1974 Sherwood Rowland & Mario Molina Calculated that CFCs were lowering the average concentration of Ozone in the stratosphere. Chemical Time Bomb: Spray cans Leaky refrigeration and air conditioning equipment Production and burning of foam plastics trichlorofluoromethane dichlorofluoromethane Take years to reach the stratosphere Turbulent atmospheric mixing Transport on aerosols 1

O3O3O3O3 As a secondary air pollutant in the troposphere, ozone forms as part of photochemical smog. In the lower stratosphere, the formation and breakdown of ozone absorbs UV radiation. This is vital to all life on Earth. Ozone: Is an unstable reactive oxidizer Is a health threat to elderly and young Contributes to forest decline. Reduces crop yield Oxidizes stable organics (plastic, rubber) Is a highly efficient greenhouse gas Ozone damage to potato plants. 2

Earth’s atmosphere is layered with each layer having its own characteristic composition, density and temperature ranges. This presentation will focus on the Ozone concentrated in the lower stratosphere at to meters. Thermosphere Mesosphere Stratosphere Troposphere Mesopause Stratopause Tropopause 3

Ozone data source : /neumayer_station/observatories/ meteorological_observatory/upper_air_soundings/ozone_soundings/ From this page, use their search function. Type in Ozone Soundings The Alfred Wegener Institute conducts many types of atmospheric and oceanographic research. Ozone monitoring is only one. You will also find links to Arctic research as well 4

2004 Antarctic ozone profile. stratosphere

Day O Ozone profile data 6

7 2012

8 6 Sept 16 Oct

10

Oct 6 Sept 11

6 Sept16 Oct 12

6 Sept16 Oct Austral winter Ozone depletion m profile 13

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2006 Arctic Ozone data 21 March 6 Sept16 Oct 15

16 Lower depletion : Warmer temperatures Weaker polar vortex

O 2 + uv > 2 O 2O + 2 O > 2O 3 2O3 + uv > 3O 2 Both processes absorb ultraviolet radiation (UVB) 17 Once Earth’s atmosphere began to be enriched with oxygen, beginning about 2.2 billion years ago during the Early Proterozoic, the stage was set for the eventual emergence of life on to the land.

18 Factors contributing to Ozone Depletion Halogenated hydrocarbons Chlorofluorocarbons---- CFC’s Methyl Bromide ---- Soil fumigants Fire fighting compound Biomass burning Volcanic eruptions Volatile cleaning compounds Carbon tetra chloride Trichloroethane

How these heavy molecules get to the stratosphere. Antarctica Antarctic winter:Extremely cold air isolated over Antarctica Polar Stratospheric Clouds transport HH on ice crystals Warmer air circulating with the West Wind Drift. Antarctic Polar Vortex S. America Through the mixing which occurs between global convection cells, these compounds are transported to high latitudes. 19

What happens. Chlorofluorocarbons and methyl bromide CCl 2 F 2 CH 3 Br With the onset of the Austral spring and the return of sunlight to the Antarctic region, simplified reactions result in the breakdown of ozone in the lower stratosphere over Antarctica. CCl 2 F 2 + uv > CClF 2 + Cl Cl + O > ClO + O 2 The halogen acts as a catalyst in the destruction of Ozone without the benefit of UV absorption. The residence time for these halogens can be years. Cl and Br are the primary destructive halogens 20 This is a simplified illustration. The link below has the complex chemistry

NASA provides global ozone images. 21

22 Units used in Ozone measurement. Nanobars ( nb ) = millibars Millipascals ( mPa ) = millibars 1.0 mPa = 10 Nb 14 mPa = 140 nb Conversion necessary to compare Arctic and Antarctic ozone pressure Dobson unit DUUsed on ozone mapping images from NASA A Dobson unit (DU) would produce a layer of gas.01mm thick at STP. ie. 300DU = a layer 3.0mm thick 1 DU is equivalent to about.8 nb