high as 200 cm/s in one case, while vertical currents were observed to reach 30 cm/s. The Shields parameter for this environment exceeds 0.1, indicating that the ISW-induced currents are sufficient to suspend and transport the available sediment, supporting the hypothesis that the ISW's are the generation mechanism of the very large subaqueous sand dunes on the upper continental slope of the northwestern SCS.