Simon Ebert

The presence and volume of high-mountain cryospheric features are drastically affected by rising air temperatures – on global scale. In the Dry Andes, precipitation is extremely scarce, shifting the hydrological significance towards the solid water storages, glaciers and ground ice. While glaciers decrease in surface area and volume, periglacially stored waters, e.g., in rock glaciers, react more retarded to atmospheric forcing, potentially buffering future water availability. Despite rising air temperatures, recent studies suggest stable permafrost conditions in the Dry Andes based on borehole investigation and rock glacier kinematics for the last decade. This apparent stability may partly reflect the extreme aridity conditions, limit snow insulation and liquid-water input, thereby damping inter-annual variability in ground thermal conditions and associated changes in rock glacier creep. We investigate vertical surface changes of 19 glaciers, three debris-covered glaciers and 59 rock glaciers in the Rodeo basin (Dry Andes, Argentina) for the time period 2019–2025. Further, we calculate rock glacier velocities for 47 of the 59 rock glaciers for which we have data for all time periods. Photogrammetric principles are followed using (tri)stereo, panchromatic Pléiades imagery to generate projected optical imagery and DEMs in Ames Stereo Pipeline. Resulting DEMs are co-registered prior to DEM differencing for vertical surface change calculation. To derive rock glacier velocities, a feature tracking approach is applied to panchromatic Pléiades orthoimagery. We detect glacier surface lowering of up to −8.99 m (total change, 2019–2025) and dominantly annual surface lowering for all glaciers investigated. Vertical surface lowering on debris-covered glaciers falls well below the magnitude of glaciers, but is higher than for rock glaciers – the latter not exceeding a decimetre. Average rock glacier velocities fall between 0.28 and 0.82 m yr⁻¹ (Levels of Detection, LoDs: ±0.16, ±0.61). The presence of highest magnitude of horizontal velocities is different between rock glaciers, with highest horizontal velocities partially reached in the upper or lower part of the rock glacier surface. Across the 47 rock glaciers investigated, no regional trend of increasing velocities is found. In conclusion, the declining glacial domain contrasts with unchanged rock glacier velocities which elucidate stable permafrost conditions. We infer a delayed reaction of the periglacial domain to the rising temperatures that lead to the surface lowering of glaciers and highlight the need for ongoing, long(er)-time surface change monitoring in this crucial, dynamic point in time.

Erosion at rock glacier fronts can supply sediment to adjacent torrents, which can be mobilized as damaging debris flows. Understanding the mechanisms which govern this erosion process is therefore critical for hazard management in affected areas. Previous research shows that rock glacier advance and liquid water input are the two main drivers of erosion at rock glacier fronts. However, earlier studies that calculated erosion volumes at rock glacier fronts were limited to temporal resolutions ranging from months to years. Therefore, these studies exhibit a high uncertainty due to the opposing influences of rock glacier front advance and retrogressive erosion. This prevented an in-depth understanding of the underlying drivers of these processes and their magnitudes on a short timescale. To overcome this limitation, we adapt the setup by Aaron et al. (2023) and use a permanently installed LiDAR sensor to monitor surface changes at a rock glacier front. By calculating Digital Elevation Models of Difference (DoDs) with respect to the local surface normal, we are able to compute erosion volumes at an hourly temporal resolution. This enables the quantification of short-term and small-scale geomorphic changes at the rock glacier front, which could not be detected by previous studies.Our study site is the fast-moving Ritigraben rock glacier (front velocity > 1cm/day) in the Mattertal (Valais). Its front is directly connected to a torrential channel, which regularly produced debris flows in the past and has been monitored for more than 30 years. Preliminary results show a link between erosion events and short-term precipitation with camera images showing signs of surface runoff in the affected areas. However, erosive events are triggered by comparatively common rainfall events. Small-scale reworking of material at the rock glacier front also occurs completely independently of precipitation events in some cases. Further investigation is needed to determine if the release of material is due to failure disposition from prior events and the rock glacier creep, or the influence of meltwater from the rock glacier body. ReferencesAaron, Jordan, Raffaele Spielmann, Brian W. McArdell, and Christoph Graf (2023). “High-Frequency 3D LiDAR Measurements of a Debris Flow: A Novel Method to Investigate the Dynamics of Full-Scale Events in the Field”. In: Geophysical Research Letters 50.5. doi: 10.1029/2022GL102373.

The presence and volume of high-mountain cryospheric features are drastically affected by rising air temperatures – on global scale. In the Dry Andes, precipitation is extremely scarce, shifting the hydrological significance towards the solid water storages, glaciers and ground ice. While glaciers decrease in surface area and volume, periglacially stored waters, e.g., in rock glaciers, react more retarded to atmospheric forcing, potentially buffering future water availability. Despite rising air temperatures, recent studies suggest stable permafrost conditions in the Dry Andes based on borehole investigation and rock glacier kinematics for the last decade. We investigate vertical surface changes of 19 glaciers, three debris-covered glaciers and 59 rock glaciers in the Rodeo basin (Dry Andes, Argentina) for the time period 2019–2025. Further, we calculate rock glacier velocities for 47 of the 59 rock glaciers for which we have data for all time periods. We follow photogrammetric principles using (tri)stereo, panchromatic Pléiades imagery to generate projected optical imagery and DEMs in Ames Stereo Pipeline that we co-register prior to DEM differencing for vertical surface change calculation. We conduct feature tracking on the panchromatic Pléiades imagery for the calculation of rock glacier velocities. We detect glacier surface lowering of up to −8.99 m (cumulative, 2019–2025) and dominantly negative annual surface lowering for all glaciers investigated. We find vertical surface lowering on debris-covered glaciers to be well below the magnitude of glaciers but higher than for rock glaciers – the latter not exceeding a decimetre. We quantify rock glacier velocities of in average 0.28 to 0.82 m/yr (LoDs: ± 0.16, ± 0.61) and can categorize three rock glacier groups – large and fast, small and fast and small and slow. Across the 47 rock glaciers investigated, we do not find a regional trend of increasing velocities. In conclusion, we observe a declining glacial domain to contrast with rock glacier velocities which elucidate stable permafrost conditions. We infer a delayed reaction of the periglacial domain to the rising temperatures that lead to the surface lowering of glaciers and highlight the need for ongoing, long(er)-time surface change monitoring in this crucial, dynamic point in time.

The presence and volume of high-mountain cryospheric features are drastically affected by rising air temperatures – on global scale. In the Dry Andes, precipitation is extremely scarce, shifting the hydrological significance towards the solid water storages, glaciers and ground ice. While glaciers decrease in surface area and volume, periglacially stored waters, e.g., in rock glaciers, react more retarded to atmospheric forcing, potentially buffering future water availability. Despite rising air temperatures, recent studies suggest stable permafrost conditions in the Dry Andes based on borehole investigation and rock glacier kinematics for the last decade. We investigate vertical surface changes of 19 glaciers, three debris-covered glaciers and 59 rock glaciers in the Rodeo basin (Dry Andes, Argentina) for the time period 2019–2025. Further, we calculate rock glacier velocities for 47 of the 59 rock glaciers for which we have data for all time periods. We follow photogrammetric principles using (tri)stereo, panchromatic Pléiades imagery to generate projected optical imagery and DEMs in Ames Stereo Pipeline that we co-register prior to DEM differencing for vertical surface change calculation. We conduct feature tracking on the panchromatic Pléiades imagery for the calculation of rock glacier velocities. We detect glacier surface lowering of up to −8.99 m (cumulative, 2019–2025) and dominantly negative annual surface lowering for all glaciers investigated. We find vertical surface lowering on debris-covered glaciers to be well below the magnitude of glaciers but higher than for rock glaciers – the latter not exceeding a decimetre. We quantify rock glacier velocities of in average 0.28 to 0.82 m/yr (LoDs: ± 0.16, ± 0.61) and can categorize three rock glacier groups – large and fast, small and fast and small and slow. Across the 47 rock glaciers investigated, we do not find a regional trend of increasing velocities. In conclusion, we observe a declining glacial domain to contrast with rock glacier velocities which elucidate stable permafrost conditions. We infer a delayed reaction of the periglacial domain to the rising temperatures that lead to the surface lowering of glaciers and highlight the need for ongoing, long(er)-time surface change monitoring in this crucial, dynamic point in time.

The presence and volume of high-mountain cryospheric features are drastically affected by rising air temperatures – on global scale. In the Dry Andes, precipitation is extremely scarce, shifting the hydrological significance towards the solid water storages, glaciers and ground ice. While glaciers decrease in surface area and volume, periglacially stored waters, e.g., in rock glaciers, react more retarded to atmospheric forcing, potentially buffering future water availability. Despite rising air temperatures, recent studies suggest stable permafrost conditions in the Dry Andes based on borehole investigation and rock glacier kinematics for the last decade. We investigate vertical surface changes of 19 glaciers, three debris-covered glaciers and 59 rock glaciers in the Rodeo basin (Dry Andes, Argentina) for the time period 2019–2025. Further, we calculate rock glacier velocities for 47 of the 59 rock glaciers for which we have data for all time periods. We follow photogrammetric principles using (tri)stereo, panchromatic Pléiades imagery to generate projected optical imagery and DEMs in Ames Stereo Pipeline that we co-register prior to DEM differencing for vertical surface change calculation. We conduct feature tracking on the panchromatic Pléiades imagery for the calculation of rock glacier velocities. We detect glacier surface lowering of up to −8.99 m (cumulative, 2019–2025) and dominantly negative annual surface lowering for all glaciers investigated. We find vertical surface lowering on debris-covered glaciers to be well below the magnitude of glaciers but higher than for rock glaciers – the latter not exceeding a decimetre. We quantify rock glacier velocities of in average 0.28 to 0.82 m/yr (LoDs: ± 0.16, ± 0.61) and can categorize three rock glacier groups – large and fast, small and fast and small and slow. Across the 47 rock glaciers investigated, we do not find a regional trend of increasing velocities. In conclusion, we observe a declining glacial domain to contrast with rock glacier velocities which elucidate stable permafrost conditions. We infer a delayed reaction of the periglacial domain to the rising temperatures that lead to the surface lowering of glaciers and highlight the need for ongoing, long(er)-time surface change monitoring in this crucial, dynamic point in time.

The presence and volume of high-mountain cryospheric features are drastically affected by rising air temperatures – on global scale. In the Dry Andes, precipitation is extremely scarce, shifting the hydrological significance towards the solid water storages, glaciers and ground ice. While glaciers decrease in surface area and volume, periglacially stored waters, e.g., in rock glaciers, react more retarded to atmospheric forcing, potentially buffering future water availability. Despite rising air temperatures, recent studies suggest stable permafrost conditions in the Dry Andes based on borehole investigation and rock glacier kinematics for the last decade. We investigate vertical surface changes of 19 glaciers, three debris-covered glaciers and 59 rock glaciers in the Rodeo basin (Dry Andes, Argentina) for the time period 2019–2025. Further, we calculate rock glacier velocities for 47 of the 59 rock glaciers for which we have data for all time periods. We follow photogrammetric principles using (tri)stereo, panchromatic Pléiades imagery to generate projected optical imagery and DEMs in Ames Stereo Pipeline that we co-register prior to DEM differencing for vertical surface change calculation. We conduct feature tracking on the panchromatic Pléiades imagery for the calculation of rock glacier velocities. We detect glacier surface lowering of up to −8.99 m (cumulative, 2019–2025) and dominantly negative annual surface lowering for all glaciers investigated. We find vertical surface lowering on debris-covered glaciers to be well below the magnitude of glaciers but higher than for rock glaciers – the latter not exceeding a decimetre. We quantify rock glacier velocities of in average 0.28 to 0.82 m/yr (LoDs: ± 0.16, ± 0.61) and can categorize three rock glacier groups – large and fast, small and fast and small and slow. Across the 47 rock glaciers investigated, we do not find a regional trend of increasing velocities. In conclusion, we observe a declining glacial domain to contrast with rock glacier velocities which elucidate stable permafrost conditions. We infer a delayed reaction of the periglacial domain to the rising temperatures that lead to the surface lowering of glaciers and highlight the need for ongoing, long(er)-time surface change monitoring in this crucial, dynamic point in time.