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Paradigm shift happens.
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« on: March 12, 2011, 02:49:58 PM »
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New findings on Antarctica's Gamburtsev range:

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"Antarctica's ice sheet formed about 32-million years ago but [Tom Jordan of BAS] said that experts now believed the oldest ice was only 1.4-million years old." - The Daily Mail


Is it possible that BAS means that the ice in that particular area dates back only 1.4 million years because much of the ice there is thawed and refrozen-ice?

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The findings, published in the journal Science, confound a traditional view that ice sheets are almost solely formed by snow that lands on top, gets compressed into ice and flows slowly towards the oceans because of gravity.

'We usually think of ice sheets like cakes - one layer at a time added from the top. This is like someone injected a layer of frosting at the bottom - a really thick layer,' Robin Bell, lead author at Columbia University in New York, said.

The scientists said that about 24 per cent of the ice in an area around Dome A, a 13,800ft high plateau the size of California that forms the top of East Antarctica, was formed by re-frozen ice.

'In some places up to half the ice thickness has been added from below,' they wrote of ice above the invisible Gamburtsev Mountain range.

Jordan's statement, or misstatement, is clearly made in general reference to the entire ice sheet. Unless it was quoted out of context.

The age of the Antarctic ice sheet has dropped by millions in the past, but this would be a phenomenal drop percentage wise. Are we just one find away from the ice sheets being dated in thousands of years?

-Doug

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« Reply #1 on: March 26, 2011, 03:35:12 PM »
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UPDATE:

I received a reply from BAS and they have confirmed that they still maintain the 32-million-year timeframe. As I partially suspected, the journalist appears to have made an incorrect assumption and erroneously drew contrasts between the two dates:

   
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"Antarctica's ice sheet formed about 32million years ago but Jordan said that experts NOW believed the oldest ice was only 1.4million years old."

Correct statement should perhaps have been:

     
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Antarctica's ice sheet formed about 32million years ago and Jordan said that experts believed the oldest ice was only 1.4million years old.

To clarify, the oldest dating of the ice via an ice core is 800,000 years. Theoretically, the oldest remaining ice is 1.4 million years based on the current rate of ice flow.

The ice sheet, on the other hand, is believed to have originated 32 mya with more than 30 million years of ice having been shed from the sheet as it flows out beyond the continent and cleaves free.

According to Tom Jordan's response, the 32 million figure has been established by the following:

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"Firstly glacial drop stones found far out in the ocean, which can only have been carried by icebergs. These are dated using the micro-fossils found with them.

Secondly there is a change in the isotopic composition of the oceans recorded in fossil shells, indicating lots of water was locked away in an ice sheet.

Thirdly there was a global drop in sea level, related to storage of a large volume of ice on the continents."

-Doug

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