ABSTRACT
Abstract An inverse, or negative, estuary is a semi-enclosed sea or embayment within which loss of fresh water is more than the gain by runoff and precipitation combined. The tide-averaged internal circulation comprises an outflow of saline water near the bottom and an inflow of less saline water near the surface. Inverse estuaries are not uncommon features of the world’s coastal environment and one can distinguish two subsets according to geographical location. The first subset includes those estuaries in which freshwater removal is the result of an excess of evaporation over precipitation. These mostly occur in low latitudes of both hemispheres and are associated with arid conditions (e.g. the Red Sea, the Mediterranean, the Arabian Gulf, the Adriatic and the South Australia gulfs). The second subset covers those estuarine systems in which freshwater removal is achieved by freezing and the production of sea ice, which involves rejection of salt from the ice crystal lattice and hence increases the salinity of the underlying fluid. This type is therefore confined to high latitudes and principally the polar regions (e.g. the Weddell Sea, the Ross Sea and the Beaufort Sea). Although there have been many observational and numerical studies of the dynamics of classical positive estuaries since Pritchard’s pioneering work in the early 1950s, inverse estuaries have received relatively little attention. This paper reviews available literature relating to physical processes in several inverse estuarine systems and provides a framework for better understanding their characteristics and dynamics, hence providing another perspective on estuarine processes in general.
