On the response of Black Sea level to external forcing: altimeter data and numerical modelling

In this work, we address the Black Sea setup of Nucleus for European Modelling of the Ocean (NEMO), and in particular some model enhancements associated with the most important characteristic of ocean dynamics in this semi-enclosed basin, that is the sea-level variability and its relationship with water cycles and wind. Forcing data are presented in detail and compared with previously used coarser-resolution data. One emphasis in this paper is on the statistical analyses of forcing data and outputs from simulations with a focus on the sea level and its change. Numerical simulations are carried out as free run, and alternatively, altimeter data assimilation based on displacement of water properties in the pycnocline is used. Comparisons between the two runs identify the robustness of circulation driven by water balance and winter intensification. Problems in the model to replicate the redistribution of water properties between the two sub-basins in free-run mode are also discussed, which are observed during years with extreme climatic conditions.