Tidal energy fluxes and dissipation on the European continental shelf

The spatial distribution of the energy flux, energy dissipation, current ma gnitude, and surface elevation amplitude of the major tidal constituents ov er the northwest European shelf are examined in detail. These distributions are obtained from the harmonic analysis of a 6 month three-dimensional sim ulation of 28 tidal constituents. The model currents are validated by a com parison of computed tidal harmonics against those derived from a harmonic a nalysis of up to 278 current time series. A similar comparison is performed for tidal elevations based on 257 tide gauges. Calculations show that for the most significant tidal constituents (e.g., M-2, S-2 and K-2) there is a major energy flux in the deep water along the shelf edge off the northwest of Scotland, with some energy leaking onto the shelf and into the North Se a. A second source of energy is across the shelf edge at the southern end o f the Celtic Sea, with this energy flux propagating into the Irish Sea and southern North Sea, where the majority of the energy is dissipation in the shallow regions. Significantly different distributions are found for the di urnal and shallow water constituents, and the spatial distributions of ener gy flux and dissipation of the various constituents are considered. The acc uracy of separating tidal current harmonics using model data of less than a synodic period is examined with reference to the S-2 and K-2 tide. Calcula tions suggest that the accuracy of computed currents comparable to those ob tained from observations can be obtained from an analysis of a 60 day perio d compared with the synodic period for S-2 and K-2 of 182 days, a significa nt saving in computer time.