Upwelling dynamics in the Baltic Sea studied by a combined SAR/infrared satellite data and circulation model analysis*

Data from the space-borne synthetic aperture radar (SAR) aboard the Envisat satellite and MODIS spectroradiometers on board the Terra/Aqua satellites, and the high resolution Sea Ice-Ocean Model of the Baltic Sea (BSIOM) have been used to investigate two upwelling events in the SE Baltic Sea. The combined analysis was applied to the upwelling events in July 2006 along the coasts of the Baltic States, and in June 2008 along the Polish coast and Hel Peninsula. Comparisons indicated good agreement between the sea surface temperatures and roughness signatures detected in satellite imagery and model results. It is shown that BSIOM can simulate upwelling events realistically. The utilization of modelled hydrodynamics and wind stress data together with SAR and SST information provides an extended analysis and deeper understanding of the upwelling processes in the Baltic Sea.During the active phase of upwelling when the wind is strong, the resulting coastal jet is controlled by vorticity dynamics related to depth variations in the direction of the flow. Typical upwelling patterns are related to the meandering coastal jet and thus associated with topographic features. The longshore transport of the coastal jet is of the order of 104 m s− 1, and the offshore transport at the surface is of the order of 103 m s−1, which respectively correspond to the total and largest river runoff to the Baltic Sea.