Greenland Fossil Discovery Stuns Scientists, Confirms Center of Ice Sheet Melted in Recent Past

Greenland’s story is getting greener and scarier. A new study provides the first direct evidence that the center, not just the edges, of the Greenland ice sheet melted in the recent geological past, and that the island, now covered in ice, was once home to a landscape of verdant tundra.

A team of scientists reexamined a few centimeters of sediment from the bottom of a three-kilometer-deep ice core extracted from the heart of Greenland in 1993 and preserved for 30 years in a Colorado warehouse. They were astounded to discover soil containing willow wood, bits of insects, fungi and a perfectly intact poppy seed.

“These fossils are beautiful,” says Paul Bierman, a University of Vermont scientist who co-led the new study with UVM graduate student Halley Mastro and nine other researchers, “but, yes, we’re getting worse and worse,” in what that implies about the impact of human-caused climate change on the melting of the Greenland ice sheet.

The study, published in the Proceedings of the National Academy of Sciences on August 5, confirms that Greenland’s ice melted and the island turned green during an earlier warm period, likely within the last million years, suggesting that the giant ice sheet is more fragile than scientists had realized until recent years.

If the ice covering the center of the island has melted, then most of the rest of the island must have melted, too. “And probably for several thousand years,” Bierman said, enough time for soil to form and an ecosystem to take root.

“This new study confirms and extends the fact that much of the sea level rise occurred at a time when the causes of warming were not particularly extreme,” said Richard Alley, a leading climate scientist at Penn State University who reviewed the new research, “providing a warning about the damage we could do if we continue to warm the climate.”

Sea levels are now rising more than an inch per decade. “And it’s getting faster and faster,” Bierman said.

Sea levels are likely to rise several meters higher by the end of the century, when today’s children will be grandparents. And if greenhouse gas emissions from burning fossil fuels are not drastically reduced, he added, the near-total melting of Greenland’s ice sheet over the next few centuries to millennia could cause sea levels to rise by some 23 feet.

“Look at Boston, New York, Miami, Mumbai, or pick any coastal city in the world and add 20 feet of sea level to it,” Bierman said. “It’s submerged. Don’t buy a beach house.”

Fundamental assumptions

In 2016, Columbia University’s Joerg Schaefer and his colleagues tested rocks from the bottom of the same 1993 ice core (called GISP2) and published a then-controversial study suggesting that the current Greenland ice sheet could be no older than 1.1 million years; that there were long ice-free periods during the Pleistocene (the geological period that began 2.7 million years ago); and that if the ice melted at GISP2, 90 percent of the rest of Greenland would melt as well. It was a major step toward overturning the long-held narrative that Greenland is an implacable ice fortress, frozen solid for millions of years.

In 2019, UVM’s Paul Bierman and an international team reexamined another ice core, this one taken from Camp Century, near the coast of Greenland, in the 1960s. They were astonished to find twigs, seeds, and bits of insects at the bottom of the core, revealing that the ice had melted within the last 416,000 years. In other words, the walls of the ice fortress had collapsed much more recently than previously thought.

“Once we made the discovery at Camp Century, we were like, ‘Hey, what’s at the bottom of GISP2?’” said Bierman, a professor in UVM’s Rubenstein School of Environment and Natural Resources and a member of the Gund Institute for the Environment.

Although the ice and rock in that core have been studied extensively, “no one has looked at the top three inches of till to see if it’s soil and if it contains plant or insect remains,” he said. So he and his colleagues asked for a sample from the bottom of the GISP2 core stored at the National Science Foundation Ice Core Facility in Lakewood, Colorado.

Now, this new study in PNAS The study confirms that the 2016 “fragile Greenland” hypothesis is correct. It deepens the grounds for concern, showing that the island was warm enough, for long enough, for an entire tundra ecosystem, perhaps with stunted trees, to have established itself where the ice is now three kilometres thick.

“We now have direct evidence that not only is the ice gone, but that plants and insects were living there,” Bierman said. “And it’s irrefutable. You don’t have to rely on calculations or models.”

Flowers

The initial discovery that there was intact biological material—not just gravel and rock—at the bottom of the ice core was made by geoscientist Andrew Christ, who completed his PhD at UVM and was a postdoc in Bierman’s lab. Then Halley Mastro took over and began studying the material closely.

“It was amazing,” she said. Under the microscope, what looked like mere specks floating on the surface of the molten core sample were actually windows onto a tundra landscape.

Working with Dorothy Peteet, a macrofossil expert at the Lamont-Doherty Earth Observatory and a co-author of the new study, Mastro was able to identify spores of spike moss, the bud scale of a young willow, the compound eye of an insect, “and then we found Arctic poppy, just a seed of it,” she said. “It’s a little flower that’s really adaptable to the cold.”

But it’s not all that good. “It lets us know that the Greenland ice melted and there was soil there,” Mastro explained, “because poppies don’t grow on miles of ice.”