Quantifying Overestimated Permafrost Extent Driven by Rock Glacier Inventory

• Published in: Geophysical research letters 2021-04, Vol.48 (8), p.n/a
• Main Authors: Cao, Bin, Li, Xin, Feng, Min, Zheng, Donghai
• Format: Article
• Language: English
• Subjects: permafrost; rock glacier; scale effects
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL092476

Rock glaciers (RGs) are normally used as “ground‐truth” observations to indicate the presence of permafrost, and hence extensively used in training permafrost distribution models. However, the unique structure and composition of RGs enhance ground cooling effects, leading to more favorable conditions for permafrost presence than in adjacent ground. We therefore hypothesized and confirmed that permafrost extent is overestimated using RG‐driven models. The results indicate that the permafrost zonation index was overestimated by about 8.4%–13.1% in a model driven by RG observations compared to a model using in situ measurements of permafrost presence/absence. The bias is particularly pronounced in discontinuous permafrost region, where it is thought to be highly sensitive to climate change, resulting in about a 41.8%–90.8% overestimation in permafrost region and 7.0%–18.6% misclassification. In order to better use the large RG datasets available to understand permafrost conditions, we provide a method to correct this bias in a fundamental model. Plain Language Summary Permafrost is a hidden phenomenon that cannot be easily observed. Rock glaciers (RGs) are normally used as “ground‐truth” observations to indicate the presence or absence of permafrost. Therefore, RG are extensively used in compiling permafrost distribution. However, the high porosity and presence of ice in RGs enhance cooling effects on ground temperature, leading to more favorable conditions for permafrost presence than in adjacent ground. We therefore hypothesized and confirmed that permafrost extent is overestimated using models driven by RG observations. Our results indicate that the simulated permafrost zonation index was overestimated by about 8.4%–13.1% in a model driven by RG observations compared to a model using in situ measurements. The bias is particularly pronounced in discontinuous permafrost region, where is highly sensitive to climate change, resulting in about a 41.8%–90.8% overestimation in permafrost region and 7.0%–18.6% misclassification. In order to better use the large RG datasets available to understand permafrost conditions, we provide, for the first time, a method to correct this bias in a fundamental model. Key Points Models driven by rock glacier observations overestimated permafrost zonation index by about 8.4%–13.1% About 41.8%–90.8% of the discontinuous permafrost region is overestimated when using models driven by rock glacier observations Remarkable overestimati