Observations of a reversal in vertical and horizontal strain-rate regime during a motion event on Unteraargletscher, Bernese Alps, Switzerland

Gudmundsson, Hilmar (2002) Observations of a reversal in vertical and horizontal strain-rate regime during a motion event on Unteraargletscher, Bernese Alps, Switzerland. Journal of Glaciology, 48 (163). pp. 566-574. ISSN 0022-1430

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Abstract

During a motion event on Unteraargletscher, Bernese Alps, Switzerland, in spring 1996, surface velocities were measured up to eight times a day at four different locations along the central flowline using global positioning system equipment. In addition, accumulated vertical strains over the uppermost 50 and 100 m were measured at a location where the total ice thickness is 260 m. The motion event was accompanied by high horizontal and vertical strain rates as compared to annual mean values. A reversal in strain regime was observed, with horizontal strain rates changing to extension while vertical strain rates became compressive. This strain-rate reversal coincided, within the temporal resolution of the data, with a maximum in vertical ice displacement at the surface.Within a day, variations in vertical strain from 0.04 a−1 to −0.06 a−1 were observed over the uppermost 100 m. Vertical stretching is estimated to have contributed to at least 20% of the anomalous vertical ice movement at the surface. There were significant differences between measured longitudinal strain, averaged over a distance corresponding to a few ice thicknesses, and measured vertical strain. In spring 1997 a similar, but more detailed, set of measurements was collected at the same measuring site, and vertical strain rates were found to vary non-uniformly with depth, with the largest values closest to the surface.

Item Type:	Article
Subjects:	F800 Physical and Terrestrial Geographical and Environmental Sciences
Department:	Faculties > Engineering and Environment > Geography and Environmental Sciences
Depositing User:	Becky Skoyles
Date Deposited:	21 Feb 2019 11:54
Last Modified:	10 Oct 2019 23:18
URI:	http://nrl.northumbria.ac.uk/id/eprint/38165

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