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| Titel |
Cosmic-ray attenuation by seasonal snow cover revealed by neutron-detector monitoring: implications for cosmic-ray exposure studies in mountainous areas |
| VerfasserIn |
Romain Delunel, Didier Bourlès, Peter van der Beek, Emmanuel Paquet |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052991
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| Zusammenfassung |
| Attenuation of secondary cosmic-ray particles due to snow cover and its consequences for the
production rates of Terrestrial Cosmogenic Nuclides (TCN) is a major source of uncertainty
for cosmic-ray exposure dating in high-altitude and/or high-latitude regions. The snow-cover
dependence of production rates for in-situ produced cosmogenic nuclides, and therefore of
calculated cosmic-ray exposure ages and/or denudation rates, is usually modeled from
scenarios inferring the thickness, duration and density of snow cover obtained from modern
snow records, when these exist. We present cosmic-ray flux data monitored in a
natural setting, which allow direct quantification of the effect of snow cover on
cosmic-ray flux attenuation. Assuming that cosmic-ray flux measured during the
summer season represents the theoretical radiation dose received by rock surfaces
without snow cover, the cosmic-ray flux attenuation induced by snow cover can be
estimated from the ratio between the yearly-averaged daily cosmic-ray flux and the
summer-averaged flux. Moreover, comparing cosmic-ray flux data with water-equivalent
snow thickness obtained through snow-pack core sampling reveal that cosmic-ray attenuation
calculated using a simple depth-dependant exponential decrease of cosmic-ray flux is
erroneous. Our results show that secondary neutrons are much more strongly attenuated
in snow than previously documented, leading to systematic underestimations of
cosmic-ray attenuation by snow cover. Considering an apparent neutron attenuation
length of 150 g.cm-2, a ~40% underestimation of the real cosmic-ray attenuation is
reached for a snow pack of ~30 cm water-equivalent thickness. Therefore, our results
highlight that cosmic-ray shielding due to snow cover has to be correctly and carefully
treated in mountain areas prone to seasonal snow cover, as studies inferred from
cosmogenic nuclide measurements in such areas may contain large and systematic errors. |
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