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

Jennifer Kasbohm博士被授予NSF EAR博士后奖学金，以开展研究，调查中新世气候最佳发生的时间和原因。她在耶鲁大学皮切利·赫尔博士的指导下进行了这项研究。中新世气候最佳时期(MCO)是大约发生在1700万至1500万年前的全球变暖时期，在此期间，地球经历了全球气温上升和大气二氧化碳(CO2)浓度升高，与今天一样高。有人提出，这种变暖可能是由哥伦比亚河玄武岩群(CRBG)的大规模火山活动引起的，该火山活动向大气中释放了大量二氧化碳，并覆盖了美国西北部一堆超过半英里厚的熔岩流。在攻读博士学位期间，卡斯博姆博士使用放射性同位素测年技术显示，CRBG的爆发速度比之前认为的要快得多，她的博士后研究现在集中在MCO的时间上。作为一名NSF EAR博士后，卡斯博姆博士正在对微化石进行地球化学测量，以估计MCO期间的大气二氧化碳水平，并确定CRBG是否可能导致了MCO。这项研究将对地球对大规模二氧化碳注入的反应速度产生新的见解，类似于地球今天正在经历的情况。这项研究还将调查气温和大气二氧化碳水平下降需要多长时间。在耶鲁大学进行这项研究时，卡斯博姆博士将指导初级研究人员，接受STEM教育方面的培训，并为地球科学领域的女性同事建立部门支持网络，以增强多样性并改善女性在该领域的留存。地球科学家之间的一个争论话题是，大型火成岩省的就位会在多大程度上导致全球气候和生物变化。CRBG和MCO之间的潜在关系为测试这种联系提供了一个理想的机会。各种古气候指标记录了MCO，但到目前为止，还没有一个受到绝对辐射日期的限制。在她的博士后研究中，卡斯博姆博士正在进行一种新颖的整合，将耶鲁大学进行的二氧化碳分压的B-11替代物与普林斯顿大学进行的高精度U-Pb锆石年代学相结合，以重建MCO期间大气二氧化碳波动的时间线。该项目将对校准气候记录年龄模型的几种方法提供关键的绝对限制，并加强不同地点的MCO的相关性，从而提高我们对这一事件的全球动态的理解。卡斯博姆博士将通过在耶鲁大学建立女性地球和行星科学(WEPSY)来推动她的工作产生更广泛的影响，这是一个部门支持网络，将寻求改善女性早期职业研究人员在地球科学领域的经验和留住他们。这个项目得到了古气候变化展望计划地球科学部分的共同资助。这个奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.