Estimating volume change of mountain glaciers using SRTM and map-based topographic data

This paper describes a method for estimating the volume change of mountain glaciers using the Shuttle Radar Topography Mission (SRTM) C-band data (2000) and a digital elevation model (DEM) generated from topographic maps. This approach was developed with SRTM data and topographic maps of 1 : 25 000 scale (1977) from the Akshiirak glaciers (Tien Shan, Central Asia). The DEM for 1977 was generated using 10-m contour lines from 18 map sheets covering the Akshiirak massif and surrounding area. The nominal vertical accuracy of the maps is 3.3 m. The standard deviation of the differences between the map-derived DEM and the SRTM data on glacier-free areas of less than 25/spl deg/ is 6.3 m. A single localized region in the western periphery of the study area with systematic error in the SRTM data from -20 to 12 m on a 30-km spatial scale was found and excluded from the error analysis. Assuming a 10-m map error on the upper snow-covered glacier areas, the estimated root-mean-square error of the glacier surface change is 8.2 m. From 1977 to 1999, the average glacier surface thinning is 15.1 m, and the estimated volume loss is 6.15 km/sup 3/. The rate of the Akshiirak glacier volume loss has increased by 2.7 times, compared with historical data from 1943 to 1977. The SRTM data show an opportunity for quantifying climatic and dynamic surface elevation changes in mountain glaciers. Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry and SRTM data could also be used for the estimation of short-term surface changes of mountain glaciers.