A new study published Monday finds most of Greenland’s ice sheet melted away in the recent geological past.
Co-authored by University of Vermont researchers Halley Mastro and Paul Bierman, the paper shows the presence of fossils in an ice segment taken from the center of Greenland’s ice sheet. The scientists say this shows life existed in an iceless environment less than 1.1 million years ago.
“I think the picture that's coming into my mind now is that Greenland is fragile, and that during prior warm periods, it did melt,” said Bierman, a geoscientist with UVM’s Gund Institute for Environment.
That could have implications for today’s warming world, where melting ice sheets are raising global sea levels.
The study also included researchers from NASA/Goddard Institute for Space Studies, the University of Washington, Williams College, Purdue University, Lawrence Livermore National Laboratory, the Geological Survey of Denmark and Greenland, and the University of New Hampshire.
It builds on Bierman’s previous research. In 2019, his team published a paper showing fragments of soil containing fossils and biomolecules were found in an ice core taken close to Greenland’s coast, at a location called Camp Century, where the ice is thinner. This revealed that the ice had melted within the last 400,000 years — more recently than previously believed.
Bierman said that made them wonder what might be at the bottom of GISP2, a core taken from a deeper area, closer to the center of Greenland’s ice sheet. UVM requested a sample held at the National Science Foundation Ice Core Facility in Colorado, and were given a 3 inch specimen from 2 miles beneath the top of the ice sheet.
“I thought, you know, maybe we'd get a chunk,” Bierman said. “But in fact, we got a little baggy that you could hold in the palm of your hand with 30 grams, about an ounce of brown, dry sand and silt, a little bit of gravel in there.”
They were able to identify organic material in the sediment.
“If you imagine like on Lake Champlain … when you see all the debris like washing up onto the shore, you can sort of imagine how it floats sort of differently than like, the dirt and stuff,” said Halley Mastro, a research assistant at UVM. “So that's sort of what it looks like on a very tiny scale.”
The sample from the core contained material Mastro had never seen before. There were bits of rock spike moss, the preserved eye of an unknown insect and the seed of an Arctic poppy flower.
“So what the new findings mean right now is that not only do we have this isotopic evidence with mathematical models of the disappearance of the center of the ice sheet, but we actually have this tangible, tractable [thing],” Bierman said. “I mean, when you find a fossil, you can explain that to anybody, right? 'I’ve got a poppy seed under two miles of ice, how’d it get there?'”
For each of these remnants of life to have existed, it meant that in the last million years, the ice had to have melted by at least 90% to allow nature to thrive.
The researchers say the sample, taken from where the ice is thickest, at the center of the sheet, expands on the "coastal" findings of Camp Century and gives scientists a better understanding of what has happened with Greenland’s ice sheet in the past.
Rising sea levels
According to a 2015 study, when Greenland’s ice sheet melted 400,000 years ago, sea levels rose between 6 and 13 meters above what they are now.
Today, Greenland holds the equivalent of between 6 and 7 meters of global sea rise in its ice. If it were all to melt, it would pose a catastrophic threat to coastal communities around the world.
But Bierman said data also shows at some point after 400,000 years ago, the ice sheet did return to the landscape.
“So this is not all doom and gloom, but it came back when atmospheric carbon dioxide was 280 or 290 parts per million, not when it was 420 [parts per million and] headed up fast,” Bierman said, referencing the current measure of carbon dioxide in the atmosphere. “So I think there's a big warning in here that, yes, Greenland's ice sheet is fragile, but we are pushing that ice sheet to melt right now, and we're pushing it really hard by warming the climate.”
He said that should be a wake up call.
“It takes time to melt the ice sheet, but we are headed right now — unless we get the carbon dioxide out of the atmosphere, we're headed for that tens of thousands of years of warmth,” Bierman said.
Sea levels are currently rising over 1 inch each decade. Bierman says right now, reducing carbon emissions and working to remove existing carbon from the atmosphere is the number one priority in keeping sea levels from rising.
As for the fossil findings, Bierman and Mastro said they came as a complete surprise and can serve as a tool to paint a picture of Greenland in a different geological time, a stark portrait of a scene they’re hoping to prevent.
“I think the poppy seed is sort of a good thing to sort of highlight, just because people understand what a poppy flower looks like, and can sort of get the vision much easier of the landscape,” Mastro said. “People know what flowers are, but rocks, moss, doesn't really bring anything to the eye. But I think they all gave us different bits of information … and so does Arctic poppy, but knowing that together, we can sort of build this picture of this ecosystem at that time.”
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