Published online 29 April 2008 | Nature | doi:10.1038/news.2008.787

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Antarctic ice threatened by ozone-hole recovery

Global winds could accelerate melting.

The ozone hole (here shown in September 2006) may have delayed Antarctic warming.NASA

Recovery of the ozone hole above Antarctica could warm the Antarctic and cause more ice to melt in coming decades, researchers say. As the ozone hole heals, wind patterns that shield the interior of the polar region from warm air may break down, causing warming in the Antarctica as well as warmer and drier conditions in Australia.

Despite global temperatures rising, the interior of Antarctica has experienced a unique cooling trend during its summer and autumn over the last few decades. Scientists attribute this cooling to the hole in the ozone layer, which alters atmospheric circulation patterns and strengthens the westerly winds that swirl around the continent. These winds have isolated the Antarctic interior from the warming patterns seen on the continent’s peninsula and throughout the rest of the world.

“The warming of the Antarctic may have been delayed because of the ozone hole,” says atmospheric scientist Judith Perlwitz, a climate scientist at the of the University of Colorado at Boulder and the National Oceanic and Atmospheric Administration.

But thanks to the 1987 Montreal Protocol that banned the release of ozone-depleting substances, most scientists agree that the ozone hole has probably reached its largest and that ozone levels will recover by the end of the century.

Model system

Perlwitz and her colleagues simulated the interaction between stratospheric ozone dynamics and atmospheric conditions between 1950 and the end of the twenty-first century. They conclude that as ozone levels recover, the lower part of the stratosphere above Antarctica — some 10-20 kilometres above Earth’s surface — will absorb more ultraviolet radiation, and rise in temperatures by as much as 9ºC, reducing the existing strong north-south temperature gradient1.

Along with balmier temperatures in Antarctica, a weakening of the westerly winds could also produce warmer and drier temperatures in Australia and increased precipitation in South America.

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Climate models, including those used in the Intergovernmental Panel on Climate Change’s (IPCC) fourth assessment, have not accounted for these details of ozone chemistry. Most models do not extend beyond 30 kilometres above the Earth’s surface, and adequate representation of the stratosphere would require modelling up to 60 kilometres. “This paper opens the discussion about how ozone depletion and recovery in the twentieth and twenty-first centuries can be included in climate models,” Perlwitz says.

“If we get the feedbacks and the ice-melt wrong in our climate models, then that means we could be really wrong in terms of what a safe level of carbon dioxode is,” says Theodore Shepherd, an atmospheric scientist at the University of Toronto, Canada, who was not involved in the study. Biological productivity of the oceans is driven largely by ocean and atmospheric circulation patterns, so the next step, he says, is to couple ocean dynamics to ozone chemistry and climate. 

  • References

    1. Perlwitz, J., Pawson, S., Fogt, R. L., Nielsen, J. E. & Neff, W. D. Geophys. Res. Lett. 35, L08714 doi:10.1029/2008GL033317 (2008). | Article |
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