Scientists find clues to ice cap longevity: study

Millions of microscopic plants called phytoplankton colour the waters of the North Atlantic in this image captured on June 23, 2007 by the Moderate Resolution Imaging Spectroradiometer. The upper left edge of the image is bounded by Greenland while Iceland is in the upper right.

LONDON (Reuters) - Scientists using DNA extracted from ice buried deep below the surface have found evidence that a lush forest once existed in southern Greenland, a finding that sheds light on how climate change affects Earth's frozen areas.

The researchers analyzed ice cores 2-3 km below the surface from several locations in southern Greenland and discovered what they believe to be the oldest authenticated DNA ever recorded.

Eske Willerslev, a biologist at the University of Copenhagen in Denmark, said scientists know very little about fossils hidden below ice and glaciers -- which cover about 10 percent of the earth's surface -- because usable DNA samples tend to be buried so deep and are difficult to get.

"We have shown a principle and now you can move around to other ice cores and try to do the same thing," he said in a telephone interview. "We have limited knowledge about the Antarctic ice sheet and the biology there."

Willerslev said drilling techniques developed over the past few years allowed him and his colleagues to search far below the surface to discover evidence of an ancient forest.

Writing in the journal Science on Thursday, they said their research showed it was possible to explore and understand Earth's vast frozen areas by sampling basal ice that sits far below the surface.

Basal ice is soil trapped at the bottom of ice and, because the dirt holds on to biological material, offers a richer source of DNA to study past life and climate change than clean ice near the top.

In southern Greenland they found a wide range of plant and insect life, including pine, spruce and alder tries along with beetles, flies, spiders, butterflies and moths, from 450,000 to 800,000 years ago.

Scientists had thought the area was last ice-free about 120,000 years ago during the last interglacial but the study showed southern Greenland was still covered in ice at that time.

This suggests the southern Greenland ice sheet is more stable than thought and might not be as big a contributor to sea level rises caused by rising temperatures, Willerslev said.

This does not change the view that climate change is problematic but could force scientists to rethink their models looking at the impact of warming temperatures, he said.

"If we have found evidence that the ice didn't melt away then people have to take that into account when modeling how ice caps might react in the future to climate change," he said.