Ice melt estimation using Unmanned Aerial Vehicle (UAV) of Ponkar Glacier, Manang, Nepal

Assessing ice melt under debris to better understand glacier melt spatially and the ice melt contribution in river discharge is physically challenging. Remote sensing techniques are best to incorporate such glaciological studies in an inaccessible region like the Himalayas. In this study, Unmanned Aerial Vehicle (UAV), a DJI Phantom Quad Copter and ablation stakes are used and surveyed over the lower ablation region of the Ponkar Glacier (3881 m asl), Manang in the Nepalese Himalayas in March and July 2016 to estimate the glacier ice melt. The temporal data from the UAV are processed to an Orthomosiacs image to create a high resolution Digital Elevation Model (DEM of 2 cm) by the surface from motion (SfM) technique. Three ablation stakes are installed to compare the melt estimation from UAV. The change in surface elevation in the two survey periods corresponds to the ice melt beneath the debris. The ice melt under the debris thickness of 11 and 20 cm on the lower ablation region of the Ponkar Glacier from 20 March to 5 July 2016 are 94 cm and 68 cm (0.88 to 0.64 cm day-1), respectively derived from two DEMs prepared based on two UAV surveys on those dates. Similarly, the ice melt observed on the installed ablation stakes on the above debris thickness are 101 cm and 69 cm (0.95 and 0.65 cm day-1), respectively for the same observation period. These melt rates are very similar to what we found in Langtang Valley, Rasuwa and Phu Valley in Manang. The observation is continuing and a fixed wind UAV will be used for survey in near future so that the whole glacier can be covered. Such a remote sensing technique with high resolution DEM has great potential to quantify the temporal and spatial ice melt of the Himalayan glaciers.