Numerical modeling of the dynamics of the Mer de Glace glacier, French Alps: comparison with past observations and forecasting of near-future evolution

Vincent Peyaud,Olivier Gagliardini,Fabien Gillet-Chaulet,Delphine Six,Coline Bouchayer,Olivier Laarman,Christian Vincent

doi:10.5194/tc-14-3979-2020

Abstract

Abstract. Alpine glaciers are shrinking and rapidly loosing mass in a warming climate. Glacier modeling is required to assess the future consequences of these retreats on water resources, the hydropower industry and risk management. However, the performance of such ice flow modeling is generally difficult to evaluate because of the lack of long-term glaciological observations. Here, we assess the performance of the Elmer/Ice full Stokes ice flow model using the long dataset of mass balance, thickness change, ice flow velocity and snout fluctuation measurements obtained between 1979 and 2015 on the Mer de Glace glacier, France. Ice flow modeling results are compared in detail to comprehensive glaciological observations over 4 decades including both a period of glacier expansion preceding a long period of decay. To our knowledge, a comparison to data at this detail is unprecedented. We found that the model accurately reconstructs the velocity, elevation and length variations of this glacier despite some discrepancies that remain unexplained. The calibrated and validated model was then applied to simulate the future evolution of Mer de Glace from 2015 to 2050 using 26 different climate scenarios. Depending on the climate scenarios, the largest glacier in France, with a length of 20 km, could retreat by 2 to 6 km over the next 3 decades.

Highlights

Mountain glacier mass balances show a strong sensitivity to climate change and can be used to assess the impact of climate change in remote areas (Oerlemans, 2001; Zemp et al, 2019)
The first studies of individual glaciers (e.g., Huybrechts et al, 1989; Letréguilly and Reynaud, 1989; Stroeven et al, 1989; Greuell, 1992) were constrained to flow line models related to the local driving stress, while studies on a regional scale focused on empirical approaches in which ice dynamics is not explicitly taken into account and glacier evolution is based on parameterizations calibrated with either equilibrium-line altitude (ELA) models (e.g., Zemp et al, 2006), extrapolations of observed geometry changes (e.g., Huss et al, 2008; Huss, 2012; Huss and Hock, 2018), or volume and length–area scalings (e.g., Marzeion et al, 2012; Radicet al., 2014)
According to Thibert et al (2008), we can expect uncertainties on ablation estimated from a network of stakes on the order of 0.15 m yr−1 in ice equivalent thickness, which is low relative to the mean ablation measured on the tongue of Mer de Glace

Summary

Introduction

Mountain glacier mass balances show a strong sensitivity to climate change and can be used to assess the impact of climate change in remote areas (Oerlemans, 2001; Zemp et al, 2019). During the 20th century, all alpine glaciers showed a strong recession (Zemp et al, 2015) This observed trend is expected to continue in the future under a warming climate (IPCC, 2019) with important impacts on watershed hydrology (Huss and Hock, 2018; Brunner et al, 2019), tourism and hydropower resources (e.g., Welling et al, 2015; Stewart et al, 2016), accompanied by the emergence of new risks (e.g., Kääb et al, 2018) and sea-level rise (Hock et al, 2019; Marzeion et al, 2020).

Methods

Results

Discussion

Conclusion