The Effect of Bubbles Released from a Melting Ice Wall on the Melt-Driven Convection in Salt Water

Abstract

The buoyancy created by the release of air bubbles from melting glacial ice walls results from both the upward drag of the bubbles and the density defect caused by the steady-state distribution of bubbles in the water. Calculations using typical antarctic ice bubble concentrations and Southern Ocean temperatures and salinities show that the bubble buoyancy is comparable to the dilution for vertical ice length scales greater than 100 m. A comparison of laboratory experiments using 0.6 m long sheets of both bubbly and bubble-free ice shows two additional bubble effects. First, the bubbly ice melts in an irregular fashion that produces indentations in the ice which measure 20 mm long, 25 mm wide and 5 mm deep, while the bubble-free ice melts smoothly, Second, the ice-water interface salinity in the bubbly case is higher than in the bubble-free case. Finally, the observed melt rates lie within 10% of the observed melt rates from the bubble free experiments.