The cores-shrink-wrapped since the early 1980s-held geochemical information about the volcanics erupted during the PETM. Gernon and colleagues examined volcanic rocks in sediment cores drilled from several locations in the region. “I gave some time to focus a bit and think more about it.” That thinking led to a new idea about carbon in the North Atlantic. The opportunity to research presented itself “kind of serendipitously during the lockdown-you know, when you turn to that data and that project you didn’t quite finish,” he said. Gernon has been working on sediments and volcanics in the North Atlantic for the past decade, but only during the COVID-19 pandemic did he have the chance to dive deep. He and his colleagues found that typical volcanism in the province could account for only one fifth of the carbon needed to cause the PETM, suggesting an even larger source was present. “It’s really hard to get that much carbon from conventional volcanic processes,” Gernon said. Researchers have calculated that 10,000–15,000 gigatons of carbon were required to cause the shifts in global climate seen during this time. “It’s really hard to get that much carbon from conventional volcanic processes.” And there were active volcanoes at the time: The North Atlantic Igneous Province (an expansive volcanic field covering parts of Greenland and the United Kingdom) was erupting 1.8 million square kilometers of basalt-and along with it, loads of carbon. Volcanism, however, could release the isotopic mixture of carbon consistent with the fossil evidence. Later evidence indicated that the isotopic makeup of such releases did not match that seen in fossilized organisms that would have taken this carbon up into their shells. Magmas within mid-ocean ridges would have heated up surrounding mudrocks, releasing methane (CH 4) through the vents. Previously, scientists had suggested the carbon came from hydrothermal vents on the ocean floor. Get the most fascinating science news stories of the week in your inbox every Friday. “The rate of emissions had to be really high-almost the same order of magnitude as fossil fuel emissions.” That suggests multiple sources of carbon, he said. What makes the PETM so unusual is its rapid onset, said James Zachos, a paleoceanographer at the University of California, Santa Cruz, who researches the event but was not involved in the new study. The warm spell raised sea surface temperatures roughly 5☌, acidified the oceans, and wiped out some deep-sea creatures.

“ was one of the most extreme global warming events in the recent geologic past,” said Thomas Gernon, a geologist at the University of Southampton. “ was one of the most extreme global warming events in the recent geologic past.” New research published in Nature Geoscience suggests a massive belch of carbon from deep below the northern Atlantic Ocean could have played a key role. The event, known as the Paleocene-Eocene Thermal Maximum (PETM), ushered in a wave of evolutionary shifts. Fifty-six million years ago, Earth endured a heat wave that lasted 170,000 years.

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