An Integrated Approach to Modelling Hydrology and Water Quality in Glacierized Catchments

Abstract

The results are summarized of an integrated investigation of glacier geometry, ablation patterns, water balance, meltwater routing, hydrochemistry and suspended sediment yield. The ultimate objective is to evaluate the assumptions of lumped, two-component mixing models as descriptors of glacier hydrology, and to develop a semi-distributed physically based model as an alternative. The results of the study demonstrate that a reconstruction of probable subglacial drainage alignments can be achieved through a combination of terrain modelling based on estimated potential surface and dye tracing experiments. Recession curve analysis, evidence of the seasonal instability of the englacial and subglacial electrical conductivities assumed in a mixing model, evidence of the non-conservative behaviour of water chemistry in the presence of suspended sediment, and evidence of the seasonal evolution of the subglacial drainage system based on dye tracing all indicate that an alternative to a lumped, static model of the hydrology is necessary. The alternative presented in this paper is based on the combination of an energy balance model for surface melt which operates on an hourly time step and accounts for the changing spatial distribution of melt through the day as shading patterns change, and routing procedures that transfer surface melt to moulins on the basis of glacier surface gradients, then route water through reconstructed conduit systems using a hydraulic sewer-flow routing procedure. *Now at Department of Geophysics and

Hydrological and biogeochemical cycling along the Greenland ice sheet margin

“…Additionally, the larger volumes of water passing through the subglacial system may facilitate turbulent incidental contact that allows the meltwaters to mobilize terrestrial sources of DOC at the glacier base (i.e., previously overridden soil and vegetation). Previous work in alpine catchments has illustrated that suspended sediment concentrations increase throughout a melt season as sediment sources are accessed by an extending and integrating subglacial drainage network (Clifford et al, 1995;Richards et al, 1996). This reasoning is also consistent with previous fluorescence spectroscopy work by at a polythermal Canadian high Arctic glacier, which showed that the late season subglacial meltwaters bear a terrestrially-derived signature.…”

“…In alpine glaciers, subglacial flowpaths seasonally evolve from a delayed-flow (channelized system) to a quick-flow (distributed system) drainage (Paterson, 1994;Richards et al, 1996). However, the seasonal evolution of subglacial drainage is poorly constrained for the GrIS.…”

The concept of glacier storage: a review

“…On Midtdalsbreen storage occurs throughout the period of measurement (22 June -30 August, 1987), also implying that net release must occur during the cooler part of the year. Similarly, Richards et al (1996) show water balance calculations for Haut Glacier d'Arolla, Switzerland where storage occurs during the first part of the drainage season only to revert to release during the later half of the melt season. They attribute this change to the seasonal reorganisation of subglacial drainage rather than firn and snow storage.…”

Glacier Biogeochemistry

“…The idea was to monitor drainage system evolution by using changes in the hydrochemistry of the bulk meltwaters leaving the glacier, in tandem with an intensive programme of dye injections into multiple supraglacial streams and moulins that would provide a direct measure of water transit times though the glacier and their changes over a full melt season (Richards et al, 1996). HGA ( Fig.…”

“…As a result, we were limited to conducting one experiment every 2-3 days. We were also detecting the dye by manually collecting samples from the stream and pouring Tranter et al, 1996). them through a fluorometer, which meant that someone had to sit by the stream for hours at a time to collect and run the samples.…”