Experimental investigation of sediment dynamics in response to breaking high-frequency internal solitary wave packets over a steep slope

Abstract

Abstract Previous studies have found that internal solitary waves (ISWs) can erode, resuspend and transport seabed sediments and form intermediate nepheloid layers (INLs) and bottom nepheloid layers (BNLs). In our recent flume experiments, the function of the BNLs and the fate of suspended sediment were studied by breaking high-frequency ISW packets over a steep slope. We found that a considerable amount of sediment was resuspended down the slope with the vortex, and it reached across the entire water column at almost the same time due to the vertical ejection (pump) of flow at the head of the bore by the breaking ISW. The maximum height of the suspended sediment reached the pycnocline. The suspended sediment may be transported slightly up to the top of the slope via the BNL. The downslope transporting distance was very short and the suspended sediment did not reach the foot of the slope via the BNL. The suspended sediment was mainly redeposited around the middle of the slope, and some fine-grained sediment suspended offshore was spread along the pycnocline via the INL to greater distances. The changes in slope elevation might be influenced by successive scouring, the redeposition of sediment, and the migration of sand waves. Our study was performed under low Iribarren number conditions, which can facilitate the development of new field experiments designed to obtain direct measurements and insights on the interactions between ISWs and seabed sediments.