Frozen ground and periglacial processes relationship in temperate high mountains: a case study at Monte PerdidoTucarroya area (The Pyrenees, Spain)

Seasonally frozen ground,mountain permafrost and cryogenic geomorphological processes are important components of the Pyrenean high mountains. This work presents the results of a study on the distribution of frozen ground in a marginal and paraglacial environment of temperate mountains. An inventory was made of landforms and indicators of frozen ground,and frozen ground was mapped accordingly. During 2014 and 2016 ground temperatures and thermal regimes were monitored,basal temperatures of snow-cover (BTS) were measured and a thermal map was drawn. Differential thermal behaviours were detected among different elevations and slope orientations. Periglacial processes are the most widespread,in which frost weathering and nivation,together with gelifluction and cryoturbation,are the most efficient processes; the latter two are generally linked to the presence of frozen ground. The fall in air and ground temperatures with altitude,slope orientations,and snowpack thickness and evolution determine ground thermal regimes. In the study area,three types of thermal regimes were established: climate-controlled,snowcover-controlled,and frozen ground-controlled. Seasonally frozen ground occurs across a broad range of elevation between 2650 and 3075 m asl,whereas possible permafrost only occurs above 2750 m asl.