Multi-decadal (1953–2017) rock glacier morphodynamics analysed by high-resolution topographic data in the Upper Kauner Valley, Austria

Abstract

Abstract. Permafrost is being degraded worldwide due to the change in external forcing caused by climate change. This has also been shown to affect the morphodynamics of active rock glaciers. We studied these changes, depending on the analysis, on nine or eight active rock glaciers with different characteristics in multiple epochs between 1953 and 2017 in Kauner Valley, Austria. A combination of historical aerial photographs and airborne laser scanning data and their derivatives are used to analyse surface movement and 3D displacements. In general, the studied landforms show a significant acceleration of varying magnitude in the epoch 1997–2006 and a volume loss to varying degrees throughout the investigation period. Besides, we detect rock glaciers that show indication of inactivation. By analysing meteorological data (temperature, precipitation and snow cover onset and duration), we are able to identify possible links to these external forcing parameters. The combined investigation of horizontal and vertical 3D displacements shows that these are temporally decoupled on some rock glaciers. The catchment-wide survey further reveals that, despite the general trend, timing, magnitude and temporal peaks of morphodynamic changes indicate a slightly different sensitivity, response or response time of individual rock glaciers to fluctuations and changes in external forcing parameters.

Comment on tc-2021-77

“…10 and 2017. Both, the significant jump in magnitude as well as the delay could be the consequence of the changes in the above described external forcing in combination with the known ice body of the rock glacier (Hausmann et al, 2012). It seems that the external forcing leads to a significant melting of the permafrost body, which "stimulates" the rock glaciers to increase the flow velocity.…”

“…On the Ölgrube, the first velocity studies were already carried out by Finsterwalder (1928) and Pillewizer (1957) and more recent studies continue their research and contribute additional information about its hydrology, internal and external structure and morphodynamics (Berger et al, 2004;Krainer and Mostler, 2006;Hausmann et al, 2012;Groh and Blöthe, 2019). The area of the investigated rock glaciers ranges from 0.02 km² (RG 07) to 0.237 km² (RG 01).…”

“…In the case of the rock glaciers RG 03, RG 04 and RG 09 a complete or partial covering of the rock glaciers by the LIA glacial extent (Fischer et al, 2015) suggests a glacial genesis after 1850 or at least a glacial influence during and after this time as described by Dusik et al (2015) for RG 09. Some detailed studies about Innere Ölgrube (RG 01) exist, revealing information on internal structure (Hausmann et al, 2012) and genesis (Berger et al, 2004). Berger et al (2004) show that both lobes of the rock glacier developed from debris covered glaciers after the peak of the Little Ice Age (LIA) (~1850).…”

“…Berger et al (2004) show that both lobes of the rock glacier developed from debris covered glaciers after the peak of the Little Ice Age (LIA) (~1850). The rock glacier is composed of a 4 m to 6 m active layer, a 20 m to 30 m thick ice rich permafrost body and a underlying 10 m to 15 m ice free sediment layer and has an ice content of 40% to 60% (Hausmann et al, 2012).…”

“…The ice-rich permafrost body constitutes the main body of the rock glacier. The volumetric ice content varies between 40% -90% (Arenson et al, 2002;Haeberli et al, 2006;Hausmann et al, 2012) and the debris size is smaller than in the active layer, which is explained by fall sorting, washing away and kinetic sieving (Haeberli et al, 2006). The thermal regime of the permafrost layer is mainly controlled by heat conduction, therefore temperature signal from the surface is linearly delayed and its amplitude exponentially decreases with depth (Haeberli et al, 2006).…”