Stratification and circulations are most commonly set up in an estuary when a river flows into its head. Less usual, but in some regions very important, is the case where property anomalies are produced by heating and evaporation at the shallow end, as in Spencer Gulf in South Australia. A series of exploratory laboratory experiments has been carried out to model such an 'inverse estuary'. Density differences and outflows were generated in a tank of homogeneous salt solution by heating and evaporation on a shallow shelf, connected to a region of uniform depth through a steep slope. Two distinct regions of circulation and types of layering developed. Counterflowing layers of hot salty water above colder fresher water were seen near the surface, with salt fingers between. The dense, warm salty water deposited by the fingers at the top of the slope, and very salty water originating on the shelf, formed gravity currents which flowed to the bottom and also away from the slope at mid-depth. This built up vertical gradients in the 'diffusive' sense; these and the circulations became quasi-steady after several days. The development and final structure were dominated by double-diffusive effects, which are quite different from those due to a simple source of buoyancy on the shelf.
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