Landsat-based inventory of glaciers in western Canada, 1985-2005

摘要

We report on a glacier inventory for the Canadian Cordillera south of 60 degrees N, across the two western provinces of British Columbia and Alberta, containing similar to 30.000 km(2) of glacierized terrain. Our semi-automated method extracted glacier extents from Landsat Thematic Mapper (TM) scenes for 2005 and 2000 using a band ratio (TM3/TM5). We compared these extents with glacier cover for the mid-1980s from high-altitude, aerial photography for British Columbia and from Landsat TM imagery for Alberta. A 25 m digital elevation model (DEM) helped to identify debris-covered ice and to split the glaciers into their respective drainage basins. The estimated mapping errors are 3-4% and arise primarily from seasonal snow cover. Glaciers in British Columbia and Alberta respectively lost - 10.8 +/- 3.8% and - 25.4% +/- 4.1% of their area over the period 1985-2005. The region-wide annual shrinkage rate of - 0.55% a(-1) is comparable to rates reported for other mountain ranges in the late twentieth century. Least glacierized mountain ranges with smaller glaciers lost the largest fraction of ice cover: the highest relative ice loss in British Columbia (-24.0 +/- 4.6%) occurred in the northern Interior Ranges, while glaciers in the northern Coast Mountains declined least (- 7.7 +/- 3.4%).