Effect of rotation rate on the melt mechanics of ice disks

As glaciers in the cryosphere melt, smaller icebergs break off and float freely in the oceans. Icebergs release frozen freshwater far from their source, and this transported meltwater can adversely affect sea ice formation and marine ecosystems. The mechanisms by which icebergs melt is crucial to their effects on the oceans; however, further research on the fundamental melt mechanics of free-floating ice is required. In this study, the melt rate and flow structures of melting ice are investigated for both circular and elliptic rotating ice disks of equivalent aspect ratio (cross-sectional area/height). Experiments are conducted in a quiescent freshwater tank at room temperature. Three rotational cases are studied: axially fixed, free to rotate, and forced to rotate at constant angular velocity. Flow structures beneath the ice are captured via both flow visualization and particle image velocimetry (PIV), and the melt rate is quantified via image-based methods. In the free rotation case, vortical flow structures are observed below the ice. These structures are the result of the density difference between the cold meltwater and the ambient quiescent water, and cause viscous entrainment on the ice-water boundary layer, resulting in the observed rotation. It is found that rotating ice disks have a faster melt rate than fixed ice, and elliptic ice disks exhibited higher rotation rates than circular ice disks.