On a late Saturday afternoon in June 2022, Andrew Christ was about to be discovered at the University of Vermont. A postdoctoral researcher studying the interactions between glaciers and landscapes at the time, Christ was washing a sample taken from the depths of a 30-year-old glacier from the center of the Greenland ice sheet – just 30 grams of sediment the mud left behind. ice grinding against rock. As he watched, mud settled at the bottom of the plastic tub and small black particles began to fly through the water.
“Oh my god, I’ve seen this before,” Christ thought. He had seen a similar phenomenon in a sample from another area that his laboratory was examining, but he did not expect to see it in the middle of the Greenland ice sheet. After looking at the shells under a microscope, he discovered that they were fragments of ancient poppies, insect fragments and tree bark—reminiscences of ice-free Greenland. well preserved in time.
This week, the University of Vermont team that analyzed the sample published a study concluding that the discovery of plant and insect life from the center of the continent indicates that the land was free of ice, or perhaps not at all. at some point 1.1 million years.
The new evidence that Greenland lived up to its green reputation in the past may represent an exciting scientific advance, but it also heralds dire possibilities for humanity’s future. Today’s level of atmospheric carbon dioxide is higher than it has been in millions of years; evidence of Greenland’s ice-free past means it may take less warming than expected to eliminate the continent’s most important ice cap. The ice cap that covers Greenland contains enough fresh water to raise sea levels by 23 meters – an incredible volume that could change coastlines around the world.
As global temperatures exceed levels not seen in 125,000 years, that melting is already underway. Since satellite records began in 1992, the antarctic and arctic ice sheets have lost a staggering 7.5 billion tons of ice combined. Less than a foot of sea level rise since the turn of the century has caused flooding in coastal communities around the world.
Predicting the future of ice is a tricky business. Scientists haven’t been able to create computer models that match the real-time melting they’re seeing, leaving world governments uncertain about sea level rise. how much. But as mounting evidence seems to suggest, what once melted can melt again, leaving scientists worried that Greenland’s ice is at risk of disappearing completely.
“Studies like this are rare because we don’t have much access to the depth of the Greenland ice sheet,” said Tyler Jones, a glaciology researcher at the University of Colorado, of this week’s new research. (Jones was not involved in the University of Vermont paper, but he studied temperature records inside the ice.) “It can certainly help us understand how it might behave in a warmer future world.”
Halley Mastro / University of Vermont
For their study, the University of Vermont team began by collecting a sediment sample from where the 1993 Greenland Ice Sheet Project 2, or GISP2, ice core fell — one of the few samples of its kind. . It came from 2 kilometers under the ice and, along with the rest of the core, took five years to drill.
Halley Mastro, a graduate student who led the study with Paul Bierman, a professor of lithology at the University of Vermont and author of a forthcoming book on the Greenland ice sheet, said: “Ice cores are amazing books, like archives of the Earth’s past. loss. According to Mastro, scientists have previously searched ice cores for pure ice, where crystal bubbles hold gases and chemicals that reflect past climates.
“But what we have is 8 inches of dirt from the bottom – that was not important at the time,” he added.
Bierman thinks that part of the reason his team was the first to find fossils is because ice scientists are trained to look for chemical clues instead. But in 2019, as he was washing mud from the bottom of Camp Century, a 1960s glacier near the Greenland ice sheet, he saw black arrows floating.
“Not having been trained as a basic ice scientist, I had worked in a sediment lake for the first 10 years of my career, and I knew how to find fossils,” he said. Beerman. “It was totally lucky timing.”
In 2021, Bierman and Christ published their findings at Camp Century. Then, in 2023, they named the oldest plants they found 416,000 years ago – showing that the tip of Greenland must have been free of ice at that time. Now, after finding fossils in GISP2 — evidence of a thriving tundra ecosystem in central Greenland as well — Bierman and Mastro think the continent as a whole was at least 10 percent ice-free. 90 1.1 million years ago. . As Mastro puts it, “No ice can have a big hole in the middle.”
“If you find plants underneath, it means the ice is gone everywhere,” said Dorothy Peteet, a macrofossil expert who helped Mastro examine the sample. Researchers have found fragments of moss, fungus, poppy seeds, willow bark, an insect’s eye and legs. According to Peteet, the rarity of these types of specimens makes the discovery particularly remarkable: It means that when the ice was forming, it must not have moved much, or it would have destroy these pieces as you crash into the rock.
For Peteet, the most exciting part of the discovery is the comparison of today’s vegetation, and what that shows about past climates. The presence of poppy seeds, for example, could indicate that the continent enjoys a cooler temperature of 40 degrees Fahrenheit, according to the paper.
He said: “Certain fossils tell you that the plant was there, then you can print the climate it was in based on a modern analogue.”
Jones, a glaciologist at the University of Colorado, said that the new study points to the need for more research, given the possible consequences for the loss of ice in the future.
“We’re going to create a planet that’s warmer than any time in the last few million years at some point,” he told Grist. It is possible that we are creating a world where this ice will melt.
On the other hand, scientists may not have to wait another 30 years for other samples: Next year, a team of researchers from the Danish Institute of Ice and Climate plans to return to the area of an ice core near the center of Greenland, just 19 kilometers from GISP2.
Meanwhile, according to Jones, the evidence suggests an urgent need to reduce greenhouse gas emissions and limit global warming and sea level rise.
“Once you melt that Greenland ice sheet, it’s irreversible,” he said. “It won’t come back for a very, very long time.”
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