Crevasse ages on the northern margin of Ice Stream C, West Antarctica
Abstract:In the 1997/98 austral summer field season, we conducted a ground-penetrating radar survey on the northern shear margin of Ice Stream C, West Antarctica. The radar data were used to identify features near the surface of the ice, including internal layers and buried crevasses. The survey was intended to determine the variation in the age of buried crevasses along the ice stream. A procedure was developed by which the accumulation rate and the age of buried crevasses can be estimated based on radar records, firn-core measurements and the assumption that the crevasses were once open to the surface. With this method we were able to determine the age of buried crevasses with a standard error of 15-20%. We discuss our new results in conjunction with those of Retzlaff and Bentley (1993) on the southern margin of the ice stream. Typical crevasse ages were found to range from 120 to 200 years, although crevasses in a few areas were significantly younger. The youngest crevasses are at the extreme upstream end of the survey, but the next youngest were found midway along the ice stream. Crevasses upstream and downstream are older, with ages 40-80 years greater than those in the middle. Crevasses on the northern shear margin of tributary C2 were 30-50 years older than those on the southern margin. These patterns of crevassing suggest that variability in shear margin response to changes in ice-stream flow played an essential role in determining the time at which crevassing became inactive.
Document Type: Research Article
Publication date: January 1, 2002
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