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  (Source: Travelvivi)
But scientists say it did not contribute to global warming today

Lawrence Livermore National Laboratory (LLNL) scientist, along with his team, recently used radiocarbon dating to trace carbon dioxide released to the atmosphere from the deep ocean at the end of the last ice age.

Radiocarbon dating employs the use of radioisotope carbon-14 to figure out the age of ancient and prehistoric carbonaceous materials. This process can be used on materials as old as 62,000 years old. 

Tom Guilderson, a scientist at the LLNL's Center for Accelerator Mass Spectrometry and an author of the study, found that an increase in atmospheric CO2 concentrations corresponded with a decreased amount of carbon-14 relative to carbon-12 in the atmosphere. 

"This suggests that there was a release of very 'old' or low 14/12CO2 from the deep ocean to the atmosphere during the end of the last ice age," said Guilderson. He noted that CO2 release may increase the rate at which ice melts after an ice age. 

Ocean circulation regulates radiocarbon in the atmosphere, and in turn, this regulates the sequestration of carbon dioxide in the deep ocean by atmosphere-ocean carbon exchange. Around 110,000 to 10,000 years ago when the last ice age occurred, lower atmospheric carbon dioxide levels coincided with increased atmospheric radiocarbon concentrations, which have been "credited to great storage of CO2 in a poorly ventilated abyssal ocean." The circulation of the ocean was drastically different back then, and Guilderson admits that he and his team do not fully understand the manner in which carbon was stored in deep ocean at that time. 

The team dated two sediment cores from the subtropic South Pacific near New Zealand and the sub-Antarctic to be approximately 13,000 and 19,000 years old. Guilderson was able to determine when the large CO2 release occurred using the carbon-14 in the cores. Also, he was able to determine the ocean pathway by which it escaped. 

"In this case, the absence of a signal is telling us something important," said Guilderson. "Deeper waters substantially depleted in carbon-14 were drawn to the upper layers and this is the main source of the CO2 during deglaciation. Data suggests that the upwelling of this water occurred in the Southern Ocean, near Antarctica. In our cores off New Zealand, which lie in the path of waters which 'turn over' in the Southern Ocean, we don't find anomalously low carbon-14/12 ratios.

"This implies that either water which upwelled in the Southern Ocean, after 16,500 years ago, had a vigorous exchange with the atmosphere, allowing its 14C-clock to be reset, or the circulation was significantly different than what the current paradigm is. If the paradigm is wrong, then during the glacial and deglaciation, the North Pacific is much more important than we give it credit for."

This carbon dioxide release sped up the melting, but when asked about CO2's contribution to

global warming today, Guilderson said this release of CO2 from the last ice age "is not relevant." But he did mention that he has used radiocarbon dating on CO2 in the atmosphere today, and that isotopic signature shows that use of fossil fuels is what is causing global warming. 

The study was published in the August 26 edition of Nature



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RE: just read
By Jyrioffinland on 8/30/2010 10:45:09 AM , Rating: 2
quote:
...an increase in atmospheric CO2 concentrations corresponded with a decreased amount of carbon-14 relative to carbon-12 in the atmosphere.


That sounds a whole lot like a piece of legit data to me.


RE: just read
By Denigrate on 8/30/2010 11:21:16 AM , Rating: 2
What did they base it on? They jump in a time machine and check the atmosphere levels? The amount of guess work that is now ordained as science is frightening.


RE: just read
By Jyrioffinland on 8/30/2010 11:41:53 AM , Rating: 2
According to the article, they did something very mysterious called "measuring".

quote:
The team dated two sediment cores from the subtropic South Pacific near New Zealand and the sub-Antarctic to be approximately 13,000 and 19,000 years old. Guilderson was able to determine when the large CO2 release occurred using the carbon-14 in the cores.


What is there so difficult to understand? If it's beyond you, maybe you'll be able to understand it once you've finished school.


RE: just read
By kattanna on 8/30/2010 12:33:39 PM , Rating: 2
quote:
The team dated two sediment cores


WOW a whole 2 cores, and that tells them how the entire world was?

come on, even today region to region can have varying levels, but supposedly in the past everywhere was equal?


RE: just read
By Jyrioffinland on 8/31/2010 4:48:54 AM , Rating: 2
quote:
WOW a whole 2 cores, and that tells them how the entire world was?


First off, if you think of the oceans, they are in constant move and gases do get distributed pretty evenly in the long run so these kind of core samples are not 'local' in nature.

Secondly, the sea bed sediments come about extremely slowly (from the human perspective) so the time scale will also even out short-lived peaks and dips.


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