Morphodynamics of melting ice over turbulent warm water streams*

The morphodynamics of ice melting over warm water currents is characterized by complicated interface patterns commonly observed under ice shelves that depend on the flow velocity. Since these features can affect the interfacial heat transfer, a precise appraisal of these phenomena, which is not fully addressed in most ice melting models, has major implications for quantifying global melt rates. We investigate ice morphodynamics using direct numerical simulations of Navier-Stokes and energy equations, coupled with a phase field method in an open channel configuration. At low Reynolds number, streamwise undulations appear that can be linked to the near-wall turbulent streaks. As Reynolds number increases, these undulations combine with spanwise ripples of much greater length scale. These ripples are generated by a melting mechanism controlled by the instability originating from the ice-water interactions. Through a melting/freezing process, ripples evolve downstream with a migration velocity much slower than the turbulence characteristic velocity. This instability is due to a relative phase lag between the shear and heat flux at the ice-water interface, which generates from induced pressure anomalies and is not explainable by the Reynolds analogy.