The Secrets In Ice Cores
by Daniel Grossman

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The LC-130 military transport unloads its cargo at the NGRIP research station in Greenland

Measuring History on a Giant Glacier

The absolute best place in the world to get a detailed record of the climate in the last 140,000 years is in the middle of Greenland. There, European scientists, flown in on military transport planes, have set up a scientific research station on a massive glacier nearly two miles thick and about the size of the United States east of the Mississippi river. Blindingly white ice and snow stretch for hundreds of miles in all directions.

The researchers hope to drill a core containing ice tens of thousands of years older than any previous ice-core sampled in the northern hemisphere. They're at work in a cavern they dug just below the surface.

Chief scientist Dorthe Dahl Jensen and driller Thorsteinn Thorsteinsson lower the core drill by a slender cable of steel wound on a spool the size of a trash can.

Dorthe Dahl Jensen - photos by Daniel Grossman

Imagine the ice sheet is a two-mile thick chocolate layer cake. Imagine that the drill is a motorized cookie cutter. The scientists cut out core samples about one yard-long at a time. Then the device is hoisted to the surface and the sample is removed.

It's taken seven years for the European teams to get a taste of the very bottom layers.

"Ice from the last 100 meters is ice that is 130 to 115 thousand years old," says Dahl Jensen. "It is ice from a climate period when the climate was slightly warmer than our present climate. We call it the Eemian period."

These are the only good samples from the Eemian period ever collected in the northern hemisphere. Sigfus Johnsen, Danish glaciologist and professor at the University of Copenhagen, says the chunks of frozen water contain critical clues to our future.

"Our aim here was to look at the last warm period. How did it end? If we are disturbing our climate, and we're doing that with pollution with CO2 [Carbon Dioxide], we need to understand how a warm period is actually ending without that disturbance; in order to better predict how our own warm period is going to end."

It will take some time before researchers can use the new Greenland core to make better predictions about how our own warm period will end. But previous cores drilled in Greenland contain ominous hints that the closing act might have a surprise ending. Scientists have discovered that in the past, climate has at times responded with alarming abruptness to gradual changes in natural factors like fluctuations in the sun. Some researchers say the gradual heating caused by increased carbon dioxide could have a similar sudden impact.

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