Ice melting in saltwater: formation of a stratifiedsystem in laboratory experiments

We report results on the melting of a tubular ice cuboid in saltwater heatedfrom below. We develop a meter-scale experimental setup capable of detectingthe ice-water interface and measuring the temperature, salinity, and velocity fields simultaneously, offering a route to quantitative understanding of multi-component systems with phase changes. We show that during melting, a two-layer system can form spontaneously due to the competition between the destabilizing temperature gradient and the stabilizing salinity gradient. The upper layer, closeto the ice, is quiescent while the lower layer is convective. Such a layered system displays a large vertical gradient of kinetic energy, which is characterized by means of a novel multi-step PIV approach that allows us to increase the signal-to-noise ratio in the velocity fields obtained by particle image velocimetry. Using a staircase profiling method, we enable reliable and non-intrusive temperature and salinity measurements. Using the measured salinity and temperature profiles of the two-layer system, we derive a model for the melting of ice which compares quantitatively well with experimental data.