Collaborative Research: Evaluating Climate Change and Kill Mechanisms Associated with the End-Cretaceous Mass Extinction: A Model-Data Comparison Approach

6600万年前，在白垩纪-古近纪边界（KPB），一颗小行星撞击Yucatán半岛，导致地球上75%的物种灭绝。作为地球历史上最近的、有充分记录的、快速的大灭绝，对KPB灭绝的研究是了解气候变化对生物多样性影响的理想选择。然而，KPB灭绝的原因仍然不确定。该项目将结合新型气候模型模拟和地质记录，探索与小行星撞击有关的气候变化和杀伤机制。测量来自整个KPB的各种地质记录将限制小行星撞击排放的类型和大小。然后，这些排放估计将用于气候模型模拟，以确定地球系统对小行星撞击的响应。项目结果将提供对KPB灭绝的机制理解，这反过来将改善对这一时期许多记录的解释，提供对生态系统崩溃和恢复的见解，并导致有价值的气候模型开发。拓展活动包括创建一个KPB展览，开发一个地球化学高中项目，招募三名代表性不足的本科生实习生，以及在德克萨斯大学格兰德谷分校（一所以西班牙裔为主的大学）招募学生研究人员。为了确定可能导致KPB灭绝和随后环境恢复的各种过程的相对重要性，pi将使用地球系统模型来模拟小行星撞击的作用力来执行KPB模拟。该模式包含一个明确的气溶胶解析方案和高顶大气，这两者对于捕获与这些扰动相关的过程都是必不可少的。此外，海洋生物地球化学模块的开发和实施将允许与整个KPB的古生物学，化学和同位素记录进行直接比较。pi还将收集高分辨率烟尘、温度和生物标志物记录，以约束和验证KPB模拟。将对样品进行烟尘和多环芳烃分析，以验证小行星撞击火灾假说，并为模拟提供精细的烟尘排放数据。对撞击后温度变化的新估计将从磷酸盐微化石和生物标志物中产生。这些记录将提供次千禧年到千禧年尺度上的温度约束，并结合模拟和烟尘估算，提供一种减少与撞击相关的二氧化碳排放的方法。最后，高分辨率的生物标志物工作将揭示海洋浮游生物恢复的速度，并将其与海洋生物地球化学模拟进行比较。该奖项反映了美国国家科学基金会的法定使命，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。

Sixty-six million years ago at the Cretaceous-Paleogene boundary (KPB), an asteroid impact in the Yucatán Peninsula resulted in the loss of about 75% of all species on Earth. As the most recent, well documented, and rapid mass extinction in Earth’s history, study of the KPB extinction is ideal for understanding the effects of climate change on biodiversity. However, the causes of the KPB extinctions remain uncertain. This project will use a combination of novel climate model simulations and geologic records to explore climate change and kill mechanisms associated with the asteroid impact. Measuring various geologic records from across the KPB will constrain the types and magnitudes of emissions from the asteroid impact. These emission estimates will then be used in climate model simulations to determine the Earth system responses to the asteroid impact through time. Project results will provide a mechanistic understanding of KPB extinction, which, in turn, will improve interpretation of many records from this time period, deliver insights into ecosystem collapse and recovery, and lead to valuable climate model development. Outreach activities include creation of a KPB exhibit, develop of a geochemistry high school project, recruitment of three underrepresented undergraduate interns, and engagement of student researchers at the University of Texas Rio Grande Valley, a Hispanic majority university. To determine the relative importance of various processes that could have led to the KPB extinction and subsequent environmental recovery, the PIs will use an Earth system model to perform KPB simulations that mimic forcings from the asteroid impact. The model contains an explicit aerosol resolving scheme and high-top atmosphere, both essential for capturing the processes associated with these perturbations. Further, development and implementation of an ocean biogeochemistry module will allow for direct comparison with paleontological, chemical, and isotopic records across the KPB. The PIs will also collect high resolution soot, temperature, and biomarker records to constrain and validate the KPB simulations. Samples will be analyzed for soot and polycyclic aromatic hydrocarbons to test the asteroid impact fires hypothesis and provide refined soot emission data for the simulations. New estimates of temperature change after impact will be generated from phosphatic microfossils and biomarkers. These records will provide sub-millennial to millennial scale constraints on temperature, and in combination with simulations and soot estimates, a means to backout CO2 emission associated with the impact. Finally, high resolution biomarker work will shed light on the rate of marine planktonic recovery, which will be compared with the ocean biogeochemistry simulations.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.