Diurnal variability of subglacial drainage conditions as revealed by tracer experiments
Article first published online: 15 JUN 2004
Copyright 2004 by the American Geophysical Union.
Journal of Geophysical Research: Earth Surface (2003–2012)
Volume 109, Issue F2, June 2004
How to Cite
2004), Diurnal variability of subglacial drainage conditions as revealed by tracer experiments, J. Geophys. Res., 109, F02008, doi:10.1029/2003JF000082., , and (
- Issue published online: 15 JUN 2004
- Article first published online: 15 JUN 2004
- Manuscript Accepted: 20 APR 2004
- Manuscript Revised: 2 APR 2004
- Manuscript Received: 26 AUG 2003
- glacier hydrology;
- tracer tests;
- subglacial drainage;
 The morphology of the drainage system of Unteraargletscher, Switzerland, and the diurnal variability of drainage conditions were investigated by conducting a series of tracer tests over a number of discharge cycles during the ablation season 2000. Dye injections into a moulin were repeated at intervals of a few hours and were accompanied by simultaneous measurements of discharge of supraglacial meltwater draining into the moulin and bulk runoff in the proglacial stream. Fast transit velocities in conjunction with low dispersion values suggest that the tracer was routed through a hydraulically efficient, channelized drainage system. However, detailed analyses reveal a large diurnal variability in terms of transit velocity and dispersion coefficient. This finding underlines the difficulty of detecting a possible drainage system evolution based on single tracer tests conducted at coarse temporal intervals. Furthermore, the obtained velocity-discharge relationships display pronounced hysteresis. We suggest that the evolution of the cross-sectional area of an ice-walled conduit and the modulation of inflow at the junction of a tributary moulin to a main subglacial channel are responsible for the observed behavior.