Effect of Wind and Hydrographic Conditions on the Transport of Vistula Lagoon Waters Into the Baltic Sea: Results of a Combined Experiment

The influence of wind and hydrodynamic processes on the spreading of turbid waters from the Vistula Lagoon into the Baltic Sea was studied. Our research is based on joint analyses of remote sensing data and those from concurrent in situ measurements of the three-dimensional structure of the outflow. A strong difference in the water optical properties of the Baltic Sea and the Vistula Lagoon caused by an intense summer bloom of cyanobacteria allowed studies of the evolution and transformation of the outflow in mid-July-early August 2014 using Ocean Color satellite data. Our in situ measurements revealed that waters from the Vistula Lagoon were exclusively present in the upper water layer. The study was conducted under various wind and, therefore, under different upwelling/downwelling conditions, thereby determining different patterns of wind-driven currents, which enabled us to assess their impact on the propagation of the lagoon outflow. One of these patterns was reaching to the south, along the Vistula Spit, and another one reaching to the north, along the Sambia Peninsula. We show that the main spreading direction of the plume strongly coincides with that of wind-driven currents. However, if vortical structures are present in the Bay of Gdańsk, they also affect the plume transformation, and that should be taken into account when the propagation of water pollution is forecasted.