Three dimensional circulation modeling in the Dee Estuary

In estuarine areas nonlinear wave-current-stratification interaction is important in determining the 3D current circulation. A 3D ocean model has been implemented in the Dee estuary, Liverpool Bay (UK), to evaluate its performance and describe the coastal oceanography of a shallow estuarine region. The model includes both barotropic and baroclinic processes arising from tides, rivers and full atmospheric forcing, and is coupled to a spectral wave model. The model is evaluated by means of comparison with in situ salinity, current and wave data. The model accurately predicts sea level elevations finding errors in the order of a few cm. Velocity however is less accurate and very sensitive to geographical location. The timing of the model is correct, however, the magnitudes are underestimated when comparing with the ADCP data, this occurs mainly at flood tide. The consideration of 3D stratification effects improved the estimations of the residual velocities when compared with ADCP data, this was more evident in the cross-channel component which is less tidal dominant. Density distribution is mainly controlled by salinity which presents a tidal signal. Wave effects are relatively small; taking into account their associated processes did not improve the model when simulating currents or salinity distribution.