Collaborative research: Climate controls on carbon accumulation in upland permafrost at millennial scales

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Permafrost, or perennially frozen ground, holds a large reservoir of carbon. The overarching goal of this study is to look to the recent geologic past to improve understanding of how future changes in climate may impact carbon accumulation and release. The investigators have combined expertise in paleoecology, paleoclimatology, surficial geology, geochronology, and quantitiative geomorphology. Together, they will quantify the relationship between climate and the mass of carbon that accumulated under distinctly different climates of the past 40,000 years in hilly upland regions of the Arctic, which will complment previous work on the effects of climate change on permafrost carbon in lakes and peatlands of low-lying terrain. Results will add paleo perspectives to the Permafrost Carbon Network, part of the Study of Environmental Arctic Change. The project will provide training for graduate and undergraduate students, and the team of investigators includes an early career scientist.In this study, the investigators will combine field-collections, analysis of sediment cores, and modeling to quantify the millennial scale relationship between climate and permafrost carbon accumulation at an upland study site in the Eight Mile Lake watershed in the northern foothills of the Alaska Range. They will take multiple sediment cores along hillslope transects to map the underlying stratigraphic framework; contrast the surficial materials mantling both a short and a long slope to infer the relative roles of slope-length- versus slope-angle-dependent transport processes; and use these data in a numerical model to simulate hillslope evolution and assess downslope geomorphic processes that transfer sediment and sequester carbon. The investigators will also use radiocarbon dating of macrofossils to determine the extent to which organic matter has been stratigraphically mixed and to distninguish millennial-scale periods of accumulation; evaluate pollen and macrofossiles for community characteristics and grain size distributions; and analyze sediment sequences for a suite of bio-physical properties to quantify carbon mass, accumulation, and decomposition.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.