Title : PR 93-57 World's Deepest Ice Core Yields Unique Climate Archive Type : Press Relea

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Title : PR 93-57 World's Deepest Ice Core Yields Unique Climate Archive Type : Press Release NSF Org: OD / OPP Date : July 15, 1993 File : pr9357 Lynn Simarski June 29, 1993 (202) 357-9498 NSF PR 93-57 WORLD'S DEEPEST ICE CORE THROUGH GREENLAND ICE SHEET YIELDS UNIQUE CLIMATE ARCHIVE After five years of drilling through the Greenland ice sheet, National Science Foundation (NSF)-sponsored researchers have extracted the world's deepest ice core reaching 3052 meters (10,013 feet) on June 29 and are about to hit rock bottom. The 5.2" diameter core through the summit of the ice sheet, along with a European core completed last year 30 kilometers (18.6 miles) away, is furnishing the longest, most detailed record available of the Northern Hemisphere's climate, reaching back about 250,000 years. Together, the cores are altering ideas about the very nature of the earth's climate system. The cores reveal a climate history whose dynamism has startled researchers. "The biggest surprise so far is that climate changes much more rapidly and frequently than we ever believed before," said Paul Mayewski, chief scientist for the Greenland Ice Sheet Project (GISP 2), which includes scientists from more than 20 U.S. universities and laboratories, and is part of NSF's Arctic Systems Science initiative. Patterns of past climate stored in the ice show that climate changed substantially every few thousand years, until the end of the last ice age. One climatic interlude recorded in the ice, the so-called Younger Dryas, has drawn great scientific attention because of its abrupt onset and conclusion, as described by Richard B. Alley of Pennsylvania State University and coauthors in the April 8, 1993, issue of the journal Nature. The last ice age ended about 15,000 years ago and warmer temperatures reigned; about 2,000 years later, climate chilled again dropping 7 degrees C in Greenland during the Younger Dryas. Then, the earth switched very rapidly, in perhaps as little as three years, to the relatively balmy conditions that have persisted until today. What is more, climatic conditions over central Greenland also fluctuated back and forth within just a few decades well within a human lifespan before finally settling into a new state. These findings were described by Ken C. Taylor of the Desert Research Institute and coauthors in the February 4, 1993, issue of Nature. The swings in temperature and atmospheric chemistry recorded inthe ice may reflect massive shifts in the circulation of the atmosphere and oceans, researchers suggest. The GISP core was drilled over five summers, during which about 50 scientists, drillers, and camp staff have lived atop the flat, white expanse of the ice meet, extracting and processing lengths of core. All staff and supplies are flown in on ski-equipped LC-130 planes of the 109th Air National Guard of Scotia, N.Y. The Polar Ice Coring Office of the University of Alaska-Fairbanks developed the drill and outfitted the camp, while the GISP 2 Science Management Office of the University of New Hampshire developed the core-processing facility and coordinates the project. The American and European ice cores harbor the best records of climate obtainable--more continuous and with finer detail than the information stored in tree rings, coral growth layers, or the annual sediments of lakes. The ice archive was created as snow fell over Greenland year after year, trapping the gases, chemicals, and dust of the atmosphere, which are valuable clues to volcanic activity, biological productivity, desertification, and atmospheric circulation at the time the snow fell. The layers of snow eventually compressed together into the massive ice cap. The Greenland cores comprise a unique record for the Northern Hemisphere, particularly in light of evidence that the circulation of the north Atlantic Ocean seems to play a key role in climate dynamics--possibly even triggering the switch-overs between glacial and interglacial periods. The cores also contain greater detail than the Antarctic cores currently available: the annual ice layers in the cores from Antarctica, extracted at locations with less snowfall than at the Greenland site, are thinner and harder to read. The cores reveal that climate has been remarkably stable during the Holocene, the period since the last ice age ended. "But the richly detailed record also shows climate fluctuations during this time," Mayewski said. "These were relatively minor compared to changes in glacial times, but had a significant impact on human society." The Medieval Warm Period, for example, coincided with Viking expansion into Iceland, Greenland, and Newfoundland, while the Little Ice Age, from about 1400-1900 A.D., contributed to the abandonment of colonies in the north Atlantic and northern Europe. The cores may also shed light upon the consequences of the global warming apparently being fostered by human activity. "It's clear that our climate system has been capable of rapid change in the past," said Michael Morrison, associate director of the GISP 2 Science Management Office, "while human impact on the atmosphere is also obvious in the ice core. "Industrial activity has actually changed the same constituents in the atmosphere such as carbon dioxide, sulfate, nitrate, and methane that have varied with natural climate changes in the past." The climate history housed in such fine detail by the Greenland cores may ultimately permit researchers to unravel the mechanisms of climate change and help to assess whether human activity might once again set off such changes. -end- The National Science Foundation is an independent agency of the federal government established in 1950 to promote and advance scientific progress in the United States. NSF accomplishes its mission primarily by competitively awarding grants to educational institutions for research and education in the sciences, mathematics, and engineering. This and other information is available electronically on STIS, NSF's Science and Technology Information System. For more information about STIS contact the Publications Section at (202) 357-7861 and request the "STIS Flyer," NSF Publication #91-10, or send an E-mail message to stisinfo@nsf.gov (INTERNET) or stisinfo@NSF (BITNET).


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