Gliders for studies of multi-scale variability in the Baltic Sea

The Baltic Sea consists of several sub-basins. They all have their own physical characteristics and motion scales. General circulation and meso-scale eddies in the basins are in continuous interaction. Traditional monitoring by research ships, gives a general impression on the conditions, but that impression is not detailed unless towed instruments are used. Gliders have extensively been used for ocean research and monitoring in last decade. In Europe, a pan-European glider infrastructure is being planned in a EU funded project, Gliders for Research, Ocean Observation and Management (GROOM). Finnish Meteorological Institute (FMI) and Plataforma Oceánica de Canarias (PLOCAN) organized a joint experiment to Bothnian Sea and Archipelago Sea, two sub-basins of the northern Baltic Sea, to study the use and potentials of gliders in these shallow, low-salinity environments. The horizontal length scale of the glider observations in 100 m deep waters is about 200 m. It is well below the local internal Rossby-radius of deformation. Thus gliders give good possibilities to study multi-scale interactions and exchange processes between coastal and open-sea waters in detail. We used the glider in section mode in an open sea area and as a virtual mooring in a semi-enclosed small basin within an archipelago. These experiments proved the usefulness of gliders in the Baltic Sea research.