09 Jan 2023
09 Jan 2023
Status: this preprint is currently under review for the journal TC.

Heterogeneous grain growth and vertical mass transfer within a snow layer under temperature gradient

Lisa Bouvet1,2, Neige Calonne1, Frédéric Flin1, and Christian Geindreau2 Lisa Bouvet et al.
  • 1Univ. Grenoble Alpes, Université de Toulouse, Météo-France, CNRS, CNRM, Centre d’Études de la Neige, Grenoble, France
  • 2Université Grenoble Alpes, Grenoble INP, 3SR, CNRS, Grenoble, France

Abstract. Inside a snow cover, metamorphism plays a key role in snow evolution at different scales. This study focuses on the impact of temperature gradient metamorphism on a snow layer in its vertical extent. To this end, two cold-laboratory experiments were conducted to monitor a snow layer evolving under 100 K m−1 using X-ray tomography and environmental sensors. The first experiment shows that snow evolves differently in the vertical: at the end, coarser depth hoar are found in the center part of the layer, with covariance lengths about 50 % higher, compared to the top and bottom areas. We show that this heterogeneous grain growth could be related to the temperature profile and the associated crystal growth regimes, and to the profile of vapor supersaturation. In the second experiment, a non-disturbing sampling method was applied to enable a precise observation of the basal mass transfer in the case of dry boundary conditions. An air gap, characterized by a sharp drop in density, developed at the base and reached more than 3 mm after a month. The two reported phenomena, heterogeneous grain growth and basal mass loss, create heterogeneities in snow – in terms of density, grain and pore size, and ice morphology – from an initial homogeneous layer. Finally, we report the formation of hard depth hoar associated with an increase of SSA observed in the second experiment with higher initial density. These micro-scale effects may strongly impact the snowpack behavior, e.g. for snow transport processes or snow mechanics.

Lisa Bouvet et al.

Status: open (until 06 Mar 2023)

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Lisa Bouvet et al.

Lisa Bouvet et al.


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Short summary
This study presents two new experiments of temperature gradient metamorphism in a snow layer using tomographic time series and focusing on the vertical extent. The results highlight two phenomena little known: the development of morphological vertical heterogeneities from an initial uniform layer, which is attributed to the temperature range and the vapor pressure distribution; and the quantification of the mass loss at the base caused by the vertical vapor fluxes and the dry lower boundary.