Fluid dynamics of subglacial lakes*

Subglacial lakes are isolated, low-temperature and high-pressure water environments hidden under ice sheets. The fluid dynamics of subglacial lakes is controlled by the geothermal flux, which forces vertical convection, and the tilt of the ice-water interface (ceiling), which can drive a baroclinic horizontal flow (due to the pressure-dependence of the freezing point). On Earth, the effect of the geothermal flux is likely to dominate in many subglacial lakes. Thus, in this talk, I will discuss the properties of vertical convection flows in subglacial environments. I will highlight the differences between Rayleigh-Bénard convection and turbulent convection in subglacial lakes due to the nonlinearity of the water equation of state and the fixed-flux bottom boundary condition. I will describe the mixed convective and stably-stratified (two-layer) dynamics of subglacial lakes and discuss how to derive scaling laws for the Nusselt and Reynolds numbers. Implications for flow velocities and the habitability of subglacial lakes on Earth and elsewhere in the solar system (icy moons) will be briefly mentioned.