The Southern Ocean, one of the Earth's most important carbon sinks, is losing its ability to absorb CO2
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SYDNEY: The Southern Ocean, one of the Earth's most important carbon sinks, is losing its ability to absorb carbon dioxide because of climate change – a factor that could further accelerate global warming.
Published today in the U.S. journal Science, an international study revealed that since 1981, the Southern Ocean has been taking up less carbon dioxide – five to 30 per cent less per decade – than was previously thought. At the same time, carbon dioxide (CO2) emissions rose by 40 per cent.
Sink or swim?
"This is serious," said Corinne Le Quere, of the University of East Anglia, U.K, who led the research, a collaboration between 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 per cent – absorb about half of all human carbon emissions," she said. "All climate models predict that this kind of feedback will continue and intensify during this century."
It was assumed that, as human activities released more CO2 into the atmosphere, ocean sinks would keep pace, absorbing a comparable percentage of the greenhouse gas. While the breakdown in efficiency of carbon sinks was an expected outcome of climate change, most models predicted the decline wouldn't come until some time in the second half of the 21st Century.
Turbulent Waters
According to the researchers, since 1958, human-produced greenhouse gases and ozone depletion have caused circumpolar winds around Antarctica to move closer to the poles and increase in speed. This has resulted in intensified storms over the Southern Ocean, and greater turbulence on the ocean's surface.
Since more CO2 is stored in deeper waters, mixing and upwelling caused by the storms has increased the amount of CO2 released from the ocean to the atmosphere – reducing the net absorption of CO2.
Paul Fraser, of CSIRO Marine and Atmospheric Research, a specialist division of Australia's national science agency, the CSIRO, said levels of greenhouse gases in the atmosphere would be higher in future than was recently predicted by the Intergovernmental Panel on Climate Change, since their latest report hadn't factored in the find.
This means that stabilising CO2 below catastrophic levels will be more difficult to achieve than was previously thought, said Fraser, adding that the only way we can compensate for the declining ocean sink is to ramp up our efforts reduce emissions.
In the study, 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.
with AFP
