TY - JOUR
T1 - Rapid Glacier sliding, reverse ice motion and subglacial water pressure during an autumn rainstorm
AU - Fudge, T. J.
AU - Harper, J. T.
AU - Humphrey, N. F.
AU - Pfeffer, W. T.
PY - 2009
Y1 - 2009
N2 - Measurements of basal water pressure from 15 boreholes located at both local (tens of meters) and regional (kilometers) length scales were used to elucidate the pressure/sliding relationship during an autumn rapid motion event on Bench Glacier, Alaska, USA. The 8 day event had two distinct phases, each with a ten-fold speed-up with respect to winter velocity. The water pressure in all 15 boreholes varied synchronously during the speed-up. The first phase of rapid sliding began after a peak in basal water pressure and continued while the pressure was elevated and stable, or decreasing. The second phase of rapid sliding occurred when the basal water pressure was low but increasing, and terminated before the pressure peaked. Pressure and velocity do not appear unrelated, but the pressure/sliding relationship was not consistently linked to increasing, decreasing or a critical water pressure. The pressure variations and sliding accelerations are a response to a warm rainstorm, although equally large input events occurred in weeks prior with no apparent response. Drainage system evolution therefore appears to play a key role in both the acceleration and the pressure/velocity relationship. Basal cavity dynamics are likely responsible for three episodes of reverse (up-valley) motion observed after enhanced sliding.
AB - Measurements of basal water pressure from 15 boreholes located at both local (tens of meters) and regional (kilometers) length scales were used to elucidate the pressure/sliding relationship during an autumn rapid motion event on Bench Glacier, Alaska, USA. The 8 day event had two distinct phases, each with a ten-fold speed-up with respect to winter velocity. The water pressure in all 15 boreholes varied synchronously during the speed-up. The first phase of rapid sliding began after a peak in basal water pressure and continued while the pressure was elevated and stable, or decreasing. The second phase of rapid sliding occurred when the basal water pressure was low but increasing, and terminated before the pressure peaked. Pressure and velocity do not appear unrelated, but the pressure/sliding relationship was not consistently linked to increasing, decreasing or a critical water pressure. The pressure variations and sliding accelerations are a response to a warm rainstorm, although equally large input events occurred in weeks prior with no apparent response. Drainage system evolution therefore appears to play a key role in both the acceleration and the pressure/velocity relationship. Basal cavity dynamics are likely responsible for three episodes of reverse (up-valley) motion observed after enhanced sliding.
UR - http://www.scopus.com/inward/record.url?scp=70350111026&partnerID=8YFLogxK
U2 - 10.3189/172756409789624247
DO - 10.3189/172756409789624247
M3 - Article
AN - SCOPUS:70350111026
SN - 0260-3055
VL - 50
SP - 101
EP - 108
JO - Annals of Glaciology
JF - Annals of Glaciology
IS - 52
ER -