Preprints
https://doi.org/10.5194/egusphere-2023-3074
https://doi.org/10.5194/egusphere-2023-3074
08 Feb 2024
 | 08 Feb 2024
Status: this preprint is open for discussion.

Future permafrost degradation under climate change in a headwater catchment of Central Siberia: quantitative assessment with a mechanistic modelling approach

Thibault Xavier, Laurent Orgogozo, Anatoly S. Prokushkin, Esteban Alonso-González, Simon Gascoin, and Oleg S. Pokrovsky

Abstract. Permafrost thawing as a result of climate change has major consequences locally and globally for the biosphere as well as for human activities. The quantification of its extent and dynamics under different climate scenarios is needed to design local adaptation and mitigation measures and to better understand permafrost climate feedbacks. To this end, numerical simulation can be used to explore the response of soil thermo-hydric regimes to changes in climatic conditions. Mechanistic approaches minimize modelling assumptions by relying on the numerical resolution of continuum mechanics equations, but involve significant computational effort. In this work, the permaFoam solver is used along with high-performance computing resources to assess the impact of four climate scenarios of the Coupled Model Intercomparison Project – Phase 6 (CMIP6) on permafrost dynamics within a pristine, forest-dominated watershed in the continuous permafrost zone. Using these century time-scale simulations, changes in soil temperature, soil moisture, active layer thickness and water fluxes are quantified, assuming no change in vegetation cover. The most severe scenario (SSP5-8.5) suggests a dramatic increase in both active layer thickness and annual evapotranspiration, with maximum values on the watershed reached in 2100 of +46 % and +29 % respectively. For the active layer thickness, in current climatic conditions it would correspond to a 560 km southward shift. Moreover, in this scenario thermal equilibrium of near-surface permafrost with the new climatic conditions would not be reached in 2100, suggesting a further thawing of permafrost even in case of halting the climate change.

Thibault Xavier, Laurent Orgogozo, Anatoly S. Prokushkin, Esteban Alonso-González, Simon Gascoin, and Oleg S. Pokrovsky

Status: open (until 21 Mar 2024)

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Thibault Xavier, Laurent Orgogozo, Anatoly S. Prokushkin, Esteban Alonso-González, Simon Gascoin, and Oleg S. Pokrovsky
Thibault Xavier, Laurent Orgogozo, Anatoly S. Prokushkin, Esteban Alonso-González, Simon Gascoin, and Oleg S. Pokrovsky

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Short summary
Permafrost (permanently frozen soil at depth) is thawing as a result of climate change. However, estimating its future degradation is particularly challenging due to the complex multi-physical processes involved. In this work, we designed and ran numerical simulations for months on a supercomputer to quantify the impact of climate change in a forested valley of Central Siberia. There, climate change could increase the thickness of the seasonally thawed soil layer in summer by up to 45 % by 2100.