A Tidal and Surge Model of the North East Atlantic

Marcel Curé and Kieran Lyons
The Marine Institute, Ireland


It is surprisingly difficult to improve the tidal height predictions made by two dimensional tidal models, by using a 3D model. This poster examines the issues and difficulties in developing a ROMS model for the NE Atlantic, tuned to forecast tide surges and absolute tidal heights in shallow waters adjacent to a steep continental slope.

Our model extends to the Hatton Bank, Shetland and north Spain. It has a horizontal resolution of 2.5 km, 40 levels, and a bathymetry derived from SWATH survey over crucial slope areas. We have added code to include tidal potential for 22 constituents using the Doodson method. The latest version of the Oregon State model TPXO 7 is used at the model boundary. By running the model twice :- with and without atmospheric forcing we can arrive at a good surge prediction.

We compare model runs with and without tide potential and find it to be important in bays and estuaries where the continental margin is narrowest. We compare the model runs with tide gauge data from several Irish and UK gauges and find that whereas the phases are in excellent agreement, the amplitudes are in error by about 10 percent. Initial attention focuses on variable shear bed stress parameterisation using BBL models in ROMS, but in deep water we find departures from the independently generated FES2004 tide model of up to 0.2 m r.m.s. We examine the role of dissipation by internal waves and problems in accurately modelling this important process in our models.