PREDICTIONS OF THE GENERATION AND PROPAGATION OF INTERNAL WAVES AND MIXING IN A PARTIALLY STRATIFIED ESTUARY

A period of intense mixing, causing an increase in the salinity of the surface layer from 2 to 7%, occurs during the ebb tide in the upper reaches of the Tees estuary. This follows the passage of internal waves of 1-2 min period. Assuming an upstream direction of propagation, the measurements indicate that the internal waves would have been released on the previoius ebb tide. The waves, which would then advect with the ensuing flood, could break and cause the mixing period. However, the waves may alternatively travel downstream, and other mechanisms may be responsible for the mixing. It may be, for instance, that the mixing was generated at one of two bridges 2-3 km upstream from the observation station, and then advected downstream on the ebbing tide. Further studies are needed to clarify the situation.