Mixing and sediment resuspension associated with internal bores in a shallow bay

Eiji Masunaga*, Hikaru Homma, Hidekatsu Yamazaki, Oliver B. Fringer, Takeyoshi Nagai, Yujiro Kitade, Akio Okayasu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Observations of the run-up of internal bores in a shallow bay were made with a tow-yo instrument and mooring arrays with high spatial and temporal resolution. Shoreward propagating internal bores have been studied with laboratory experiments and numerical models, but few observational studies have shown the detailed structure of the run-up of internal bores induced by internal tides. Our observations showed that internal bores propagate along the slope, accompanied by strong turbulent mixing and strong sediment resuspension in a shallow bay. The isothermal displacement due to the bores reached 20m vertically in a water depth of 40m. Turbidity measurements showed suspended particles transported from the sloping bottom and offshore above the thermocline, forming an intermediate nepheloid layer (INL). At the head of the bore (dense water), a vortex accompanied by strong vertical motion induced strong vertical sediment resuspension and a steep isothermal displacement. The rate of turbulent kinetic energy dissipation reached 10-6Wkg-1 at the head of the wave. A nonhydrostatic numerical simulation in a two-dimensional domain reproduced fine features associated with the run-up of an internal bore and the vortex motion at its head.

Original languageEnglish
Pages (from-to)85-99
Number of pages15
JournalContinental Shelf Research
StatePublished - 1 Nov 2015
Externally publishedYes


  • Internal bores
  • Internal tides
  • Nonlinear internal waves
  • Sediment resuspension
  • Turbulent mixing


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