Direct Numerical Simulations of Forced Turbulence within an Ice-Shelf Ocean Boundary Layer

Ice sheets in Antarctica and Greenland have the potential to cause catastrophic sea level rise. However, their fate is highly uncertain. Part of this uncertainty lies in the interaction between ice shelves, the floating extensions of ice sheets, with a warming ocean. Here, we use idealized direct numerical simulations (DNS) to investigate melting beneath an ice shelf. The simulations are based on recent measurements made beneath the George VI ice shelf in West Antarctica (Kimura et al., 2015). The measurements suggest that turbulence associated with double-diffusive convection may influence the melt rate of the ice shelf. We investigate this scenario by forcing turbulence in the far field, away from the ice, where the temperature and salinity are relaxed towards imposed background values. A dynamic boundary condition allows the melt rate and the associated heat and salt fluxes to respond to the turbulence. The fluid density can be stabilizing or de-stabilizing depending on the parameters and initial conditions, and the melt rate changes accordingly. A comparison of the results with simulations of shear-driven turbulence and the observations suggests improvements to existing parameterization schemes.