The surface of most of Greenland is now 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 that would have been similar to what is currently found in many regions of Canada.
The Greenland forest contained pine trees, yews, and aspens, where a profusion of insect life, including beetles, flies, months, and butterflies flitted among the plants.
The surprising discovery, made by an international team of scientists, including some from Canada, 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 recent geological past, Greenland had to be far warmer than it is today, and a substantial part of the island was forested, unlike today, when about 85 per cent of its surface is ice-covered and the rest is inhospitable Arctic tundra.
”We have shown for the first time that southern Greenland, which is currently hidden under more than two kilometres of ice, was once very different to the Greenland we see today,” said Prof. Eske Willerslev, a bio-archaeology 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, although they could not rule out the possibility that it might have been around as recently as 130,000 years ago.
A paper outlining the discovery is appearing in the current issue of the journal Science.
To support the type of trees found at the site, which is now entirely ice-bound, average temperatures in summer would have been warmer than 10 degrees, while winters would not have fallen below –17 degrees. It would have been a time when Greenland would have really matched the name Erik the Red gave it more than a 1,000 years ago, when it is believed the Norse explorer gave the bucolic appellation to lure more settlers to his colony.
Although the climate that gave rise to the ancient forest would not 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 Dr. 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.
Because this area is buried deep under ice, there is no fossil record for scientists to assemble that would indicate the type of environments that once existed in the area. Sampling in non-glaciated areas of Greenland has found fossils indicating forests, but those date from around 2.4 million years ago.
The scientists were confident that the DNA they found accurately portrayed forest conditions existing in the area and did not arrive on wind or precipitation from more southerly parts of the world.
As a test, they analyzed ice from the bottom of a glacier that formed in the past few thousand years on Ellesmere Island, and found that 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 – did not contain DNA.
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 six metres.
The ice sheet covering the ancient forest existed during the warm, interglacial period that existed 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,” Prof. Willerslev said.
But if this part of the ice sheet does melt, it would have major implications for current sea coasts. Water levels would likely rise one to two metres.
”That's not a big deal 400,000 years ago when the human population was essentially non-existent,” said Dr. Sharp, but today ”you've got 104 million people living within a metre of sea level.”
