It’s reasonably well known (!) that carbon dioxide levels in the atmosphere are increasing… it’s also reasonably well known that increased carbon dioxide levels in the atmosphere are leading to increased carbon dioxide levels in the oceans (leading to ocean acidification). However, new research reported in New Scientist, Issue 2715 [04 July 2009] suggests that in the Southern Ocean, the picture isn’t quite that simple. Measurements from the Southern Ocean show that carbon dioxide levels have flattened off in recent decades (having previously increased) and a new modelling study points the finger of “blame” for this at the hole in the ozone layer in this region. Lower levels of atmospheric ozone (at high levels) and increased levels of carbon dioxide (at lower levels) have changed the energy balance in the atmosphere, generating stronger westerly winds, enhancing ocean circulation and encouraging carbon-rich water to rise up from the deep (a process known as upwelling). The result is surface water that is less able to absorb carbon dioxide from the atmosphere. This is a great example of an unexpected feedback effect of one part of the Earth-atmosphere system with another and just goes to show how complex and inter-connected all of these processes really are.
Tim O'Hare 