The role of supraglacial snowpack hydrology in mediating meltwater delivery to glacier systems
This thesis investigates the role that superglacial snowpack hydrology plays in mediating meltwater delivery to glacier systems. The movement of water through glaciers is of fundamental importance as a control on proglacial hydrograph amplitude and timing, subglacial and proglacial geomorphic processes, the hydrochemistry of glacial runoff, and glacier dynamics, and as such has been the subject of considerable research effort. Although studies in non-glacial environments have shown that meltwater waves are both dampened and delayed by passage through snow, the role of supraglacial snowcover in mediating water inputs to the rest of the glacier system ahs received limited attention in studies of glacier hydrology to date. It has been suggested, however, that the varying thickness, and ultimately removal, of the superglacial snowpack may play a role in controlling the timing and magnitude of ice velocity events. Despite this suggested importance there have been few field observations of the hydrological behaviour of supraglacial snowpacks or of the way in which this behaviour evolves during the melt season. A thorough assessment of the linkages between supraglacial snowpack conditions and glacier dynamic events has therefore not been possible. This study helps fill this gap in our knowledge by explicitly investigating the hydrological behaviour of the supraglacial snowpack at an alpine glacier and its evolution during the summer melt season. Field data was collected during two summer field seasons (2003 and 2004) at Haut Glacier d’Arolla, Valais, Switzerland. Dye tracing experiments were used as the primary method of obtaining information about water flow through the snowpack. Dye was used both qualitatively, to give a visual impression of flow patterns through the snowpack, and quantitatively, with return curves detected by fluorometer providing detailed information about rates of dye movement and dispersion through the snowpack. Physically-based modelling representations of water flow through snow also informed consideration of the characteristics of snowpack runoff. Experiments were designed to determine: i) the nature of water flow through the supraglacial snowpack; ii) if, and in what way, this evolves over the course of the melt season; and iii) what factors control water movement, and the importance of their roles. In order that links between supraglacial snowpack hydrology and other parts of the glacier system could be considered, season-long records of glacier dynamics, proglacial meltwater discharge, and water quality parameters indicating subglacial conditions were also collected.