New global warming threat
2007-05-18 09:30
San Francisco - Climate change has weakened the Southern Ocean's ability to absorb the globe's excess carbon dioxide, a factor that could accelerate global warming, international scientists have found.
A study published in the journal Science revealed that since 1981, the Southern Ocean has been taking up less carbon dioxide -five to 30% less per decade - than researchers had predicted previously.
At the same time carbon dioxide emissions rose by 40%, the study found. The reason for the slowdown is more winds over the Southern Ocean since 1958, caused by human-produced greenhouse gases and ozone depletion.
The winds have led to a release of stored carbon dioxide into the atmosphere. This prevented further absorption of greenhouse gases in the ocean's carbon "sink" - a natural carbon reservoir, according to the study.
"This is serious," said Corinne Le Quere, a scientist who led the research by the University of East Anglia, the British Antarctic Survey, and the Max Planck Institute for Biochemistry in Jena, Germany.
"The Earth's carbon sinks - of which the Southern Ocean accounts for 15% - absorb about half of all human carbon emissions."
With the Southern Ocean reaching its saturation point, more carbon dioxide will stay in the atmosphere, Le Quere said.
Over the next 25 years, the problem will continue - affecting atmospheric carbon dioxide for centuries, she said.
The team of researchers - from Europe, Japan, the United States, South Africa, Australia and New Zealand - collected and analysed data from 11 stations in the Southern Ocean and 40 stations around the globe over a period of four years.