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The Cryosphere An interactive open-access journal of the European Geosciences Union
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Volume 10, issue 2
The Cryosphere, 10, 665-679, 2016
https://doi.org/10.5194/tc-10-665-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
The Cryosphere, 10, 665-679, 2016
https://doi.org/10.5194/tc-10-665-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 16 Mar 2016

Research article | 16 Mar 2016

Estimating ice albedo from fine debris cover quantified by a semi-automatic method: the case study of Forni Glacier, Italian Alps

Roberto Sergio Azzoni1, Antonella Senese1, Andrea Zerboni1, Maurizio Maugeri2, Claudio Smiraglia1, and Guglielmina Adele Diolaiuti1 Roberto Sergio Azzoni et al.
  • 1Università degli Studi di Milano, Dipartimento di Scienze della Terra “A. Desio”, Milan, Italy
  • 2Università degli Studi di Milano, Dipartimento di Fisica, Milan, Italy

Abstract. In spite of the quite abundant literature focusing on fine debris deposition over glacier accumulation areas, less attention has been paid to the glacier melting surface. Accordingly, we proposed a novel method based on semi-automatic image analysis to estimate ice albedo from fine debris coverage (d). Our procedure was tested on the surface of a wide Alpine valley glacier (the Forni Glacier, Italy), in summer 2011, 2012 and 2013, acquiring parallel data sets of in situ measurements of ice albedo and high-resolution surface images. Analysis of 51 images yielded d values ranging from 0.01 to 0.63 and albedo was found to vary from 0.06 to 0.32. The estimated d values are in a linear relation with the natural logarithm of measured ice albedo (R  =  −0.84). The robustness of our approach in evaluating d was analyzed through five sensitivity tests, and we found that it is largely replicable. On the Forni Glacier, we also quantified a mean debris coverage rate (Cr) equal to 6 g m−2 per day during the ablation season of 2013, thus supporting previous studies that describe ongoing darkening phenomena at Alpine debris-free glaciers surface. In addition to debris coverage, we also considered the impact of water (both from melt and rainfall) as a factor that tunes albedo: meltwater occurs during the central hours of the day, decreasing the albedo due to its lower reflectivity; instead, rainfall causes a subsequent mean daily albedo increase slightly higher than 20 %, although it is short-lasting (from 1 to 4 days).

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In spite of quite abundant literature focusing on fine debris deposition over snow of glacier accumulation areas, less attention has been paid to the ice of the glacier melting surface. Accordingly, we developed a method for estimating ice albedo from fine debris cover quantified by a semi-automatic method. Our procedure was tested on the surface of the Forni Glacier (Italian Alps), acquiring parallel data sets of in situ measurements of ice albedo and high-resolution images.
In spite of quite abundant literature focusing on fine debris deposition over snow of glacier...
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