How does water circulation in a hypersaline lagoon differ from circulation in an estuary?

In a typical estuary, water circulation is driven by the interaction between fresh water and seawater. Because fresh water is less dense, it tends to form a distinct surface layer that flows toward the sea, while a compensatory landward flow of denser seawater occurs near the bottom.12

In contrast, water circulation in a hypersaline lagoon located in a hot, arid region operates in reverse. In these environments, high rates of evaporation cause surface waters to become denser than the underlying seawater. This dense surface water sinks to the bottom, and seawater flows into the lagoon at the surface to replace the volume lost to evaporation. This creates a circulation pattern that is the reverse of the estuarine model. In these hypersaline conditions, the denser, highly saline water remains at the bottom, where mixing is generally limited.1