Formation of Sand Dunes by Internal Solitary Waves in the South China Sea
Abstract
In 2007 large sand dunes, with lengths of approximately 300 m and heights up to 15 m, were discovered on the upper slope in the South China Sea (Reeder et al., 2011), the site of the world???s largest observed internal solitary waves. The dunes, unique in their slope location and possible formation by ISW, are of interest intrinsically and because similar seafloor features in other locations are known to refract and focus low-frequency sound. Recent analysis of the 2007 data indicates that the dune wavelength is consistent with generation by bottom boundary layerflows induced by repeated shoaling of large internal solitary waves. However, a consistent dynamical understanding of the bottom boundary layer dynamics and consequences for sediment transport, dune formation, and enhanced internal solitary wave dissipation is needed. Here wepropose to use numerical simulations and newly obtained oceanographic observations to test the hypothesis that the ISW form the dunes by means of flow-seabed interaction in the bottom boundary layer. The objectives of the research are (1) determination of the physical processesthat control ISW characteristics on the shelf and slope of the South China Sea; (2) develop a dynamical understanding of the processes by which internal solitary waves form sand dunes on the upper continental slope; (3) explore the role of dunes on ISW dissipation; and (4) develop atested capability for predicting the occurrence of dunes and their wavelength, shape, and amplitude, which could be used to predict the presence, scales, and impacts of dunes in other regions. Reeder, D. B., Ma, B. B., Yang, Y. J. 2011. Very large subaqueous sand dunes on the uppercontinental slope
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 26, 2018
- Source ID
- N000141812542
Entities
People
- Karl Helfrich
Organizations
- Office of Naval Research
- United States Navy
- Woods Hole Oceanographic Institution