General information: Monthly mean of the Maximum density gradient (in kg.m-4) derived from the GTEM hydrodynamic model results. GETM solves the three-dimensional hydrostatic equations of motion applying the Boussinesq approximation and the eddy viscosity assumption (Burchard and Bolding, 2002). A detailed description of the GETM equations could be found in Stips et al. (2004) and at http://www.getm.eu. GETM has been successfully applied to different EU regional seas including the Baltic (Lessin et al., 2014), North Sea (Stips et al., 2004), Mediterranean (Macias et al., 2013; 2014a and 2014b) and the Black Sea (Miladinova et al., 2015). Other contextual information: The product is stored in NetCDF data and available for download.