Geochemical characterization of supraglacial debris via in situ and optical remote sensing methods: a case study in Khumbu Himalaya, Nepal

Abstract

Abstract. Surface glacier debris samples and field spectra were collected from the ablation zones of Nepal Himalaya Ngozumpa and Khumbu glaciers in November and December 2009. Geochemical and mineral compositions of supraglacial debris were determined by X-ray diffraction and X-ray fluorescence spectroscopy. This composition data was used as ground truth in evaluating field spectra and satellite supraglacial debris composition and mapping methods. Satellite remote sensing methods for characterizing glacial surface debris include visible to thermal infrared hyper-and multispectral reflectance and emission signature identification, semi-quantitative mineral abundance indicies and spectral image composites. Satellite derived supraglacial debris mineral maps displayed the predominance of layered silicates, hydroxyl-bearing and calcite minerals on Khumbu Himalayan glaciers. Supraglacial mineral maps compared with satellite thermal data revealed correlations between glacier surface composition and glacier surface temperature. Glacier velocity displacement fields and shortwave, thermal infrared false color composites indicated the magnitude of mass flux at glacier confluences. The supraglacial debris mapping methods presented in this study can be used on a broader scale to improve, supplement and potentially reduce errors associated with glacier debris radiative property, composition, areal extent and mass flux quantifications.

A global high-resolution map of debris on glaciers derived from multi-temporal ASTER images

“…However, these models were only applied to individual glaciers at local scales because it is unrealistic to measure such parameters over a large area. Although studies using satellite data have presented supraglacial debris mapping on a relatively large scale (~40 km), they have focused only on the spatial distribution of debris cover, or debris thickness in limited specific areas, and have not estimated the effects of debris on glacier melting because of the lack of data on the thermal conductivity of the debris layer (e.g., Lambrecht et al, 2011;Mayer 20 et al, 2011;Casey et al, 2012;Frey et al, 2012). Hence, the creation of a global-scale debris map including thermal variables remains to be achieved.…”

Climate–Glacier Dynamics and Topographic Forcing in the Karakoram Himalaya: Concepts, Issues and Research Directions

“…Mapping debris-cover and estimating its depth are active research areas in glaciology [62,121,[126][127][128][129][130][131]]. An innovative study by Casey and Kääb [132,133] also mapped geochemical composition of debris-cover cover through in-situ and remote sensing spectral analysis.…”

Estimation of Supraglacial Dust and Debris Geochemical Composition via Satellite Reflectance and Emissivity

“…The fine powder was then prepared into XRD measurement discs and XRF sample tablets for measurement-further detailed in [50]. Note, mineralogy and geochemical composition of Eyjafjallajökull tephra is taken from [51] "explosive ash" as field samples were not collected in this region.…”

“…Hyper-and multispectral satellite sensors, data products and acquisition dates of scenes used for analysis are given in Table 4. Emissivity supraglacial dust and debris mapping utilized the ASTER AST 05 surface emissivity product to investigate supraglacial debris silica weight percent composition (after [58], detailed in [50]). ASTER AST 05 TIR estimates of silica weight percent were calculated in all regions and compared with field sample XRF geochemical results.…”