Million-year-old plant fossils warn the Greenland ice sheet

Earth pots taken from a Cold War-era military hug and stuck in a freezer for decades could contain crucial new information about climate change and sea level rise. to study published Monday in the Proceedings of the National Academy of Scientists says plant fossils found in a sample of earth collected a mile under the ice in the mid-1960s suggest that the world’s prehuman climate was at one point warm enough to melt completely. the Greenland ice cap.

Dirt researchers inspected are a sample of sediment from the bottom of an ice core, recovered by drilling from the ice cap that covers much of Greenland. It is quite difficult to reach the bedrock when taking samples due to the incredible pressure exerted by the ice, explained Drew Christ, lead author of the study and postdoctoral researcher at the University of Vermont. There are only a few expeditions that actually obtained sediment from the bottom of the glacier. “We have less [sediment] than moon rocks, ”said Christ.

This particular sample yielded a lot of plant material, some of which was visible to the naked eye. “It’s like you’re hiking and have a bunch of twigs and forest floor stuff in the bottom of your boot and pour it down 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 isotopic analyzes of various elements that helped researchers unravel the last time the samples were exposed to the sun and cosmic rays. Dating has shown that the plant material is around 1 million years old.

Before analyzing this particular sample, Christ said, scientists had “circumstantial” evidence that the Greenland ice sheet had once completely melted. But the discovery of these fossils definitely suggests that Greenland was once sufficiently free of ice to support a variety of plants. And that’s bad news for us right now. The Greenland ice sheet is a climate time bomb, with some estimates predicting the ice sheet could raise sea level by 6.1 meters (20 feet). if it has completely melted. Although it is not expected to melt completely tomorrow, the ice cap is now melt six times faster than it was in the 1980s. The changes set in motion by rising carbon dioxide will take centuries to materialize as the climate adjusts to a new equilibrium. Knowing its history is essential to understanding the future of the ice cap.

“The Greenland ice cap disappeared into a climate system that had no human influence,” Christ explained. “Before humans added hundreds of parts per million of fossil fuels to the atmosphere, our climate was capable of melting the ice cap. In the future, as we continue to warm the planet at an uncontrollable rate, we may force the Greenland ice sheet to exceed a certain threshold and melt it and raise the sea level.

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

While the dirt sample itself is remarkable, since the Camp Century attempt was the first ice core ever to be mined from Greenland, the researchers were mostly interested in what the ice itself could tell them, and less invested. in the dirt that accompanied the carrot.

“I was pulling twigs an inch long from this thing. We could see with our naked eyes, like, it’s definitely plant material, ”Christ said. “Looking at it like someone who was born long after everything that’s happened, it’s like, how [the scientists] don’t think about looking more carefully? I think they had more than one priority to analyze the ice and then the ground was not analyzed.

In what Christ describes as a “strange thing in history,” the soil was such a low priority for seekers that it was ultimately lost when the expedition returned home. The samples were pushed into the back of an army freezer at the University of Buffalo, then moved incognito along with a bunch of other materials to another freezer at a research center in Denmark in the 1990s. It wasn’t until 2017, when JP Steffensen, one of Christ’s mentors and journalist, was doing an inventory to help this facility prepare its freezer for a move, that the samples were rediscovered and were able to be analyzed more fully.

And while researchers in the 1960s may not have known what they got from digging up ancient earth, Christ is grateful that their work provided him with one of the most exciting moments of his scientific career.

“The day we found the fossils was one of those ‘eureka’ moments. I never thought those days were actually happening for scientists, but it happened to me, ”he said, describing how he first saw spots of plant material as his team cleaned up. sediment samples for analysis. “I was jumping into the lab. It was so exciting. “