The hole in the Earth's ozone layer may be on the mend, but that doesn't mean its environmental impacts are over. A new review study has examined in detail the effects that the extra UV radiation is having on the environment, such as shifting climate zones, changing ocean temperatures and making some species more vulnerable.
Much like climate change is today, the ozone hole was the big environmental crisis of the 1980s and 90s. This protective layer sits high in the Earth's atmosphere and reflects back a large portion of the Sun's damaging UV rays, playing a vital role in keeping the planet habitable. But in the mid-80s scientists discovered a hole in it over Antarctica.
The culprit was traced to chemicals called chlorofluorocarbons (CFCs), which were commonly used as refrigerants and in making aerosols. When in the atmosphere in large amounts, these chemicals were found to react to sunlight and start dissolving ozone. Realizing the danger, the world signed The Montreal Protocol in 1987, phasing out the use of CFCs in what would come to be considered a successful intervention.
More than three decades on and the hole seems to be on track to heal – assuming new emissions of CFCs are contained. But that repair process is still slow going, and the hole is still having some impact on the environment. And now, researchers from the United Nations' Environmental Effects Assessment Panel have conducted a review study to get a better understanding of just what those effects have been.
The biggest change seems to be on the Antarctic Oscillation. This wind belt wraps around the lower Southern Hemisphere and naturally shifts north and south over time. But the review study found that the ozone layer hole, which is directly above Antarctica, has moved the oscillation further south than it's been in about a thousand years.
The drift of the Antarctic Oscillation has dragged climate zones southward, shifting patterns of rainfall, sea-surface temperatures and ocean currents. This is changing the climate in the entire hemisphere, with effects felt across Australia, New Zealand, Antarctica, South America, Africa and the Southern Ocean.
Different parts of the oceans are becoming warmer or cooler, which has effects on the ecosystems in those areas. Warmer waters are damaging kelp beds around the Australian island state of Tasmania, and coral reefs off the coast of Brazil. But cooler areas are actually seeing some benefits, with greater numbers of fish and krill feeding populations of penguins, seals and birds.
"What we're seeing is that ozone changes have shifted temperature and precipitation patterns in the Southern Hemisphere, and that's altering where the algae in the ocean are, which is altering where the fish are, and where the walruses and seals are, so we're seeing many changes in the food web," says Kevin Rose, co-author of the study.
Other creatures are suffering more thanks to the combined effects of the climate and ozone layer hole. Higher levels of CO2 in the atmosphere are making the oceans more acidic, which is giving shellfish thinner shells and leaving them more vulnerable to damage by the extra UV radiation coming through the hole.
There also seems to be a feedback loop between the changing climate and the ozone layer hole.
"Greenhouse gas emissions trap more heat in the lower atmosphere which leads to a cooling of the upper atmosphere," says Rose. "Because ozone is depleted at colder temperatures, the colder upper atmosphere is slowing the recovery of the ozone layer."
Reports like these are important to fill in some of the gaps that climate models might not take into account, and give us a clearer idea of the future we're heading for.
The research was published in the journal Nature Sustainability.
Source: Rensselaer Polytechnic Institute
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