EAR-PF: Calibrating timescales and measuring pCO2 to test the role of volcanic forcing in the Miocene Climate Optimum

Kasbohm, Jennifer Jean, Princeton NJ

Investigators

Abstract

Dr. Jennifer Kasbohm has been awarded an NSF EAR Postdoctoral Fellowship to carry out research investigating when and why the Miocene Climate Optimum occurred. She is conducting this research at Yale University under the mentorship of Dr. Pincelli Hull. The Miocene Climate Optimum (MCO) is a period of global warming that occurred approximately 17 to 15 million years ago, during which Earth experienced elevated global temperatures and atmospheric carbon dioxide (CO2) concentrations that were as high as they are today. It has been suggested that this warming could have been caused by massive volcanism from the Columbia River Basalt Group (CRBG), which released large amounts of CO2 into the atmosphere and blanketed the northwestern United States with a pile of lava flows more than half a mile thick. During her PhD, Dr. Kasbohm used radioisotopic dating to show that the CRBG erupted much faster than previously thought, and her postdoctoral research is now focused on the timing of the MCO. As an NSF EAR Postdoctoral Fellow, Dr. Kasbohm is performing geochemical measurements on microfossils to estimate atmospheric CO2 levels during the MCO and determine whether the CRBG is likely to have caused the MCO. This research will yield new insights into how quickly Earth responds to massive injections of CO2, similar to what the planet is experiencing today. The research will also investigate how long it takes for temperatures and atmospheric CO2 levels to decline. While conducting this research at Yale, Dr. Kasbohm will mentor junior researchers, undergo training in STEM education, and establish a departmental support network for fellow women in Earth Science, to enhance diversity and improve retention of women in the field. A topic of debate among earth scientists is the extent to which large igneous province emplacement can cause global climatic and biotic change. The potential relationship between the CRBG and the MCO provides an ideal opportunity to test this connection. A variety of paleoclimate proxies document the MCO, but until now, none have been constrained by absolute radiometric dates. In her postdoctoral research, Dr. Kasbohm is pursuing a novel integration of the boron-11 proxy for pCO2, performed at Yale University, with high-precision U-Pb zircon geochronology, undertaken at Princeton University, to reconstruct the timeline of atmospheric CO2 fluctuations during the MCO. This project will provide critical absolute constraints on several means by which age models for climate records are calibrated, as well as enhanced correlations of the MCO at different locations, thereby improving our understanding of the global dynamics of this event. Dr. Kasbohm will advance the broader impacts of her work by establishing Women in Earth & Planetary Sciences at Yale (WEPSY), a departmental support network that will seek to improve the experiences and retention of female early career researchers in Earth Science. This project received co-funding from the Earth Science section of the Paleo Perspectives on Climate Change program. 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.