The model has shown excellent performance in different applications, from basin-scale estimates of the upwelling features in the entire Baltic Sea and mean circulation and water age of the Gulf of Finland (Andrejev et al. 2004a,b) down to the small-scale reproduction of surface buoy drift (Gästgifvars et al. 2006). The quality of the simulation of the hydrophysical fields is analysed in detail within the framework of a model intercomparison for the Gulf of Finland (Myrberg et al. 2010). The model resolution for the Gulf of Finland was originally restricted to 1 nm in order to match the available bathymetric information

for the entire Baltic Sea (Seifert Protein Tyrosine Kinase inhibitor et al. 2001) but has been recently increased

to 0.25–0.5 nm. A detailed description of the features and approximations of the latest high-resolution version of the model is presented in Andrejev et al. (2010). GSK2118436 concentration In order to ensure comparability of the results with earlier studies (Andrejev et al. 2004a,b, Soomere et al. 2010), we used the simulation period of 1 May 1987–31 December 1991. The OAAS model was run for the Gulf of Finland to the west of longitude 23° 27′E (Figure 2) at three different horizontal resolutions – 0.5, 1 and 2 nm – but with an otherwise identical vertical resolution (1 m) and forcing and boundary conditions. The impact of the rest of the Baltic Sea is accounted for in the form of the relevant boundary conditions along this longitude, optionally with the sponge layer approach (see Andrejev et al. 2010 for details). The

boundary conditions (salinity, temperature and sea-level elevation) were extracted at 6 hour intervals from simulations performed with the Rossby Centre coupled ice-ocean model (RCO, Meier et al. 2003). The RCO model is based on the Bryan-Cox-Semptner primitive equation ocean model with a free surface but contains several parameterizations with a special importance for the Baltic Sea, such as a two-equation turbulence closure scheme, open boundary conditions and a sea-ice model. It was run with a horizontal resolution of 2 nm that is usually sufficient for eddy-resolving runs Ponatinib order in the Baltic Proper (Lehmann 1995). The initial sea water temperature and salinity fields for all the OAAS model resolutions were constructed by an interpolation of the RCO data. The modelling in the Gulf of Finland started from the resting water masses and with the sea level equal to the barometric equilibrium. Owing to the realistic initial data and high-quality boundary information, the modelled fields are plausible from the very beginning of calculations and the final spin-up of the model takes ca 1–2 weeks for the surface layer dynamics.