Modelling changes in Mediterranean thermohaline circulation 1987–1995

The observed changes in the eastern Mediterranean thermohaline circulation between 1987 and 1995 are investigated using an ocean general circulation model. A number of different surface forcing regimes are imposed to investigate the possible causes of the formation of new Aegean deep water. The formation and spreading of the Aegean deep water is assessed in terms of chlorofluorocarbon distributions and the changes in salt content in comparison with observation. It is found that three observed cold winters (of 1987, 1992 and 1993) are enough to generate new Aegean deep water in the model. The addition of anomalous winter wind stresses for the period 1988–1995 increases the southward transport of cool north Aegean water, but does not lead to a significant extra outflow of deep water. The modelled water properties agree well with the observation, but the overall volume of the new deep water is too low and there is no outflow at the straits to the west of Crete. The salt budget is examined to highlight the roles of both vertical redistribution and net inflow of salt at Sicily.