Observations of Enhanced Sediment Transport by Nonlinear Internal Waves
Andrew Zulberti, Nicole L. Jones, Gregory N. Ivey
Abstract
Abstract The mechanisms responsible for sediment resuspension and transport by nonlinear internal waves (NLIWs) remain poorly understood largely due to a dearth of detailed field measurements. We present novel observations of the turbulent benthic boundary‐layer (BBL) beneath trains of NLIWs of depression in the ocean. At the 250 m deep, low‐gradient (<0.2%) continental shelf site the BBL was near well mixed to an average height of about 10 m above the bottom. Above this bottom mixing‐layer, stratification constrained the extent of vertical sediment transport. NLIWs drove sediment transport by a combination of bed‐stress intensification, turbulent transport, and a vertical pumping mechanism associated with the compression and subsequent expansion of the mixing‐layer. There was no evidence that the observed dynamics were associated with a global instability, as proposed in previous studies. The results have implications for cross‐shelf mass transport and highlight future challenges for measuring and modeling boundary‐layer processes within shelf seas.