Data assimilation and horizontal structure of the barotropic diurnal tides on the Newfoundland and southern Labrador Shelves

A large set of in situ currents and elevation data, and a direct inverse data assimilation model are used in conjunction with global inverse tidal solutions to obtain high-resolution regional assimilative model solutions for the barotropic K-1 and O-1 tides on the southern Labrador and Newfoundland Shelves. The regional model assimilates the in situ data and a first estimate of the boundary conditions provided by the global model, so that the regional solutions draw on both regional and larger-scale observations and dynamics. The regional assimilative solutions have r.m.s. observational misfit values of the order of 2 cm for elevation and 2 cm s(-1) for currents, which are reduced (compared with non-assimilative regional solutions) by 21% and 61% for K-1 and O-1 elevations respectively, and by 61% and 54% for K-1 and O-1 currents. A striking feature of the regional model solutions is a series of small-scale (radius of approximately 100 km) eddy-like features along the shelf edge. Singular value decomposition (SVD) of the assimilative elevation fields reveals the existence of topographically-trapped waves at the shelf edge. There are amplified diurnal currents over the outer shelf and slope associated with the topographic waves, pointing to the potential for topographic amplification of other subinertial currents in the region.