Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography & Environmental Studies

Faculty/School

Faculty of Arts

First Advisor

Scott Munro

Advisor Role

Thesis Co-Supervisor

Abstract

This thesis examines the relationship between the energy balance and hydrology of a glacier at the ice surface interface during the melt season. Experimental sub-catchments were established on the ablation area of the Peyto Glacier, Alberta, Canada, during the summers of 1994, 1995 and 1997. These sub-catchments were equipped with meteorological and hydrological instrumentation to examine relationships in the surface layer. Specifically, the development of a phenomenon known as the weathering crust is followed by examining the ratio between potential surface lowering (calculated from energy available for melt) and actual surface lowering (as measured in the field). This enables an indirect division of weathering crust development into growth and decay stages. Weathering crust growth is driven by K* while decay is driven by positive inputs of QH + QE + L*. Analysis was undertaken within periods of weathering crust growth, crustal decay and when little or no apparent melt was occurring. Actual differences between measured and potential surface lowering were also calculated. Further, associated stage records for the 1997 field season were examined for periods of weathering crust growth and decay in order to examine lags within the system. This analysis led to the simulation of ice densities at increasing depths within an ice column, based on weathering crust processes. The simulation was driven by data collected in the field. An addition to the simulation which allows for re-freezing of water within the crust indicates that the effect of re-freezing of ice during the melt season is virtually negligible. Further, subsurface priming is indicated under daytime conditions when there is a net energy loss at the surface. It is proposed that the results from the simulations produce a suitable surrogate for indicating the resultant changes in ice density given weathering crust development, thus providing an insight into events in the field. It is concluded that the weathering crust phenomenon is a complex relationship between energy inputs, initial crustal conditions and mechanical thresholds. Daytime weathering crust decay is the most complicated to analyse, as growth and decay are occurring simultaneously, even though decay is the dominant process. Daytime growth and nocturnal decay are the most straightforward cases. Weathering crust development appears to dampen catchment response by increasing storage in the lower density ice in the late morning. Further, the storage capacity of a highly developed weathering crust can result in drainage from the system overnight. This overnight drainage can be compounded by nocturnal crustal decay.

Convocation Year

2001

Convocation Season

Fall

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Glaciology Commons

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