Characterization of glacier debris cover via in situ and optical remote sensing methods: a case study in the Khumbu Himalaya, Nepal

Field spectrometry and physical samples of debris, snow and ice were collected from the ablation zones of Ngozumpa and Khumbu glaciers of the Khumbu Himalaya, Nepal in November and December 2009. Field acquired spectral reflectances and mineral and chemical composition of samples were used as ground truth for comparison with satellite optical remote sensing data. Supraglacial debris was characterized by several optical remote sensing methods, including hyperspectral reflectance analysis, multispectral band composites and indices, spectral angle relationships, thermal band temperature and emissivity analysis, as well as repeat image derived glacier velocity and theoretical supraglacial particle transport. Supraglacial mineral components were identified and mineral abundances were estimated on Khumbu Himalayan glaciers. Mass flux was estimated by false color composites and glacier velocity displacement fields. Supraglacial temperatures were compared with mineral abundances, implying potential parameters to estimate differential melt. Overall, glaciologic implications of debris cover characterizations are applicable to (1) glacier energy balance, (2) glacial kinematics and (3) mapping glacial extent. The methods presented can be used in synergy to improve supraglacial debris quantification and reduce errors associated with debris covered ice extent mapping, surface radiative properties, as well as debris covered ice mass flux and loss estimations.