Doctoral Dissertation Research: The Impact of Permafrost Thaw on the Magnitude and Timing of Soil Organic Carbon Pool Change

Permafrost - perennially frozen soil in the Arctic - contains one-third of the world’s soil organic carbon. As the Arctic continue to warm, these massive stores of carbon are thawing and decomposing. Microbial decomposition of newly thawed soil carbon releases carbon dioxide and methane to the atmosphere, driving further warming. Disproportionately large stores of soil carbon combined with unprecedented warming in the Arctic means that thawing permafrost has the potential to alter the global carbon cycle, so it is critically important to understand the interaction between permafrost thaw and soil carbon release. This study will add to our understanding of the magnitude (how much net soil carbon will leave) and timing (when it will leave) of permafrost carbon emissions by directly measuring how soil carbon amounts change in a permafrost warming experiment. Direct measures of soil carbon pool change following permafrost thaw are crucial for understanding the whole-ecosystem response to warming. Additionally, permafrost thaw rapidly changes the soil environment and will alter known soil organic carbon protection mechanisms like temperature limitation, excess surface moisture, spatial protection, and chemical bonding of carbon to mineral surfaces. This study will directly quantify soil organic carbon pool change at two comparative sites: (1) a long-term permafrost warming experiment that experienced active layer deepening and (2) at sites with higher ice content that experienced erosion and thermokarst in response to permafrost thaw. This study will link changes to shifting environmental conditions and use soil carbon density fractionation methods and radiocarbon tools to understand changing soil organic carbon protection mechanisms. Direct measures of soil organic carbon pool change following permafrost thaw are central to this study and will improve understanding of the magnitude and timing of permafrost carbon release in a warmer world. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.