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Soil data and age models used to investigate the effects of permafrost thaw on carbon storage, Interior Alaska

October 29, 2021

We quantified permafrost plateau carbon (C) and post-thaw C stocks across a peatland permafrost thaw chronosequence in Interior Alaska to evaluate whether C losses occurred with thaw . Peat core macrofossil reconstructions revealed three stratigraphic layers of peat: (1) a base layer of fen/marsh peat, (2) forested permafrost plateau peat and, (3) where permafrost thaw has occurred, collapse-scar bog peat. Radiocarbon dating revealed that peat initiated at all sites within the last 2,500 years, and dating transitions between stratigraphic layers allowed us to determine that permafrost aggraded during the Little Ice Age and degraded within the last several decades. We found the timing of permafrost thaw within each feature was not related to thaw bog size, as hypothesized. The rate of expansion may be more influenced by local factors, such as ground ice content and subsurface water inputs. We found C losses in the century following thaw were lower than losses previously described in other Alaskan peatland chronosequences. We hypothesize that the difference stems from the process by which permafrost aggraded, with sites that formed permafrost epigenetically, i.e. significantly later than the majority of peat accumulation, experiencing less C loss with thaw than sites that formed syngenetically, i.e. simultaneously with peat accumulation. We suggest that N concentration and C:N ratios can provide a first order estimate of how much peat has been processed prior to permafrost aggradation, helping to predict the magnitude of C loss with thaw.