Suursaar, Ü. and Kullas, T., 2013. Hindcast of wind-driven circulation in a system of straits between the Baltic subbasins in 1966–2011.

The paper presents a study of currents and sea level variations in the nearly tideless sub-basins of the Baltic Sea, the Gulf of Riga and the West Estonian Archipelago Sea, using a high-resolution (of order 1 km grid) shallow sea hydrodynamic model. The model was forced by the measured wind and sea level data obtained from the data-base of the Estonian Meteorological and Hydrological Institute over the period 1966–2011 and validated using the measurements of currents obtained with a bottom-mounted RDCP in the Northern Gulf of Riga in summer 2011 and by sea level measurements at the Pärnu tide gauge in 2011. Flows within the two sub-basins and in the five straits were wind-dependent, each location having its specific wind directions for switching between the patterns. All the straits take part in the water exchange, functioning together as an interconnected oscillatory system and provoking movements in the hydrochemical front between the water masses of different properties. Owing to the factual seasonality in the wind conditions, northward flows prevailed in the centrally located Suur Strait in autumn and winter, but southward flows in summer. Annual net (northward) outflows prevailed in the straits of Suur, Hari and Voosi, but inflows in the Irbe and Soela Straits. The reconstructed long-term variations in water exchange over 46 years indicated climatologically induced interannual variations which are probably related to changes in atmospheric circulation above Northern Europe.