Future fluctuations of Mer de Glace, French Alps, assessed using a parameterized model calibrated with past thickness changes

Simulations of glacier evolution are needed to assess future changes in the runoff regime of mountain catchments. A simplified parameterized model is applied here to simulate future thickness changes and glacier retreat of Mer de Glace, French Alps. A normalized thickness change function describing the spatial distribution of surface-elevation changes as a function of elevation has been determined. The model reveals that under present climatic conditions Mer de Glace will continue to shrink dramatically in the coming decades, retreating by 1200m between now and 2040. The method has certain limitations related to the uncertainties of the normalized function based on thickness change data. An error of 10% in the normalized function leads to uncertainties of 46%, 30% and 18% in Mer de Glace front, surface area and glacier-wide mass-balance changes respectively in 2040. Because the difference of the normalized function largely exceeds 10% from one glacier to another, even within a given glacier size class and elevation range, it would be very risky to extrapolate the normalized function to unmeasured glaciers. Consequently, the method is applicable only on glaciers where past surface elevation changes are well constrained.