Climatic and morphometric controls on the altitudinal range of glaciers, British Columbia, Canada

To examine the relation between climate and glacier extent, we compared gridded, monthly temperature and precipitation data to the altitudinal range of glaciers in British Columbia, Canada. We related glacier relief to ablation season temperature (June-August), accumulation season precipitation (September-March), and morphometric variables that included slope, glacier order, and a shape index for 523 alpine glaciers that ranged from 5 to 15 km² in surface area. A 1°C increase in mean June-August temperature equates to a 109 to 182 m decrease in glacier relief, and a 1 mm increase in mean monthly September-March precipitation equates to a 0.78 to 2.20 m increase in glacier relief. The most important morphometric controls on this glacier-climate relation include average surface slope, glacier order (analogous to stream order), and the ratio of upper accumulation area to lower ablation area width, all of which are positively related to glacier relief. We note strong relations between glacier relief and climate in all mountain regions of British Columbia, with glaciers of the interior ranges being most sensitive to spatial climatic variability. We show how our approach can be used to estimate past climatic conditions based on historical ice extents, such as at the 'Little Ice Age' maximum, and to predict potential future equilibrium glacier extents in a changed climate regime, such as those predicted by general and regional circulation models.