Convective regimes of radiatively heated ice-covered waters

Research based on field measurements shows that solar radiation can sustain convection in water bodies covered by ice. Consequently, radiatively driven convection (RDC) can provide motion and mixing in otherwise quiescent under ice environments. There are two distinctive elements that make under ice RDC different from other examples of convection. First, the fluid is internally heated, that is, thermal energy is transferred directly to the bulk of the fluid. The energy absorption is prominent near the ice surface as it decays exponentially with depth. Second, the density of water has a strong nonlinear dependence on the temperature around the temperature of maximum density, about 4°C. The equation of state can be well approximated by a quadratic model between 0°C and 8°C. We will show that in the aforementioned range of temperatures, different quasi-steady-state regimes of under ice RDC can be observed. These regimes are identified by a theoretical analysis of the equations of motions, and are confirmed by direct numerical simulations.