First results of investigations on hydrothermal processes within the active layer above alpine permafrost in steep terrain

The aim of this study is to obtain a better understanding of the interactions of hydrological and thermal processes in the active layer of alpine permafrost in steep terrain with coarse-grained blocky surface material. Specially developed measuring equipment was installed in the active layer of a steep scree slope above Pontresina on Muot da Barba Peider, in the Upper Engadin, Switzerland, to determine ground temperatures, heat flux, water infiltration rate, soil water contents, surface level of the saturated zone, electrical water conductivity, vapour flux and downslope displacement. In addition, meteorological parameters such as air temperature and snow depth were measured. First results obtained during a thawing period showed that hydrological and thermal parameters in the ground, slope stability and meteorological parameters are closely correlated in time. An instantaneous increase in ground temperature is caused by the non-conductive heat transfer mechanisms of water convection and release of latent heat due to phase change of infiltrated snow meltwater. Downslope displacement also begins simultaneously, during meltwater infiltration, and can be ascribed to the presence of excess water in the ground. These are the first hydrothermal investigations that have been effected in a steep, coarse-grained active layer above alpine permafrost.

Keywords:

• active layer
• alpine permafrost
• hydrothermal processes
• scree slope

Acknowledgements

This study is funded by the Swiss National Science Foundation. We thank Martin Hiller, Reto Wetter, Pascal Winistörfer and Christian Simeon for their assistance with the preparation and installation of the equipment, Helibernina for safe transport to the study site by helicopter, Stump ForaTec for their cooperation, and the reviewers of this article for their constructive comments and suggestions.