Sensitivity of free and forced oscillations of the Adriatic Sea to sea level rise

The expected global warming will cause a sea level rise (SLR) that, in addition to direct effects on coastal areas, will affect ocean dynamics. In the Adriatic Sea, seiches, tides and storm surges will change in a way that will depend on the possible human interventions to counteract floods. Such actions have 2 extremes: a full compensation strategy (FCST), preserving the present coastline by dams, and a no compensation strategy (NCST) that allows a free expansion of the sea into the low plains. Numerical models were used to describe the different scenarios. FCST would result in increased wave speed and reduced friction, while NCST would give a larger basin extension. In the former case, the resonant period was shortened and moved away from the period of tides: the amplitude of these, and also the surge height, would be reduced (if all other conditions are maintained), while seiches would show an overall larger range. In contrast, the absence of countermeasures would lengthen the resonant period, giving larger tidal range in the northern part and stronger surges. In the case of NCST, assuming an extreme 10 m SLR, dramatic effects would be observed on the semidiurnal tide and the second seiche that would almost double their range at the coast. The results emphasize the strong difference stemming from alternate compensation strategies, but they also show that the changes in the amplitude of the sea surface oscillations are small with respect to the SLR; indeed, not relevant for the variations of level expected for the next 100 yr.