On the Role of Internal Tides in Sediment Resuspension

In deep water over continental slopes, where the influence of surface waves is weak, near-seabed flows can often be dominated by semi-diurnal internal tides. This work investigates the potential for such flows to create sufficient seabed stress to resuspend fine sediment. Model results are presented from a first mode internal tide propagating over idealized topography, including slopes that are critical with respect to the internal tide characteristics. Results and observations show that, over sloping topography in the presence of stratification, there can be strong asymmetry between the periodic up- and down-slope flows. This asymmetry results in varying shear and vertical mixing between the up- and down-slope flows, and this impacts on the process of sediment resuspension. Numerical results from the Australian North West Shelf demonstrate the potential of internal tides to resuspend sediment. In addition, the interaction of barotropic tidal currents with the internal tidal flows can both enhance and reduce bottom stress, depending on the phase relationship between the flows.