Circulation and mixing in the water masses of the N.W. Aegean Sea (noting effects of waste disposal in Thermaikos Gulf)
Circulation, mixing and other physical oceanographic features within the water masses of Thermaikos Gulf are studied. The study area is situated in the N.W. Aegean Sea, to the north of 40°l7' of latitude. Data were collected during the years 1975-1977, using NIO bottles, driftcards, cruciform drogues and Aunderna current meters. Water masses analysis shows that three major factors control the distribution of water properties and their mixing processes. These are freshwater discharge into the sea from rivers in the northwest of the study area, intrusion of high salinity Aegean Sea water, predominantly from the southeast, and air-sea interaction. Analyses of both Lagranginn and Eulerian current measurements show that horizontal water movements within the bay are dominated by the wind and the flow of the freshwater input from the nearby rivers. Sea surface flows relate to wind direction and during winter are predominantly towards the Aegean Sea. Nearshore upper layer currents are quasi-parallel to the coast and their velocity (speed and direction) is strongly dependent on both the wind speed and direction. Mid-depth and near bottom currents are quite variable and dependent on local winds. Low frequency currents (< 3 days) are attributed to the Etesian winds. In the high frequency range currents are generated by the highly energetic sea-breeze system. Circulation patterns in the study area are modelled numerically. Comparisons between the predictions of the model and both field data and satellite imagery demonstrates that the model is capable of reproducing natural processes with anaccuracy acceptable for engineering purposes. Some consideration is given to dispersion patterns of wastes from the proposed sewage outfalls in the study area.