Glacial decline next to stable permafrost in the Dry Andes? Vertical glacier surface changes and rock glacier kinematics based on Pléiades imagery (Rodeo basin, 2019–2025)

Abstract. 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.