ESTUARINE CIRCULATION

A circulation pattern typical of estuaries. Seawater (see seawater composition) flows into the estuary along the bed and mixes with more buoyant, fresh river water through tidal action. Over long timescales, estuarine circulation is recognised by the mean flow of deeper salty water inland and shallow fresher water offshore. When tidal mixing is minimal, salty ocean water flows into an estuary at the base of the water column, promoting water column density stratification and producing a saltwater wedge. The Mediterranean Sea loses fresh water and heat to the atmosphere from its surface water, through evaporation, which promotes anti-estuarine circulation and intermediate water or deep water formation. During sapropel deposition, which occurred episodically during the pleistocene, it is thought that this anti-estuarine circulation weakened, promoting high organic carbon export flux and deep water anoxia.

[See alsoestuarine environments, saltwater intrusion, tides]