SEASONAL-CHANGES IN THE MORPHOLOGY OF THE SUBGLACIAL DRAINAGE SYSTEM,HAUT GLACIER DAROLLA, SWITZERLAND

Citation
P. Nienow et al., SEASONAL-CHANGES IN THE MORPHOLOGY OF THE SUBGLACIAL DRAINAGE SYSTEM,HAUT GLACIER DAROLLA, SWITZERLAND, Earth surface processes and landforms, 23(9), 1998, pp. 825-843
Citations number
32
Categorie Soggetti
Geografhy,"Geosciences, Interdisciplinary
ISSN journal
01979337
Volume
23
Issue
9
Year of publication
1998
Pages
825 - 843
Database
ISI
SICI code
0197-9337(1998)23:9<825:SITMOT>2.0.ZU;2-7
Abstract
Dye tracing techniques were used to investigate the glacier-wide patte rn of change in the englacial/subglacial drainage system of Haut Glaci er d'Arolla during the ablation seasons of 1990 and 1991. Analysis of breakthrough curve characteristics indicate that over the course of a melt season, a system of major channels developed by headward growth a t the expense of a hydraulically inefficient distributed system. By th e end of the melt season, this channel system extended at least 3.3 km from the snout of the 4 km long glacier and drained the bulk of supra glacially derived meltwater passing through the glacier. The upper lim it of the channel system closely followed the retreating snowline up-g lacier. Rates of headward channel growth reached c. 65 md(-1), althoug h these rates decreased in the upper 1 km of the glacier where snowlin e retreat exposed a patchy firn aquifer. It appears that the removal o f snow (with its high albedo and significant water storage capacity) f rom the glacier surface resulted in a dramatic increase in the volume of runoff into moulins, and in the peakedness of daily runoff cycles. This induced transient high water pressures within the distributed dra inage system, which caused it to evolve rapidly into a channelised sys tem. It is therefore likely that, at a local scale, channel growth occ urred down-glacier from moulins, and that the overall up-glacier-direc ted pattern of channel formation was caused by the retreating snowline exposing new moulins and crevasses to inputs of ice-derived meltwater . Damping of diurnal melt inputs by storage in the firn aquifer accoun ts for the slowing of channel growth in the upper glacier. (C) 1998 Jo hn Wiley & Sons, Ltd.