IN-SITU MEASUREMENTS OF BASAL WATER-QUALITY AND PRESSURE AS AN INDICATOR OF THE CHARACTER OF SUBGLACIAL DRAINAGE SYSTEMS

Continuous subglacial measurements of turbidity and electrical conduct ivity - two indicators of basal water quality can be used to help char acterize subglacial drainage systems. These indicators of water qualit y yield information that complements that provided by water pressure m easurements. Quantitative attributes of subglacial drainage systems, s uch as water velocity and subglacial residence time, as well as qualit ative behaviour - for example, spatial and temporal variations in syst em morphology - can be deduced using water quality measurements. Inter pretation is complicated by the many potential influences on turbidity and electrical conductivity, but when these complications are appreci ated a richer interpretation results. To demonstrate the utility of ba sal water quality measurements, observations from Trapridge Glacier, Y ukon Territory, Canada were examined. The data reveal complex behaviou r of the drainage system, but constraints imposed by basal water quali ty measurements help to clarify the nature of the subglacial flow syst em. The measurement and interpretation methods described and demonstra ted are applicable to other glaciers. As such, they should prove usefu l for characterizing different subglacial drainage configurations and behaviours, thereby improving our general understanding of the hydrolo gy and dynamics of wet-based glaciers.