COASTAL AND SHELF SEA INTERACTIONS
Water Quality Models
Processes in regions of freshwater influence - PROFILE
 PROFILE, a POL co-ordinated EU MAST 2 project, generating understanding of processes relating to hydrodynamics, sediments dynamics and microbiology, incorporated in a tested fully coupled model for regions of freshwater influence (ROFIs) was completed successfully in 1996.

Studies of the discharge into an idealised Clyde Sea using the POL 3D-B model showed that the area of freshwater startification near the river mouth, forming a bulge of a typical river plume in a low friction, low entrainment case, could readily form a persistent region of anticyclonic circulation. This can then affect the direction of subsequent discharges as the outflow varies in time. Figure 9 shows an example.

Collaborative work on the PROFILE model will continue in a follow-on MAST 3 project, "COHERENS".

Applications in contrasting coastal areas
 The 3D-B model was applied to Pelorus Sound, a complex system of channels on South Island, New Zealand. Episodic rainfall and river inflows rapid transform the normally well-mixed waters of the sound into a two-layer system. Tidal mixing then takes approximately 20 days to erode this stratification.

The model reproduced aspects of the observed salinity structure in the sound and indicated how these changes impacted on the circulation.

An atlas of tidal current and effects of winds and the Savannah River discharge on surface currents was produced by applying the model to Wassaw Sound, Georgia, providing guidance to the British Olympic sailing team at the 1996 Atlanta Games.

NOMADS - North Sea Model Advection Dispersion Study
 In Nomads, a POL co-ordinated EU MAST 2 concerted action completed in February 1997, the variability of results from

advection-dispersion models in use on the NW European shelf was investigated. Idealised test case simulations and a realistic (southern North Sea) simulation were carried using 2-D and 3-D models. Equivalent outputs from different models showed general coherence but larger than acceptable disagreement. This arose from a combination of factors such as differences in meteorological forcing, geographical extent of the model domain, type of model, numerical advection-dispersion scheme and model implementation. The project demonstrated uncertainties remaining in advection-dispersion modelling and warned that care must be taken in use of model results.

Model salinity and currents
Figure 9
Computed surface salinity and surface currents from the 3D-B model applied to a gulf, showing an anticyclonic gyre and a coastal current bounded by fronts. These were produced by a previous river discharge at the centre of the right-hand boundary.

Last updated: 12th May 1998. Please send comments to A.Lane@pol.ac.uk