- 1Department of Estuarine and Delta Systems, Royal Netherlands Institute for Sea Research (NIOZ), ‘t Horntje, The Netherlands
- 2Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands
- 3Climate Change and Marine Geology group, Department of Earth Science, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
- 4Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
- 5Operational Directorate Earth and History of Life, Institute of Natural Sciences, Brussels, Belgium
- 6Naturalis Biodiversity Center, Leiden, The Netherlands
- 7MSP, Department of Science and Engineering, Maastricht University, Maastricht, The Netherlands
The early to middle Eocene (56 – 41 Ma) is characterized by high atmospheric CO2 concentrations between 1,000 and 1,500 ppm, making it the warmest interval of the Cenozoic [1,2]. The future atmospheric CO2 concentration could reach similar levels around 2100, based on the high CO2 emissions scenario SSP5-8.5 [3]. By studying the Eocene climate, we gain understanding of how our climate system could operate under these extreme conditions.
An important aspect of climate is the seasonal temperature variability: the differences between summer and winter temperatures. Past seasonality can be reconstructed from sub-annually resolved climate archives such as the incremental growth bands of mollusk shells. We performed clumped isotope analysis on micro-samples of 11 fossil shells of early to middle Eocene age from shallow marine settings in northwestern Europe: 8 bivalves (species Venericor planicosta) and 3 gastropods (Haustator solanderi).
We obtained seasonal shell chronologies from the variability in the oxygen isotope records of the micro-samples, and we used the corresponding clumped isotope records to reconstruct the seasonal temperature variability of the seawater independent of its isotopic composition [4].
Our results suggest a moderate seasonal temperature variability of approximately 6 – 7 °C during both the early (56 – 48 Ma) and middle (48 – 41 Ma) Eocene. A comparison with Eocene climate model simulations suggests that models overestimate the observed seasonality due to colder winter temperatures in the model simulations compared to the reconstructions. This temperature record sheds light on the role of seasonality in mid-latitude shallow marine environments in hothouse climates and can aid our understanding of regional and seasonal scale model-data discrepancies.
[1] Rae, J. W. B., Zhang, Y. G., Liu, X. et al. (2021). Atmospheric CO2 over the past 66 million years from marine archives. Annual Review of Earth and Planetary Sciences, 49(1). https://doi.org/10.1146/annurev-earth-082420-063026
[2] The Cenozoic CO2 Proxy Integration Project Consortium (2023). Toward a Cenozoic history of atmospheric CO2. Science, 382(6675). https://doi.org/10.1126/science.adi5177
[3] Chen, D., Rojas, M., Samset, B. H. et al. (2021). Framing, context, and methods. In V. Masson-Delmotte, et al. (Eds.), Climate change 2021: The physical science basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (pp. 147–286). Cambridge University Press.
[4] de Winter, N.J., Agterhuis, T., & Ziegler, M. (2021). Optimizing sampling strategies in high-resolution paleoclimate records. Climate of the Past, 17(3). https://doi.org/10.5194/cp-17-1315-2021
How to cite: Goudsmit-Harzevoort, B., de Winter, N., Vellekoop, J., Wesselingh, F., Witbaard, R., and Ziegler, M.: Reconstructing Seasonality in Northwest Europe during the Early to Middle Eocene using Clumped Isotope Thermometry on Fossil Mollusks, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-5563, https://doi.org/10.5194/egusphere-egu25-5563, 2025.
