A giant "burp" of carbon dioxide stored under the ocean between South Africa and Antarctica may have helped end the last ice age more than 18,000 years ago, according to a new study.
The study, led by a scientist from Cambridge University, is "the first concrete evidence that carbon dioxide was more efficiently locked away in the deep ocean during the last ice age."
The team made its discovery by doing radiocarbon dating on shells under the Southern Ocean from tiny foraminifera creatures, says the study, which was published in Science magazine.
Carbon locked in ocean
Dr Luke Skinner's team measured carbon-14 levels in the shells and compared this with carbon levels in the atmosphere at the time to work out how long the CO2 had been locked in the ocean.
"Our results show that during the last ice age, around 20,000 years ago, carbon dioxide dissolved in the deep water circulating around Antarctica was locked away for much longer than today," Skinner said.
This could clarify "how ocean mixing processes lock up more carbon dioxide during glacial periods," he said.
According to the study, "pulses or 'burps' of C02 from the deep Southern Ocean helped trigger a global thaw every 100,000 years or so. The size of these pulses was roughly equivalent to the change in CO2 experienced since the start of the industrial revolution."
Large transfers of carbon
"If this theory is correct, we would expect to see large transfers of carbon from the ocean to the atmosphere at the end of each ice age."
Skinner said the findings will help understand the feasibility of proposals to tackle global warming by pumping carbon dioxide into the deep sea.
"Such carbon dioxide would eventually come back up to the surface, and the question of how long it would take would depend on the state of the ocean circulation, as illustrated by the last deglaciation," Skinner said. - (Sapa, May 2010)