Sediment remobilization over subaqueous sand waves: In-situ observation in the northern South China Sea

• Published in: Earth and planetary science letters Vol. 643; p. 118927
• Main Authors: Zhao, Yulong, Zhang, Yanwei, Ma, Pengfei, Zhang, Xiaodong, Liu, Zhifei
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-10-2024
• Subjects: Internal solitary wave; Internal tide; Sediment resuspension; South China Sea; Subaqueous sand waves; Tripod observation; Internal solitary wave; Tripod observation; Internal tide; South China Sea; Sediment resuspension; Subaqueous sand waves
• ISSN: 0012-821X
• DOI: 10.1016/j.epsl.2024.118927

•High resolution observations of sediment remobilization over subaqueous sand waves.•Internal solitary waves are the primary force driving sediment remobilization.•Internal wave induced sediment resuspension and ejection with different dynamics.•Daily high turbidity in bottom water due to critical reflection of internal tides.
High-resolution tripod observations were conducted in a subaqueous sand-wave field in the northern South China Sea. The objective was to gain insight into the dynamic mechanism by which sandy sediments are remobilized by oceanic dynamic processes, in particular internal solitary waves and internal tides. Daily-recurring high suspended sediment concentrations were observed, likely due to lateral transport of sediments resuspended by critical reflection of diurnal internal tides at the shelf break. The passage of extreme internal solitary waves results in resuspension of sediments from the seabed and ejection of these sediments out of the boundary layer. The resuspension of sediments from the seabed is controlled by current-induced strong bed shear stress, while the ejection of sediments out of the bottom boundary layer is driven by the compression and subsequent expansion of the mixing layer, together with the developments of the separation bubbles behind the internal solitary waves. These findings provide new insights into understanding the dynamic mechanism of sediment remobilization by internal solitary waves. Moreover, they contribute to our understanding of the migration of subaqueous sand waves.