New Research Traces 540 Million Years of Sea Level Fluctuations

In a groundbreaking study, researchers from Utrecht University, in collaboration with institutions in the United Kingdom and the United States, have reconstructed sea level changes over a span of 540 million years, revealing fluctuations that occurred on both million-year and thousand-year timescales. Published on July 3, 2025, in the journal *Earth and Planetary Science Letters*, this research marks a significant advancement in our understanding of ancient climate dynamics.

According to Dr. Douwe van der Meer, a guest researcher at Utrecht University and the lead author of the study, this research sheds light on sea level variations that are crucial for understanding subsurface geological structures and their implications for green energy resources. "Taking these rapid sea level variations into account is important for understanding the structure of the subsurface and the applications to green energy resources," Dr. van der Meer stated in the report.

Historically, scientists have utilized fossil records and sediment analysis to estimate sea level changes primarily on a million-year scale, but this study introduces a method to assess variations over much shorter periods. As Dr. van der Meer explained, "In time steps of about a million years, you can derive an average sea level for as far back as there are fossils, about 540 million years. That varied by as much as 200 meters. We suspected that sea level could go up and down enormously in much shorter periods as well, but there is not enough data to make those shorter time steps."

To accomplish this, researchers analyzed sedimentary deposits, likening the process to reading tree rings. By examining rocks from the last few million years, they were able to infer climate conditions and corresponding sea levels during various geological epochs. This innovative approach allowed for the reconstruction of sea level changes that could fluctuate by as much as 100 meters during ice ages, a phenomenon that had not been quantifiably established in previous studies.

The research also highlights distinct periods of significant sea level variation, such as the late Carboniferous era, characterized by extensive ice caps in the southern hemisphere, compared to the Jurassic and Cretaceous periods when sea level changes were considerably less pronounced due to minimal land ice presence. The findings suggest that during colder climatic phases, rapid sea level oscillations could occur in response to the rhythmic wobbling of Earth's spin axis, further impacting marine and terrestrial ecosystems.

The implications of this research extend beyond academic interest; understanding past sea levels is essential for contemporary applications in energy and waste management. As Dr. van der Meer elaborated, "Knowledge of sea levels in the geological past has many different applications. Today, we seek methods for underground CO2 and hydrogen storage, or geothermal energy. Sandstone, deposited at low sea level, is important here because it can be used as a reservoir. Claystone, deposited at high sea level, acts as a seal through which water or CO2 cannot easily pass."

This study not only enhances the scientific community's knowledge of historical sea level variations but also provides a more robust framework for predicting future sea level changes and their potential impacts on global ecosystems and human infrastructure. As climate change continues to influence sea levels today, the lessons learned from the past will be crucial for developing adaptive strategies for coastal communities worldwide.

In conclusion, the research conducted by Dr. van der Meer and his colleagues is a significant contribution to paleoclimatology, providing insights that are vital for understanding both the Earth's history and the challenges posed by current and future sea level rise. The methodologies and findings presented in this study will undoubtedly encourage further investigations into related geological and environmental phenomena.