July 09, 2007
Monday

The surface of most of Greenland is entombed by a thick ice cap, but some time during the past 800,000 years, the southern part of the island actually lived up to its name. It was covered by a thick, verdant boreal forest similar to that now found in many regions of Canada.

The Greenland forest contained pine trees, yews and aspens, where a profusion of insect life -- including beetles, flies, moths and butterflies -- flitted among the plants.

The surprising discovery, made by an international team of scientists and outlined in the current issue of the journal Science, was based on an analysis of tiny fragments of DNA preserved in ice drawn from cores drilled nearly to the bottom of Greenland's ice sheet.

The finding suggests that at some point in the relatively recent past, Greenland had to be far warmer than it is now, and a substantial part of the island was forested, unlike today, when about 85 percent is ice-covered and much of the rest is inhospitable Arctic tundra.

"We have shown for the first time that southern Greenland, which is currently hidden under more than two kilometers (about 1 and 1/4 miles) of ice, was once very different to the Greenland we see today," said Eske Willerslev, a bio-archeology fellow at the University of Copenhagen, who headed the research team. "Back then, it was inhabited by a diverse array of conifer trees and insects."

Although it is not known exactly when the ancient forest died out, the researchers said it most likely existed between 450,000 and 800,000 years ago, perhaps even as recently as 130,000 years ago.

This Greenland would have matched the name Erik the Red gave it more than a 1,000 years ago, a bucolic moniker apparently intended to lure more settlers to the Norse explorer's nascent colony.

Although the climate that gave rise to the ancient forest wouldn't be described as balmy, it was probably not too far different than the middle latitudes of Canada, where the boreal forest is the predominant ecosystem.

"Parts of the boreal forest in summer can be a pleasant environment, so there is no reason to think it wouldn't have been similar in Greenland," said Martin Sharp, a glaciologist at the University of Alberta, who worked on the project.

Dr. Sharp said the ice at the bottom of the cores acted like a natural freezer, preserving many of the living things that existed at the time the forest was buried in snow. The ice, drawn from a thin layer just before bedrock begins, contained a mix of silt, small pebbles and bits of organic matter.

Why was this debris so significant?

Because, in the absence of a fossil record in this ice-encrusted area, scientists had to rely on other indicators to determine the type of environments that once existed there.

They were confident the DNA they found accurately portrayed forest conditions in the area and didn't arrive on wind or precipitation from more southerly parts of the world.

To test this hunch, they analyzed ice from the bottom of a glacier that formed in the past few thousand years on Ellesmere Island, and found the DNA it contained closely matched plant species growing nearby. In addition, ice layers from parts of the core drawn in Greenland just above the bottom -- representing more recent snow deposits - didn't contain DNA.

Sharp said it is likely that parts of Northern Canada, such as southern Baffin Island, would have been forested at the time that Greenland was also heavily wooded. At present, the closest boreal forest to Greenland is along the Labrador coast and parts of northern Quebec.

The findings have mixed implications for the current concern over global warming and the stability of Greenland's vast ice sheet, which, if it melted in its entirety, would raise global sea levels by about 20 feet.

The research indicates that within the relatively recent past, due entirely to natural fluctuations in climate, Greenland was as warm or warmer than many of the predictions made for human-caused global warming.

Scientists say the ice sheet covering the ancient forest existed during the warm, interglacial period that occurred 116,000 to 130,000 years ago, when temperatures were about five degrees warmer than today. "If our data is correct, then this means that the southern Greenland ice cap is more stable than previously thought," Willerslev said.

But if this view is wrong, and this part of the ice sheet does melt, it would have major implications for sea coasts. Water levels would likely rise 3 to 6 feet. "That's not a big deal 400,000 years ago when the human population was essentially non-existent," Sharp said. But today, "you've got 104 million people living within a meter of sea level."

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