This video shows a numerical simulation of the surface layer of the ocean. In a box roughly 1 km by 1 km in horizontal extent and 100 m deep, currents are generated by two processes. Atmospheric cooling renders surface waters denser and lets them sink, resulting in convection. On a slower time scale, there is an internal so-called baroclinic instability, which slides warm water over cold water laterally. In the video, which shows temperature at the surface of the ocean, convection is visible in the puffy structures that develop very quickly. Baroclinic instabilities evolve more slowly, but eventually develop on top of convection and generate a domain-filling vortex.