The Freshwater Balance of the Adriatic Sea: A Sensitivity Study

The Adriatic Sea is a narrow semi‐enclosed basin with considerable freshwater inflow, connected to the saltier Mediterranean Sea through a narrow strait. The northern and central parts of the basin are characterized by a shallow shelf, while the southern part features a pit exceeding 1,200 m in depth. We conducted a series of modeling experiments over a 16‐year period (2000–2015) using different runoff configurations and different sources of atmospheric forcing to investigate the sensitivity of the Adriatic Sea circulation and hydrology to freshwater balance and heat loss. Our results show that the shelf salinity and the salinity of the surface layers in the southern Adriatic are part of a self‐amplifying loop involving dense water formation, water exchange with the Mediterranean Sea, and salty water intrusions to the shelf. Therefore, the characteristics of the basin and the water circulation are highly sensitive to the freshwater budget and heat losses. River discharge is subject to large interannual variations and is poorly known for many of the Adriatic freshwater sources. To improve the accuracy of the freshwater budget, we created a new climatology for three Albanian rivers and modulated the monthly climatological discharge in accordance with the rivers Po and Isonzo (Soča). Evaporation, precipitation, and heat losses vary strongly among the available atmospheric reanalyses and we show that the choice of atmospheric forcing has a substantial impact on the hydrology and circulation of the Adriatic Sea. Plain Language Summary The Adriatic Sea is a well‐known dense water (DW) formation site with the densest water forming in the northern part of the basin. Our modeling experiments show that the salinity of the surface water in the Adriatic Sea has a strong influence on DW formation and on circulation down to the bottom of the deepest part of the basin. The model proves to be very sensitive to freshwater input (rivers, precipitation) and evaporation, as well as to heat losses during strong wind events, which means that the implementation of river runoff and the choice of atmospheric forcing have a decisive influence on the water exchange between the Adriatic and the Mediterranean Sea and the behavior of the whole Adriatic basin down to the deepest layers. The differences between model runs are considerable and can reach an order of magnitude for some variables. Key Points The positive‐feedback mechanism amplifies the Adriatic sensitivity to freshwater bal