Cj. Vanderveen et Im. Whillans, LOCATION OF MECHANICAL CONTROLS ON COLUMBIA GLACIER, ALASKA, USA, PRIOR TO ITS RAPID RETREAT, Arctic and alpine research, 25(2), 1993, pp. 99-105
Data collected in 1977, before the start of the major retreat in 1981,
are used to compute stresses acting on Columbia Glacier. Contrary to
the situation in many other glaciers, where the driving stress is a go
od measure of basal drag, horizontal strain rates are large and spatia
lly variable and the associated viscous forces are large. These result
in important force transmissions along and across the glacier. Basal
friction is more constant than is the driving stress, except near the
terminus where basal resistance is concentrated at certain sites. The
use of a valley shape factor as used in many one-dimensional models is
tested against the present, more thorough analysis. It is found to be
valid for longitudinal averages over more than about three ice thickn
esses (about 1500 m). The average shape factor is 0.78, meaning that 7
8% of the flow resistance to a flowline at the center of the glacier i
s due to drag at the glacier base.