Ozone hole healing but more impact on Antarctica – UC expert

The ozone hole affecting the Antarctic and New Zealand is slowly healing due to the reduction of ozone destroying chlorofluorocarbons (CFCs) substances, a University of Canterbury expert said today.

The projections of when the ozone will recover back to natural levels are uncertain because of the complexity of their interactions between greenhouse gases and their impacts at different levels of the atmosphere, UC lecturer Adrian McDonald said.

``But ozone levels above Antarctica are projected to return to 1980 levels (previous to the ozone hole) after 2050. The Montreal Protocol means that emissions of ozone depleting substances (CFCs) have largely been banned worldwide.

``The future recovery of the Antarctic ozone hole and increases in greenhouse gases are expected to have opposite effects on the winds and circulation in the southern hemisphere. The increasing ozone hole has until now acted to change the circulation of the southern hemisphere so that the strong winds linked to the jet streams have moved towards the pole.’’

Ozone is present only in small amounts in Earth’s atmosphere. Nevertheless, it is vital to human wellbeing and ecosystem health.

Ozone recovery should act to move the winds back towards the equator. The jet streams positions are one of the main things that helps control the width of tropical and polar weather belts. So their position changing is very important to New Zealand’s climate, he said.

The southward shift of jet streams due to the ozone hole has been linked to a range of climate trends at mid- to high-latitudes during summer. These include warming over the Antarctic peninsula and cooling over the rest of Antarctica.

``Ironically, ozone depletion may have protected Antarctica from the worst of greenhouse gas-related warming. With the ozone recovery the future of Antarctic climate is less certain. Though the complex interactions in the atmosphere associated with climate change makes this region particularly hard to predict. We have a lot of research to carry out so we can understand how ozone recovery will impact on the southern hemisphere.

``My scientific work is focusing on understanding how winds and circulation in the atmosphere impact ozone depletion and the set of complex interactions which cause ozone depletion in the stratosphere (roughly 25km above Earth surface) from impacting surface climate.

``One of the key unknowns is whether changes in the circulation patterns caused by climate change will impact the recovery of the ozone hole. For example, some models predict that ozone hole won’t recover at all because of complex interactions between the transport of air and the chemical sources (production of ozone) and the destruction of ozone.

``By measuring the winds at the edge of space using the Scott Base radar, we measure a flow of air that goes from pole to pole. By measuring this over the last 30 years we have been able to examine how greenhouse gases have impacted the circulations and get some ideas about how that may impact the formation of the ozone hole in  the future.’’

Dr McDonald’s summer scholarship will examine data from Scott Base as part of his Antarctic research.