Towards deciphering the contribution of permafrost and active layer to summer runoff in a small alpine catchment

High-mountain regions are very sensitive to climatic changes, which is particularly visible in the drastic retreat of Alpine glaciers. Concomitant with retreating glaciers, permafrost degradation affects large parts of high-mountain regions. In recent years, the hydrological significance of permafrost ice has therefore increasingly come into focus. However, surprisingly little is known about the current state and size of water resources in alpine permafrost. Moreover, it remains unknown whether the thawing of permafrost is already making a significant contribution to late summer runoff in alpine catchments.

In this study we combine UAV-derived volumetric change detection with the hydro-chemical analysis of δ18O and δ2H isotope signatures and the radio nuclide ¹²⁹I in the discharge from the Kaiserberg rock glacier in the Austrian Alps. The combination of these methods allows a direct and indirect quantification of permafrost degradation. Furthermore, the isotopic signatures help to decipher the relative and absolute permafrost contribution to discharge over the summer months.

First results from the analysis of digital elevation models show an average volume loss of several thousand cubic metres per year between 2017 and 2019. In addition, geochemical data on δ¹⁸O- and δ²H-isotopes and the radionuclide ¹²⁹I indicate an increased contribution of meltwater from the permafrost body of the Kaiserberg rock glacier in the summer months, which is dominant on single days in late summer.