Glacier mapping and inventory in Northern B.C. using Landsat imagery

The importance of finding an accurate means by which to map and monitor glaciers in northern British Columbia was discussed. Alpine glaciers contribute to summer river flows bringing with them temperature modifications that can be critical to some fish species. In the last 20 years, mapping of glaciers in difficult to reach areas has been made possible through the use of remotely sensed satellite imagery. Field work, however, is still needed to validate findings. In this field study northeast of Prince George, B.C., the use of optical sensors such as the Landsat Thematic Mapper (TM) and other radar data showed that aerial photography taken during the British Columbia TRIM glacier mapping program between 1985 and 1996 was too generalised and inaccurate. The TRIM data gave an overestimate of glacier extents. The image processing in the study involved the creation of enhanced channels from seven TM bands. The combination of channels yielded the best classification for glacier surfaces to derive the following classes: areas of accumulation and ablation, firn, plus water and non-glacier areas. The study showed that there has been a significant change (loss) in glaciation between 1992 and 1997. The Monkman Glacier was reduced by about 3 sq. km. and the Ice Mountain group was reduced by 8 sq. km. This represents a loss of about 20 to 20 per cent over a five year period and suggests that the glaciers may disappear in 25 to 50 years. 4 refs., 1 tab., 5 figs