Under the Greenland Ice Sheet, scientists were greatly surprised to discover an ancient tundra landscape. The finding provides strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming. Image: Joshua Brown, Univ. of VermontGlaciers and ice sheets 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 a team of university scientists and a NASA colleague were greatly surprised to discover an ancient tundra landscape preserved under the Greenland Ice Sheet, below two miles of ice.








Piece of the GISP2 ice core that the researchers analyzed for the isotope beryllium-10, showing silt and sand embedded in ice. Soon after this picture was taken, the ice was crushed in the University of Vermont clean lab and the sediment was isolated for analysis. Image: Paul Bierman, Univ. of VermontThe researchers expected to only find soil eroded from glacier-scoured bedrock in the sediment at the bottom of the ice core. But the silt they did find had very high concentrations of beryllium-10 when the team measured it on a particle accelerator at Lawrence Livermore National Laboratory, in Livermore, Calif.

"On a global basis, we only find these sorts of beryllium concentrations in soils that have developed over hundreds of thousands to millions of years," said co-author Joseph Graly, who analyzed the beryllium data while at the Univ. of Vermont, Burlington, Vt.

The new research, supported by funding from the National Science Foundation, shows that the soil had been stable and exposed at the surface for somewhere between 200,000 and one million years before being covered by ice.

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 co-author Andrea Lini at the Univ. of Vermont. The composition of the material suggested that the pre-glacial landscape may have been a partially forested tundra.

"Greenland really was green! However, it was millions of years ago," said Rood. "Before it was covered by the second largest body of ice on Earth, Greenland looked like the green Alaskan tundra." To confirm their findings about this ancient landscape, the researchers also measured beryllium levels in a modern permafrost tundra soil on the North Slope of Alaska and found that the values were very similar.

With an eye toward better understanding its future behavior, many geologists are seeking a long-term view of the history of the Greenland Ice Sheet, including how it moves and has shaped the landscape beneath it. Its 656,000 square miles of ice contain enough water, if fully melted, to raise global sea levels twenty-three feet. “Yet, we have very little information about what is happening at the bed with regards to erosion and landscape formation," said Corbett.


Source: NASA's Goddard Space Flight Center