Preprints
https://doi.org/10.5194/tc-2021-145
https://doi.org/10.5194/tc-2021-145

  30 Jun 2021

30 Jun 2021

Review status: this preprint is currently under review for the journal TC.

A local model of snow-firn dynamics and application to Colle Gnifetti site

Fabiola Banfi and Carlo De Michele Fabiola Banfi and Carlo De Michele
  • Department of Civil and Environmental Engineering, Politecnico di Milano, Milano, Italy

Abstract. The regulating role of glaciers on catchment run-off is of fundamental importance in sustaining people living in low lying areas. The reduction in glacierized areas under the effect of climate change disrupts the distribution and amount of run-off, threatening water supply, agriculture and hydropower. The prediction of these changes requires models that integrate hydrological, nivological and glaciological processes. In this work we propose a local model that combines the nivological and glaciological scales. The model describes the formation and evolution of the snowpack and the firn below it, under the influence of temperature, wind speed and precipitation. The model has been implemented in two versions: (1) a multi-layer one that considers separately each firn layer, and (2) a single-layer one that models firn and underlying glacier ice as a single layer. The model was applied at the site of Colle Gnifetti (Monte Rosa massif, 4400–4550 m a.s.l.). We observed an average reduction of annual snow accumulation due to wind erosion of 2 · 103 kg m−2 y−1 to be compared with a mean annual precipitation of about 2.7 · 103 kg m−2 y−1. The conserved accumulation is made up mainly of snow deposited between April and September, when temperatures above melting point are also observed. End of year snow density, instead, increased in average of 65 kg m−3 when the contribution of wind to snow compaction was added. Observations show a high spatial and interannual variability in the characteristics of snow and firn at the site and a correlation of net balance with radiation and number of melt layers. The computation of snowmelt in the model as a solely function of air temperature may therefore be one of the reasons of the observed mismatch between model and observations.

Fabiola Banfi and Carlo De Michele

Status: open (until 25 Aug 2021)

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Fabiola Banfi and Carlo De Michele

Fabiola Banfi and Carlo De Michele

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Short summary
Climate changes require a dynamic description of glaciers in hydrological models. In this study we focus on the local modeling of snow and firn. We tested our model at the site of Colle Gnifetti, 4400–4550 m a.s.l. The model shows that wind erodes all the precipitation of the cold months, while snow is in part conserved between April and September, since higher temperatures protect snow from erosion. We also compared modeled and observed firn density obtaining a satisfying agreement.