Scientists were greatly surprised to discover an ancient tundra landscape below two miles of ice, preserved under the Greenland Ice Sheet.
"We found organic soil that has been frozen to the bottom of the ice sheet for 2.7 million years," University of Vermont geologist Paul Bierman said.
This discovery provides strong evidence that the Greenland Ice Sheet has persisted much longer than previously known, enduring through many past periods of global warming.
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 ancient soil under the Greenland ice sheet helps to unravel an important mystery surrounding climate change," Dylan Rood a co-author on the new study from the Scottish Universities Environmental Research Centre and the University of California, Santa Barbara said, "how did big ice sheets melt and grow in response to changes in temperature?"
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 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," notes Ben Crosby, a member of the research team from Idaho State University.
The findings are published in the journal Science.