The air-sea interactions and the interior mixing are key processes of the global oceanic meridional overturning circulation and in setting the properties (temperature, salinity, chemical concentration) of water masses. Such processes are only crudely parameterized in global ocean models and coupled climate models due to their relatively coarse resolution and the lack of physical understanding of the mixing processes. Due to its unique geometry; to its relatively small size and to its similarities with the global overturning circulation, the Mediterranean Sea offers the possibility to better comprehend the role of mixing processes. Moreover, the substantial changes observed in the Mediterranean water mass properties, in particular the formation of a new warmer and saltier type of deep water in the western Mediterranean Sea, have shown that anomalous surface events cant impact on the deepest layers of the Mediterranean Sea over very short time scales. To understand the future evolution of the anomalous water masses, their impact on the Mediterranean Overturning Circulation and ecosystems, it is critical to better comprehend mixing processes. The aim of this proposal is to provide new insights on the role of mixing processes in the Mediterranean Overturning Circulation. We will investigate the combined role of surface mixing due to air-sea induced and interior mixing in setting the Mediterranean thermohaline structure, by applying a consistent theoretical framework based on the inclusion of air-sea fluxes in the recently developed tracer-contour inverse method. Further more, the results of the tracer-contour inverse method will be combined with nutrients climatological fields to calculate nutrient fluxes and to identify sources and sinks. The outcome of this work will lead to the first estimate of the mixing rates in the Mediterranean Sea based on observations and provide some useful insight on the role of the circulation in controlling the distribution of nutrients.