What was done
Satellite radar measurements of the grounding line of Pine Island Glacier from 1992 to 1996 were studied to determine whether or not this major ice stream in remote West Antarctica is advancing or retreating.

What was learned
Analysis of the radar data led the author to conclude that Pine Island Glacier's grounding line has retreated inland at a rate of 1.2 ± 0.3 kilometers per year over the four-year period of the study. The author suggests that this retreat may be the result of a slight increase in ocean water temperature, which, though not measured, is not unlikely for the deep water of the southeast Pacific.

What it means
The retreat of Pine Island Glacier's grounding line has elicited speculation that, given the slope of the ground on which the glacier resides, the glacier's retreat may accelerate, ultimately leading to the collapse of the West Antarctic Ice Sheet in a couple of centuries. Because this study utilizes only four years of data, however, questions concerning the long-term stability of the West Antarctic Ice Sheet, in the words of the author, "cannot be answered at present." In addition, although the glacier's grounding line has been found to be retreating, more recent satellite images suggest that the location of the ice front has remained stable.