Posted on 09/08/2003 7:22:36 AM PDT by forsnax5
An ice core recently shipped from Antarctica has yielded its first, eagerly awaited results. The tests confirm that the 3200-metre core dates back at least 750,000 years, making the ice the oldest continuous core ever retrieved.
Gases and particles trapped in the layers of an ice core provide information about the Earth's climate and atmosphere. Oxygen and hydrogen isotopes reveal the temperature when the ice formed, for example, while high carbon dioxide and methane levels indicate periods of global warming.
A group of research teams called the European Project for Ice Coring in Antarctica (EPICA) has been drilling cores at two sites - Dome Concordia in the Pacific sector and Dronning Maud Land in the Atlantic sector.
At Dronning Maud Land, a large amount of ice has been laid down every year, giving very detailed information over recent time periods. The 1565 metres of ice retrieved so far dates back to around 50,000 years ago and is being analysed at the Alfred Wegener Institute in Bremerhaven, Germany.
At Dome Concordia the ice has been laid down more slowly, so this core spans a much longer period of time. The EPICA team hit a depth of 3200 metres in January 2003, just 100 metres from the bedrock.
This core has now been cut into sections and shipped to labs in the 10 European countries in the EPICA collaboration. The researchers revealed results of their first tests on the ice at the 7th International Symposium on Antarctic Glaciology in Milan, Italy, last week.
One way to date the ice in a core is to count the layers laid down annually, but in the Dome Concordia core they are too thin to distinguish. So the researchers used markers such as dust, gas and electrical conductivity in the ice to match different layers to known events that have already been dated, such as volcanic eruptions or ice ages.
The results confirm that the first 3140 metres of the core dates back 750,000 years. The next step is to check that all the layers of the core are still in chronological order. If they are, models of the ice flow suggest that the deepest ice could be up to a million years old.
The top section of the core, corresponding to the past 420,000 years, has already been matched up to another core taken from above Lake Vostok, a giant lake trapped under the Antarctic ice. But if the ice of the Dome Concordia core has moved over rocks or slopes in the past, it is possible that the deeper layers could have been jumbled up while leaving the surface layers intact.
The Vostok core was the last deep core to be retrieved from Antarctica, in 1999 (New Scientist print edition, 4 December 1999, p 34). At 3600 metres it is thicker than the Dome Concordia core, but analysis was halted at 420,000 years as the ice layers below seemed to be jumbled.
If the layers in the Dome Concordia core are intact, it will give ice researchers their first information about climate changes before that time. A period between ice ages known as Stage 11, which occurred about 450,000 years ago, is of particular interest because the Earth's orbit at that time is believed to have been very similar to its orbit today.
It could give us our best picture of what today's climate would be like without man-made pollution or global warming, says Eric Wolff of the British Antarctic Survey.
He also hopes the core will reach as far back as 780,000 years ago, when the Earth's magnetic field last reversed. Very little is known about what such a reversal would do to the planet's climate. "If the stratigraphy is OK, we'll certainly reach the reversal," he says.
The researchers hope to publish their first climate results in the next few months. The analysis may even allow more information to be retrieved from the Vostok core. After seeing the Dome Concordia results, Jean Jouzel of the Vostok team says he is hopeful the Vostok core's deeper layers might be intact after all.
That's the Y2K for compass makers.
Yeah, sure. And the world will come to an end on Dec 31, 1999.
A period between ice ages known as Stage 11, which occurred about 450,000 years ago, is of particular interest because the Earth's orbit at that time is believed to have been very similar to its orbit today.
Would you happen to know how the similarity of Earth's present orbit to a prior period's orbit is determined?
Gosh. You mean there have been periods of global warming prior to now? Must have been those previous civilizations and their nasty, dirty industries.
Orbits are mathematically predictable ... in both directions. Using a bit of calculus, astronomers can pretty much determine the configuration of any orbit for any time period. I've got a cheapy astronomy program on my machine at home that generates night skies for any date and time over the past several thousand years and into the future several thousand years.
PaleoRepublicans?
You know, I've got one of those too, and it didn't even occur to me. I tend to think of those as star mappers or, as you described yours -- it "generates night skies." Of course, it would have to calculate Earth's position to do that.
Duh!
What a crock!
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