14 DAY TRIAL // A new study carried out by Tom Guilderson, a scientist at Lawrence Livermore National Laboratory's Center for Accelerator Mass Spectrometry and colleagues, suggests that CO2 release may speed up the melting following an ice age.
Guilderson used radiocarbon dating to trace the pathway of carbon dioxide released from the deep ocean into the atmosphere after the last ice age.
Radiocarbon dating uses the carbon-14 carbon-12 isotopes to determine the age of everything from ancient artifacts to prehistoric corals on the bottom of the ocean.
The researchers used two sediment cores from the sub-Antarctic and subtropic South Pacific near New Zealand, which they dated to be between 13,000 and 19,000 years old.
Guilderson used the carbon-14 in the cores as a tracer to see when the large carbon dioxide release happened and also on which ocean pathway did it escape on.
The study says that the lack of a signal is important as “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.
Guilderson adds that “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.
He finally explained that “if the paradigm is wrong, then during the glacial and deglaciation, the North Pacific is much more important than we give it credit for.”
Research showed that when the carbon dioxide concentrations within the atmosphere rose, the amount of carbon-12 and carbon-14 decreased.
This implies that during the end of the last ice age, there might have been a release of a very 'old' or low 14/12CO2 from the deep ocean into the atmosphere, according to Guilderson.
Normally, the radiocarbon level in the atmosphere is regulated mainly by ocean circulation, that also controls the amount of CO2 in the deep sea.
It seems that during the last ice age, some 110,000 to 10,000 years ago, lower levels of atmospheric carbon dioxide were accompanied by high atmospheric concentrations of radiocarbon, that have been caused by a poorly ventilated abyssal ocean that accumulated increased levels of CO2.
“The ocean circulation was significantly different than it is today and carbon was being stored in the deep ocean in a manner that we don't completely understand," said Guilderson, adding that the large CO2 release sped up the melting of the ice.
On the other hand, our problem today with global warming has nothing to do with this CO2 release, argued the scientist.
He even added that “we can radiocarbon date the CO₂ in the atmosphere now and what we've found is that the isotopic signature indicates that it is really due to the use of fossil fuels.”
The study appears in the August 26 edition of the journal Nature.