Experiments on turbulent horizontal convection at high Schmidt numbers.

We explore regimes of turbulent horizontal convection at high Schmidt numbers in a laboratory experiment. This study unveils flow regimes, previously observed at intermediate Prandtl numbers, which are diagnosed using the relationship between fresh and salt-water fluxes at the surface and the resulting overturning flow. We set up the experiment using a transparent acrylic tank. Along the top of the tank are two wells made up of two semipermeable membranes. One has fresh water continuously pumped in and out, while the other has salt water. The diffusion of the salt ions across the membranes act as a horizontally driving force. To measure the overturning circulation, we perform particle image velocimetry together with conductivity measurements to determine the properties of the horizontally-driven convective flow. Results are analyzed using the scaling laws theoretically predicted by Shishkina et al. (2016) and Griffith et al. (2005). These results allow for drawing new conclusions on the regime diagram of horizontal convection and complement our understanding on the role of large-scale horizontal buoyancy gradients in driving large-scale overturning circulations.