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Wobbling Of Earth's Orbit Explains Antarctic Warming
That Ended Last Ice Age

17 August, 2013

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MessageToEagle.com - Earth's ice ages are caused by the wobbling of the planet's orbit, which changes its orientation to the sun and affects the amount of sunlight reaching higher latitudes, particularly the polar regions.

This knowledge is known for more than a century. A West Antarctica Ice Sheet Divide project researcher stands in a snow pit next to an ice core with data from 68,000 years ago. The prominent line across the middle of the ice separates one year's ice and snow accumulation from the next year's.

A new research shows that Antarctic warming began at least two, and perhaps four, millennia earlier than previously thought.



"Sometimes we think of Antarctica as this passive continent waiting for other things to act on it. But here it is showing changes before it 'knows' what the north is doing," said T.J. Fudge, a University of Washington doctoral student in Earth and space sciences and lead corresponding author of the Nature paper.

The findings come from a detailed examination of an ice core taken from the West Antarctic Ice Sheet Divide, an area where there is little horizontal flow of the ice so the data are known to be from a location that remained consistent over long periods.

The ice core is more than 2 miles deep and covers 68,000 years, though so far data have been analyzed only from layers going back 30,000 years.

Near the surface, 1 meter of ice covers one year, but at greater depths the annual layers are compressed to centimeters.

Fudge identified the annual layers by running two electrodes along the ice core to measure higher electrical conductivity associated with each summer season.

Evidence of greater warming turned up in layers associated with 18,000 to 22,000 years ago, the beginning of the last deglaciation. "This deglaciation is the last big climate change that we're able to go back and investigate," he said.

"It teaches us about how our climate system works."

West Antarctica is separated from East Antarctica by a major mountain range. East Antarctica has a substantially higher elevation and tends to be much colder, though there is recent evidence that it too is warming.

"It's not surprising that West Antarctica is showing something different from East Antarctica on long time scales, but we didn't have evidence for that before," Fudge said.

The warming in West Antarctica 20,000 years ago is not explained by a change in the sun's intensity but how how the sun's energy was distributed over the region.

"It not only warmed the ice sheet but also warmed the Southern Ocean that surrounds Antarctica, particularly during summer months when more sea ice melting could take place."

Changes in Earth's orbit today are not an important factor in the rapid warming.

"Earth's orbit changes on the scale of thousands of years, but carbon dioxide today is changing on the scale of decades so climate change is happening much faster today," Fudge said.

Paper.


See also:
Strange Behavior Of Earth's Poles

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