The distribution and classitication of bottom crevasses from radar sounding of a large tabular iceberg

Bottom crevasses at the base of an iceberg or ice shelf are identified in radar sounding observations from their long echo tails. In November 2001, a radar sounding survey was conducted over iceberg B15A, which calved off from the Ross Ice Shelf, Antarctica, in March 2000. Pervasive basal cracking was observed, and the distribution of bottom crevasses along the flight lines is presented. The echo tails were quantitatively analyzed using a physically based model for backscattering from bottom crevasses. The identified crevasses are classified as either major water-filled crevasses or incipient/freezing crevasses, and estimates for crevasse heights are given.