History of Pine Island Glacier with Landsat Imagery

Landsat instruments have been collecting high-resolution imagery of the earth for more than a quarter century. In remote areas, this record often constitutes the longest observation record. Despite persistent clouds shrouding the Antarctic coast, fourteen mostly clear Landsat images of Pine Island Glacier have been collected from as early as 1973 to as recently as 2001. Some of these images have been analyzed by others to determine surface velocity and terminus variability. More recently, Pine Island Glacier has been documented to be accelerating while retreating at its grounding line and thinning in its catchment. Examination of the complete 28-year record of imagery shows a fascinating evolution of the glacier's floating tongue. The calving front was farthest advanced in 1973 and 2001 with less extended positions during the intervening period. Identification of major fractures confirms that these define the boundaries of the major icebergs and that smaller calving events contribute only a minor amount to mass loss from the glacier. The glacier has widened over 3 km near the calving front, an increase of nearly 10% of its width. The major change responsible for this change is a new area of intense crevassing along the northern glacier margin. The leading edge of an ice rise adjacent to the glacier has lengthened, indicating a thinning of the bounding ice shelf. This thinning was been inferred from recent SAR analysis by others. The height of the ice rise will be quantified by photoclinometry of the most recent imagery and an estimate of the thinning will be made. Along the glacier's southern margin, less significant widening has occurred with no indication of thinning in adjacent ice. Various theories for the cause of these changes will be proposed and discussed.