The effect of straits on mesoscale variability in the Azov–Black Sea basin

This paper describes a regional configuration of the NEMO modeling framework for the Azov-Black Sea basin with a regular horizontal grid and a resolution of approximately 1.2 km. The same resolution is applied to reproduce water exchange through the Kerch and Bosporus straits. The simulation for the narrow Bosporus Strait is carried out with the use of the “partially closed cell” technique. The regional configuration is used to simulate mesoscale variability in the Azov-Black Sea basin forced with the ERA5 reanalysis and spanning the period of 2008–2009.The proposed configuration allows the reproduction of major observed features of Black Sea stratification and current variability. Additionally, the model approach reasonably well reproduces currents structure and their variability in both the Bosporus Strait and the Kerch Strait. Furthermore, a comparison of the simulation results with the ADCP observations obtained from autumn 2008–winter 2009 in the different parts of the Bosporus Strait revealed good consistency in the intensities of upper and lower layer transport. Additionally, the model reproduces the observed events of upper and lower current blockings rather well.The simulation revealed that events involving intense inflow of more saline water to the Black Sea basin can result in the formation of lens-like structures similar to Meddies in the Atlantic Ocean. These structures are rather stable and can be traced over long periods of time.A comparison of the high spatial resolution simulation results with space imagery also reveals a realistic representation of the variability in water exchange through the Kerch Strait and related mesoscale features in the Black and Azov Seas.Thus, the application of the high-resolution Azov-Black Sea model together with the relatively simple representation of the Bosporus and Kerch strait dynamics is very efficient for the accurate description of basin mesoscale variability.