NEW OBSERVATIONS ON BOTTOM CURRENTS IN THE SOUTHERN ADRIATIC AND IONIAN SEAS (EASTERN MEDITERRANEAN-SEA)

In this paper we describe and discuss the bottom motion of a vein of dense water which flows from the Adriatic into the Ionian Sea and then into the deepest layers of the Eastern Mediterranean basin. In particular, we present the results of two cruises (GLADYS 87 and CACTUS 87) on board the Italian R/V Bannock, forming part of the P.O.E.M. project. The data consist of CTD casts and dissolved oxygen measurements; our analysis is focused in particular on the physical effects governing the flow of the vein. The data first show that a strong mixing and deepening process occurs in the Southern Adriatic Sea, where a canyon intersects the shelf off Bari. Over this shelf, dense water flows along the isobaths, in agreement with the conservation of potential vorticity, and therefore cannot circumnavigate the canyon. This dense water is consequently forced down into the canyon, causing the above mentioned mixing and deepening processes. Observations made further downstream show impressive evidence of the massive arrival of a new cold Adriatic bottom water south of the Otranto Channel. This water subsequently flows, approximately following the isobaths, along the Italian shelf break into the Gulf of Taranto and then into the deepest layers of the Eastern Mediterranean Sea. Its dynamics are in agreement with the predictions given by the theoretical models of other investigators.