Long‐term monitoring of sporadic permafrost at the eastern margin of the European Alps (Hochreichart, Seckauer Tauern range, Austria)

Abstract

Delineating the spatial extent and the altitudinal lower limit of mountain permafrost is difficult due to complex topo‐climatic and variable ground thermal conditions within short distances. Little information exists regarding sporadic permafrost existence, its thermal characteristics and its long‐term changes at the eastern margin of the European Alps. To reduce this gap, permafrost monitoring was initiated in 2004 in the Seckauer Tauern mountains, Austria. Research was carried out in the summit region of Mt Hochreichart (2416 m a.s.l.) and at several nearby cirques and valleys, all with rock glaciers. Geomorphic mapping, numerical permafrost modeling, measurements of the bottom temperature of the winter snow cover, continuous ground temperature monitoring, electrical resistivity tomography and optical snow cover monitoring were applied. Results indicate sporadic permafrost occurrence in the summit region with mean annual ground temperatures slightly below 0°C at the surface and −1.4°C at 2.5 m depth. Permafrost lenses also exist in the transition zone between the rock glacier and the talus slope behind attributed to coarse‐grained, blocky material causing additional ground cooling. Thanks to long‐term data, statistically significant trends of atmospheric and ground warming were observed in 2000–2018. Permafrost at this site will presumably disappear within the next few decades.

Deciphering the evolution of the Bleis Marscha rock glacier (Val d'Err, eastern Switzerland) with cosmogenic nuclide exposure dating, aerial image correlation, and finite-element modelling

“…5b) we believe that the ice is as old as its covering debris mantle and of early Holocene age, otherwise the surface must look more disrupted and collapsed. Self-preservation of ground ice thanks to its high heat capacity and the cooling effect of air circulation in the overlying coarse-debris mantle is a commonly observed phenomenon in rock glaciers (Guodong et al, 2007, Colucci et al, 2019Kellerer-Pirklbauer, 2019). For example, preservation of early-Holocene subsurface ice through the mid-Holocene warm period is interpreted by Krainer et al (2015) for the the Lazaun rock glacier.…”

“…Haeberli et al, 2017;Anderson et al, 2018) via the 'thermal semi-conductor' effect (Harris and Pedersen, 1998;Humlum, 1998;Hanson and Hoelzle, 2004;Guodong et al, 2007). The ground cooling effect of a coarse-debris mantle (Schneider et al, 2012;Wicky and Hauck, 2017) favours a large negative thermal offset and permafrost conditions even at mean annual ground temperature (MAGT) close to 0 °C (Kellerer-Pirklbauer, 2019). Furthermore, the creep of millennia-old rock glaciers is tied to the ice-supersaturation of the debris and hence to the preservation of ground ice over their entire lifetime (Barsch, 1996;Haeberli et al, 2003).…”

Permafrost and periglacial processes in mid‐ and low‐latitude mountain regions

“…In the eastern margin of the European Alps, Kellerer‐Pirklbauer investigate the characteristics and distribution of sporadic permafrost. The main results of this work indicate sporadic permafrost occurrence in the summit sector of the study area, with mean annual temperatures close to 0°C at the soil surface, and −1.4°C at 2.5 m depth, as well as the existence of permafrost patches in the transition area between rock glaciers and talus cones.…”

The first consistent inventory of rock glaciers and their hydrological catchments of the Austrian Alps

“…Collapse structures and extensive vegetation cover are typical features of relict rock glaciers. But even morphologically relict-looking rock glaciers still may contain substantial volumes of permafrost ice, therefore a clear distinction between intact and relict rock glaciers based on morphology is still challenging (Sorg et al, 2015;Colucci et al, 2019;Kellerer-Pirklbauer, 2019). Depending on the genesis and elevation of the landforms (e.g.…”