Preprints
https://doi.org/10.5194/tc-2022-4
https://doi.org/10.5194/tc-2022-4
 
17 Mar 2022
17 Mar 2022
Status: this preprint is currently under review for the journal TC.

Post Little Ice Age rock wall permafrost evolution in Norway

Justyna Czekirda1, Bernd Etzelmüller1, Sebastian Westermann1, Ketil Isaksen2, and Florence Magnin3 Justyna Czekirda et al.
  • 1Department of Geosciences, University of Oslo, 0316 Oslo, Norway
  • 2Department of Research and Development, Norwegian Meteorological Institute, 0313 Oslo, Norway
  • 3EDYTEM, Université Savoie Mont-Blanc, CNRS, 73000 Chambery, France

Abstract. Around 10 % of unstable rock slopes in Norway are possibly underlain by widespread permafrost. Permafrost thaw and degradation may play a role in slope destabilization and more knowledge about rock wall permafrost in Norway is needed to investigate possible links between ground thermal regime, geomorphological activity and natural hazards. Here, we assess spatio-temporal permafrost variations in selected rock walls in Norway over the last 120 years. We model ground temperature using the two-dimensional ground heat flux model CryoGrid 2D along nine profiles crossing monitored rock walls in Norway. The simulation results show the distribution of sporadic to continuous permafrost along the modelled profiles. Ground temperature at 20 m depth in steep rock faces increased by 0.2 °C decade-1 on average since the 1980s. Rates of ground temperature change increase with elevation within a single rock wall section. Multi-dimensional thermal effects are in general smaller in Norway than in e.g. the European Alps due to gentler mountain topography and less aspect-related variations in ground surface temperature. Nevertheless, the steepest mountains are still sensitive to even small differences in ground surface temperature. This study further demonstrates how rock wall permafrost distribution and/or rock wall temperature increase rates are influenced by factors such as surface air temperature uncertainties, surface offsets arising from the incoming shortwave solar radiation, snow conditions in, above and below rock walls, rock wall geometry and size, adjacent blockfield-covered plateaus or glaciers.

Justyna Czekirda et al.

Status: open (until 15 Jun 2022)

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Justyna Czekirda et al.

Justyna Czekirda et al.

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Short summary
In this study we use a two-dimensional model of permafrost to simulate the distribution of permafrost in nine rock walls in Norway since 1900. Permafrost probably occurs at most sites. All simulations show increasing ground temperature from the 1980s. Our simulations show that rock wall permafrost with a temperature of -1 °C at 20 m depth could thaw at this depth within 50 years if the rate of atmospheric warming remains unchanged.