The Dosen Rock Glacier in Central Austria: A key site for multidisciplinary long-term rock glacier monitoring in the Eastern Alps

Rock glaciers are distinct landforms in high mountain environments indicating present or past permafrost conditions. Active rock glaciers contain permafrost and creep slowly downslope often forming typical flow structures with ridges and furrows related to compressional forces. Rock glaciers are widespread landforms in the Austrian Alps (c. 4600). Despite the high number of rock glaciers in Austria, only few of them have been studied in detail in the past. One of the best studied ones is the 950 m long Dosen Rock Glacier located in the Hohe Tauern Range. This rock glacier has been investigated since 1993 using a whole suite of field-based and remote sensing-based methods. Research focused on permafrost conditions and distribution, surface kinematics, internal structure and possible age of the landform. Results indicate significant ground surface warming of the rock glacier body during the period 2007-2015 accompanied by a general acceleration of the rock glacier surface flow velocity (max. 0.66 m/a) over the last two decades. This speed-up is possibly related to higher ice temperature and water content. As judged from various geophysical measurements, the maximum thickness of the rock glacier is about 30-40 m with an active layer of several meters depending on the location. The permafrost thickness beneath the active layer was quantified to be between 10 m (at the margins) and 40 m (at the central and upper parts). Massive sedimentary ice has not been observed or detected by geophysics so far at the central and lower part but might exist to in the rooting zone of the rock glacier as indicated from field evidences. The Dosen Rock Glacier is primarily a talus-derived rock glacier although a small glacier might have existed some times in the past in the eastern part of the rooting zone. Age estimations of the rock glacier by using the Schmidt-hammer exposure-age dating method indicate a formation period of several thousand years with alternating periods of faster and slower evolution. Research findings at this typical alpine rock glacier in the Austrian Alps clearly point out that the morphogenesis, the internal structure as well as the climate-rock glacier relationship is complex but typical for such peculiar alpine landforms.