The Turbulent Convective Plume at Ice Shelf Fronts and the Sides of Tabular Icebergs

We present laboratory experiments and theoretical analysis that quantify the turbulent buoyant plume formed by the dissolution of a vertical ice face in homogeneous salt water. In our experiments, we vary the temperature and salinity of the salt water and measure the dissolution rate of the ice, the temperature of the ice-water interface, the maximum vertical velocity of the buoyant plume, and the rate at which the laboratory tank becomes stratified with buoyant fluid. Using this experimental information, we then construct a theoretical model of the turbulent buoyant plume as a function of height. The plume has a top-hat entrainment coefficient of 0.048 ± 0.006, and is found to have substantial drag. The plume model is used to calculate a plume width, velocity, buoyancy and Reynolds number for typical dissolving icebergs and ice shelf fronts.

Our laboratory experiments also examine the effect of a linear salinity gradient on the dissolution of a vertical ice face. As the stratification is increased, the dissolution rate, the interface temperature and the maximum vertical plume velocity all decrease, and their dependence on height changes. Based on plume theory in a homogeneous ambient fluid, we define a critical height, z_c = 11 Φ^1/2N^-3/2, that defines where stratification will become important. Our experimental results are consistent with this theoretical critical height. We calculate values of z_c for a selection of glaciers around Antarctica and Greenland and find that stratification typically becomes important after several tens of metres. Our results also suggest that the Antarctic and Greenland ice shelves are highly sensitive to any changes in ocean stratification.