HiddenMysteries: DNA discovery reveals Greenland's warm past

Alok Jha

Scientists have uncovered evidence that within the past million years southern Greenland was warmer than previously thought, and even covered in lush forests, a discovery suggesting its ice sheet could be more stable than previously thought against climate change temperature rises.

An analysis of DNA found at the bottom of ice cores drilled to a depth of more than a mile (2km) in south Greenland, and dated to between 450,000 and 800,000 years ago, has shown a surprising variety of plant and insect life was present then.

There were trees such as alder, spruce, pine and members of the yew family, and invertebrates related to beetles, flies, spiders, butterflies and moths.
"We have shown for the first time that southern Greenland, which is currently hidden under more than 2km of ice, was once very different to the Greenland we see today," said Eske Willerslev, an archaeologist at the University of Copenhagen. "Back then it was inhabited by a diverse array of conifer trees and insects."

Martin Sharp, a glaciologist at the University of Alberta and co-author of the paper, said that the silty ice found underneath the Greenland glacier created a natural freezer that preserved prehistoric DNA - the samples have provided the oldest authenticated DNA obtained to date. "These findings allow us to make a more accurate environmental reconstruction of the time period from which these samples were taken." The area was "significantly warmer than most people thought".

The results of the studies are published today in the journal Science.

Over geological timescales the Earth's temperature rises and falls, leading to ice ages and periods of relative warmth. Between 450,000 and 800,000 years ago it would have been about 10C in summer and -17C in winter. When temperatures later fell the area was covered in ice and this ice sheet seems surprisingly to have remained in place when temperatures rose again about 130,000 years ago. During this last interglacial period temperatures were 5C warmer than today.

"If our data is correct, then this means that the southern Greenland ice cap is more stable than previously thought," said Professor Willerslev. "This may have implications for how the ice sheets respond to global warming."

According to climate change models, a two-degree rise in global temperatures could cause a collapse of the Greenland ice sheet and dangerously high sea levels by the end of the century. Recent data suggests the rate of ice loss from Greenland has tripled since 2004.

The results also show that biological molecules from the ice cores can be used to reconstruct environments - the material available is in very low concentrations but the information would be worth the effort, said Enrico Cappellini, of York university. "Given that 10% of the terrestrial surface is covered by thick ice sheets it could open up a world of new discoveries."

http://environment.guardian.co.uk/

DNA discovery reveals Greenland's warm past

Saturday, July 07 2007 @ 11:56 AM CDT