Weather in a tank is being implemented at multiple universities (UMass Dartmouth, Penn State, UW Madison, Johns Hopkins University and Millersville University led by MIT) to incorporate lab experiments in the curriculum at many levels. These experiments demonstrate essential phenomenon related to atmospheric and ocean circulation, and are linked to theory and observations related to the atmosphere and ocean. Here we describe its use in an undergraduate research project.

The Weather in a tank setup is used here to design a new experiment which illustrates wind driven Ekman divergence for a stratified ocean. A two layer system is setup using dyed denser water as the bottom layer upon which a layer of less dense water is added. Salt is used to vary the density of water. Computer cooling fans are used to blow wind on a rotating two layer system. When the wind blows cyclonically, it forces the surface layer water to the edges of the tank. The resulting Ekman divergence of the top layer raises the interface between the two layers. The effect is very clear at high fan speeds since the interface between the two layers rises visibly at the center of the tank. The flow can be visualized further using potassium permanganate to trace flow along the bottom, methylene blue for the surface, and pre-soaked tapioca for the interface. This demonstration can be used to illustrate circulation in the sub-polar ocean gyres. Other experiments being tried involve using this setup to illustrate Ekman convergence and wind-driven upwelling over a stratified ocean.