Million-Year-Old Plants Show Greenland Was Once Ice-Free

icebergs float away as the sun rises near Kulusuk, Greenland.
icebergs float away as the sun rises near Kulusuk, Greenland.
Photo: Felipe Dana (AP)

Jars of dirt taken from a Cold War-era military caper and lost in a freezer for decades could hold crucial new information about climate change and sea level rise. A study published on Monday in Proceedings of the National Academy of Scientists says that plant fossils found in a sample of dirt collected from a mile beneath the ice in the mid-1960s suggest that the world’s pre-human climate was at one point warm enough to completely melt the Greenland ice sheet.

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The dirt researchers inspected is a sediment sample from the bottom of an ice core, retrieved by drilling down into the ice sheet that covers the majority of Greenland. It’s pretty hard to actually reach all the way down to bedrock when taking samples due to the incredible pressure from the ice, explained Drew Christ, the study’s lead author and a postdoctoral fellow at the University of Vermont. There are only a few expeditions that have actually gotten sediment from the bottom of the glacier. “We have less of this [sediment] than moon rocks,” Christ said.

This particular sample yielded a lot of plant matter, some of which was visible to the naked eye. “It’s like if you went hiking, and got a bunch of twigs and forest floor stuff in the bottom of your boot and poured it out at the end of the day,” Christ said. “It’s kind of like that, but it’s been frozen for 1 million years.”

Christ and the team behind the study used isotope analyses of various elements that helped the researchers tease out the last time the samples were exposed to the sun and cosmic rays. The dating showed the plant matter is roughly 1 million years old.

Before analyzing this particular sample, Christ said, scientists had “circumstantial” evidence that the Greenland ice sheet had once melted away completely. But the discovery of these fossils definitively suggests that Greenland was once ice-free enough to provide a home for a variety of plants. And that’s bad news for us right now. The Greenland ice sheet is a ticking climate bomb, with some estimates projecting that the sheet could raise sea levels by 20 feet (6.1 meters) if it fully melted. While it’s not slated to completely melt tomorrow, the ice sheet is now melting six times faster than it was in the 1980s. The changes put in motion by rising carbon dioxide will take centuries to play out as the climate adjusts to a new equilibrium. Knowing its history is crucial to understanding the ice sheet’s future.

“The Greenland ice sheet has disappeared in a climate system that didn’t have any human influence,” Christ explained. “Before humans added hundreds of parts per million of fossil fuels to the atmosphere, our climate was able to melt away the ice sheet. In the future as we continue to warm the planet at an uncontrollable rate, we could force the Greenland ice sheet past some threshold and melt it and raise sea levels.”

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A microscopic view of twigs and moss from the dirt sample.
A microscopic view of twigs and moss from the dirt sample.
Image: University of Vermont

The dirt sample Christ and his team used to reach these conclusions has its own incredible backstory, including that it was almost lost to history. The sample was originally recovered from the first ice core of Greenland ever taken during a 1966 expedition to a military base called Camp Century. The actual purpose of the expedition was a top-secret James Bond-esque style mission called Project Iceworm (yes, really) to try and hide nuclear missiles under the ice near the Soviet Union (we’re not making this up). The scientific part of the expedition, while valid, was created mostly to give cover to this Cold War caper. Project Iceworm eventually failed, but at least we got this fascinating ice core out of this. (On the downside, though, climate change is melting out Camp Century, and could cause a toxic waste spill from leftover Cold War-era supplies and chemicals.)

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Even though the dirt sample is itself remarkable, since the Camp Century attempt was the first ice core ever retrieved from Greenland, researchers were mostly interested in what the ice itself could tell them, and less invested in the dirt that came with the core.

“I was pulling out inch-long twigs out of this stuff. We could see with our bare eyes, like, this is definitely plant material,” Christ said. “Looking at this as someone who was born way after any of this went down, it’s like, how did [the scientists] not think to look more carefully? I think they had more of a priority to analyze the ice and then the soil didn’t get analyzed.”

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In what Christ describes as a “weird trick of history,” the soil was such a low-level priority for researchers that it eventually got lost when the expedition got home. The samples were shoved in the back of an army freezer at the University of Buffalo, then moved incognito with a bunch of other material to another freezer at a research facility in Denmark in the 1990s. It was only in 2017, as JP Steffensen, one of Christ’s mentors and an author on the paper, was doing inventory helping that facility prepare its freezer for a move, that the samples were rediscovered and able to be more fully analyzed.

And even though researchers in the 1960s may not have known what they got when they dug up ancient dirt, Christ is grateful that their work provided him with one of the more exciting moments of his scientific career.

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“The day that we found the fossils was one of those ‘eureka’ moments. I never thought that those days actually happen for scientists, but it did happen for me,” he said, describing how he first saw specks of plant material as his team was cleaning the sediment samples for analysis. “I was jumping around in the lab. It was so exciting.”

Writing about climate change, renewable energy, and Big Oil/Big Gas/Big Everything for Earther. Formerly of the Center for Public Integrity & Nexus Media News. I'm very tall & have a very short dog.

DISCUSSION

rvincent1960
Times up, time to leave!

Just keep in mind, the last time the atmospheric CO2 was above 400ppm was over 3 million years ago during the Mid Piacenzian Warm Period. At this time sea level was 10m higher than it is now, the arctic was mostly ice free and so was Greenland. No people then.

The earth is normally in some kind of “hothouse” mode, the Mid Piacenzian Warm Period wasn’t a true hothouse, as the “warm” suggests and that’s where we are heading right now. However as we are already well on the way to 450ppm and beyond it’s sobering to look at where that leads.

A hundred million years ago when dino’s ruled and most of the shit being burnt to cause us all this trouble was being laid down the CO2 was at 800ppm and there was no ice at the poles. Sea level was around 100m higher than now and it was really, really hot. Again no people, and few flowering plants, they were new to the scene.

The earth likes being hothouse, it’s easily tipped there, many things help it get there and stay there. Humans evolved in one of the rare, short ice worlds. We have no idea if humans and other land mammals can survive in a hothouse earth. Many, if not most of the plants we rely on for food will not tolerate those conditions, along with stock animals like cows and sheep.

It is worth noting that the famous James Black, senior scientist working for Exxon in the 1970's first confirmed that their products, if development followed the pace at the time, would cause a massive greenhouse effect warming the planet. His predictions indicated a range of CO2 between 900 and 1500ppm by the start of the 22nd century. They knew this was an uninhabitable planet scenario yet decided it would be better for business to keep it under wraps.

None of this is news, none of this is a revelation, all of this was preventable.