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Antarctic Ice Core over 500,000 Years Old Extracted

CAMBRIDGE, UK, March 14, 2002 (ENS) - Ice more than half a million years old has been taken from deep below the East Antarctic ice sheet, setting what is believed to be a new record.

The multi-nation European Project for Ice Coring in Antarctica (EPICA) drilling at Dome Concordia has recovered ice believed to be around 530,000 years old, according to the British Antarctic Survey.

Previously the Russian Vostok ice core, dating back 420,000 years, was regarded as the oldest ice to be drilled from Antarctica.

camp

EPICA scientific site in Antarctica (Photo courtesy ESF)
The EPICA team, from 10 countries, recovered their ice from a drill hole that reached 2,864 metres (9,396 feet) in depth - compared to the Vostok hole's 3,538 metres (11,607 feet).

According to British Antarctic Survey scientist Rob Mulvaney, the answer to this paradox lies in differences in the rates of thinning of the ice sheet at the two sites, which is linked to what lies beneath them.

At Dome Concordia, high on East Antarctica's plateau, the ice lies on rock, whereas at Vostok, it stands over the huge Lake Vostok.

"If the bottom of the ice sheet lies on rock, and there is no melting, then the ice at the very bottom is almost infinitely old, and the annual layers infinitely thin," Mulvaney said.

"Because Vostok ice is melting at the base, the oldest layers have been lost, and the vertical column of ice does not need to thin so rapidly to maintain the surface equilibrium."

The EPICA project exceeded its targets in the past season, drilling more than 350 metres (1148 feet) beyond its goal, and leaving just 380 metres (1246 feet) to be drilled next season.

The British Antarctic Survey (BAS) said field analysis already suggests that the ice retrieved coveres four glacial and interglacial periods, with every prospect of several more climate cycles before the team reached either disturbed ice or bedrock.

EPICA's chief scientist, BAS's Eric Wolff, said the drilling program took scientists back to the future. "Information about how climate worked in the past is locked in the ice," he said. "Understanding this helps predict future changes."

map

Map of Antarctic showing ice core drilling sites (Photo courtesy British Atmospheric Data Centre)
The EPICA project has also begun drilling 3,000 kilometers (1,864 miles) from Dome Concordia in Dronning Maud Land in search of more detailed information at a site that receives double the snowfall of Dome Concordia.

Even so, it is cores at Dome Concordia that will provide the longest possible record of the past atmosphere, BAS said.

The single most important source of information about past climate change and the associated composition of the atmosphere are the two large ice caps of Greenland and Antarctica, EPICA says in its mission statement.

"Analysis of ice cores is therefore the most powerful means we have to determine how climate has changed over the last few climate cycles, and to relate this to changes in atmospheric composition, in particular to concentrations of the principal greenhouse gases - CO2, CH4 and N2O - carbon dioxide, methane, and nitrous oxide."

EPICA says the program "has been motivated primarily by the urgent need to predict more accurately how global climate is likely to respond to increased emissions of greenhouse gases as a result of human activities."

{Published in cooperation with The Antarctican at: http://www.antarctican.com}



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