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Ice Thickness Data, Gulkana Glacier, Alaska
On March 28, 1976, a portable ground-based
5 MHz monopulse ice-radar system was used to measure ice thickness at 19
locations: one near measurement site D, seven along a cross profile of the glacier near
measurement site B, and 11 along a cross profile of the glacier near measurement site
A The cross profile of the glacier near measurement site B was roughly located in the field
by walking along a range line that extends from survey monument No through survey monument
Yes and on across the glacier. A similar process was executed for the cross profile near
measurement site A except that in this case the reference survey monuments, There and M,
are located on opposite sides of the glacier. See March (2000)
for more detail about this data.
Location of ice radar midpoints and survey
monuments M, There, No, and Yes in Gulkana Glacier Basin. No, which is
difficult to distinguish from Yes at the scale of this map, lies about 23
m to the northwest of Yes. (Map coordinates are UTM, zone 6; datum is
NAD1983.)
From our measurements of
the glacier surface altitude at sites A, B, and D, we know that the
glacier ice thickness undergoes both seasonal variation and longer term
variations as the glacier adjusts itself to changes in climate. If we
assume that the glacier bed has not eroded significantly between 1976 and
1995, then the surface lowering indicates that the cumulative glacier
thinning from March 1976 (the date of our radar measurements) to March
1995 along the glacier centerline is about 23 m at site A and 7 m at site
B with no cumulative change at site D. The seasonal variation in glacier
surface altitude indicates that the ice thickness varies over the whole
glacier by about 2-5 m from a peak thickness in May or June to a minimum
in August or September. (Click here
for ASCII version of data table.)
Maintainer: Rod March
Last update:
Thursday, February 26, 2004 12:18 PM
URL: http://ak.water.usgs.gov/glaciology/gulkana/ice_thickness/index.htm
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