THE ADRIATIC SEA HYDROGRAPHY AND CIRCULATION IN SPRING AND AUTUMN (1985-1987)

The Adriatic basin-wide circulation and its temporal variability are r eviewed on the basis of results from the analysis of hydrographic data collected during four POEM cruises. Major well known features in the circulation are revealed in the data set which covers the period from October 1985 to April 1987. A prominent signal associated with the sea sonal variability is identified in the water outflowing along the Ital ian coast. Differences between autumn and spring in the vein of cold a nd fresh water flowing along the Italian shelf manifest mainly in the temperature field. During the stratified season the fresh water spread s over the entire surface layer of the southern Adriatic. On the other hand, during spring, when the sea is vertically homogeneous, the fres h water remains confined to the surface longshore boundary layer over the entire length of the Italian coast. Layers below the seasonal ther mocline at the eastern portion of the sea display very weak seasonal s ignals. A strong signal associated with the inter-annual variations al so has been documented from the analysed data set; it mainly appears i n the salinity field. It is shown that in spring 1986, the salinity av eraged over the entire water column north of the Palagruza Sill is low er by 0.3 psu than in spring 1987. A similar, but less prominent diffe rence is noted in the southern Adriatic. An attempt is made to associa te these differences with variations in climatic conditions over the a rea, the river runoff and the Mediterranean water inflow.