ABSTRACT: Measurement of deflation of a debris-covered glacier in Opabin Basin, Yoho National Park.

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Abstract

Although debris-covered glaciers comprise a significant fraction of the world’s ice masses, they have not been well studied, in part due to the lack of practical methods to measure or predict melt rates of ice under rock debris. For two years, the Opabin Basin in the Lake O’Hara watershed in Yoho National Park has been monitored by an international team of hydrogeologists and geophysicists to gain an understanding of hydrological responses of alpine basins to climate warming. A large contribution to the basin’s runoff is glacially derived, but difficult to predict due to the large debris-covered component of the Opabin Glacier. This study quantifies the deflation of this geomorphic feature by comparing photogrammetrically derived digital elevation models (DEMs) of the glacier surface in 1962 to the present-day glacier surface. This is the first study in Canada that quantifies the deflation of a debris-covered glacier, and the first time this methodology has been used in North America. The application of this technique to this study area is of additional interest as geophysical analyses and interpretation have also been done on the Opabin debris-covered ice, yielding unverified results. The DEM comparison in this study can be used as an independent test of those interpretations. Aerial photographs were used to generate stereo images and DEMs with remote sensing and GIS programmes. Comparison of DEMs created from photographs taken in 1962 and 2006 provides a method of quantifying the deflation that has occurred over the 44 year time interval, as well as serving to identify which regions of the debris-covered glacier experienced the greatest loss of ice. Preliminary observations suggest (1) several meters of downwasting of the debris-covered glacier, particularly along parts of its east edge, and (2) development of localized depressions that are interpreted to be thermokarst. Final results will follow DEM calibration.

Bibliography of Canadian Geomorphology