Diurnal variations in vertical strain observed in a temperate valley glacier

During a period of diurnal fluctuations in glacial flow speed, vertical strain was measured with sub-daily temporal resolution on Unteraargletscher, Switzerland. Mean vertical strain in boreholes up to 300-m deep in 400-m-thick ice was found to fluctuate diurnally. Vertical strain rates were tensile in the daytime and compressive at night, with a magnitude of up to 10(-3) day(-1). Horizontal surface strain was observed to fluctuate in a manner consistent with the vertical deformation. Diurnal surface flow speed variations correlated well with basal water pressure suggesting a basal control on temporal flow variations. Nevertheless, the strain rate measurements indicated that changes in surface flow speed are affected by internal ice deformation and not a direct measure of local basal motion. Basal conditions in the surrounding neighborhood and their temporal variations take an important role in short-term glacial flow fluctuations.

Details

Publication status:
Published
Author(s):
Authors: Sugiyama, Shin, Gudmundsson, G. Hilmar

On this site: Hilmar Gudmundsson
Date:
1 January, 2003
Journal/Source:
Geophysical Research Letters / 30
Page(s):
4pp
Digital Object Identifier (DOI):
https://doi.org/10.1029/2002GL016160