Preprints
https://doi.org/10.5194/egusphere-2023-3006
https://doi.org/10.5194/egusphere-2023-3006
04 Mar 2024
 | 04 Mar 2024
Status: this preprint is open for discussion.

Modelling active layer thickness in mountain permafrost based on an analytical solution of the heat transport equation, Kitzsteinhorn, Hohe Tauern Range, Austria

Wolfgang Aumer, Ingo Hartmeyer, Carolyn-Monika Görres, Daniel Uteau, and Stephan Peth

Abstract. The active layer thickness (ALT) refers to the seasonal thaw depth of a permafrost body and is an essential parameter for natural hazard analysis, construction, land-use planning and the estimation of greenhouse gas emissions in periglacial regions. The aim of this study is to model the annual maximum thaw depth for determining ALT based on temperature data measured in four shallow boreholes (SBs, 0.1 m deep) in the summit region of the Kitzsteinhorn (Hohe Tauern Range, Austria, Europe). We set up our heat flow model with temperature data (2016–21) from a 30 m deep borehole (DB) drilled into bedrock at the Kitzsteinhorn north-face. For modeling purposes, we assume 1D conductive heat flow and present an analytical solution of the heat transport equation through sinusoidal temperature waves resulting from seasonal temperature oscillations (damping depth method). The model approach is considered successful: In the validation period (2019–21), modeled and measured ALT differed by only 0.1±0.1 m. We then applied the DB-calibrated model to four SBs and found that the modeled seasonal ALT maximum ranged between 2.5 m (SB 2) and 10.6 m (SB 1) in the observation period (2013–2021). Due to small differences in altitude (~ 200 m) within the study area, slope aspect had the strongest impact on ALT. To project future ALT deepening due to global warming, we integrated IPCC climate scenarios SSP1-2.6 and SSP5-8.5 into our model. By mid-century (~ 2050), ALT is expected to increase by 48 % at SB 2 and by 62 % at DB under scenario SSP1-2.6 (56 % and 128 % under scenario SSP5-8.5), while permafrost will no longer be present at SB 1, SB 3 and SB 4. By the end of the century (~ 2100), permafrost will only remain under scenario SSP1-2.6 with an ALT increase of 51 % at SB 2 and of 69 % at DB.

Wolfgang Aumer, Ingo Hartmeyer, Carolyn-Monika Görres, Daniel Uteau, and Stephan Peth

Status: open (until 01 May 2024)

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Wolfgang Aumer, Ingo Hartmeyer, Carolyn-Monika Görres, Daniel Uteau, and Stephan Peth
Wolfgang Aumer, Ingo Hartmeyer, Carolyn-Monika Görres, Daniel Uteau, and Stephan Peth

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Short summary
The summertime thaw depth of permanently frozen ground (active layer thickness, ALT) is of critical importance for natural hazard management (e.g. rock avalanches), construction (foundation stability) and greenhouse gas emissions (decomposition rates) in permafrost regions. We presented the first analytical heat transport model for simulating ALT on borehole scale. Our results show that the ALT will likely increase by more than 50 % until 2050 at 3000 m a.s.l. in the European Alps.