The risk of a “catastrophic” sea-level rise that would swamp some of the world’s major cities has increased after scientists made a worrying discovery.
They have found that Greenland’s ice melted away during a warm period within the last one million years.
Detailed analysis suggests that the giant ice sheet is more fragile than previously realized — and increases the risk of a massive sea-level rise, say scientists.
The new study provides the first direct evidence that the center — rather than just the edges — of Greenland’s ice sheet melted away in the recent geological past and the now-ice-covered island was then home to a green, tundra landscape.
Scientists re-examined a few inches of sediment from the bottom of a two-mile-deep ice core extracted at the very centre of Greenland in 1993 — and held for 30 years in a storage facility in Colorado in the United States.
The team were amazed to discover soil that contained willow wood, insect parts, fungi, and a poppy seed in pristine condition.
Study co-leader Professor Paul Bierman, of the University of Vermont (UVM) in the US, said: “These fossils are beautiful.”
But he added “we go from bad to worse” in what the discovery implies about the impact of human-caused climate change on the melting of the Greenland ice sheet.
The findings, published in the Proceedings of the National Academy of Sciences, confirm that Greenland’s ice melted and the island “greened” during a previous warm period likely within the last million years.
Prof Bierman explained that if the ice covering the centre of Greenland melted, then most of the rest of it had to be melted too — “and probably for many thousands of years,” enough time for soil to form and an ecosystem to take root.
Leading climate scientist Professor Richard Alley, of Penn State University and who reviewed the research, said: “This new study confirms and extends that a lot of sea-level rise occurred at a time when causes of warming were not especially extreme, providing a warning of what damages we might cause if we continue to warm the climate.”
Prof Bierman says sea level today is rising more than an inch each decade — and “it’s getting faster and faster.”
It is likely to be “several feet” higher by the end of the century, when today’s children are grandparents.
Prof Bierman says that if the release of greenhouse gases — from burning fossil fuels — is not “radically” reduced, the near complete melting of Greenland’s ice over the next centuries to a few millennia would lead to some 23 feet of sea level rise.
He said: “Look at Boston, New York, Miami, Mumbai or pick your coastal city around the world, and add 20-plus feet of sea level.
”It goes underwater. Don’t buy a beach house.”
In 2016, researchers 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 be no more than 1.1 million years old.
It was a major step towards overturning the longstanding theory that Greenland is an implacable fortress of ice, frozen solid for millions of years.
Then, in 2019, Prof Bierman and an international team re-examined a 1960s ice core from Greenland.
They were stunned 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 fortress” had failed much more recently than had been previously imagined possible.
Prof Bierman said: “Once we made the discovery at Camp Century, we thought, ‘Hey, what’s at the bottom of GISP2?’
“Though the ice and rock in that core had been studied extensively, no one’s looked at the three inches of till to see if it’s soil and if it contains plant or insect remains.”
He and his colleagues requested a sample from the bottom of the GISP2 core held at the National Science Foundation Ice Core Facility in Lakewood, Colorado.
The new study provides confirmation that the 2016 “fragile Greenland” hypothesis is correct.
And it deepens the reasons for concern, showing that the island was warm enough, for long enough, that an entire tundra ecosystem, perhaps with stunted trees, established itself where today ice is two miles deep.
Prof Bierman said: “We now have direct evidence that not only was the ice gone, but that plants and insects were living there.
“And that’s unassailable. You don’t have to rely on calculations or models.”
Under a microscope, study co-author Halley Mastro discovered that what had looked like no more than specks floating on the surface of the melted core sample, was, in fact, a window into a tundra landscape.
She was able to identify spores from spikemoss, the bud scale of a young willow and the compound eye of an insect.
UVM graduate student Ms Mastro said: “Then we found Arctic poppy, just one seed of that.
“That is a tiny flower that’s really good at adapting to the cold.”
She added: “It lets us know that Greenland’s ice melted and there was soil, because poppies don’t grow on top of miles of ice.”
