Deep ice stirs debate on climate stability.In some realms, such as musical tastes or gustatory gus·ta·to·ry or gus·ta·tive
Of or relating to the sense of taste. traditions, Europeans are seen as more conservative than their neighbors across the Atlantic. But stereotypes often fall apart. This week, a group of U.S. scientists played the cautionary role when they raised doubts about some extraordinary climate findings reported earlier this year by a European team studying ice buried deep within Greenland's frozen blanket.
Over the last four years, the Years, The
the seven decades of Eleanor Pargiter’s life. [Br. Lit.: Benét, 1109]
See : Time U.S. and European groups have drilled separate holes through the Greenland ice sheet Greenland Ice Sheet
Single ice cap, Greenland. Covering about 80% of the island of Greenland, it is the largest ice mass in the Northern Hemisphere, second only to the Antarctic. to collect samples containing clues about the last ice age and the interglacial in·ter·gla·cial
Occurring between glacial epochs.
A comparatively short period of warmth during an overall period of glaciation. warm period immediately preceding it. The ice cores can provide such information because the glacial cap built up layer upon layer over hundreds of thousands of years, trapping details about past temperatures, winds, greenhouse gas greenhouse gas
Any of the atmospheric gases that contribute to the greenhouse effect.
greenhouse gas changes, and other aspects of climate.
The seven-nation European team made headlines in July when it reported that the last interglacial - called the Eemian stage - had a highly erratic climate that sometimes shifted abruptly into frigid ice age conditions and then snapped back into warmer weather (SN: 7/17/93, p. 36). The findings raise concern because scientists had long thought that interglacial spans -- such as the current one -- were immune from the unstable climate swings that characterize glacial epochs.
American researchers, in collaboration with several European scientists, now raise questions about the evidence of climate instability during the Eemian, which lasted from 135,000 to 115,000 years ago. At a meeting of the American Geophysical Union The American Geophysical Union (or AGU) is a nonprofit organization of geophysicists, consisting of over 50,000 members from over 140 countries. AGU's activities are focused on the organization and dissemination of scientific information in the interdisciplinary and in San Francisco San Francisco (săn frănsĭs`kō), city (1990 pop. 723,959), coextensive with San Francisco co., W Calif., on the tip of a peninsula between the Pacific Ocean and San Francisco Bay, which are connected by the strait known as the Golden and in the Dec. 9 NATURE, the investigators report that although the two ice core records yield identical information for the glacial period, they disagree about the Eemian.
"There's clearly a discrepancy between the two cores. We have to sort out what's going on What's Going On is a record by American soul singer Marvin Gaye. Released on May 21, 1971 (see 1971 in music), What's Going On reflected the beginning of a new trend in soul music. ," says Kendrick C. Taylor of the University of Nevada University of Nevada could refer to either of the universities in the Nevada System of Higher Education:
The Europeans drilled their ice core at the summit of Greenland's ice cap, while the U.S. team worked on the flank, 30 kilometers away - an arrangement designed to capture the very differences now surfacing. Taylor and his colleagues announce that the upper 90 percent of the 3,000-meter-long ice cores match almost perfectly: Both show the same rapid shifts in climate during the last ice age and record the remarkable stability of the current interglacial period, which started 10,000 years ago.
But measurements of oxygen isotopes in the ice and of the ice's electrical conductivity do not match for the lower tenth of the cores. In the U.S. record, this deepest section contains folded patterns suggesting that layers of ice have overturned as the glacier flowed over hills in the bedrock. Any turnovers would break the chronological ordering of layers and alter the true climate record.
Researchers are divided on how to apply these findings to the European ice. That core also contains evidence of overturning, but such questionable layers appear in ice older than the Eemian period. As yet, the investigators have not found signs of scrambled layers within that crucial interglacial span, says Heinz Miller of the Alfred Wegener Institute for Polar and Marine Research The Alfred Wegener Institute of Polar and Marine Research is a scientific organization located in Bremerhaven, Germany. The institute was founded in 1980 and is named after revolutionary meteorologist climatologist, and geologist Alfred Wegener. in Bremerhaven, Germany. The integrity of layering plus evidence from chemical and isotopic studies suggest that the climate actually did fluctuate dramatically during the Eemian, Miller told SCIENCE NEWS.
But some U.S. researchers say more work is needed to resolve the question of Eemian climate instability. "We're not saying they're wrong. We're simply saying it's more complicated than a nice layer-cake situation. Maybe we'll prove that they're right. We'll just have to wait and see," says Taylor.