The story of Greenland keeps getting greener—and scarier.
A new study provides the first direct evidence that the center—not just the edges—of Greenland’s ice sheet melted away in the recent geologic past, and that the now ice-covered island became home to a living tundra landscape.
A team of scientists reexamined a few inches of sediment from the bottom of a two-mile-deep ice core extracted at the very center of Greenland in 1993, and held for 30 years in a Colorado storage facility. They discovered soil that contained willow wood, insect parts, fungi and a poppy seed in pristine condition.
“These fossils are beautiful,” said 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. The bad news: its implication that human-caused climate change could melt the ice sheet again.
The study, published in the Proceedings of the National Academy of Sciences, confirms that the Greenland Ice Sheet melted and the island greened during a warm period likely within the last million years. This adds to growing evidence that Greenland is more fragile than scientists had realized until recently. The researchers say that if the ice covering the center of the island melted, most of the rest of it had to have melted too, allowing enough time for soil to form and an ecosystem to take root.
In 2016, Joerg Schaefer of Columbia University’s Lamont-Doherty Earth Observatory and colleagues tested rock from the bottom of the same 1993 ice core (called GISP2) and published a study suggesting that the current Greenland ice sheet could be no more than 1.1 million years old. They said there had been extended ice-free periods over the past 2.7 million years, and that if the ice was melted at the GISP2 site, then 90% of the rest of Greenland would have also melted. It was a first step toward overturning the longstanding story that Greenland is an implacable fortress of ice, frozen solid for millions of years.
In 2019, Bierman and a team including Lamont-Doherty geochemist Sidney Hemming examined another ice core, this one extracted at Camp Century, near the coast of Greenland, in the 1960s. They were stunned to discover twigs, seeds and insect parts at the bottom of that core; it revealed the ice there had melted within the last 416,000 years.
“Once we made the discovery at Camp Century, we thought, ‘Hey, what’s at the bottom of GISP2?’” said Bierman. Though the ice and rock in that core had been studied extensively, no had looked to see if it contained plant or insect remains.
The new study lends further credence to the “fragile Greenland” hypothesis: An entire tundra ecosystem established itself where today ice is two miles deep.
The researchers found that under the microscope, what had looked like no more than specks floating on the surface of the melted core sample was, in fact, a window into this landscape. Dorothy Peteet, an expert on macrofossils at Lamont-Doherty and coauthor of the study, worked with Mastro to identify among other things spores from a primitive plant called Selaginella, the bud scale of a young willow, the compound eye of an insect (probably a fly) and a seed of an Arctic poppy.
“The astounding thing is the beauty of preservation after being under all that ice, and how much it can tell us about conditions at that earlier time,” said Peteet. “The climate was warm enough for most of the ice to go away. It’s a warning for us today.”
Sea level today is rising more than an inch each decade, and much of this is coming from melting of the Greenland ice. If Greenland undergoes near complete melting over the next centuries to a few millennia, it could lead to some 23 feet of sea level rise.
“Look at Boston, New York, Miami, Mumbai or pick your coastal city around the world, and add 20-plus feet of sea level,” said Bierman. “Don’t buy a beach house.”
Adapted from a press release by the University of Vermont.
