The EPICA consortium (the European Project for Ice Coring in Antarctica) is drilling deep ice cores in Antarctica to build a record of past climatic and atmospheric change. The first core, drilled at the Franco-Italian Concordia research station, is now available for study. It covers 740,000 years, the longest time period of any drilled so far. Data from this 'Dome C core', published in this issue, confirm that Antarctica has seen recurring warm and cold phases at 100,000-year intervals, although the pattern altered 430,000 years ago, when contrasts between warm and cold grew greater. There is more of the 3,190-metre core to be analysed, extending back to 800,000 years. The cover (by C. W. M. Swithinbank) shows annual snow strata on the face of an iceberg about 25 metres high.
The September issue of Nature publicized results of research on subterranean ice core in Antarctica by European scientists in the past 8 years. Ice samples for the past 740,000 years confirm that the temperature of atmosphere and the intensity of greenhouse gases is growing at an unpresedented speed.
The Greenland ice cover contains ice cores of the past 100,000 years since the last ice age, but the Vostok ice core in Antarctica has a history of 400,000 years. The new ice core being drilled in eastern Antarctica is estimated to be 800,000 years old.
Scientists have drilled down over 3km through the ice cover in the past 8 years, and are going to reach the bedrock in next year. The ice cover 3 km under the ground level had been frozen 740,000 years before, when human ancestors had not left Africa for the other continents.
The subterranean ice cover offers a temporally successive sample for the temperature of atmosphere and the intensity of greenhouse gases. Eric Wolff, director of this research program, says that the ice sample testifies that the climate change of our present time is out of gear.
Wolff says, “we only need to get into the bubbles frozen inside the ice samples to obtain the intensity of CO2 and methane at that time. The present intensity of CO2 is higher by 30 % than any time in the past, and the intensity of methane has doubled. Professor Stocker from Bonn University, Switzerland, who is also a member of EPICA, says that the present growing amplitude of greenhouse gases is over 100 times higher than that of any time we can detect from the subterranean ice cover in Antarctica.”
These data confirm the conclusion drawn from initial research on marine sedimentation, i.e., the globe has undergone 8 glacial cycles, each lasting about 100,000 years, and at the intervals are relatively warm interglacial periods, lasting averagely 10,000 years.
Although the last ice age ended 12,000 years ago, scientists don’t think there will an ice age soon. The interglacial period the climate of which resembles that of today most appeared 430,000 years ago and had lasted 28,000 years, which may indicate that the nice climatic conditions fit for human inhabitation may continue for many more years.
