Paleoclimate and Paleoecology in High Latitude, Terrestrial Vertebrate Communities from the Early-Middle Eocene of Ellesmere Island, Nunavut, Arctic Canada

主要研究人员将通过对加拿大Ellesmere岛（~79°N）早-中始新世地区脊椎动物牙釉质中生物源磷酸盐的d18O（PO4）、d18O（CO3）和d13C值进行古气候和生态重建，验证始新世全球暖期假说及其对高纬度陆地生态系统的影响。具体来说，他们将验证这样一个假设，即生活在高北极地区的始新世脊椎动物更喜欢与它们现存的类似物相似的温度和栖息地，因此它们是准确的古气候和古生态代用物。通过与已公布的海表温度（SSTs）进行比较，首席研究人员将检验一种假设，即北方高纬度陆地环境的定量气候变化与高纬度开阔海洋环境的定量气候变化相关。该项目将通过确定共存于北美中纬度和高纬度地区的多种脊椎动物类群（如短吻鳄、brontotis和貘）的d18O值来量化纬度梯度。埃尔斯米尔岛早始新世至中始新世地区的定量气候估计也应该为理解新生代冷却趋势的开始提供关键数据，据称该趋势始于中始新世早期。将埃尔斯米尔岛始新世哺乳动物，特别是大型食草动物与现存的近亲和类似物进行比较，并结合其牙齿中生物源磷酸盐的d13C分析，应该能够深入了解它们的栖息地偏好（即开放栖息地与封闭树冠）。此外，比较在中高纬度地区共存的同一属（例如，Coryphodon和brontoses Eotitanops和Palaeosyops）的d13C值可以阐明重要的古生态差异，否则它们在形态上不明显。主要研究人员在埃尔斯米尔岛尤里卡海峡群始新世地层进行了广泛的古生物实地工作，提供了从植物和动物化石中推断出的古气候和古环境估计，以及进行同位素分析的大量标本。该项目将产生第一个全面的、定量的古气候数据集，这些数据集来自北方高纬度陆地环境，用于过去6500万年（始新世早期）最重要的全球变暖事件，这对于理解未来全球变暖对地球生物群的影响至关重要。该研究将为研究始新世气候变率和纬向温度梯度的古气候建模者提供重要的高纬度陆地数据点。这项研究将首次在碳氧同位素耦合分析的基础上（结合与中纬度分类群和现代类似物的比较）推断高北极陆生脊椎动物群落的古生态。该项目将吸引学生、公众（包括因纽特人社区）和科学家参与多学科合作研究联盟，并促进国际和跨文化对话。研究结果将广泛传播给科学界和非专业人士。

The Principal Investigators will test hypotheses concerning the Eocene global warm period and its effects on high-latitude terrestrial ecosystems by reconstructing paleoclimate and -ecology from d18O(PO4), d18O(CO3), and d13C values of biogenic phosphate in vertebrate tooth enamel from Early-Middle Eocene localities on Ellesmere Island, Canada (~79degrees N). Specifically, they will test the hypothesis that Eocene vertebrates inhabiting the High Arctic preferred temperatures and habitats similar to their living analogs and are therefore accurate paleoclimate and paleoecologic proxies. By comparison to published sea surface temperatures (SSTs), the Principal Investigators will test the hypothesis that quantitative climate changes in northern high-latitude terrestrial environments correlate to those determined for high-latitude open marine environments. The project will provide quantification of latitudinal gradients by determining d18O values of multiple vertebrate taxa (e.g., alligators, brontotheres, and tapirs) that co-occur in mid- and high-latitude North America. Quantitative climate estimates for Early - Middle Eocene localities on Ellesmere Island should also provide data critical to understanding the onset of the Cenozoic cooling trend, purported to have begun with during early Middle Eocene time. Comparison of the Eocene mammals, particularly the large herbivores, from Ellesmere Island with living relatives and analogues, combined with d13C analysis of the biogenic phosphate in their teeth, should provide insight into their habitat preferences (i.e., open habitat vs. closed canopy). Additionally, comparison of d13C values from the same genera coexisting at both mid- and high-latitudes (e.g., Coryphodon and the brontotheres Eotitanops and Palaeosyops) may illuminate important paleoecological differences that would otherwise not be evident in their morphology. Extensive paleontological field work in Eocene strata of the Eureka Sound Group on Ellesmere Island by the Principal Investigators provides paleoclimatic and paleoenvironmental estimates that are inferred from the fossil plants and animals, in addition to numerous specimens on which to conduct isotope analysesBroader Impacts: This project will result in the first comprehensive, quantitative paleoclimate data set from northern high-latitude terrestrial environments for the most significant global warming event in the last 65 million years (the Early Eocene), which is critical to understanding the impacts of future global warming on Earth's biota. The research will provide important high-latitude terrestrial data points for paleoclimate modelers concerned with Eocene climatic variability and latitudinal temperature gradients. This study will be the first to infer paleoecology of a high Arctic terrestrial vertebrate community on the basis of coupled carbon and oxygen isotope analyses (in conjunction with comparisons to mid-latitude taxa and modern analogs). The project will engage students, the general public (including the Inuit community), and scientists in a multidisciplinary, collaborative research alliance, and foster international and intercultural discourse. Results of the research will be broadly disseminated to scientific and lay audiences.