By looking at the ancient corals that once thrived just beneath the ocean’s surface, scientists have uncovered a chilling clue about Earth’s future. A team of international researchers studying coral fossils from the Seychelles Islands found that sea levels can spike suddenly—and catastrophically—when ice sheets begin to collapse. The study, published in Science Advances, suggests that our warming world may be closer to such rapid sea-level jumps than we realize.
Led by Professor Andrea Dutton of the University of Wisconsin-Madison and PhD student Karen Vyverberg of the University of Florida, the team focused on fossilized coral species that only grow near the ocean’s surface. These coral “snapshots” are nature’s sea level markers, capturing the position of ancient shorelines.
Their findings date back to the Last Interglacial period, approximately 123,000 years ago, when global temperatures were comparable to those of today. But what they uncovered went beyond what anyone expected.
“This is not good news for us as we head into the future,” says Andrea Dutton, a professor of geoscience. But that’s not all. The team found evidence of not one, but three sharp surges in sea level during the 6,000 years leading up to that peak. In between these bursts were periods when the sea receded.
The surges, according to the study, were likely tied to the sudden melting of polar ice sheets in Greenland and Antarctica. Even though the Seychelles are thousands of miles away from the poles, the sea-level fingerprints left behind clearly show the ice was undergoing intense changes.
These changes didn’t happen slowly and steadily; they happened in jumps. Dutton explained that these ups and downs suggest the northern and southern ice sheets weren’t melting at the same time. “These swings suggest that the polar ice sheets were growing and shrinking out of phase with each other, as a result of temperature changes in the two hemispheres that were also not aligned,” she noted.
That’s a critical insight because, in today’s world, both hemispheres are warming at the same time.
One of the sharpest sea-level spikes matched a time when the last pieces of North America’s ancient ice sheet were collapsing into the sea. That’s a big deal, even though that ice sheet is gone today. The event suggests that large, rapid shifts in sea level are possible if major ice bodies fall apart.
Dutton pointed out that if the North American ice was still melting during the Last Interglacial, then the rest of the sea-level rise likely came from Antarctica.
The idea that sea levels could suddenly rise by several meters sounds like a far-off scenario. But Dutton believes the past is a warning. According to her, based on the level of global warming that has already taken place, future sea levels could potentially rise by as much as 10 meters on average worldwide.
Such a rise would reshape coastlines, flood major cities, and force millions to relocate. For coastal planners, risk managers, and policy makers, this research isn’t just interesting, it’s urgent.
The silver lining: Dutton believes there’s still time to act. While the fossil record reveals what is possible, our future depends on the choices we make today. According to her, reducing greenhouse gas emissions quickly and effectively could help prevent the worst-case climate scenarios from turning into reality.
This powerful study was supported by the National Science Foundation, and brought together researchers from the University of Sydney, the University of Minnesota, Victoria University of Wellington, and the University of Massachusetts Amherst.
As the script of ancient coral reefs rise from the past, their message is clear: if we ignore the signs, we may face a flood of consequences.
For more details, refer to this article published in Science Advances.
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