Convectively driven exchange in a shallow coastal embayment

Shark Bay is a large coastal embayment(length similar to 250 km, width simi lar to 100 km) located on the central west coast of Australia. The Bay is c omprised of two major reaches, which are characterised by average depths of 10 m and salinities which increase with longitudinal distance away from th e Bay entrance. Maximum salinities in the Bay exceed 60 (Practical Salinity Scale), and occur in Hamelin Pool at the southern end of Hopeless Reach, t he eastern region of the Bay. Exchange between Hamelin Pool and Hopeless Re ach is severely restricted by the presence of a sill, and occurs predominan tly through a single 2 km wide, 6 m deep channel (Herald Loop). CTD measure ments taken in Hopeless Reach show variable stratification: vertically well -mixed in summer and strongly stratified during the winter survey. A shallo w cavity natural convection model was applied to the Herald Loop channel to determine the contribution of the saline discharge from Hamelin Pool to th e observed variable stratification. The model shows that the discharge from Hamelin Pool is a diffusive process. Thus while the discharge is an import ant salinity source, it will not directly contribute to the variability obs erved in Hopeless Reach. (C) 1999 Elsevier Science Ltd. All rights reserved .