Ozone hole cuts ocean carbon sink

THE Southern Ocean has lost its appetite for carbon dioxide, and it appears the ozone hole is to blame. In theory, oceans should absorb more CO2 as levels of the gas in the atmosphere rise, but this is not happening in the Southern Ocean, where absorption has flattened off in recent decades. To figure out why, Andrew Lenton of the Pierre and Marie Curie University in Paris, France, and colleagues built a climate model that included the interactions between the ocean and atmosphere. Running it with and without the stratospheric ozone lost since 1975 revealed that the ozone hole must be partly responsible ( Geophysical Research Letters, DOI: 10.1029/2009gl038227 ). Decreasing stratospheric ozone and rising greenhouse gases are altering the radiation balance of the Earth’s atmosphere. This is thought to be strengthening westerly winds over the Southern Ocean. As these winds enhance ocean circulation, they may be encouraging carbon-rich waters to rise from the deep, say the team, meaning that surface water is less able to absorb CO2 from the atmosphere. “No one would ever have predicted from first principles that increasing CFCs would have the effect of decreasing uptake of ocean CO2,” says Andrew Watson of the University of East Anglia, UK.

Source of Information : New Scientist July 4 2009