C056-0012
Recent Trend of Glacial Surface Lowering in Khumbu Glacier, Everest Region, Nepal

Tuesday, 15 December 2020
Poster
Bhuwan Awasthi1, Ananta Prasad Gajurel2, Alex Tait3, Sandra Elvin3, Aurora C Elmore4, Aaron E Putnam5, Peter Strand6, Laura Mattas7 and Paul Andrew Mayewski8, (1)Tribhuvan University, Kathmandu, Nepal, (2)Tribhuvan University, Department of Geology, Kathmandu, Nepal, (3)National Geographic Society, Washington, DC, United States, (4)National Geographic, Washington, DC, United States, (5)Columbia University of New York, Palisades, NY, United States, (6)University of Maine, School of Earth and Climate Sciences and Climate Change Institute, Orono, ME, United States, (7)Climate Change Institute, Maine, United States, (8)University of Maine, Climate Change Institute, Orono, ME, United States
Abstract:
The Khumbu glacier lies in the eastern region of Nepal and northern most part of Sagarmatha National Park, Solukhumbu district. The aim of this study is to know the glacial surface lowering and increase in number and area of supraglacial ponds from Everest base camp to terminus of Khumbu glacier. In this study, statistical method and DEM co-registration method were used to know the glacial surface lowering in the ablation zone. In statistical method, DEMs of ALOS PALSAR (2006 and 2009 AD), HMA (2015 and 2017 AD) and LiDAR (2019 AD) were reprojected to Everest 1830 (1937 adjustment) MUTM and resampled to 5x5m using resample tool of QGIS. Then, the DEMs were corrected for vertical elevation differences with respect to 36 GCPs within boulders of right lateral moraine using the point sampling tool plugin of QGIS. The GCPs were collected using dGPS on boulders which have remained stable over the years. Then, a longitudinal profile was drawn along the flowline of glacier using profile plugin of QGIS. The surface lowering along the flowline for the period of (2019 - 2006 AD) is -2.0 ± 0.69 m/year. The limitation of this method is unevenness of GCPs throughout the glacier and medium – coarse resolution of DEMs. Hence, the DEM co-registration method developed by Nuth and Kääb (2011) was used to correct the horizontal and vertical biases. The co-registration of DEMs was performed using python algorithm developed by Shean et al., (2016). The surface lowering of the co-registered DEMs for the period of (2019 - 2006 AD) is -1.44 ± 0.04 m/year. The supraglacial ponds have increased in number and area from 108 and 0.106 km2 in 2009 AD to 206 and 0.252 km2 in 2019 AD from Everest base camp to terminus. The coalescence with increase in number and area of supraglacial ponds indicates a trajectory towards larger lake development which if breached can result in glacial lake outburst flood (GLOF). Hence, the monitoring of supraglacial ponds is important to protect the lives and property downstream and to mitigate GLOF hazard in the future.
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