Preprints
https://doi.org/10.5194/egusphere-2022-630
https://doi.org/10.5194/egusphere-2022-630
25 Jul 2022
 | 25 Jul 2022

Investigating the thermal state of permafrost with Bayesian inverse modeling of heat transfer

Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike

Abstract. Long-term measurements of permafrost temperatures do not provide a complete picture of the Arctic subsurface thermal regime. Regions with warmer permafrost often show little to no long-term change in ground temperature due to the uptake and release of latent heat during freezing and thawing. Thus, regions where the least warming is observed may also be the most vulnerable to permafrost degradation. Since direct measurements of ice and liquid water contents in the permafrost layer are not widely available, thermal modeling of the subsurface plays a crucial role in understanding how permafrost responds to changes in the local energy balance. In this work, we first analyze trends in observed air and permafrost temperatures at four sites within the continuous permafrost zone, where we find substantial variation in the apparent relationship between long-term changes in permafrost temperatures (0.02 K yr−1 to 0.16 K yr−1) and air temperature (0.09 K yr−1 to 0.11 K yr−1). We then apply recently developed Bayesian inversion methods to link observed changes in borehole temperatures to unobserved changes in latent heat and thaw depth using a transient model of heat conduction with phase change. Our results suggest that the degree to which recent warming trends correlate with permafrost thaw and variations in latent heat is heavily dependent on both local soil properties as well as historical climatology. At the warmest site, a nine meter borehole near Ny-Ålesund, Svalbard, modeled annual maximum thaw depth increases by an average of (12 ± 1) cm K−1 rise in mean annual ground temperature. In stark contrast, modeled thaw rates for a borehole on Samoylov Island in the Lena River Delta (northeastern Siberia) appear far less sensitive to temperature change, with an almost negligible increase of (1 ± 1) cm K−1. Although our study is limited to just four sites, the results urge caution in the interpretation and comparison of warming trends in Arctic boreholes, indicating substantial uncertainty in their implications for the current and future thermal state of permafrost.

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Journal article(s) based on this preprint

24 Aug 2023
Investigating the thermal state of permafrost with Bayesian inverse modeling of heat transfer
Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike
The Cryosphere, 17, 3505–3533, https://doi.org/10.5194/tc-17-3505-2023,https://doi.org/10.5194/tc-17-3505-2023, 2023
Short summary
Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-630', Anonymous Referee #1, 08 Nov 2022
    • AC1: 'Reply on RC1', Brian Groenke, 30 Jan 2023
  • RC2: 'Comment on egusphere-2022-630', Anonymous Referee #2, 09 Dec 2022
    • AC2: 'Reply on RC2', Brian Groenke, 30 Jan 2023

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-630', Anonymous Referee #1, 08 Nov 2022
    • AC1: 'Reply on RC1', Brian Groenke, 30 Jan 2023
  • RC2: 'Comment on egusphere-2022-630', Anonymous Referee #2, 09 Dec 2022
    • AC2: 'Reply on RC2', Brian Groenke, 30 Jan 2023

Peer review completion

AR: Author's response | RR: Referee report | ED: Editor decision | EF: Editorial file upload
ED: Publish subject to revisions (further review by editor and referees) (08 Feb 2023) by Adrian Flores Orozco
AR by Brian Groenke on behalf of the Authors (22 Mar 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish subject to revisions (further review by editor and referees) (26 Mar 2023) by Adrian Flores Orozco
ED: Referee Nomination & Report Request started (08 May 2023) by Adrian Flores Orozco
RR by Anonymous Referee #2 (22 May 2023)
ED: Publish subject to minor revisions (review by editor) (21 Jun 2023) by Adrian Flores Orozco
AR by Brian Groenke on behalf of the Authors (08 Jul 2023)  Author's response   Author's tracked changes   Manuscript 
ED: Publish as is (11 Jul 2023) by Adrian Flores Orozco
AR by Brian Groenke on behalf of the Authors (25 Jul 2023)  Manuscript 

Journal article(s) based on this preprint

24 Aug 2023
Investigating the thermal state of permafrost with Bayesian inverse modeling of heat transfer
Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike
The Cryosphere, 17, 3505–3533, https://doi.org/10.5194/tc-17-3505-2023,https://doi.org/10.5194/tc-17-3505-2023, 2023
Short summary
Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike

Model code and software

Study code repository Brian Groenke https://gitlab.awi.de/sparcs/analysis/boreholetrendstudy

Transient heat conduction model: CryoGrid.jl (v0.10.3) Brian Groenke, Jan Nitzbon https://doi.org/10.5281/zenodo.6801740

Brian Groenke, Moritz Langer, Jan Nitzbon, Sebastian Westermann, Guillermo Gallego, and Julia Boike

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Latest update: 18 Sep 2024
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Short summary
It is now well known from long-term temperature measurements that Arctic permafrost, i.e. ground that remains continuously frozen for at least two years, is warming in response to climate change. Temperature, however, only tells half of the story. In this study, we use computer modeling to better understand how the thawing and freezing of water in the ground affects the way permafrost responds to climate change and what temperature trends can and cannot tell us about how permafrost is changing.