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

迄今为止，地球经历了化石燃料二氧化碳驱动的全球变暖略高于1°C。这种变暖对全球水文循环的影响已经很明显。在一切照旧使用化石燃料的情况下，预计到2300年将升温4-5°C，这将进一步加剧水文循环。由此对社会的水安全产生的影响将是巨大的，并可能给地球仪各国，无论贫富，造成广泛的困难。气候模型是规划和尽量减少这些影响的重要工具，其复制过去气候变化的能力得到了检验。古新世-始新世热峰（PETM，大约5500万年前）是测试气候模型的重要案例研究。它还提供了气候系统对大量二氧化碳输入的敏感性的真实例子。拟议的项目将利用沿海沉积物来开发整个PETM的水化学和陆上水文的替代记录。这些新的数据将与古代自然气候事件的气候模型研究进行比较。拟议项目的教育广泛影响包括对研究生和本科生参与者的支持。尽管存在大量地质证据表明PETM期间水文气候发生了变化，但需要进行额外的观测以评估区域/当地变化，特别是与年度或较短时间尺度上的极端事件有关的变化。 为此，本项目将利用露头和岩心中的浅海硅质岩剖面，估算美国沿海沿着水文/化学的区域变化。 初步数据表明，径流（侵蚀）和降水量发生了重大变化，很可能是干湿循环和/或强降水事件（如大气河流、热带气旋）的幅度发生了重大变化。 在先前结果的基础上，与同事合作，将采用新的同位素和地球化学代理，沿着传统代理，以限制沿海海洋水文/化学的局部变化。观测结果将与最近完成的利用高分辨率模型（包括社区大气模型）对古东印度热期进行的GCM模拟的结果进行比较。比较的主要重点将是降水的季节性周期变化和极端事件的频率（即，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值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.