Accomplishment Based Renewal: Intensification of the Hydrologic Cycle during the Paleocene-Eocene Thermal Maximum

到目前为止，地球经历了化石燃料二氧化碳导致的全球变暖，温度略高于1摄氏度。这种变暖对全球水文循环的影响已经很明显了。在正常使用化石燃料的情况下，预计到2300年升温4-5摄氏度，这将进一步加剧水文循环。由此产生的对社会水安全的影响将是巨大的，并可能给全球各国带来广泛的困难，无论是富国还是穷国。气候模型经过测试，能够复制过去的气候变化，是规划和减少这些影响的重要工具。古新世-始新世最高温度(PETM，大约5500万年前)是检验气候模型的关键案例研究。它还提供了一个真实世界的例子，说明气候系统对大量二氧化碳输入的敏感性。拟议的项目将使用沿海沉积物来开发跨PETM的水化学和陆上水文学的替代记录。这些新数据将与对那次古代自然气候事件的气候模型研究进行比较。拟议项目对教育的更广泛影响包括对研究生和本科生的支持。尽管有相当多的地质学证据表明在PETM期间水气候发生了变化，但需要更多的观测来评估区域/局部变化，特别是与年度或更短时间尺度上的极端事件有关的变化。为此，该项目将利用露头和岩心中的浅海硅质碎屑切片，估计美国两个海岸的沿海水文/化学的区域变化。初步数据表明，径流(侵蚀)和降水发生了重大变化，很可能是湿/干循环和/或强降水事件(如大气河流、温带气旋)的幅度。在以往成果的基础上，将与同事们合作，采用新的同位素和地球化学指标以及传统的指标，以限制沿海海洋水文/化学方面的局部变化。观测结果将与最近完成的利用包括共同体大气模式在内的高分辨率模式对PETM进行的GCM模拟的输出进行比较。比较的主要焦点将是降水的季节性周期和极端事件(即强降水或干旱)的频率的变化。这一奖项反映了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。

Earth has experienced just over 1°C of fossil fuel carbon dioxide-driven global warming to date. The impacts of this warming on the global hydrologic cycle are already evident. The projected 4-5°C of warming by 2300 under a business-as-usual fossil fuel use scenario is predicted to further intensify the hydrologic cycle. The resulting impacts on societies’ water security would be significant, and likely create widespread hardship for nations across the globe, rich and poor. Climate models, tested by their ability to replicate past changes in climate, are an important tool to plan for and minimize those impacts. The Paleocene-Eocene Thermal Maximum (PETM, roughly 55 million years ago) serves as a crucial case study to test climate models. It also provides a real-world example of the sensitivity of the climate system to a massive carbon dioxide input. The proposed project will use coastal sediments to develop proxy records of water chemistry and onshore hydrology across the PETM. These new data will be compared with climate model studies of that ancient natural climate event. The educational Broader Impacts of the proposed project include support for a graduate student and for undergraduate participants.Although considerable geologic evidence exists for a shift in hydroclimate during the PETM, additional observations are required to assess regional/local changes, particularly as relates to extremes on annual or shorter time scales. To this end, this project will estimate regional changes in coastal hydrography/chemistry along both coasts of the US utilizing shallow marine siliciclastic sections in outcrops and cores. Preliminary data indicate significant changes in runoff (& erosion) and thus precipitation, very likely in the amplitude of wet/dry cycles and/or heavy precipitation events (e.g. atmospheric rivers, extratropical cyclones). Building on prior results, in collaboration with colleagues novel isotopic and geochemical proxies will be employed, along with traditional proxies, to constrain local changes in coastal ocean hydrography/chemistry. The observations will be compared against output of recently completed GCM simulations of the PETM utilizing high resolution models including the Community Atmosphere Model. The primary focus of the comparisons will be on changes in the seasonal cycles of precipitation and frequency of extreme events (i.e., heavy precipitation or droughts).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.