Preprints
https://doi.org/10.5194/egusphere-2023-41
https://doi.org/10.5194/egusphere-2023-41
 
16 Jan 2023
16 Jan 2023
Status: this preprint is open for discussion.

Simulating ice segregation and thaw consolidation in permafrost environments with the CryoGrid community model

Juditha Aga1, Julia Boike2,3, Moritz Langer2,3, Thomas Ingeman-Nielsen2,4, and Sebastian Westermann1,5 Juditha Aga et al.
  • 1Department of Geosciences, University of Oslo, Oslo, Norway
  • 2Alfred Wegener Institute (AWI), Helmholtz Centre for Polar and Marine Research, Potsdam, Germany
  • 3Geography Department, Humboldt-Universität zu Berlin, Berlin, Germany
  • 4Department of Environmental and Resource Engineering, Technical University of Denmark, Lyngby, Denmark
  • 5Centre for Biogeochemistry in the Anthropocene, University of Oslo, Oslo, Norway

Abstract. The ground ice content in cold environments influences the permafrost thermal regime and the thaw trajectories in a warming climate, especially for very ice-rich soils. Despite their importance, the amount and distribution of ground ice are often unknown due to lacking field observations. Hence, modelling the thawing of ice-rich permafrost soils and associated thermokarst is challenging as ground ice content has to be prescribed in the model set-up. In this study, we present a model scheme, which is capable of forming segregated ice during a model spin-up together with associated ground heave. It provides the option to add a constant sedimentation rate throughout the simulation. Besides ice segregation, it can represent thaw consolidation processes and ground subsidence under a warming climate. The computation is based on soil mechanical processes, soil hydrology by Richards equation and soil freezing characteristics. The code is implemented in the CryoGrid community model (version 1.0), a modular land surface model for simulations of the ground thermal regime.

The simulation of ice segregation and thaw consolidation with the new model scheme allows us to analyze the evolution of ground ice content in both space and time. To do so, we use climate data from two contrasting permafrost sites to run the simulations. Several influencing factors are identified, which control the formation and thaw of segregated ice. (i) Model results show that high temperature gradients in the soil as well as moist conditions support the formation of segregated ice. (ii) We find that ice segregation increases in fine-grained soils and that especially organic-rich sediments enhance the process. (iii) Applying external loads suppresses ice segregation and speeds up thaw consolidation. (iv) Sedimentation leads to a rise of the ground surface and the formation of an ice-enriched layer whose thickness increases with sedimentation time.

We conclude that the new model scheme is a step forward to improve the description of ground ice distributions in permafrost models and can contribute towards the understanding of ice segregation and thaw consolidation in permafrost environments under changing climatic conditions.

Juditha Aga et al.

Status: open (until 13 Mar 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Juditha Aga et al.

Model code and software

Parameter files and model code for simulations in "Simulating ice segregation and thaw consolidation in permafrost environments with the CryoGrid community model" Juditha Aga https://zenodo.org/record/6884775

Juditha Aga et al.

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Short summary
This study presents a new model scheme for simulating ice segregation and thaw consolidation in permafrost environments, depending on ground properties and climatic forcing. It is embedded in the CryoGrid Community Model, a land surface model for the terrestrial cryosphere. We describe the model physics and functionalities, followed by a model validation and a sensitivity study of controlling factors.