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Drilling Down
With advanced radar technology, researchers at the north Greenland site are producing the first detailed pictures of large areas of the ice-sheet base, with particular attention to pockets of water. Previous technology could detect large lakes underneath the ice. But the new technology, honed at the University of Kansas and deployed by researchers from both Kansas and the University of Copenhagen, can detect even a few millimeters of water, which are just as dangerous. What’s more, whereas previous radar equipment took measurements only of the ice directly beneath it, the new technology also provides information about ice layers and the ice sheet’s base in a three-kilometer-wide swath of ice cap.

During the winter of 2005-2006–summer in Antarctica–scientists from Kansas lugged the new system down to the West Antarctic Ice Sheet and collected data on a 30-by-10-­kilometer grid. Early results show much more detail about which parts of the ice sheet’s base are sitting on water and which are still frozen to the ground. Whether the water came from geothermal heat, friction from ice in motion, or accumulation of surface meltwater is not yet clear. But the new data should help improve ice-sheet models, says Claude Laird, a research scientist at the University of Kansas and a member of both the Antarctic and the north Greenland expeditions. This summer, Laird and the other scientists used the technology to map a 370-kilometer swath of Greenland. When the results start coming in, they should give a clear picture of that swath, and of how much water lies within the ice or beneath the sheet.

Meanwhile, the scientists are seeking clues from the past. At the north Greenland base station, amid the huts and vehicles, an aluminum pole is staked to the ice cap. Next summer, the scientists will return to the spot and start drilling out an ice core, boring about 2,500 meters to bedrock. They are particularly interested in one key geologic period, called the Eemian interglacial. During this stretch of time, from around 130,000 to 115,000 years ago, the planet warmed. Greenland hit temperatures 7 to 8 ºC warmer than today’s, and sea levels surged at least three to five meters higher than they are now. If this happened today, much of south Florida, Bangladesh, and many other low-lying coastal areas and islands would be submerged.

The warming during the Eemian period was caused by eccentricities in Earth’s orbit that periodically allow more solar energy to hit the planet. An understanding of how the climate and ice sheets responded during the Eemian warm-up should sharpen our picture of how they’ll respond today. Already, a record of Eemian sea levels is available from existing geological sites. But scientists would like to know more about short-term climatic variations–coolings and warmings–within the Eemian period. That should help them better understand current climate changes and more accurately predict how sea levels will rise.

Glaciers accrete over time, and different layers contain records of Earth’s past climate. A ­sample of ice spanning the whole Eemian period–never before found in the northern hemisphere–would provide a wealth of information. Identifying oxygen isotopes within water molecules can reveal what temperatures prevailed when snow fell. Trapped air bubbles inside ice contain samples of the old atmosphere. The thickness of ice layers can reveal how much snow fell. And bits of dust and organic matter will allow accurate dating. After conducting radar analysis, the researchers at north Greenland think the spot marked by the aluminum pole–dubbed NEEM, for “North Greenland Eemian”–will contain a 120-meter-thick chunk of ice representing the entire period (see “Quest for Ancient Ice”). “We can get even better data on these fast climate oscillations,” says Laird. “And we can get some forecasting about what climate change will mean.”

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Credit: David Talbot

Tagged: Energy

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