An experiment in a rectangular basin of water is used to demonstrate that a large-scale circulation will result from a zero-mean thermal forcing. The thermal force is a spatially periodic pattern of heating and cooling at the top surface, achieved with an interdigitated array of hot and cold tubes. The experimental results show a very robust, steady flow with ascending flows at each end of the tank and a single descending jet near the left wall. These results suggest that small-scale forcing in surface-driven flows may result in significant large-scale subsurface motion.
