MONITORING ROCK GLACIER DYNAMICS IN THE HOHE TAUERN MOUNTAINS:INSIGHT INTO RECENT ALPINE PERMAFROST CHANGES

Abstract

Changes in mountain permafrost are of major scientific and societal interest due to associated potential risks to mountain communities. Rock glaciers, which are slowly creeping debris-ice landforms typical of mountainous permafrost regions, are key indicators of permafrost dynamics. Their movement serves as a critical parameter for the Essential Climate Variable (ECV) permafrost. This study investigates the movement of two rock glaciers in the Hohe Tauern Mountain Range, Austria: Tschadinhorn rock glacier (TRG) and Leibnitzkopf rock glacier (LRG), during 2023–2024 and compares derived movement rates to previous rock glacier velocity studies of these sites, as well as to ground and air temperature records. For rock glacier velocity quantification, we used unoccupied aerial vehicles (UAVs) with real time kinematic capabilities to create geodatasets of high spatial resolution and accuracy for both years. Rock glacier movement patterns were calculated using orthoimages, aligned to an existing geodetic network, using a state of the art image correlation algorithm (GeoCosiCorr3D). Results show that TRG exhibited the highest published, photogrammetrically derived mean RGV to date, 3.8 m/year in 2023–2024, exceeding previous maxima of interpolated point measurements reported for 2014–2015 and photogrammetric data from 2015–2016. At LRG, the maximum velocity reached 6.2 m/year, surpassing the previously published maximum of 5.8 m/year, but with a spatial shift in the location of peak movement. Spatial patterns at LRG indicate deceleration within central sectors and acceleration at the frontal zone, whereas TRG shows a more uniform acceleration. The climate context supports these trends: long term, regional station data registered an all time annual temperature record in 2024, consistent with a positive temperature-RGV relationship. However, local ground and air temperature observations since 2018 reveal site specific responses with no clear trends, but a tendency of higher movement rates in warmer years at TRG and no simle, uniform linkage at LRG, suggesting modulation by internal kinematics and spatial heterogeneities. Our findings provide robust, spatially resolved velocity evaluations for two representative alpine rock glaciers in the Alps and demonstrate recent acceleration consistent with long term ongoing warming. The results underscore the need for sustained, multi sensor monitoring to disentangle climatic forcing from internal deformation processes, thereby improving process understanding and risk assessment in high mountain permafrost environments.