Internal tides and sediment transport at the shelf break in the Celtic Sea

Abstract

Measurements of current and temperature fluctuations at a site on the European continental shelf have revealed the presence of large M 2 tidal phase current surges produced by the internal tide generated at the shelf break. These have been found to extend with little attenuation throughout the water column and to have a significant effect on the flow near the seabed. A numerical model of the internal tide has been used to investigate the surge current generation mechanism and the way in which the surges propagate across the shelf. Good agreement has been obtained between the model predictions and the observations for surges propagating onto the shelf. The model is also used to examine sediment transport at the shelf break. In particular it is shown that for realistic shelf edge topography, the shelf break is likely to be an area of bed load parting. The sedimentological and geological implications of this result are discussed in the light of what is known concerning the present day relief of the shelf-break region and likely processes of sediment transfer from the continental margins to the deep ocean.