The hydrographic-hydrochemical state of the Baltic Sea in 2009

The article summarizes the hydrographic-hydrochemical conditions in the western and central Baltic Sea in 2009. Based on the meteorological conditions, the horizontal and vertical distribution of temperature, salinity, oxygen/hydrogen sulphide, inorganic and organic nutrients are described on a seasonal scale.

In Warnemünde, the year 2009 was too warm on average and continued the series of positive anomalies. This is also reflected in the water temperature. All in all, the year 2009 was, after the last four years, the fifth warmest in the investigation period since 1990.

In 2009, two larger barotropic inflow events were observed, in September/October and in November. The last one could be seen in the Bornholm Basin only in January 2010. Whereasthe deep water of the Bornholm Basin remained oxic throughout the whole year, the stagnation period in the Gotland Basin was intensified. Hydrogen sulphide concentrations as well as ammonium and phosphate concentrations of the deep water were in the same range as observed at the end of the last stagnation period in 2002/2003.

Dr. Günther Nausch