Collaborative Research: Paleohydrology of the Paleocene-Eocene Thermal Maximum: A Multiple Proxy Reconstruction

这项合作赠款将开发古新世-始新世最热时期(PETM)期间的陆地水文学的多代理记录，这是大约5580万年前发生的一个突然、短暂和大规模的全球变暖时期。PETM是新生代最温暖的时期，与向大气中大量释放碳有关，恰好与陆地脊椎动物和植物的戏剧性反应相吻合。了解PETM期间水文循环的响应和反馈对于模拟未来气候对人为二氧化碳水平增加的响应具有直接意义。该项目将使用四个指标来重建PETM的古水文学：1)植物脂肪的特定化合物氢同位素比率，2)哺乳动物牙齿和鱼鳞化石珐琅的氧同位素比率，3)化石树叶的地貌，以及4)古土壤的形态和化学。这些替代方法将应用于最近在怀俄明州大角盆地东南部的Cabin Fork地区发现的PETM剖面，在那里已经发现了代表PETM的40米厚的区段，研究小组已经证明，露头含有丰富的脊椎动物化石、树叶、植物脂肪和古土壤。由此产生的降水、相对湿度、季节性、土壤湿度、温度和降水水分来源的记录将具有~10Ky的时间分辨率，这将使研究小组能够检测到PETM期间水文循环的变化。在高时间分辨率下重建水文循环将产生更准确的古水文重建，更好地了解PETM内的气候波动如何与大气环流的变化有关，并更好地理解PETM气候变化对陆地生态系统的环境影响。拟议的研究包括与怀俄明州杰克逊霍尔的蒂顿科学学院合作开发一个教师培训项目，名为《穿越时间的气候与生命：户外课堂上的科学家》。这所学校与一所K-12日制学校相连，为所有年龄段的学生提供自然科学和自然科学教育方面的住宿计划，每年为超过11,000名学生提供服务。拟议的计划将让个人投资者和研究生参加教师培训课程，目标是1)说明我们如何从岩石记录中了解气候和生命，以及2)向教师介绍地球科学及其实践者。这一外展计划将与在学校举行的年度合作者会议一起进行。为了接触到更广泛的受众，该团队将开发一个名为“重建古代森林生态系统”的网站，该网站将在佛罗里达自然历史博物馆托管，并链接到史密森学会的网站。该网站将探索如何利用古新世和始新世森林作为案例研究来重建古代生态系统。

This collaborative grant will develop a multiple-proxy record of terrestrial hydrology during the Paleocene-Eocene Thermal Maximum (PETM), a period of abrupt, short lived and large-scale global warming that occurred ~55.8 million years ago. The PETM was the warmest period of the Cenozoic, is associated with a massive release of carbon to the atmosphere, and precisely coincided with a dramatic response in terrestrial vertebrates and plants. Understanding the response and feedbacks of the hydrologic cycle during the PETM has direct implications for modeling future climate responses to increasing levels of anthropogenic CO2.The project will use four proxies to reconstruct the paleohydrology of the PETM: 1) compound-specific hydrogen isotope ratios of plant lipids, 2) oxygen isotope ratios of fossil enamel from mammal teeth and gar fish scales, 3) physiognomy of fossil leaves, and 4) morphology and chemistry of paleosols. These proxy methods will be applied to the recently recognized PETM sections in the Cabin Fork area of the southeastern Bighorn Basin, Wyoming, where a 40 m-thick interval representing the PETM has been identified, and where the team has already shown that the outcrops have abundant fossil vertebrates, leaves, plant lipids, and paleosols. The resulting record of precipitation, relative humidity, seasonality, soil moisture, temperature, and precipitation moisture source will have a temporal resolution of ~10 ky, which will allow the team to detect variations in the hydrologic cycle during the PETM. Reconstructing the hydrological cycle at high temporal resolution will yield more accurate paleohydrological reconstructions, better knowledge of how climatic fluctuations within the PETM relate to changes in atmospheric circulation, and a refined understanding of the environmental consequences of PETM climate change for terrestrial ecosystems.The proposed research includes the development of a teacher training program, "Climate and Life Through Time: Scientists in the Outdoor Classroom," in conjunction with the Teton Science School in Jackson Hole, Wyoming. The school is connected to a K-12 day school and hosts residential programs for students of all ages in natural science and natural science education, serving over 11,000 students a year. The proposed program will involve PIs and graduate students in a teacher training course with the goals of 1) illustrating how we learn about climate and life from the rock record and 2) introducing teachers to Earth science and its practitioners. This outreach program will be conducted in conjunction with an annual meeting of collaborators to be held at the school.To reach an even broader audience, the team will develop a web site on "Reconstructing Ancient Forest Ecosystems" that will be hosted at the Florida Museum of Natural History and linked to Smithsonian Institution websites. The site will explore how to reconstruct ancient ecosystems by using the Paleocene and Eocene forests as a case study.