| | | 18.2 An oceanographic overview |
The Adriatic Sea has an extension by latitude of about 800 km, and by longitude from 100 to 200 km. It consists of a series of three basins, characterized by decreasing depth from the southern to the northern one. An 800 m deep sill partly separates the southern basin, whose depth is greater than 1200 m, from the Ionian Sea, and a second sill, of about 130 m, separates the southern from the central basin, a transversal trench of 270 m maximal depth. Northward a steep slope separates it from the northern basin, whose bottom gently slopes from the 100 m isobath to the 30-40 m average depth of this shallow area (Figure).
The circulation and the distribution of the water masses is strongly influenced by the morphological features of the Adriatic Sea bottom. The sills control the circulation of the dense waters in the deeper part of the central and southern basins, while the thermohaline characters of the waters are strongly influenced in the southern basin by the exchange with the Ionian Sea, and in the northernmost basin by riverine inflow, mainly from the western coast.
The renewal of the whole Adriatic water is estimated to be in the range of 3 to 10 years, whereas every sub-basin and water layer within them show very different renewal time scales, owing to their different volumes, degrees of stratification and relationships between forcing factors. In all basins the small volume of water closer to the coast shows similar characters and phenomenologies, related to physical processes of mixing and circulation with short time and space scales, which also have considerable importance in a part of the shallow northern basin during some periods of the year, in relation to the vertical and cross frontal exchanges of energy and matter.
The circulation is always cyclonic, with a northward flow along the eastern side, and a southward one along the western coast. Both the extension and the intensity of flow in the opposite sides of the basin show large seasonal variations (Figure).
| | | 18.2 An oceanographic overview |