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

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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.