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, developed with the aim of a subsequent integration in hydrological distributed models. The model was derived from mass balance, momentum balance and rheological equations and describes the formation and evolution of the snowpack and the firn below it. The model was applied at the site of Colle Gnifetti (Monte Rosa massif, 4400–4550 m a.s.l.). We obtained an average net accumulation of 0.26 · 103 kg m−2 y−1 to be compared with the observed net annual accumulation that increases from about 0.15 · 103 kg m−2 y−1 to about 1.2 · 103 kg m−2 y−1 moving from the north facing to the south facing slope. The model results confirm the strong influence of wind on snow accumulation and densification, observed also from ice cores. The conserved precipitation is made up mainly of snow deposited between May and September, when temperatures above melting point are also observed. Even tough the variability of annual snow accumulation is not well reproduced by the model, the modelled and observed firn densities show a good agreement up to the depth reached by the model with the available input data.
How to cite. Banfi, F. and De Michele, C.: A local model of snow-firn dynamics and application to Colle Gnifetti site, The Cryosphere Discuss. [preprint], https://doi.org/10.5194/tc-2020-357, 2021.
Received: 08 Dec 2020 – Discussion started: 21 Jan 2021
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 May and September, since higher temperatures protect snow from erosion. We also compared modeled and observed firn density obtaining a satisfying agreement.
Climate changes require a dynamic description of glaciers in hydrological models. In this study...
Very interesting read. Could your monthly estimations of the non-eroded snow fraction help with the analysis of ice cores retrieved at the Colle? Or at other alpine sites with a similar seasonal bias.
In the (instantaneous) hourly series of Capanna Margherita, I found some instances of a frozen anemometer, with extended periods of zero wind speed (not supported by other, lower stations). Does this happen also in the hourly means, and if yes, would it have an impact on your modeled density and erosion rates?
Did you compare the performance of the Arnaud et al. (2000) densification model against Herron and Langway (1980)? The H-L model appears to perform quite well on the B76 core (Fig. 5) with parameters T = -10 °C, a = 0.3 m w.e. yr-1, ρ0 = 0.35 g cm-3.