From the Associated Press (Dan Elliott):
Smooth and milky white, the 4- to 5-inch-diameter pieces — called ice cores — provide scientists with a wealth of historical information, from air temperature to greenhouse gases to evidence of cosmic events. The record reaches as far back as 800,000 years.
The ice is the remnant of centuries of snowfall, compressed by the weight of successive years of accumulation.
“You can drill into it, and it’s much like looking at tree rings,” Fudge said. “It’s just year after year after year of climate information that’s preserved out in the ice sheet.”
Specialized drilling rigs pull the cores from as deep as 9,800 feet below the surface of the ice sheets. Crews then tuck them into protective tubes, pack them in chilled containers and ship them to the U.S. Refrigerated trucks haul them to Colorado lab, which is funded by the National Science Foundation.
In a bustling, white-walled workroom in the Lakewood freezer — kept at about minus 11 Fahrenheit — workers push the cores through a series of saws on metal frame benches, divvying up the ice according to a prearranged pattern for different experiments.
Part of every ice core is archived in another, larger room at about minus 33 degrees, so future researchers can verify old results or try new tests. The archive contains nearly 56,000 feet of ice.
Scientists tease data from the ice in various ways. Differences in the weight of molecules in the frozen water hold clues about the air temperature at the time the snow fell.
Air trapped in bubbles can be analyzed to measure how much carbon dioxide and other gases were in the atmosphere when the ice formed.
A solar flare or other cosmic events can leave distinctive radioactive atoms on the snow. Dust blown in from distant continents offers clues about atmospheric circulation.
“The ice sheets are in direct contact with the atmosphere,” said Mark Twickler, the lab’s science director. “Everything that’s in the atmosphere we capture as time goes by, and it gets buried in snow.”
The depth of the core and evidence of volcanoes help determine how old the ice is.
Scientists already know when major eruptions occurred, so a layer of volcanic residue indicates the year the adjacent ice formed. That becomes a reference point for annual layers above and below.
The record is remarkably precise, even reflecting seasonal changes, scientists say.
“It’s as if we’re standing on the ice sheet writing down the temperature for the last 800,000 years,” said Bruce Vaughn, a University of Colorado-Boulder lab manager who works with the ice. “It’s that good.”
Without a record of its depth and age, the ice has little research value, said Geoffrey Hargreaves, curator of the Lakewood lab.
“An ice core without any depth references — I shouldn’t say this — it’s good for margaritas,” he said, poker-faced.