Weekly mapping of vertical temperature and salinity fields was carried out across the Gulf of Finland in summer 2006 and spring 2007. Using successive cross-gulf vertical sections of salinity and wind data from the region the variations of estuarine and transverse circulation are described. Changes of deep layer phosphate-phosphorus concentrations are found to be related to the described variations in circulation patterns in a season with strong vertical stratification of water column. Cumulative volume transport estimates were obtained using the results of a 3D baroclinic circulation model (HIROMB). We suggest that the north-easterly winds, which intensify the estuarine circulation and lead to the upwelling events along the southern coast of the Gulf of Finland, could have a major impact to the Gulf's ecosystem by importing more saline and phosphorus rich waters. These events with many-fold more intense upward movement and mixing of deep waters (upward diapycnal transport) could contribute significantly to the ventilation of deep layers of the northern Baltic Proper.
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