EAGER: Characteristic Disruptions of the Marine Carbon Cycle

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Earth's carbon cycle consists of processes that consume and produce carbon dioxide. The geologic record shows that the balance between consumption and production has undergone many disruptions lasting thousands of years or more. This project focuses on disruptions that produce unusually high carbon dioxide levels and global warming. Previous work has related these events to carbon that is released from particular sources under the right climatic conditions. However, recent work suggests these events occur in a typical way independent of longer-term climatic trends. This project proposes that such characteristic disruptions are natural consequences of mechanisms in the carbon cycle that are always active. The project will quantify the evidence of such behavior in records from marine sediments. It will also develop mathematical models to show how such disruptions could arise. To bring this subject to a wide audience, the project will hold public question-and-answer sessions on reddit.com's “IAmA” “Ask me anything” website. It will also host a public screening of the 2019 HBO documentary Ice on Fire, which features related themes. The project will also produce new educational resources, support the training of a graduate student, and publicize its work in the news media.The project's overall goal is to understand mechanisms responsible for disruption of the long-term carbon cycle. The project hypothesizes that characteristic disruptions occur via processes of nonlinear amplification. It proposes to detect signatures of such processes in paleoclimate time series and to explain these observations by construction of new models. Past work has emphasized the role of specific sedimentary carbon reservoirs in generating certain individual events. Yet it also indicates that more general pathways to disruption may have persisted through different climate regimes. The project seeks to identify classes of such persistent phenomena related to intrinsic nonlinear dynamics of the marine carbon cycle. The project will construct mathematical models showing how this could work and will seek evidence of their predictions in past fluctuations in carbon-isotopic data. Such understanding will likely lead to new interpretations of the role of specific stressors, such as enhanced volcanism or the release of methane, as drivers of major warming events. Results will also provide insight into the long-term risks of the human perturbation of the modern carbon cycle.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.