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

该合作基金将开发古新世-始新世极热期（PETM）陆地水文的多代理记录，这是一个发生在5580万年前的突然的、短暂的、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，正好与陆生脊椎动物和植物的剧烈反应相吻合。了解PETM期间水文循环的响应和反馈对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。本项目将利用四种代用指标重建PETM的古水文：1)植物脂质化合物的氢同位素比值，2)哺乳动物牙齿和黄鱼鳞片牙釉质化石的氧同位素比值，3)树叶化石的地貌特征，4)古土壤的形态和化学特征。这些替代方法将应用于最近在怀俄明州比格霍恩盆地东南部的Cabin Fork地区发现的新世第三纪过渡带剖面，在那里已经发现了一个40米厚的代表新世第三纪过渡带的间隔，并且该团队已经表明，在那里的露头有丰富的脊椎动物化石、树叶、植物脂质和古土壤。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~10 ky的时间分辨率，这将使研究小组能够探测到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精确的古水文重建，更好地了解PETM内气候波动与大气环流变化的关系，并更好地了解PETM气候变化对陆地生态系统的环境后果。拟议的研究包括与怀俄明州杰克逊霍尔的提顿科学学校合作，制定一项教师培训计划，“气候与生命：户外教室里的科学家”。学校与一所K-12日制学校相连，为自然科学和自然科学教育的各个年龄段的学生提供住宿项目，每年为11,000多名学生提供服务。拟议中的项目将让pi和研究生参加一个教师培训课程，其目标是：1)说明我们如何从岩石记录中了解气候和生命；2)向教师介绍地球科学及其实践者。这项外展计划将与在学校举行的年度合作者会议一起进行。为了吸引更广泛的受众，该团队将开发一个关于“重建古代森林生态系统”的网站，该网站将设在佛罗里达自然历史博物馆，并与史密森学会的网站相连。该网站将以古新世和始新世森林为例，探索如何重建古代生态系统。

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.