Assessing the supraglacier extent of Karakoram glaciers located in Hunza River Basin, Pakistan

Abstract

Measuring the extent of supraglacial debris cover (SDC) in the Karakoram region has proven to be a difficult task. Semi-automatic methodologies are often used for mapping the SDC area. However, these have limitations which lead to the overestimation or underestimation of glaciated areas. Considering these facts, this study aimed to assess the glacier’s extent using a combination of satellite data and ground verification of SDC in the Hunza River Basin, Pakistan. The normalized difference snow index (NDSI) of various satellite images coupled with extensive ground survey was applied to estimate the glacier extent. Results of the glacier extents were in the range of 18–32 km2 for Gulkin, 6–18 km2 for Gulmit, and 6–17 km2 for Pissan glaciers. The ground survey indicated that satellite products are underestimating the extent of glaciers by an average of 18.018%. The comparison of on-site SDC data with Global Land Ice Measurements from Space (GLIMS) and Randolph Glacier Inventory (RGI) databases also indicates a slight variation. Overall results validate that combining satellite imagery with ground verification significantly enhances the accuracy of supraglacial extent assessment.