Characteristics of ice-rich permafrost soils and their effect on thermokarst expansion rates in Interior Alaskan peatlands

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Zwanenburg, Natalie
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University of Guelph

This thesis addresses two uncertainties concerning permafrost thaw in peatlands by quantifying: (i) how soil characteristics and collapse-scar feature morphology interact to influence lateral expansion rates of thermokarst features; and (ii) the consequences of thermokarst expansion rates on terrestrial carbon storage. I collected peat cores within and adjacent to collapse-scar features to develop a chronosequence of time-following-thaw. I explored feature morphology and soil characteristics using grain size analysis. Radiocarbon dating of the organic and mineral soils from each peat core was used to quantify lateral expansion and peat accumulation rates. Grain size was uniform across the study region, suggesting other physical characteristics (such as ice content and organic matter) influence thaw rate of collapse-scar features. Permafrost carbon stocks rapidly decrease post-thaw, while new surface peat carbon gradually accumulates. My findings suggest anywhere from 250-700 years of surface peat accumulation is required to compensate for deep permafrost carbon losses.

Thermokarst, Permafrost, Terrestrial Carbon Storage, Lateral Expansion Rates, Collapse-Scar Features, Grainsize