Ellen Phiddian
Cosmos science journalist
Fossils have provided more evidence that Greenland’s ice sheet is more transient than previously thought, raising concerns for sea-level rise.
The fossilised organic matter, found at the bottom of an ice core, indicates that the centre of Greenland was ice-free at some point in the last million years.
This suggests the ice sheet is “fragile”, and more likely to melt quickly under current human-induced global warming.
A paper describing the fossils is published in Proceedings of the National Academy of Sciences.
The research, done by US and Danish scientists, examines the base of an ice core collected in 1993 from Summit, a research station in the centre of Greenland. The station sits atop the thickest part of the Greenland ice sheet, at 3km deep.
The researchers used electron microscopes to find willow wood, insect parts, fungi, and a perfectly preserved poppy seed at the base of the ice core.
“It lets us know that Greenland’s ice melted and there was soil, because poppies don’t grow on top of miles of ice,” says study co-author Halley Mastro, a graduate student at the University of Vermont, US.
“These fossils are beautiful,” says lead author Professor Paul Bierman, a scientist at the University of Vermont.
But their presence means that the centre of Greenland was ice-free, implying that most of the rest of the island was ice-free as well.
“And probably for many thousands of years,” adds Bierman, allowing for time for soil formation and plant colonisation.
The ice is 2 million years old at most, meaning that Greenland was tundra-covered during the Pleistocene era.
“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,” says Professor Richard Alley, a climate scientist at Penn State University, US, who reviewed the research.
The research backs up other findings in the last decade which have questioned the permanence of Greenland’s ice sheet.
This includes data from an ice core taken at Camp Century, near Greenland’s north coast, in 1966, and a 2016 study on the rocks at the bottom of the Summit ice core.
“We now have direct evidence that not only was the ice gone, but that plants and insects were living there,” says Bierman. “And that’s unassailable. You don’t have to rely on calculations or models.”
The Intergovernmental Panel on Climate Change currently predicts between 28cm-188cm of sea level rise by the end of the century, depending on emissions trajectories.
Sea level rise from melting ice sheets has been accelerating in the past 30 years.
