Horizontal Convection in the Presence of a Surface Stress

Horizontal convection, the flow driven by buoyancy fluxes imposed along a horizontal boundary of a fluid, is a model of the meridional overturning circulation of the oceans. We explore features of horizontal convection in the presence of a surface stress. The buoyancy flux is achieved by injecting a plume of dense water into a fresh-water tank, while continuously imposing a fresh-water surface boundary condition. The magnitude of the stress is varied by adjusting the flow rate of fresh water traversing along the surface. We measure the steady-state density field using the Synthetic Schlieren method, and qualitatively observe the flow via discrete dye injections. The vertical and horizontal velocities are determined by PIV techniques. Our goal is to examine the eff ects of a surface stress of varying magnitude and direction on the general horizontal convection. We compare laboratory data to scaling analyses for the boundary- layer thickness and the strength of the overturning circulation. The addition of a surface stress to horizontal convection may o ffer insight into the e ffects of wind on the ocean surface, namely the implications of a kinetic energy source on the overall energetics of the circulation.