Absent kinematic response of Dos Lenguas rock glacier (Dry Andes, Argentina, 2016-2024) to warming trend: regional pattern or peculiarity?

Rock glaciers, debris-ice landforms creeping downslope, are characteristic periglacial landforms in the Dry Andes of Argentina, typically located at lower elevation than glaciers. In this arid region, where monitoring is scarce or limited in duration, rock glaciers are characterised by high hydrological significance, high density in occurrence and comparatively large size. Recently recognized as essential climate variable, long-term monitored increases in rock glacier velocity are commonly associated with changes in air temperature. Given the warming air temperature trend in the study area, rock glacier velocity increases are expected.

We present an 8-year, quasi-biannual, UAV-based monitoring of Dos Lenguas rock glacier kinematics (Dry Andes, Argentina) for the time period 2016-2024. We find surface velocities of 0.9m/yr on average, and velocities of up to 1.7m/yr in the root and centre zones were extensional flow and knickpoints in slope dominate respectively. We detect overall stable surface velocities along with a persistent spatial pattern, particularly contrasting between the two tongues of Dos Lenguas. Further, we quantify vertical surface changes of ±1.5m/yr stable in magnitude and spatial pattern within the monitored time period. We propose the arid conditions in the Dry Andes and the consequent lack of snow sheltering as a controlling factor for Dos Lenguas’ unexpected, absent kinematic response to higher air temperatures and suppose that the absence of snow cover allows winter temperatures to fully penetrate the rock glacier body, preventing acceleration. In addition to the UAV-based investigation, we explore the utility of monitoring the >50 rock glaciers in the catchment using high resolution satellite data, namely tristereoscopic Pléiades imagery – narrowing down an answer to the question: is the absent kinematic response of Dos Lenguas rock glacier representative for a regional pattern in the Dry Andes, or rather a peculiarity?