Multi-criteria technique for mapping of debris-covered and clean-ice glaciers in the Shaksgam valley using Landsat TM and ASTER GDEM

Abstract

Glaciers in the Shaksgam valley provide important fresh water resources to neighbourhood livelihood. Repeated creation of the glacier inventories is important to assess glacier–climate interactions and to predict future runoff from glacierized catchments. For this study, we applied a multi-criteria technique to map the glaciers of the Shaksgam valley of China, using Landsat Thematic Mapper (Landsat TM) (2009) and Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model version two (ASTER GDEM V2) data. The geomorphometric parameters slope, plan, and profile curvature were generated from ASTER GDEM. Then they were organized in similar surface groups using cluster analysis. For accurate mapping of supraglacial debris area, clustering results were combined with a thermal mask generated from the Landsat TM thermal band. The debris-free glaciers were identified using the band ratio (TM band 4/TM band 5) technique. Final vector maps of the glaciers were created using overlay tools in a geographic information system (GIS). Accuracy of the generated glacier outlines was assessed through comparison with glacier outlines based on the Second Chinese Glacier Inventory (SCGI) data and glacier outlines created from high-resolution Google Earth™ images of 2009. Glacier areas derived using the proposed approach were 3% less than in the reference datasets. Furthermore, final glacier maps show satisfactory mapping results, but identification of the debris-cover glacier terminus (covered by thick debris layer) is still problematic. Therefore, manual editing was necessary to improve the final glacier maps.