Optical satellite‐sensor based monitoring of glacial coverage fluctuations on Mount Kenya, 1987–2000

Abstract

This paper presents the results of glacier change detection on Mount Kenya, based on optical (Landsat) sensor data dated 25 February 1987 and 21 February 2000 from Landsat TM and Landsat ETM+, respectively. The normalized difference snow index (NDSI) was used to derive the overall glacier, snow/ice and water mass on the mountain peak. The normalized ratio between band 4 and band 5 was then used to isolate the glacier from snow and water via histogram thresholding. For the thresholding, the Landsat near‐infrared band 4 and thermal infrared band 6 were found to be an effective means to separate glacier from surroundings, and to minimize, for example, topographic influences, such that only true glacier areas remained for comparison between the two dates. The results were validated based on the historical reports and manual delineation from false colour composite images of the two dates. The results indicated that from 1987 to 2000, the total glacier area changed from 456.3 × 103 m2 to 227.7 × 103 m2. This change was based on the reduction of the area coverage of the glaciers as well as the drifting or surging attributed mainly to temperature increments. Compared to the historical glacial coverage data, dated 100 years ago, it is concluded that the depletion rate of glaciers on Mount Kenya is in the order of 13.7 × 103 m2 per annum.