5 Ozone Depletion in Stratosphere Ozone Protects earth from UV radiationPart of the electromagnetic spectrum with wavelengths just shorter than visible lightThe Ozone Layer is an implicit global ecosystem service
12 Time for Math!Suppose that 200 CFC molecules entered the stratosphere. If one chlorine atom destroys 100,000 ozone molecules, how many ozone molecules would be destroyed by 200 CFC molecules?If the same number of CFC molecules entered the stratosphere each year for the next 30 years how many total ozone molecules would be destroyed?
13 Time for Math 2.0x107 O3molecules/yr 6.0x108 O3 molecules over 30 years
14 Ozone Depletion in Stratosphere Ozone thinning/holeFirst identified in 1985 over AntarcticaCaused byhuman- produced bromine and chlorine containing chemicalsEx: CFCs
16 Hole over Antarctica Requires Two Conditions (1)Sunlight just returning to polar region(2)Circumpolar vortex- a mass of cold air that circulates around the southern polar regionIsolates it from the warmer air in the rest of the planetPolar stratospheric clouds formEnables Cl and Br to destroy ozone
18 Why an Ozone Hole?Polar winter causes a build-up of ice crystals mixed with nitrogen oxide (NO)Ideal surface for Cl2/Br2Sun reappears in Spring & UV breaks the Cl2 down again catalyzing ozone destructionThe “hole” is present in the dark of the polar winter (because it is not being made)
19 Increased UV-so What! marine phytoplankton (food webs) amphibian populationsskin cancer (melanoma)Cataractsdamage to crops & forests
20 Recovery of Ozone Layer Montreal Protocol (1987)Reduction of CFCsStarted using HCFCs (greenhouse gas)Satellite pictures in 2000 indicated that ozone layer was recoveringFull recovery will not occur until 2050
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