WASHINGTON: 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 will be published in Science
magazine.
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, CO² 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 CO² 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."
"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 CO² 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.
|
