Salinity and horizontal components of velocity of the eastern part of the Black Sea

The high resolution Black Sea circulation in 2008 - 2009 from numerical simulations obtained with NEMO modeling framework v 3.6 [Madec et al., 2016]. Such a resolution was used in order to reproduce meso- and submesoscale dynamics in the so-called Euxinus cascade, including basins of the Azov, Black and Marmara Seas [Mizyuk, Puzina, 2019; Mizyuk, Korotaev, 2020].

Below the brief description of the developed regional configuration is presented. The horizontal grid is a quasi-uniform geographical mesh with a resolution of 1/96° × 1/69° northward and eastward correspondingly. The model bottom topography is based on bathymetric data from the EMODnet v1 digital elevation model (URL: http://www.emodnet-bathymetry.eu). To reproduce adequate flow values through the Bosphorus Strait, the "partially closed cell” technique was used [Madec et al., 2016]. The calculation was carried out for the period 2008-2009. For vertical descritisation we used a partial step z-coordinate. The time step of 1 min was chosen.

Vertical turbulent mixing was performed using the k – ε model [Rodi, 1987]. The lasteral diffusion on momentum and tracers described with the bilaplacian operator. The corresponding values for turbulent viscosity and diffusivity are (-4 10⁷ m⁴/s) and (-8 10⁶ m⁴/s).

The vector form was used for momentum equations with an energy and enstrophy conserving scheme. Advection terms of tracer equations are calculated with the TVD scheme [Zalesak, 1979] . The UNESCO formula is used as the equation of state. The sea surface height is calculated using split-explicit scheme.

The initial temperature and salinity for the Black Sea (BS) basin were taken from BS Marine Forecasting Center (http://mis.bsmfc.net:8080/thredds/catalog.html). For the Sea of Marmara the initial conditions are taken from the product of the Global Ocean reanalysis of CMEMS (www.marine.coperniucs.eu).The initial conditions for the basin of the Azov Sea were considered as climate data obtained using an optimal interpolation procedure of all available in-situ measurements provided by CMEMS in-situ TAC and SeaDataNet project (https://www.seadatanet.org/).

Surface boundary conditions were obtained the product of ECMWF ERA5 reanalysis [Hersbach et al., 2020] with the spatial resolution of 1/4° and time resolution of 1 h. Open boundary conditions for Marmara Sea.