Greenland Fossil Discovery Stuns Scientists And Confirms The Center Of The Ice Sheet Melted In The Recent Past

Greenland’s story keeps 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 the now-ice-covered island was then home to a green, tundra landscape.

A team of scientists re-examined a few centimeters of sediment from the bottom of a two-mile-deep ice core drilled in central Greenland in 1993 — and kept for 30 years in a storage facility in Colorado. They were amazed to discover soil containing willow wood, insect parts, mushrooms and a poppy seed in pristine condition.

“These fossils are beautiful,” says Paul Bierman, a scientist at the University of Vermont who co-led the new study with UVM graduate student Halley Mastro and nine other researchers, “but, yes, we go from bad to worse”. what does this mean for the impact of human-caused climate change on the melting of the Greenland ice sheet.

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

If the ice covering the center of the island melted, then the rest of it had to melt as well. “And probably for many thousands of years,” Bierman said, enough time for soil to form and an ecosystem to take root.

“This new study confirms and extends that a large sea-level rise occurred at a time when the causes of warming were not particularly extreme,” said Richard Alley, a senior climate scientist at Penn State who reviewed the new research. , “giving a warning. of what damage we can cause if we continue to warm the climate.”

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

It will likely be several meters higher by the end of this century, when today’s children are grandparents. And if the release of greenhouse gases – from the burning of fossil fuels – is not radically reduced, he said, the almost complete melting of Greenland’s ice over the next few centuries to several millennia would lead to about 23 meters of sea level rise.

“Look at Boston, New York, Miami, Mumbai or pick your coastal city around the world and add 20 feet plus sea level,” Bierman said. “It goes underwater. Don’t buy a beach house.”

Core assumptions

In 2016, Joerg Schaefer at Columbia University and colleagues tested rock 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 not be more than 1.1 million years old; that there were extended ice-free periods during the Pleistocene (the geological period that began 2.7 million years ago); and that if the ice melted at the GISP2 site, then 90% of the rest of Greenland would melt as well. This was a major step towards overturning the long-held belief that Greenland is an implacable ice fortress, frozen for millions of years.

Then, in 2019, UVM’s Paul Bierman and an international team reexamined another ice core, this one taken at Camp Century off the coast of Greenland in the 1960s. They were amazed to discover twigs, seeds and insect parts at the bottom. of that core – revealing that the ice there had melted within the last 416,000 years. In other words, the walls of the ice castle had failed far more recently than previously imagined possible.

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

Although the ice and rock in that core had been studied extensively, “nobody had looked 3 centimeters down to see if it’s soil and if it contains plant or insect remains,” he said. So he and his colleagues sought a sample from the bottom of the GISP2 core held at the National Science Foundation’s Ice Core Center in Lakewood, Colorado.

Now this new study in PNAS provides confirmation that the “fragile Greenland” hypothesis of 2016 is correct. And it deepens the cause for concern, showing that the island was warm enough, for long enough, that an entire tundra ecosystem, perhaps with stunted trees, settled where the ice is two miles deep today.

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

From 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 Ph.D. worked at UVM and was a postdoctoral fellow in Bierman’s lab. Then Halley Mastro took up the case and began to study the material closely.

“It was amazing,” she said. Under the microscope, what appeared to be no more than specks floating on the surface of the molten core sample was, in fact, a window into a tundra landscape.

Working with Dorothy Peteet, a macrofossil expert at the Lamont-Doherty Earth Observatory and co-author on the new study, Mastro was able to identify spores from moss, the bud scale of a young willow, the compound eye of an insect. and then we found arctic poppies, just one seed of it,” she said. “This is a little flower that is really good at adapting to the cold.”

But not so well. “This tells us that the Greenland ice sheet melted and had land,” Mastro said, “because poppies don’t grow on top of miles of ice.”