Heterogeneity in glacier response in the upper Shyok valley, northeast Karakoram

Glaciers in the Karakoram show long-term irregular behaviour with comparatively frequent and sudden advances. A glacier inventory of the upper Shyok valley situated in northeast Karakoram has been generated for the year 2002 using Landsat ETM+ and SRTM3 DEM as baseline data for the investigations and subsequent change analysis. The upper Shyok valley contained 2123 glaciers (larger than 0.02 km(2) in size) with an area of 2977.9 +/- 95.3 km(2) in 2002. Out of these, 18 glaciers with an area of 1004.1 +/- 32.1 km(2) showed surge-type behaviour. Change analysis based on Hexagon KH-9 (years 1973 and 1974) and Landsat TM/ETM+ (years 1989, 2002 and 2011) images had to be restricted to a subset of 136 glaciers (covering an area of 1609.7 +/- 51.5 km(2) in 2002) due to adverse snow conditions. The area of the investigated glaciers, including the 18 surge-type glaciers identified, showed no significant changes during all studied periods. However, the analysis provides a hint that the overall glacier area slightly decreased until about 1989 (area 1973: 1613.6 +/- 43.6 km(2); area 1989: 1602.0 +/- 33.6 km(2)) followed by an increase (area 2002: 1609.7 +/- 51.5; area 2011: 1615.8 +/- 35.5 km(2)). Although the overall change in area is insignificant, advances in glacier tongues since the end of the 1980s are clearly visible. Detailed estimations of length changes for individual glaciers since the 1970s and for Central Rimo Glacier since the 1930s confirm the irregular retreat and advance.