Estimation of glacier mass balance using remote sensing and GIS technology in the Hindu Kush region of northern Pakistan

The Hindu Kush range of northern Pakistan has a large variety of Alpine and valley glaciers. These glaciers are subjected to volumetric changes owing to a host of factors (i.e. altitude, slope, glacier types, and aspect). The geodetic survey and field-based data are not available for assessment of glacier's Equilibrium Line Altitude (ELA) for Hindu Kush due to rough topography and rigorous climate. However, the mass balance of the alpine and valley glaciers can be obtained through ELA and Accumulation Area Ratio (AAR). Therefore, this study deals with the estimation of ELA, the hypsometrically controlled methods based on AAR and Accumulation Area Balance Ratio (AABR). Various ratios between 0.4-0.8 with 0.05 interval for AAR and 0.67-4.4 with 0.01 for AABR are applied to obtain the ELA of valley glaciers. Moreover, the glacier contours with the interval of 50 m +/- 5 m were employed for these estimations. The constant AAR and AABR ratios rather than constant glacier area adjust glacier hypsometry based on ELA variations. The results show that for AAR (0.5), 50 m ELA declined from 5409 to 5359 m and reduced (4%) the geometric area. The maximum decrease of 150 m ELA for these glaciers is reported for the AAR-AABR ratio of 0.1-4.4, showing a significant decrease. The estimated decrease in the glacier area of Hindu Kush is extremely variable specifically in Phargam, Khorabohr and Gordoghan.