The Adriatic Sea is a latitudinally elongated continental basin, with length and width of 800 km and 180 km respectively and with its major axis oriented along the northwest–southeast direction. It is located in the central Mediterranean, between the Appennines chain and the Balkans and is connected to the Ionian Sea by the 74 km wide Otranto strait. Marked morphological differences characterize the basin along its longitudinal transversal axes. Accordingly the Adriatic Sea can be divided into three sub-basins (Artegiani et al., 1996).
The northern sub-basin is characterized by a shallow average depth of ~ 35 m with a very weak bathymetric gradient toward south-east where the 100 m bathymetric line is met in front of Giulianova (Italy). Po and the other northern Italian rivers contribute to a strong river runoff (~ 3000 m3 s-1) and are believed to be the source of about 20% of the total Mediterranean river runoff (Hopkins, 1992).
The middle Adriatic is a transition zone between the northern and the southern sub-basin and is charcterized by fairly open sea conditions. It spans from the 100 m bathymetric line to the Pelagosa sill (~ 170 m depth), located around the line connecting Vieste and Split. The average depth of the middle sub-basin is ~ 140 m with the two Pomo and Jabuka depressions reaching ~ 270 m.
The southern sub-basin extends from Pelagosa sill to Otranto sill which divides it from the Ionian Sea. Each of the western and eastern coasts have a narrow continental shelf (20-30 km wide to the shelf break at 200 m depth), a steep continental slope reaching 1000 m and a fairly flat abyssal plain, with a maximum depth of 1270 m. The water exchange with the Mediterranean Sea takes place through the Otranto Channel, whose sill is 800 m deep.
The eastern coast of the Adriatic Sea is generally high and irregular and is characterized by the occurrence of many islands and a rocky steeply sloping bathymetry. The western coast is low, mostly sandy and generally regular with a gentle slope. A large number of rivers discharge into the basin, with significant influence on the circulation, particularly relevant being the Po River in the northern basin, and the ensemble of the Albanian rivers in the southern basin.