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Sub-aerial talik formation observed across the discontinuous permafrost zone of Alaska


Talik formation has long been acknowledged as an important mechanism of permafrost degradation. Currently, a lack of in situ observations has left a critical gap in our understanding of how ongoing climate change may influence future sub-aerial talik formation in areas unaffected by water bodies or wildfire. Here we present in situ ground temperature measurements from undisturbed sub-aerial sites across the discontinuous permafrost zone of Alaska between 1999 and 2020. We find that novel taliks formed at 24 sites across the region, with widespread initiation occurring during the winter of 2018 due to higher air temperatures and above-average snowfall insulating the soil. Future projections under a high emissions scenario show that by 2030, talik formation will initiate across up to 70% of the discontinuous permafrost zone, regardless of snow conditions. By 2090, talik in areas of black spruce forest, and warmer ecosystems, may reach a thickness of 12 m. The establishment of widespread sub-aerial taliks has major implications for permafrost thaw, thermokarst development, carbon cycling, hydrological connectivity and engineering.

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Fig. 1: An overview of monitoring locations and timing of talik development.
Fig. 2: FDD, TDD and snow-depth values at key sites.
Fig. 3: Example of talik formation at six sites from across the study region.
Fig. 4: PT, PF and talik thickness through time.

Data availability

Ground temperature can be obtained from, through the data repositories cited within Supplementary Table 1 or from the authors upon request. Source data are provided with this paper.

Code availability

The GIPL model used to estimate potential thaw, potential freeze and talik thickness is freely available via GitHub at


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This work was funded by NSF AON Award numbers 1832238 (L.M.F., V.E.R., D.N. and A.K.) and 1304271 (L.M.F., V.E.R., D.N. and A.K.), NSF-funded Bonanza Creek LTER project (V.E.R.), the Department of Energy Next Generation Ecosystem Experiment Arctic (NGEE-Arctic) (L.M.F., V.E.R. and A.K.) and the Tomsk State University Development Programme (Priority-2030) (D.N.). We thank B. Cable, K. Dolgikh and C. Wright for maintaining permafrost monitoring stations and B. Gaglioti for assistance calculating thawing degree day and freezing degree day values.

Author information

Authors and Affiliations



V.E.R. and L.M.F. conceived the study and conducted data collection and analysis. L.M.F. led manuscript writing. V.E.R. conducted numerical modelling. D.N. conducted model validation and data analysis. A.K. contributed to ground temperature monitoring and data collection.

Corresponding author

Correspondence to Louise M. Farquharson.

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The authors declare no competing interests.

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Nature Geoscience thanks Boris Biskaborn, Élise Devoie and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Tom Richardson, in collaboration with the Nature Geoscience team.

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Extended data

Extended Data Fig. 1 GIPL model validation for Smith Lake #2 site.

Model output is plotted against observations from ground temperature sensors in permafrost boreholes. RMSE error, 0.84 °C.

Extended Data Fig. 2 GIPL model validation for the Bonanza Creek site.

Model output is plotted against observations from ground temperature sensors in permafrost boreholes. RMSE error, 1.2 °C.

Extended Data Fig. 3 Bonanza Creek volumetric liquid water content (%) and ground temperature (°C) at 0.54 m depth between fall 2009 and summer 2019.

Note the lack of freezing during the winters of 2017–2018 and 2018–2019.

Extended Data Fig. 4 A comparison of measured active layer depths and those modeled by the GIPL model for Bonanza Creek.

Active layer depths were measured using an active layer probe at the end of the summer (late August) over an 18-year period. The labels indicate the year of measurement.

Supplementary information

Supplementary Information

Supplementary Tables 2–4 and Figs. 1–31.

Supplementary Table 1

A summary of talik formation at all sites, along with metadata and data sources

Source data

Source Data Fig. 2

Raw data for thawing degree days, freezing degree days and snowfall.

Source Data Fig. 4

Raw data from potential thaw, potential freeze, active-layer depths and talik thickness for Bonanza Creek and SL#2 sites; data include model input files for model runs and the GIPL model.exe file.

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Farquharson, L.M., Romanovsky, V.E., Kholodov, A. et al. Sub-aerial talik formation observed across the discontinuous permafrost zone of Alaska. Nat. Geosci. 15, 475–481 (2022).

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