Reconstructing Cretaceous Mean Climate and Seasonality using the Clumped Isotope Paleothermometer on Mollusks

在白垩纪时期（距今6600万年至1.44亿年），大气中的二氧化碳（CO2）水平升高，全球气温比今天更高，特别是在高纬度地区。目前的重建在这一时期变暖的幅度和空间模式上都存在分歧。该奖项支持一位博士后研究员，他建议为这一时期开发新的温度估计-使用称为碳酸盐聚集同位素古温度测定法的新代理方法-以帮助解决白垩纪气候之谜，这是了解地球对二氧化碳水平增加的反应的关键。研究员将在Kyger C教授的指导下进行为期两年的研究。密歇根大学地球环境科学系的Lohmann和Christopher J. Poulsen。 她还计划在稳定同位素实验室指导研究生和本科生研究助理，并参加该部门的地球营地，这是一个针对代表性不足的高中生的项目。该研究员将尝试使用碳酸盐凝聚同位素古温度测定法来制作第一张古18 Osw空间图。这项研究可以为白垩纪的水文循环和海洋动力学提供关键的见解。白垩纪的直接制约&这项工作产生的18 Osw将改进使用传统方法进行的温度估计，并将展示聚集同位素校准其他代理方法的能力。除温度外，碳酸盐凝聚同位素古温度计具有重建过去海水（#948; 18 Osw）同位素组成的能力。 在一个大的空间尺度上对古18 OSW的测量可以揭示过去全球环流的差异，并告诉我们过去的海洋动力学。拟议的研究包括：1）产生新的温度和季节性数据，描述白垩纪气候，一个高CO2世界的例子; 2）&在一个纬度范围内直接测量海水（#948; 18 Osw）的同位素组成，可以测试当前关于&无冰世界中#948; 18 Osw空间模式的假设，并为未来需要过去δ 18 Osw值的研究提供基础; 3）比较δ 18Osw（与盐度高度相关的量），可能揭示白垩纪全球海洋环流模式的信息。PI还将作为少数民族大学生的导师，少数民族高中生，并让他们直接参与拟议的研究。参与对社会重要的真实研究是提高所有学生在STEM领域坚持性的行之有效的方法，但对少数民族学生尤为重要。这将是对扩大参与科学的努力的重要贡献。

During the Cretaceous period (66-144 Million Years before present), atmospheric Carbon Dioxide (CO2) levels were elevated and global temperatures were warmer than today, in particular at high latitudes. Current reconstructions disagree on both the magnitude and spatial pattern of the warming during this period. This award supports a Postdoctoral Research Fellow who proposes to develop new temperature estimates for this interval - using the novel proxy method known as carbonate clumped isotope paleothermometry - in order to help resolve the enigma of climate during the Cretaceous, which is a key to understanding the Earth's response to increasing CO2 levels. The Fellow will conduct her research over a two-year period under the mentorship of Professors Kyger C. Lohmann and Christopher J. Poulsen in the Earth & Environmental Sciences Department at the University of Michigan. She also plans to mentor both graduate students and undergraduate research assistants in the Stable Isotope Laboratory and to participate in the department's EARTH CAMP, a program for underrepresented high school students. The Fellow will attempt to use carbonate clumped isotope paleothermometry to produce the first spatial map of paleo-δ18Osw. This research could provide key insights into both the hydrological cycle and ocean dynamics during the Cretaceous. The direct constraints on Cretaceous δ18Osw produced by this work will improve temperature estimates made using traditional methods, and will demonstrate the power of clumped isotopes to calibrate other proxy methods. In addition to temperature, carbonate clumped isotope paleothermometry has the ability to reconstruct the isotopic composition of seawater (δ18Osw) in the past. Measurements of paleo-δ18Osw over a large spatial scale may reveal differences in global circulation in the past and inform us about past ocean dynamics. The proposed research includes: 1) production of new temperature and seasonality data describing Cretaceous climate, an example of a high-CO2 world; 2) direct measurement of the isotopic composition of seawater (δ18Osw) across a range of latitudes that can test current assumptions about δ18Osw spatial patterns in an ice-free world and provide a basis for future studies requiring past δ18Osw values; 3) comparison of δ18Osw (a quantity highly correlated with salinity) within and between ocean basins, potentially revealing information about global ocean circulation patterns during the Cretaceous.The PI will also serve as a mentor to minority undergraduates and to minority high school students and involve them directly in the proposed research. Engagement in authentic research that is of importance to society is a proven way to increase persistence in STEM fields for all students, but is particularly important for minority students. This will be an important contribution to efforts to broaden participation in science.