Ground-penetrating radar measurements of debris thickness on Lirung Glacier, Nepal
Journal of Glaciology
Cambridge University Press
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McCarthy, M., Pritchard, H., Willis, I., & King, E. (2017). Ground-penetrating radar measurements of debris thickness on Lirung Glacier, Nepal. Journal of Glaciology, 63 (239), 543-555. https://doi.org/10.1017/jog.2017.18
Supraglacial debris thickness is a key control on the surface energy balance of debriscovered glaciers, yet debris thickness measurements are sparse due to difficulties of data collection. Here we use ground-penetrating radar (GPR) to measure debris thickness on the ablation zone of Lirung Glacier, Nepal. We observe a strong, continuous reflection, which we interpret as the ice surface, through debris layers of 0.1 to at least 2.3 m thick, provided that appropriate acquisition parameters were used while surveying. GPR measurements of debris thickness correlate well with pit measurements of debris thickness (r = 0.91, RMSE = 0.04 m) and two-way travel times are consistent at tie points (r = 0.97). 33% of measurements are <0.5 m, so sub-debris melting is likely important in terms of mass loss on the debris-covered tongue and debris thickness is highly variable over small spatial scales (of order 10 m), likely due to local slope processes. GPR can be used to make debris thickness measurements more quickly, over a wider debris thickness range, and at higher spatial resolution than any other means and is therefore a valuable tool with which to map debris thickness distribution on Himalayan glaciers.
debris-covered glaciers, debris thickness, ground-penetrating radar, supraglacial debris
M.M. is funded by NERC DTP grant number: NE/L002507/1, receives CASE funding from Reynolds International Ltd, and was provided travel support by the Jesus College Doctoral Research Fund. I.W. was funded by the BB Roberts Fund, University Travel Fund and St Catharine's College Research Fund. Equipment (GPR and DGPS) was provided under NERC Geophysical Equipment Facility grant number: 1014.
External DOI: https://doi.org/10.1017/jog.2017.18
This record's URL: https://www.repository.cam.ac.uk/handle/1810/266705
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