A high-resolution finite element model of the M 2, M 4 M 6, S 2, N 2, K 1 and O 1 tides off the west coast of Britain

Abstract

A finite element model of the west coast of Britain is used to determine the spatial distribution of the M 2, S 2, N 2, K 1, O 1, M 4 and M 6 tides in the region. A sensitivity study of the influence of bottom friction upon the M 2 tide and its higher harmonics, shows that increasing friction coefficient in an M 2 tide only calculation, from 0.0025 to 0.0030 has a larger effect than the addition of the other major constituents. Although the M 2 tidal amplitude over the west coast of Britain is sensitive to frictional effects, the co-phase distribution is not significantly influenced by friction. Detailed comparisons of the computed tide in the eastern Irish Sea with observations and an earlier high-resolution finite difference model of the region, shows an improvement in accuracy of the tidal solution derived with the finite element model. The ability of the finite element model to refine the mesh in the near coastal region contributes to this improvement in accuracy. A study of the spatial change of the computed tide in nearshore regions shows significant variability on scales of the order of 0.5 km. This suggests that detailed topography and associated mesh sizes in near coastal regions need to be below this space scale.