ABSTRACT: Projections of the climate-forced deglaciation of western Canada using a regional glaciation mode.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Over the last century, the mountain glaciers of Alberta and British Columbia, Canada, experienced substantial mass wastage. This trend is expected to continue through the 21st century and cause a dramatic decrease in the number, area, and volume of glaciers. We are completing a modeling study that simulates the dynamic response of all (>17,000) currently-existing glaciers to climate-forced changes in their mass balance. As inputs we require a digital elevation model of the deglacierized surface topography and temporally-evolving temperature and precipitation fields, downscaled to the 200 m resolution of the regional glaciation model. For the time span 1979–2005 we derive our downscaled climate from the North American Regional Reanalysis (NARR). The downscaled temperature assumes a time- and space-varying thermal lapse rate which is calculated from the NARR. The downscaled precipitation uses the linear theory of orographic precipitation together with NARR wind velocity and moisture content fields. Where necessary we apply bias adjustments to the precipitation field based on comparison with station data. The downscaling methods and their validation are fully described in Jarosch et al. [Clim. Dyn., 2010]. For the pre-NARR interval 1902–1978, we base our climate forcing on the Climate Research Unit TS2.1 dataset and for future projections (2005–2100) we use GCM output for the A2, A1B, and B1 emissions scenarios. A recent assessment of GCM performance for northwestern North America [Radic and Clarke, in press] has led us to favor six GCMs among all GCMs from the IPCC AR4. It is not challenging to simulate climate-forced ice dynamics but extremely challenging to do this properly. The greatest sources of error are associated with uncertainty in the mass balance model and bed topography. A robust conclusion of our study is that more than 50% of existing ice volume will disappear by 2100.

Bibliography of Canadian Geomorphology