Horizontal convection: ocean energetics, heat flux, upper-bounds and scaling
I’ll begin by surveying the current understanding of the mechanical energy balance of the ocean i.e., the identification of the main sources of the energy that power ocean circulation, turbulence and mixing. This motivates the study of convection driven by differential heating along one horizontal boundary (e.g., the sea surface) of a fluid-filled volume. This problem of horizontal convection is the main fluid-mechanical model used to understand the role of surface buoyancy forcing in oceanography. Horizontal convection also serves as an interesting counterpoint to Rayleigh-Benard convection. In contrast to Rayleigh-Benard convection, it is easy to show that horizontal convection violates the so-called "zeroth law of turbulence”. I’ll conclude with a discussion of rigorous bounds on the heat flux on the horizontal convection, and the large gap between those bounds and recent numerical results.