Preprints
https://doi.org/10.5194/egusphere-2024-2575
https://doi.org/10.5194/egusphere-2024-2575
02 Sep 2024
 | 02 Sep 2024
Status: this preprint is open for discussion.

Improved permafrost modeling in mountain environments by including air convection in a hydrological model

Gerardo Zegers, Masaki Hayashi, and Rodrigo Pérez-Illanes

Abstract. Permafrost occurrence in mountainous regions is influenced by complex topography and surficial geology, leading to high spatial heterogeneity. Coarse sediments create a unique thermal regime that allows permafrost to persist even under positive mean annual air temperatures due to natural convection lowering ground temperatures. Although this process has been recognized as a key factor in explaining the persistence of permafrost formation within coarse sediments, studies assessing the impact of natural convection on ground temperatures and permafrost are limited, partly due to the absence of hydrological models that take this process into account. This article expands on a well-established hydrological model to incorporate the effects of natural air convection on heat transfer. The modified model includes airflow through Darcy’s equation and the Oberbeck-Boussinesq approximation to account for density-driven buoyancy effects, as well as a heat advection-conduction equation for the air phase without assuming local thermal equilibrium between the air and the other phases. The model was tested on a talus slope in the Canadian Rockies, where conventional models failed to represent field-based evidence of permafrost. The results revealed that coarse-size sediments can lower ground temperatures by several degrees when natural convection is considered. Additionally, the study demonstrated that the local thermal equilibrium approach hinders the impact of natural convection. This enhanced model improves our understanding of permafrost dynamics in alpine landforms and enables a more accurate analysis of permafrost extent and its influence on groundwater discharges.

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Gerardo Zegers, Masaki Hayashi, and Rodrigo Pérez-Illanes

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on egusphere-2024-2575', Giacomo Medici, 06 Sep 2024 reply
  • RC1: 'Comment on egusphere-2024-2575', Anonymous Referee #1, 11 Nov 2024 reply
Gerardo Zegers, Masaki Hayashi, and Rodrigo Pérez-Illanes

Model code and software

GeoTOP-CE Gerardo Zegers https://github.com/gzegers/geotop-CE

Gerardo Zegers, Masaki Hayashi, and Rodrigo Pérez-Illanes

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Short summary
This research showed that airflow within sediment accumulations promotes cooling and sustains mountain permafrost. By enhancing a numerical model, we showed that natural air movement, driven by temperature differences between sediments and external air, allows permafrost to survive. Our work aids in predicting where and how permafrost exists, which is essential for understanding its role in mountain water systems and its response to climate change.