Modelling of storm-driven shelf waves north of Scotland — I. Idealized models

Storm-driven currents observed over the Scottish continental shelf were described by Gordon and Huthnance (1987, Continental Shelf Research, 7, 1015–1048). Their suggestion of continental shelf-wave responses is investigated here using semi-analytic and numerical models of a straight continental shelf. Grid resolution, boundary conditions, truncations and differences of depth profile are considered with the semi-analytic model, from which dispersion curves and wave forms are derived. These forms are closely matched by the fully numerical model forced by specified elevations at one end. Further numerical calculations are described, for idealized wind forcing along or across limited regions of the shelf or slope. Localized forcing of short duration gives currents of the type observed, being rotary (clockwise) with roughly 22 h period. More extensive alongshelf forcing gives predominantly alongshelf currents with a strength tending to follow the forcing; the second form of observed response. Frictional effects are considered. A companion paper (Flather and Proctor, 1988, in preparation) describes the results of numerical simulations using realistic meteorological forcing and bathymetry.