Multi-Scale Rock Glacier Kinematics in the Dry Andes of Argentina: From DEMs to the State of Permafrost Using Photogrammetry

Abstract

The high-mountain cryosphere is undergoing substantial transformation under global climate warming. In the Dry Andes of Argentina, where precipitation is scarce, glaciers and periglacial ice are critical water reserves. While glaciers rapidly lose mass and surface area, rock glaciers – landforms containing subsurface ice – respond more slowly to atmospheric forcing, temporarily buffering reduced water availability. However, limited data availability has hindered an understanding of rock glacier kinematics and their controlling factors in this region. <br/> This PhD dissertation analyses high-resolution uncrewed aerial vehicle (UAV) surveys and satellite-based photogrammetry to investigate rock glacier surface change patterns across multiple spatial scales and time periods. At the local scale, the Dos Lenguas rock glacier (30°S, 4400 m asl) is monitored using quasi-biennial UAV flights from 2016 to 2024. While the differencing of UAV-derived digital elevation models (DEMs) reveals spatially variable vertical changes (±1.5 m) predominantly linked to compressional flow and ridge-furrow morphology, feature tracking quantifies mean horizontal velocities of 0.9 m/yr and maxima of 1.7 m/yr. Despite rising temperatures, particularly in winter, both vertical and horizontal kinematics remain stable over the eight-year observation period, likely due to the area's aridity limiting insulation effects by snow cover. <br/> Comparisons of UAV-based DEMs and DEMs based on optical satellite imagery (Pléiades) show that when the latter are processed with the software Ames Stereo Pipeline following the strategy outlined in this dissertation, both datasets produce highly similar vertical change estimates. This comparability enables the extension of the methodology to the entire catchment, linking fine-scale UAV observations with regional-scale satellite-based analyses and expanding the surface monitoring to glaciers and debris-covered glaciers. <br/> At the regional scale, vertical surface changes of 19 glaciers, three debris-covered glaciers, and 59 rock glaciers in the Rodeo basin are quantified for 2019 to 2025 using panchromatic, tristereo Pléiades imagery. Further, rock glacier velocity is investigated for all 47 continuously monitored rock glaciers. Glaciers exhibit pronounced surface lowering, up to -8.99 m cumulatively, with debris-covered glaciers displaying intermediate and rock glaciers minimal lowering. No regional acceleration in rock glacier velocities is observed, supporting evidence of stable permafrost conditions. <br/> Overall, this work demonstrates stable rock glacier kinematics indicative of persistent per-mafrost, contrasting with the retreating glacial domain. The lack of snow cover combined with low high-altitude temperatures likely governs this stability. The study identifies key drivers of rock glacier velocity (creep, gravity, and elevation-related temperature) and evaluates climate effects based on ERA5 data (1940–2020). The findings highlight the need for long-term, continuous monitoring to capture process–response relationships in the rapidly changing high-Andean cryosphere at this critical point in time.