Tales from Ice Time: Two Holes through Greenland Offer a Glimpse of Climates Past and Future
Monastersky, Richard, Science News
The scene evokes images of surgeons performing a liver transplant in full football gear.
Moving quickly but gingerly, a crew of heavily outfitted drillers coaxes a long icicle from its container and hurries the glistening prize to a dumbwaiter. Room temperature here hovers at a dangerously warm level, only 10[degrees]C below freezing, and the crew must lower the ice as fast as possible into the safety of a cold snow cellar. They take care not to slip, though. The chunk of frozen water they hold is valued at more than $30,000.
This particular cylinder of ice represents one small step in a five-year effort to probe some of the hottest issues in climate-change research. The U.S. program, called the Greenland Ice Sheet Project 2 (GISP 2), aims to drill a 3,000-meter-deep hole straight through the thickest part of Greenland's glacial cap while collecting ice samples from every layer. At a nearby site, European scientists are drilling and sampling a similar core. Together, the two frozen records will give researchers their best look yet at how Earth's climate has behaved through some 2,000 centuries--a key to understanding what may lie ahead in an era of global warming.
Merely a hand's breadth across, the ice holes serve as tiny windows for gazing far back into the planet's history. Long before our ancestors invented the wheel, let alone the pollution-belching automobile, Earth passed through dramatic warm spells and ice ages. The natural forces that drove these climate shifts -- including solar radiation, greenhouse gases and even tiny algae in the ocean--left subtle clues within the Greenland glacial cap. By looking for such evidence in the millennia-old ice, scientists hope to learn what controlled the variations of the ancient environment. Only by understanding the past can experts assess how rapidly Earth will warm as greenhouse pollutants build up in the atmosphere.
Paul Mayewski, GISP 2's chief scientist, sums up the value of the project in a single word: perspective.
"Sitting in the middle of a forest, it's very hard to find out where you are," says Mayewski, a glacial geochemist with the University of New Hampshire in Durham. "If you are really want to understand whether we're changing the climate or not, you need to understand [its] natural variability. If you don't have this perspective, you won't be able to understand the relationship between climate and civilization."
From the Vantage point of the GISP 2 camp, it's not hard to imagine Earth as it was 18,000 years ago, during the coldest stage of the last ice age.
GISP 2 scientists spend their summers in a flat, frozen world some 650 kilometers north of the Arctic circle, near the highest part of the immense ice sheet blanketing more than 80 percent of Greenland. Beyond the scattered buildings and tents, a white plain stretches in every direction toward unbroken horizons. On an overcast day, sky and snow wear the same dull hue, creating a featureless void that seems to go on forever.
This is how Denmark or Detroit must have looked during the last ice age, when thick glacial sheets covered much of Europe, Asia and North America. In the United States, the glaciers reached as far south as St. Louis in the heartland and Long Island in the east. Though the ice retreated from most parts of the globe by about 10,000 years ago, it still maintains a grip on Antarctica and Greenland.
Ice sheets form layer by layer, as each year's snow covers that of previous years. With time, the intense weight from overlying layers squeezes the buried snow, transforming it into the solid ice filled with bubbles of trapped air. The ice sheet beneath the GISP 2 camp measures more than 3 kilometers deep--a load so heavy it has warped the bedrock on which it rests. Save for parts of Antarctica, Greenland's summit region has the world's thickest ice, offering scientists a chance to reconstruct the longest climate record to date. …