As human activity has already produced atmospheric carbon dioxide concentrations that have surpassed the highest levels known during of the past three million years of Earth history, it is critical for society to better understand the fate of atmospheric carbon dioxide produced by fossil fuel burning and other human activities. More accurate projections of future climate scenarios will require a more detailed understanding of how fast natural processes can remove from Earth's atmosphere the pulse of carbon dioxide that is being produced by society in the industrial era. Models of these processes predict a long tail of the pulse of human-produced carbon dioxide, suggesting that this carbon will have a long-term impact on our climate and society. As these processes play out over relatively long timescales, such predictions can be verified by looking to the geological record of past events. This project will provide a high-resolution reconstruction of how an ancient natural pulse of carbon dioxide injected into the atmosphere was neutralized by the Earth system in the geological past. As such, this study will provide important perspective from the past on the present rate at which atmospheric carbon can be taken up by natural processes, and hence help Earth scientists make more accurate projections of future climate change. The researchers will also work with a Geoscience summer residence camp for high school students and non-science major undergraduate students will participate in experiential learning in the field on the impact of climate change. Both activities will contribute to bringing students with diverse backgrounds into STEM and geoscience career paths. This research will evaluate the evolution of atmospheric CO2 on decadal timescales following a rapid pulse of large amounts of carbon dioxide injected into the atmosphere during volcanic eruptions that was part of the Columbia River Basalt Group in the US Pacific Northwest. At the same time as these eruptions and nearby in northern Idaho, an ancient lake (Miocene Lake Clarkia) was formed when basalt flows presumably dammed a local drainage system. Sediments that began to accumulate in the newly formed Lake Clarkia preserve a history of these events in the geological record that can be used to evaluate, in high-resolution, the evolution of the spike of atmospheric CO2 concentrations that resulted from the volcanic eruptions. The researchers will use micro-XRF scanning of elemental distributions to focus their study on the unoxidized, varve-like sediments. They will reconstruct the evolution of this natural pulse of CO2 using the properties of stomatal pores in fossil leaves preserved in the sediments, combined with information from the stable isotopes of carbon preserved in the fossil organic matter.
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.
