Modeling dense water mass formation and winter circulation in the northern and central Adriatic Sea

In this paper, using an eddy resolving primitive equation model, we attempt to provide quantitative answers to some of the still unresolved or poorly understood dynamical issues related to the general circulation of the northern and central Adriatic Sea. The first question we addressed relates to understanding the effects of the major driving mechanisms on the basin circulation. A series of numerical experiments are carried out to examine the circulation produced by various combinations of different forcing mechanisms. Cold air outbreaks (CAO) associated with the northeasterly bora winds, together with uniform surface cooling and freshwater discharge prescribed near the northwestern corner, give a fairly realistic circulation consistent with the observations. This pattern is comprised of an overall cyclonic gyre in the northern basin, with a strong southward flowing jet along the Italian coastline and a broader northward flow along the Croatian coast. The second question addressed is under what conditions convective mixing extends to the bottom of the Jabuka Pit. While the northern shelf is always uniformly mixed to the bottom, the extent of convection within the Pit depends on the overall stratification prior to onset of the CAO event. Strong subsurface stratification between the intermediate and near-bottom layers prevents deep convection. The third question concerns with the role of the rim current along the Italian coast vs the other circulation components in distributing the North Adriatic Dense Water (NADW) within the basin. In general, the strong density front developed across the shelf break north of the Jabuka Pit restricts the replenishment of the Pit deep layers by the NADW, Rather, the NADW is transported southward along the Italian continental slope in the form of a vein of underflow, The final question addressed is how the thermohaline structure of the water column evolves after the ending of the CAO event, and of the related convection process. (C) 1999 Elsevier Science B,V. All rights reserved.