[A-OS17] Ocean circulation and material cycle in coastal seas

[AOS17-02] River plume mixing induced by internal tide breaking

*Hironori Momma¹, Eiji Masunaga¹ (1.Ibaraki University)

Keywords:Internal tide, River plume, Numerical simulations

Internal wave breaking causes strong currents and turbulent mixing in coastal oceans. Mixing induced by internal wave breaking mixes river plumes and ambient seawater, which plays an important role in transport between coastal and open oceans. Although mixing of river plumes has been studied by observations and numerical simulations, previous studies have not revealed dynamics and mixing of river plumes resulting from internal tides. In this study, we investigated river plume mixing induced by internal tide breaking over a shallow slope using nonhydrostatic numerical simulations. When a low salinity layer exists in the surface layer, internal tide breaking disturb the river plume resulting in internal solitary waves propagating toward the coast. Internal solitary waves enhance the onshore ward internal wave energy flux leading to turbulent mixing and sediment resuspension in shallow regions. The kinetic energy in the surface layer was calculated to be 1.2 times higher than absence of a low salinity layer. Numerical simulations with various slope angles show that the internal wave energy flux propagating into the shallows decreases and sediment resuspension is weakened as the slope angle increases. In addition, the onshore ward internal wave flux and sediment resuspension were intensified as the surface salinity decreases.