Recent accumulation rates of an alpine glacier derived from firn cores and repeated helicopter-borne GPR

  • Sold L
  • Huss M
  • Eichler A
  • et al.
ISSN: 1994-0440
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Abstract

Abstract. The spatial representation of accumulation measurements is a major limitation for current glacier mass balance monitoring approaches. Here, we present a new method for estimating annual accumulation rates on a temperate alpine glacier based on the interpretation of internal reflection horizons (IRH) in helicopter-borne ground-penetrating radar (GPR) data. For each individual GPR measurement, the signal traveltime is combined with a simple model for firn densification and refreezing of meltwater. The model is calibrated at locations where GPR profiles intersect in two subsequent years and the densification can be tracked over time. Two 10.5 m long firn cores provide a reference for the density and chronology of firn layers. Thereby, IRH correspond to density maxima, but not exclusively to former summer glacier surfaces. From GPR profiles across the accumulation area, we obtain spatial distributions of water equivalent for at least four annual firn layers, reaching a mean density of 0.74 g cm−3. Refreezing accounts for 9% of the density increase over time and depth. The strongest limitation to our method is the dependence on layer chronology assumptions. The uncertainties inherent to the modelling approach itself are in the same order of conventional point measurements in snow pits. We show that GPR can be used to complement existing mass balance monitoring programs on temperate alpine glaciers, but also to retrospectively extend newly initiated time series.

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APA

Sold, L., Huss, M., Eichler, a., Schwikowski, M., & Hoelzle, M. (2014). Recent accumulation rates of an alpine glacier derived from firn cores and repeated helicopter-borne GPR. The Cryosphere Discussions, 8(4), 4431–4462. Retrieved from http://www.the-cryosphere-discuss.net/8/4431/2014/

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