A climate-driven, altitudinal transition in rock glacier dynamics detected through integration of geomorphological mapping and InSAR-based kinematics

• Main Authors: Bertone, Aldo, Jones, Nina, Mair, Volkmar, Scotti, Riccardo, Strozzi, Tazio, Brardinoni, Francesco
• Format: Text
• Language: English
• Published: 2023
• Subjects: permafrost
• Online Access: https://doi.org/10.5194/tc-2023-143; https://tc.copernicus.org/preprints/tc-2023-143/

In dry southwestern South Tyrol, Italy, rock glaciers are dominant landforms of the high-mountain cryosphere. Their spatial distribution and degree of activity hold critical information on the past and current state of discontinuous permafrost, and consequently on response potential to climate warming. Traditional geomorphologic mapping, however, owing to the qualitative expert-based nature, typically displays a high degree of uncertainty and variability among operators with respect to the dynamic classification of intact (permafrost bearing) and relict (permafrost devoid) rock glaciers. This limits the reliability of geomorphologic rock glacier inventories for basic and applied purposes. To address this limitation: (i) we conduct a systematic evaluation of the improvements that InSAR-based information can afford to the detection and dynamic classification of rock glaciers; and (ii) build an integrated inventory that wishes to combine the strengths of geomorphologic- and InSAR-based approaches. To exploit fully InSAR-based information towards a better understanding of the topo-climatic conditions that sustain creeping permafrost, we further explore how velocity and the spatial distribution of moving areas (MAs) within rock glaciers may vary as a function of simple topographic variables known to exert first-order controls on incoming solar radiation, such as elevation and aspect. Starting from the compilation of a geomorphologic inventory (n = 789), we characterize the kinematics of InSAR-based MAs and the relevant hosting rock glaciers on thirty-six Sentinel-1 interferograms computed over 6- through 342-day baselines in the 2018–19 period. With respect to the original inventory, InSAR analysis allowed identifying 14 previously undetected rock glaciers. Further, it confirmed that 246 (76 %) landforms, originally interpreted as intact, do exhibit detectable movement (i.e., ≥1 cm yr -1 ), and that 270 (60 %) of the relict labelled counterparts do not, whereas 144 (18 %) resulted kinematically undefined due to ...