MODELING HOLOCENE TIDES ON THE NW EUROPEAN CONTINENTAL-SHELF

A numerical model of the M2 tide on the NW European continental shelf has been used to estimate the effect of uniform depth changes, of the order of the Holocene eustatic variation, on tidal elevation amplitudes, sand transport paths, and the position of tide-generated fronts. Minor changes are indicated around the outer shelf, but the Southern Bight of the North Sea is seen to develop from a quiet, shallow sea of low tidal amplitude (< 0.5 m) to its present state of vigorous tidal action with mean coastal amplitudes around 2 m. Shifts in the position and strength of amphidromes are shown to cause strong spatial gradients in the rate of change of tidal amplitudes in the Irish Sea and English Channel, but the tidal contribution to absolute changes in mean high water levels is found to be everywhere less than 5% of the eustatic contribution. Development of this modelling approach requires more realistic description of bathymetric variation and an estimate of ocean tidal changes.