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 firstever 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 ISWinduced 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.