Burlington: Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock.
So scientists were greatly surprised to discover an ancient tundra landscape preserved under the Greenland Ice Sheet, below two miles of ice.
Greenland is a place of great interest to scientists and policymakers since the future stability of its huge ice sheet—the size of Alaska, and second only to Antarctica—will have a fundamental influence on how fast and high global sea levels rise from human-caused climate change.
The new discovery indicates that even during the warmest periods since the ice sheet formed, the center of Greenland remained stable; “it’s likely that it did not fully melt at any time,” Vermont’s Bierman said. This allowed a tundra landscape to be locked away, unmodified, under ice through millions of years of global warming and cooling.
“The traditional knowledge about glaciers is that they are very powerful agents of erosion and can effectively strip a landscape clean,” said study expert Lee Corbett. Rather than scraping and sculpting the landscape, the ice sheet has been frozen to the ground, “a refrigerator that’s preserved this antique landscape,” Bierman said.
“We found organic soil that has been frozen to the bottom of the ice sheet for 2.7 million years,” said expert Paul Bierman—providing strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming.
The researchers expected to only find soil eroded from glacier-scoured bedrock in the sediment at the bottom of the ice core. “So we thought we were going looking for a needle in haystack,” Bierman said.
Researcher planned to work diligently to find vanishingly small amounts of the beryllium—since the landscape under the ice sheet would have not been exposed to the sky. “It turned out that we found an elephant in a haystack,” he said; the silt had very high concentrations of the isotope when the team measured it on a particle accelerator at Lawrence Livermore National Laboratory.
To help interpret these unexpected findings, the team also measured nitrogen and carbon that could have been left by plant material in the core sample. “The fact that measurable amounts of organic material were found in the silty ice indicates that soil must have been present under the ice,” said expert Lini.