There is, however, something wrong with this concentric flow of water. A convection current is meant to carry heat from hot areas to cold areas, but with a concentric flow of water, this obviously doesn't happen. In other words, a concentric flow of water makes for an extremely inefficient thermal convection. If you speed up the rotation of the model, this concentric flow becomes unstable, and begins to meander. This is called baroclinic instability. When water meanders, it moves back and forth from hot to cold areas, carrying the heat as it goes. Compared to a concentric flow, this meandering flow transfers heat far more efficiently.