Seminar by Richard Zeebe from Professor, University of Hawaii
17 July 2025
KST 10:00
The Seminar is being held in Room 1010 (Jasmin) – Integrated mechanical engineering building. Click here for the campus map.
Past climate aberrations provide unique insight into climate-carbon cycle feedbacks in the Earth System on time scales extending far beyond the instrumental record. In this presentation, I will focus on the Paleocene-Eocene Thermal Maximum (PETM, 56 million years ago, Ma), the largest of the so-called Cenozoic hyperthermals. The PETM was associated with about 5 K global surface warming and an estimated total carbon release of several thousand Pg. The PETM is widely considered the best analog for massive carbon release. With unabated emissions of anthropogenic CO2, a total of several thousand Pg C may enter the atmosphere within a few centuries, a rate that is unprecedented during at least the past 66 million years. Hence, the outcome is difficult to predict. The geological record of aberrations such as the PETM provides case studies to help improve foresight of the Earth System’s response in the future. Furthermore, the PETM and the long-term changes recorded and archived in stratigraphic sequences across the Paleocene/Eocene show exceptional expressions of astronomical forcing. I will present geologic data and our astronomical solution, showing excellent agreement from 58 to 53 Ma. Our solution provides a new absolute astrochronology up to 58 Ma and a new Paleocene-Eocene boundary age. Notably, the PETM onset occurred near a 405-thousand-year (kyr) eccentricity maximum, suggesting an orbital trigger. We also provide an independent PETM main phase duration of about 170 kyr. Importantly, our astronomical solution requires a chaotic resonance transition in the solar system’s fundamental frequencies to have occurred around 50 Ma. Finally, I will discuss differences in boundary conditions and climate forcing between the past (PETM) and the present, including baseline climate, continental configuration, and orbital forcing.