Relative performance of empirical and physical models in assessing the seasonal and annual glacier surface mass balance of Saint-Sorlin Glacier (French Alps)

Marion Réveillet,Marie Dumont,Maxime Litt,Antoine Rabatel,Delphine Six,Christian Vincent,Matthieu Lafaysse,Vincent Vionnet,Samuel Morin

doi:10.5194/tc-12-1367-2018

Abstract

Abstract. This study focuses on simulations of the seasonal and annual surface mass balance (SMB) of Saint-Sorlin Glacier (French Alps) for the period 1996–2015 using the detailed SURFEX/ISBA-Crocus snowpack model. The model is forced by SAFRAN meteorological reanalysis data, adjusted with automatic weather station (AWS) measurements to ensure that simulations of all the energy balance components, in particular turbulent fluxes, are accurately represented with respect to the measured energy balance. Results indicate good model performance for the simulation of summer SMB when using meteorological forcing adjusted with in situ measurements. Model performance however strongly decreases without in situ meteorological measurements. The sensitivity of the model to meteorological forcing indicates a strong sensitivity to wind speed, higher than the sensitivity to ice albedo. Compared to an empirical approach, the model exhibited better performance for simulations of snow and firn melting in the accumulation area and similar performance in the ablation area when forced with meteorological data adjusted with nearby AWS measurements. When such measurements were not available close to the glacier, the empirical model performed better. Our results suggest that simulations of the evolution of future mass balance using an energy balance model require very accurate meteorological data. Given the uncertainties in the temporal evolution of the relevant meteorological variables and glacier surface properties in the future, empirical approaches based on temperature and precipitation could be more appropriate for simulations of glaciers in the future.

Highlights

The surface mass balance (SMB) of mountain glaciers is sensitive to climate change and contributes to the hydrological regime of high alpine catchments (IPCC, 2013)
The Crocus model was run over the three distinct time periods and annual and seasonal SMBs were compared to measurements (Fig. 3)
This study has evaluated the performance of the Crocus snowpack model, which was fed with SAFRAN reanalysis data, thereby simulating seasonal and annual SMBs of SaintSorlin Glacier over the last 20 years

Summary

Introduction

The surface mass balance (SMB) of mountain glaciers is sensitive to climate change and contributes to the hydrological regime of high alpine catchments (IPCC, 2013). Several studies have successfully used various calibrated temperature-index models (TIMs) to simulate glacier melt response to meteorological forcing (Braithwaite and Olesen, 1989; Hock, 2003; Pellicciotti et al, 2005) These approaches can be used over short time periods (typically a few years), but the relevance of the calibrated parameters over longer time periods is difficult to assess for several reasons, including (i) the lack of long-term in situ meteorological measurements available close to the study site, (ii) the temporal variations of melt sensitivity to temperature and (iii) the fact that the physical link between temperature and melt is not direct Transferring parameters determined for an instrumented glacier to another site decreases model performance (Carenzo et al, 2009; Réveillet et al, 2017)

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Results

Conclusion