At a Glance
- For the first time, a scientific team has created a high-resolution model detailing rapid sea level fluctuations throughout the last 540 million years of Earth’s history.
- The study established a relationship between climate and ice volume from recent geologic eras to then reconstruct the deep past with unprecedented short-term detail.
- Earth’s “icehouse” periods saw dramatic and rapid sea level swings of over 100 meters, while warm “greenhouse” eras like the dinosaur age experienced much more stable ocean levels.
- This new analysis suggests previous estimates of sea level change during warm periods were likely overestimated or resulted from factors other than the melting of continental ice sheets.
- This historical ocean data helps scientists create better geological maps for locating underground reservoirs suitable for carbon dioxide storage, hydrogen storage, and tapping into geothermal energy resources.
For the first time, an international team of scientists has produced a high-resolution reconstruction of short-term sea level change spanning the entire Phanerozoic eon, the last 540 million years of Earth’s history. The research, published July 3 in Earth and Planetary Science Letters, moves beyond long-term trends to quantify the rapid, high-amplitude fluctuations driven by the growth and decay of polar ice sheets. While previous studies could map sea level changes over millions of years, this new model details variability on timescales of just thousands of years, offering a more dynamic picture of our planet’s ancient coastlines.
The study’s innovative method addresses a long-standing challenge in geology. Earth’s sea level is primarily controlled by two factors: plate tectonics, which changes the shape and depth of ocean basins, and the amount of water locked away in land-based ice. The rise and fall of sea level due to ice volume is known as glacio-eustasy. To model this effect in the deep past, researchers from Utrecht University, the United Kingdom, and the United States developed a new approach. They used a detailed climate model of the Cenozoic era—the last 66 million years, for which abundant data exists—to establish a precise relationship between long-term climate, ice volume, and short-term, “orbital-scale” sea level changes caused by periodic wobbles in Earth’s axis and orbit. They then applied this relationship to a long-term ice volume reconstruction for the entire Phanerozoic.
The findings reveal a stark contrast between Earth’s different climate states. During “icehouse” periods, like the late Paleozoic and the Cenozoic in which we live, the planet experienced dramatic and rapid sea level swings of more than 100 meters as ice sheets advanced and retreated. Conversely, during warm “greenhouse” climates, such as the Jurassic and Cretaceous periods when dinosaurs roamed, these ice-driven fluctuations were minimal to nonexistent, likely staying within a 20- to 40-meter range. This conclusion challenges some previous sea level estimates based on stratigraphy—the study of rock layers—which suggested larger changes during greenhouse times. The authors propose that these older estimates may have been overstated or were caused by other factors, like changes in groundwater storage, a phenomenon known as aquifer eustasy.
This detailed history of ancient oceans has significant modern-day applications. A clearer understanding of past sea levels allows for the creation of more accurate global maps of ancient sand and clay deposits. Sandstone, often deposited when sea level is low, forms porous reservoirs ideal for the underground storage of carbon dioxide and hydrogen or for tapping geothermal energy. Claystone, deposited in deep water when the sea level is high, acts as an impermeable seal. “If we know that at a certain time global sea level was high, we also know that a relatively continuous layer of claystone would have been deposited,” said lead author Dr. Douwe van der Meer in a university press release. “We can use that information to create a global layer map of sand and claystone, which helps us in the safe use of the subsurface.”
References
- Utrecht University. (2025, July 7). Scientists reconstruct 540 million years of sea level change in detail. Phys.Org; Utrecht University. https://phys.org/news/2025-07-scientists-reconstruct-million-years-sea.html
- Van Der Meer, D. G., Stap, L. B., Scotese, C. R., Mills, B. J. W., Sluijs, A., & Van Hinsbergen, D. J. J. (2025). Phanerozoic orbital-scale glacio-eustatic variability. Earth and Planetary Science Letters, 667, 119526. https://doi.org/10.1016/j.epsl.2025.119526
