On man-induced variations in the circulation of the Mediterranean Sea

The response of the Mediterranean Sea to a diversion of rivers, such as the Nile, for agricultural use, is investigated by a simplified dynamical model for the Mediterranean basin. Solutions are obtained by using the principle of “hydraulic control” at the Straits of Gibraltar, volume and salinity conservations, and perturbation techniques. It is found that such a diversion causes an increase of salinity in the basin and alters the exchange between the Mediterranean Sea and the Atlantic Ocean. The predicted result is an increase in the transport through the Straits of Gibraltar. This increase of both the transport into and from the Mediterranean is about eight times larger than the amount of water which is diverted and is expected to take place within 25–50 years after the diversion. For the Nile alone, which has been diverted in the mid-1960s, an increase of ?0.5 % in the transport through the Gibraltar Straits will occur and, if all runoff flowing into the Mediterranean Sea was to be diverted, an increase of ?3.5% will take place.