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Ozone and the Ozone Hole

Ozone and the Ozone Hole. Heather Raven & Stefanie Spayd. Background. Magnitude of polar O 3 loss depends on chlorine activation which is controlled by polar stratospheric clouds that depend on temperature (Tilmes et al. , 2006) What are the important factors?

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Ozone and the Ozone Hole

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  1. Ozone and the Ozone Hole Heather Raven & Stefanie Spayd

  2. Background • Magnitude of polar O3 loss depends on chlorine activation which is controlled by polar stratospheric clouds that depend on temperature(Tilmes et al., 2006) • What are the important factors? Sunlight, Greenhouse Gases, and Temperature • The Arctic also has an ozone hole, but has greater total column ozone than in the Antarctic because of dynamical re-supply of ozone (less O3 loss) • Antarctic has larger polar vortex and colder temps than Arctic = more concerned with O3 at the southern pole (greater O3loss) • New studies predict that no statistically significant change in ozone hole decrease will occur until about 2024(Newman et al., 2006) • Full recovery sometime between 2053 and 2084

  3. Sunlight • Catalyst to breaking up the ozone layer. • Breaks up O3 into O2 and O • Breaks up CFCs to produce Cl • Cl combines with Oxygen atoms, preventing them from combining with O2 to form ozone. • Thus, creating a lack of ozone molecules in the atmosphere.

  4. Greenhouse gases warm the troposphere and cool the stratosphere. • Polar stratospheric clouds (PSCs) contain molecules with chlorine, when the molecules react they form Cl2 after which sunlight splits the molecule into Cl + Cl. • PSCs form only in very cold stratosphere. • Global warming is effectively enhancing ozone depletion! • Stopping emission of GHGs now does not get rid of them right away: • Important to note that CFCs have remained in atmosphere even after emission ceased due to Montreal Protocol (lifetime 65 – 400 years) The main players: • Chlorofluorohydrocarbons (CFCs) • CO2 • H2O Greenhouse Gases and Ozone Hole

  5. Temperature and Ozone • Climate Change = Changing Temperature in the Stratosphere • GHG ↑ Temperature ↓ Ozone hole duration ↑ (In Antarctic) • Cooling of lower-stratosphere contributes to ozone loss: • Chlorine activation below 195 K temps in stratosphere • 195 K is threshold for formation of PSCs • Antarctic below this threshold much of winter season • Arctic below this threshold less in winter season, less ozone loss from chlorine

  6. Take Home Points • Continued anthropogenic release of greenhouse gases, not only CFCs, into the atmosphere will enlarge the ozone holes, letting more harmful UV rays reach the Earth’s surface. • Temperature of the stratosphere is a key factor, as is sunlight, in the depletion of ozone. • These processes are all intimately connected through chemical, radiative, and dynamical feedbacks.

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