Energetics of Semienclosed Basins with Two-Layer Flows at the Strait

Examination of the energy budget for semienclosed seas with two-layer exchange flow at the strait shows that the energy flux at the open portion of the boundary (the strait) is proportional to the surface buoyancy flux integrated over the basin area, with the constant of proportionality given by the interface depth. When the surface buoyancy flux is positive, the energy flux is negative: these types of basins have an estuarine circulation. Antiestuarine basins have a negative surface buoyancy flux, which provides a positive energy flux, augmenting the wind work in powering the circulation. The energy budget for the semienclosed seas with vertically separated flows at the strait is examined using reanalysis products for four major semienclosed basins: the Mediterranean and Red Seas (antiestuarine) and the Black and Baltic Seas (estuarine). Important differences in the relative contribution to the energy budget of the wind work versus the surface buoyancy flux are found within basins of the same type, and these differences help explain some qualitative aspects of the basins’ flow.