Investigation of mass cross-shelf transport developed in the West- European shelf seas (Celtic sea)

Generation of nonlinear internal waves has been confirmed with the help of 2D non-hydrostatic numerical model over the Celtic sea shelf break. Results from 2D model indicate that the spring tide conditions produce greater vertical, horizontal velocities and wave amplitudes which have intensified effect on internal wave generation and circulation. The phase speed of the baroclinic wave is equal to v = 1.74 m/sec for neap tide compare to v = 1.97 m/sec for spring tide. The amplitude of the wave for neap tide is equal to 35 m and for spring tide 85 m. The mass transport associated with neap tide conditions is equal to 0.02 m/sec. For the spring tide conditions during one tidal cycle the mass transport is greater and equal to 0.09 m/sec. Therefore we have evidence that the enhanced circulation associated with internal waves particularly during the spring tide. Modelling studies of the internal tide at the Celtic Sea shelf edge also suggest mixing is associated more with spring tides (New 1988), with trains of shelf-ward–propagating internal solitons more likely to be generated at spring tides than at neap tides (Gerkema 1996). The nonlinear internal waves generated over variable bottom topogrrophy. The area under investigation, the Celtic sea shelf break, was separated into 3 zones. The width of zone I is 61 km, zone II is 81 km and width of zone III is 41 km. It was found that the wave amplitude in zone I is equal to 70 m, in zone II 84 m and in zone III 85 m. Analyses of density and horizontal velocity profiles led us to a conclusion that the circulation in zone III is stronger compare to zone I and zone II. The water circulation is very important in terms of ecology. The internal waves generated at the shelf break are of local importance and a significant source for mixing energy near the shelf edge (Green et al., 2008)