Is that a relict rock glacier?

The distribution of rock glaciers is often used to investigate the occurrence of permafrost in mountain areas and to understand their climate and paleoclimate evolution. This requires the creation of regional and global inventories capable of discriminating active and relict landforms in order to forecast the presence or absence of ice in the ground. In this paper, geomorphological, geophysical and microclimatic surveys are performed on a rock glacier of the Carnic Alps (Eastern European Alps). In the classification currently used for implementing regional inventories of permafrost evidence in the Alps, this rock glacier would be defined as relict. However the geophysical, climatological and geomorphological results indicate that internal ice is widespread in large portions of the rock glacier. These are generally interpreted as ice in pore spaces and local ice lenses, probably without layers of massive ice. Moreover the occurrence of ice during the maximum thawing season at depths <15 m, assumed here as the depth of zero annual amplitude, suggests that the ice occurring within the rock glacier is related to current cryotic conditions due to density driven air flow (i.e. the chimney effect). This research demonstrates that the current altitudinal limit of alpine permafrost can be locally several hundreds of meters lower than forecasted by empirical modeling based only on the rock glacier distribution and classification. Therefore, rock glacier classifications based only on remote sensing and geomorphological evidence as the main sources for extracting regional climate and paleoclimate signals should be treated with caution. (C) 2019 Published by Elsevier B.V.