Movement pattern analysis of the Dösen Rock Glacier (Hohe Tauern Range, Austria) using a multi-method approach

Rock glaciers are known to show changing rheological behavior related to climate forcing, resulting in varying seasonal and interannual movement velocities. We studied the relationship between movement behavior and climate forcing at the Dösen Rock Glacier, Hohe Tauern Range, using a combination of velocity data, meteorological records, ground temperature records, and a numerical modeling approach. The Dösen Rock Glacier extends from 2340 to 2620 m asl, covers an area of 0.2 km², is 950 m long and up to 300 m wide. Rather long series of annual to pluri-annual geodetic and photogrammetric movement pattern observations as well as air and ground temperature time series describing the thermal regime at the rock glacier site are available. Yet the monitoring data does not reflect movement rates on a sub-annual time scale. Hence the annual measurement campaigns performed on 17.08.2021 and 16./17.08.2022 were complemented by geodetic monitoring campaigns conducted on 06./07.07.2022 and 28.09.2022, to allow for a higher temporal resolution during summer and early fall of 2022. The observed annual movement rates between 2021 and 2022 ranged from 1.09 to 61.41 cm/a at the individual measurement points (n=34) with an overall annual mean of 33.79 cm. Analyses of the short-term monitoring indicate velocities in the range of 0.04 to 0.19 cm/d and a mean daily displacement of 0.11 cm (n=17) for the period between 06/07.07.2022 and 16/17.08.2022 whereas values ranged from 0.06 to 0.19 cm/d with a mean daily displacement of 0.14 cm (n=17) for the second period between 16/17.08.2022 and 28.09.2022. With three exceptions the horizontal movement rates at the 17 individual points, which could be measured and evaluated during both campaigns, were higher for the latter period. This reveals a general acceleration of the rock glacier during late-summer and early-autumn season.

The sub-annual geodetic dataset from 2022 is used as a starting point for bridging time scales in the supplementation of long-term monitoring efforts with numerical modeling. We present a workflow which tries to introduce climate forcing on rock glacier kinematics to the numerical mass flow simulation framework r.avaflow. For this purpose, a temperature-viscosity relation will be established. This facilitates the implementation of viscosity, variable over time, as governing input parameter for the rock glacier flow behavior. In a first step the strategy will be applied for the period from 1954 to 2022, where geodetic and photogrammetric reference data as well as digital elevation models are available, allowing for the empirical evaluation of the simulation results.

The described approach is designed to process rock glacier monitoring data (movement velocities and climate data) of different temporal resolution to be subsequently fed into an open-source modeling software with the aim to generate insights in sub-annual rock glacier movement patterns.

Acknowledgement: This work was supported by the Austrian Science Fund (FWF P18304-N10), the European Regional Development Fund (18-1-3-I) and the Hohe Tauern National Park Carinthia.