This picture shows the baroclinic instability of a coastal gravity current visualized by dye. Our experiments were carried out using a scaled model of the Black Sea mounted on a rotating table to simulate the effects of the Earth's rotation. The tank was filled with saline water while the source of fresh dyed water was located in the lower right hand corner of the model. The source allowed us to simulate the supply of fresh water by rivers in the western part of the Black Sea. The fresh water is then transported in cyclonic direction around the sea forming the so-called Rim Current. The current becomes unstable due to the baroclinic instability and forms meanders and vortices. Arrow in the picture indicates the pairing of two vortices.

Reference:

Blokhina, M. D. and Y. D. Afanasyev: Baroclinic instability and transient features of mesoscale surface circulation in the Black Sea: laboratory experiment, J. Geophys. Res. Oceans, 2003, 108 (C10), 3322, doi:10.1029/3003JC001979.