Preprints
https://doi.org/10.5194/egusphere-2025-5676
https://doi.org/10.5194/egusphere-2025-5676
19 Feb 2026
 | 19 Feb 2026
Status: this preprint is open for discussion and under review for The Cryosphere (TC).

Larger variability of winter snow depth promotes the soil thermal regime instability over boreal high latitudes

Lingyun Ai, Kai Yang, Feimin Zhang, Chenghai Wang, Tonghua Wu, Qi Qi, and Haohui Li

Abstract. Permafrost degradation in Siberia is assessed as one of the global climate tipping elements. Soil thermal regime instability (STRI) describes the amplitude and frequency of soil temperature extremes at the interannual scale, and such thermal instability can propagate downward through the soil column and affect permafrost thermal conditions, making STRI a useful indicator of permafrost vulnerability. Yet, how STRI changes and the underlying mechanism remain poorly understood. Here, regarding soil temperature variability as a proxy of STRI on interannual scale, and through combining a merged soil temperature dataset with in-situ observations, it was detected that the subsurface (40 and 160 cm) STRI over Siberian continuous permafrost region is higher compared to other regions over boreal high latitudes, most pronounced in winter. Moreover, winter STRI across the Siberia continuous permafrost region has increased suddenly since early 1990s. Increase in STRI is particularly pronounced in regions where soil thermal regime was once stable, with increase rate of STRI exceeding 0.5 °C/10a in some regions. Statistical analyses and numerical experiments reveal that this increased STRI is strongly associated with the larger interannual variability of winter snow depth through its insulation effect, with snow depth accounting for more than 50 % of the STRI increase in most regions, and influence of snow depth on STRI is detectable down to 3.6 m. These findings highlight that snow-soil interactions dominate winter soil thermal dynamics, particularly over the thick snow regions, with potential implications for permafrost stability, carbon dynamics, and ecosystem responses.

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Lingyun Ai, Kai Yang, Feimin Zhang, Chenghai Wang, Tonghua Wu, Qi Qi, and Haohui Li

Status: open (until 02 Apr 2026)

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Lingyun Ai, Kai Yang, Feimin Zhang, Chenghai Wang, Tonghua Wu, Qi Qi, and Haohui Li
Lingyun Ai, Kai Yang, Feimin Zhang, Chenghai Wang, Tonghua Wu, Qi Qi, and Haohui Li
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Short summary
Since the early 1990s, the Siberian continuous permafrost has experienced markedly increased interannual variability in winter soil temperature. This heightened thermal instability is primarily driven by more variable winter snow depth, which insulates the soil. The influence extends meters deep, threatening permafrost stability and elevating risks of carbon release and ecosystem change under climate warming.
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