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

永久冻土，或常年冻结的土地，拥有一个巨大的碳库。这项研究的首要目标是着眼于最近的地质历史，以提高对未来气候变化可能如何影响碳积累和释放的理解。研究人员结合了古生态学、古气候学、地表地质学、地质年代学和定量地貌学的专业知识。他们将共同量化气候与北极丘陵高地地区过去4万年明显不同气候下积累的碳质量之间的关系，这将补充之前关于气候变化对低洼地带湖泊和泥炭地永久冻土碳的影响的工作。这些结果将为北极环境变化研究中的永久冻土碳网络增加古视角。该项目将为研究生和本科生提供培训，调查团队包括一名早期职业科学家。在这项研究中，调查人员将结合现场收集、沉积物岩芯分析和建模，以量化气候和永冻土碳积累之间的千禧年尺度关系，该研究地点位于阿拉斯加山脉北部山麓的八里湖流域。他们将沿着山坡横断面采集多个沉积物岩芯，以绘制下层地层格架图；对比覆盖短坡和长坡的地表物质，以推断取决于坡长和坡角的输送过程的相对作用；并在数值模型中利用这些数据来模拟山坡演变，评估转移沉积物和固存碳的下坡地貌过程。研究人员还将使用巨型化石的放射性碳测年来确定有机质在地层中混合的程度，并区分千年尺度的堆积期；评估花粉和巨型化石的群落特征和粒度分布；分析沉积物序列中的一套生物物理特性，以量化碳质量、积累和分解。这一裁决反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.