Distinguishing ice-rich and ice-poor permafrost to map ground temperatures and ground ice occurrence in the Swiss Alps

Abstract

Mountain permafrost is invisible, and mapping it is still a challenge. Available permafrost distribution maps often overestimate the permafrost extent and include large permafrost-free areas in their permafrost zonation. In addition, the representation of the lower belt of permafrost consisting of ice-rich features such as rock glaciers or ice-rich talus slopes can be challenging. These problems are caused by considerable differences in genesis and thermal characteristics between ice-poor permafrost, occurring for example in rock walls, and ice-rich permafrost. While ice-poor permafrost shows a strong correlation of ground temperature with elevation and potential incoming solar radiation, icerich ground does not show such a correlation. Instead, the distribution of ice-rich ground is controlled by gravitational processes such as the relocation of ground ice by permafrost creep or by ground ice genesis from avalanche deposits or glacierets covered with talus.We therefore developed a mapping method which distinguishes between ice-poor and ice-rich permafrost and tested it for the entire Swiss Alps. For ice-poor ground we found a linear regression formula based on elevation and potential incoming solar radiation which predicts borehole ground temperatures at multiple depths with an accuracy higher than 0.6 • C. The zone of ice-rich permafrost was defined by modelling the deposition zones of alpine mass wasting processes. This dual approach allows the cartographic representation of permafrost-free belts, which are bounded above and below by permafrost. This enables a high quality of permafrost modelling, as is shown by the validation of our map. The dominating influence of the two rather simple connected factors, elevation (as a proxy for mean annual air temperature) and solar radiation, on the distribution of ice-poor permafrost is significant for permafrost modelling in different climate conditions and regions. Indicating temperatures of ice-poor permafrost and distinguishing between ice-poor and ice-rich permafrost on a national permafrost map provides new information for users.

Petrophysical Joint Inversion Applied to Alpine Permafrost Field Sites to Image Subsurface Ice, Water, Air, and Rock Contents

“…Quantification of the volumetric ground ice content is therefore an important means to understand the current state of alpine permafrost as well as to monitor its future evolution. Ground ice content can typically vary from 0 to 100%, depending on the permafrost landform, from ice-poor bedrock to ice-rich talus slope or rock glaciers (e.g., Kenner et al, 2019).…”

High mountain rockfall dynamics: rockfall activity and runout assessment under the aspect of a changing cryosphere

“…For the glacier assessment the Austrian glacier inventory for the LIA (Groß and Patzelt 2015) was used. In order to investigate a link between the presence of permafrost and the rockfall activity, we produced a map of the MAGT, which is based on a linear regression model calibrated by Kenner et al (2019). The elevation and the potential incoming solar radiation (PISR), as representor for the mean annual air temperature (MAAT) (Hoelzle and Haeberli 1995), are the two most important parameters for the surface energy balance (Hoelzle et al 2001) and have therefore a dominant influence on the distribution of ice-poor permafrost in steep slopes.…”

“…All pixels with negative modelled ground temperatures are referred to permafrost areas. Temperatures in the range of 0°C and 1°C can be described as possible patchy permafrost zone and represent a buffer of 1 K, which corresponds to about the double standard error of the model output (Kenner et al 2019). An example of the modelling results is shown in Figure 1.…”

“…We present an area-wide rockfall inventory for the mountain range of the Ötztaler Alps compiled by a 4-year Airborne Laser Scan (ALS) campaign and a detailed, qualitative runout assessment of 18 small-magnitude rockfalls (<10 4 m³). We (i) identified systematically rockfall events in an area of 610.7 km², (ii) analysed the detachment zones according spatial patterns including topographic parameters, state of glaciation at the end of the little ice age (LIA) around 1850 (Groß and Patzelt 2015) and permafrost occurrence by modelling the mean annual ground temperature (MAGT) (Kenner et al 2019), (iii) investigated the runout distance of 18 rockfall events by using the empirical models of Fahrböschung and minimum shadow angel and (iv) analysed the influence of environmental parameters on the mobility of these events.…”

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

“…Although the high, active-lobe-like deformation susceptibility might be in part explained by higher ground temperatures at lower elevations, mechanical loading exerted by the overriding younger generation (unit IV,Figs. 4,5a), and greater thickness of the two-generation stack of lobes, the ice content in the lower, transitional-inactive lobes must be significant (and mapped as ice-rich permafrost type by Kenner et al (2019)). Second, a fresh lateral boulder apron (Fig.…”