Process studies on the Po River plume, North Adriatic Sea

The coastal processes in the Adriatic Sea and in particular the development and evolution of the Po River plume are studied with a three‐dimensional, primitive equation model. Experiments are performed to examine the buoyancy‐driven flow and the interaction with topography, wind stress, and ambient stratification. The pathways of particles released from the Po are computed to simulate the transport of land‐drained materials. In the absence of wind forcing, the Po River plume consists of an offshore bulge that occupies most of the north part of the basin and a southward coastal current that is confined within the narrow coastal region along the Italian peninsula. When all Adriatic rivers are included, basinwide, buoyancy‐driven, cyclonic coastal flow is established that diminishes the seaward removal of Po waters and promotes their southward advection through the coastal current. Wind stress modifies the above. Winds that are downwelling‐favorable for the Po discharge site (like Bora) restrict offshore plume development, enhance the southward coastal current, and confine the plume within the narrow western Adriatic shelf. Conversely, upwelling‐favorable winds (like Scirocco) eliminate the baroclinic coastal current and advect low‐salinity Po waters toward the shallow parts of the Northern Adriatic. When preexisting stratification of basin waters is described, the density field is influenced by both temperature and salinity. During winter, when the coastal waters tend to be colder and fresher than offshore waters, the cyclonic circulation is sustained owing to input from rivers and particularly the Po. The intense spatial and temporal variability of wind stress and river runoff and the resulting variability in the circulation of the coastal Adriatic Sea are elaborated through a realistic simulation during January 1994.