Recent glacier retreat within the southern Canadian Cordillera

Net changes in glacier area in the region 50-51° N and 116-125° W, which includes the Columbia and Rocky Mountains (1951/52-2001), and the Coast Mountains (1964/65-2002), were determined from a comparison of historic aerial photography and recent Landsat 7 ETM+ imagery. Estimates of ice volume for both time periods were made using an empirical volume-area scaling relationship. There is a high degree of spatial variability in the magnitude of observed changes across the study area. This may be due to gradients in the nature of climate forcing over the study area, and to differences in the intrinsic sensitivity of individual glaciers to climate forcing. Over the ∼38 year time period, glaciers within the Coast Mountains experienced a net area change of -120 +/- 10 km2, corresponding to a loss of 5% from the initial ice covered area of ∼2400 kmmu2. Glaciers within this region typically lost between -2 and -10% of their initial area and volume, representing wastage of ∼0.2-2 km2 of ice depending on their size. Over the ∼50 year period, glaciers within the Columbia and Rocky Mountains underwent a net change of -20 and -6 km2 from initial areas of ∼400 and ∼40 km2 respectively, corresponding to relative changes in total area of -5 and -15%. Individual glaciers within these regions underwent area changes between +25 and -75% in some extreme cases, which suggests that the intrinsic sensitivity of glaciers is important in explaining the pattern of retreat here. These glaciers are generally much smaller than those of the Coast Mountains however, and total ice loss from individual glaciers was on the order of 0.01-0.1 km2 .