Numerical modelling and analysis of riverine influences in the Mediterranean Sea

Riverine influences in the Mediterranean Sea are investigated by means of numerical experiments performed with an ocean general circulation model implemented in the basin, along with the model capability to correctly reproduce the thermohaline properties of the basin through an improved representation of the riverine inputs. As a first step, an improved implementation of the Dardanelles Strait inflow into the Mediterranean Sea is performed, moving from a river-like parameterization to a lateral open boundary condition implementation. The river runoff impacts on the Mediterranean Sea are then evaluated by means of sensitivity experiments considering an increased number of river runoff sources, different riverine outflow salinity values, a modified mixing at river mouths and a different vertical mixing scheme adopted in the ocean model. With the purpose of further improving the representation of the estuarine processes affecting the riverine outflow salinity and volume flux, which cannot be resolved by the current resolution of the Mediterranean Sea ocean model, an Estuary Box Model simulating the estuaries dynamics is implemented at each river and 1-way offline coupled with the Mediterranean Sea ocean model. The results of the performed numerical experiments are validated with respect to in situ and satellite observations to evaluate the capability of the model to correctly represent the thermohaline properties of the Mediterranean Sea. In addition, the riverine influences are evaluated assessing the impacts of the tested river runoff forcings on the mixed layer depth, the circulation pattern, the sea surface height and the water volume transport through the major straits of the Mediterranean Sea, comparing the numerical results with available climatological data sets and reference literature.