Impact of impurities and cryoconite on the optical properties of the Morteratsch Glacier (Swiss Alps)
The amount of reflected energy by snow and ice plays a fundamental role in their melting processes. Different non-ice materials (carbonaceous particles, mineral dust (MD), microorganisms, algae, etc.) can decrease the reflectance of snow and ice promoting the melt. The object of this paper is to...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-11-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/11/2393/2017/tc-11-2393-2017.pdf |
| Summary: | The amount of reflected energy by snow and ice plays a
fundamental role in their melting processes. Different non-ice materials
(carbonaceous particles, mineral dust (MD), microorganisms, algae, etc.) can
decrease the reflectance of snow and ice promoting the melt. The object of
this paper is to assess the capability of field and satellite (EO-1
Hyperion) hyperspectral data to characterize the impact of light-absorbing
impurities (LAIs) on the surface reflectance of ice and snow of the Vadret da
Morteratsch, a large valley glacier in the Swiss Alps. The spatial
distribution of both narrow-band and broad-band indices derived from
Hyperion was analyzed in relation to ice and snow impurities. In situ and
laboratory reflectance spectra were acquired to characterize the optical
properties of ice and cryoconite samples. The concentrations of elemental
carbon (EC), organic carbon (OC) and levoglucosan were also determined to
characterize the impurities found in cryoconite. Multi-wavelength absorbance
spectra were measured to compare the optical properties of cryoconite
samples and local moraine sediments. In situ reflectance spectra showed that
the presence of impurities reduced ice reflectance in visible wavelengths by
80–90 %. Satellite data also showed the outcropping of dust during the
melting season in the upper parts of the glacier, revealing that seasonal
input of atmospheric dust can decrease the reflectance also in the
accumulation zone of the glacier. The presence of EC and OC in cryoconite
samples suggests a relevant role of carbonaceous and organic material in the
darkening of the ablation zone. This darkening effect is added to that
caused by fine debris from lateral moraines, which is assumed to represent a large
fraction of cryoconite. Possible input of anthropogenic activity cannot be
excluded and further research is needed to assess the role of human
activities in the darkening process of glaciers observed in recent years. |
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| ISSN: | 1994-0416 1994-0424 |