1CNRS, LGGE (UMR5183), 38041 Grenoble, France
2Univ. Grenoble Alpes, LGGE (UMR5183), 38041 Grenoble, France
3IRD, LGGE (UMR5183), 38041 Grenoble, France
4IRD, LTHE (UMR5564), 38041 Grenoble, France
5ICIMOD, GPO Box 3226, Kathmandu, Nepal
Abstract. Analysis of the thermal regime of glaciers is crucial for glacier hazard assessment, especially in the context of a changing climate. In particular, the transient thermal regime of cold accumulation zones needs to be modeled. A modeling approach has therefore been developed to determine this thermal regime using only near-surface boundary conditions coming from meteorological observations. In the first step, a surface energy-balance (SEB) model accounting for water percolation was applied to identify the main processes that control the subsurface temperatures in cold firn. Results agree well with subsurface temperatures measured at Col du Dôme (4250 m a.s.l., France). In the second step, a simplified model using only daily mean air temperature and potential solar radiation was developed. This model properly simulates the spatial variability of surface melting and subsurface firn temperatures and was used to accurately reconstruct the deep borehole temperature profiles measured at Col du Dôme. Results show that percolation and refreezing are efficient processes for the transfer of energy from the surface to underlying layers. However, they are not responsible for any higher energy uptake at the surface, which is exclusively triggered by increasing energy flux from the atmosphere due to SEB changes when surface temperature reach 0 °C. The resulting enhanced energy uptake makes cold accumulation zones very vulnerable to air temperature rise.