According to a new report prepared by a team of international scientists, deep-sea remains of ancient corals could be used to understand carbon dioxide in the oceans, both past and present. The report, published in the journal Nature Geoscience, uses coral fossils as a sort of time machine to investigate the rise of carbon dioxide and its role in ending the last ice age.

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The researchers extracted fossilized coral remains deposited about 15,000 years ago during the last ice age. While it is generally agreed that the ocean changes experienced at the end of the ice age were caused by a rise in CO2 levels, scientists weren’t sure what drove this increase. The researchers analyzed uranium found in small skeletons of coral fossils to identify corals from the end of the ice age, then reconstructed the oceanic changes experienced at the time through geochemical fingerprinting.

Related: The Great Barrier Reef has lost 50% of its corals to climate change

According to James Rae of the School of Earth and Environmental Sciences at the University of St Andrews, the corals can be used to trace these ancient events. “The corals act as a time machine, allowing us to see changes in ocean circulation that happened thousands of years ago,” Rae explained.

Laura Robinson, professor at the University of Bristol and leader of the research team, said, “The data show that deep-ocean circulation can change surprisingly rapidly and that this can rapidly release CO2 to the atmosphere.”

coral fossil on black background

Experts have believed that the Southern Ocean had major influence in ending the last ice age, and the new study provides further insight into this possibility.

“There is no doubt that Southern Ocean processes must have played a critical role in these rapid climate shifts and the fossil corals provide the only possible way to examine Southern Ocean processes on these timescales,” said study author Tao Li of Nanjing University.

While the study focuses heavily on understanding the happenings of the end of the ice age that occurred 15,000 years ago, it also warns on the effects of carbon dioxide in the modern era.

“Although the rise in COat the end of the ice age was dramatic in geological terms, the recent rise in COdue to human activity is much bigger and faster,” Rae said. “What the climate system will do in response is pretty scary.”

+ Nature Geoscience

Photography by Dann Blackwood, USGS via University of St Andrews