Recent observations have shown that outflowing Aegean waters have replaced about 20% of the deep and bottom waters of the eastern Mediterranean basin. This indicates changes in the hydrology of water masses in the Aegean Sea and the corresponding thermohaline circulation. In this work we estimate the driving mechanism of the thermohaline circulation, the buoyancy fluxes using 45 years of COADS data. The long term buoyancy loss is estimated to be about 5xl0'6 kg nr1 S'-\ However for certain periods lasting a few years the flux reverses sign and there is buoyancy gain . The reversal of sign is expected to lead in changes of the thermohaline circulation in the basin.