The Ozone Shield

Our clear guardian

What are we supposed to be learning?

SEV3. Students will describe stability and change in ecosystems. Describe interconnections between abiotic and biotic

factors, including normal cyclic fluctuations and changes associated with climatic change (i.e. ice ages).

• SEV5 e. Describe the effects and potential implications of pollution and resource depletion on the environment at the local and global levels (e.g. air and water pollution, solid waste disposal, depletion of the stratospheric ozone, global warming, and land uses).

Some Key Words

Go to your Vocabulary sheet and quickly fill out the know, seen and no idea section for the following words. Ozone Layer Chloroflorocarbons (CFCs Ozone Hole Polar Stratospheric clouds

What are you getting out of this?

Why is the threat to the ozone layer still continuing?

Explain how chlorofluorocarbons damage the ozone layer.

Ozone?

The Ozone layer– Section of the

stratosphere where O3 is highly concentrated

– Absorb most UV from the sun

UV damages genetic info

Acts as our plants sunscreen

What is harming O3?

Chloroflorocarbons (CFC)– Do not react at the Earth’s Surface

So thought were not harmful and were used everywhere in the 1970 and most of the 1980s

In the stratosphere• Absorbs energy from UV which breaks the CFCs apart The Cl is released and takes an O from the O3. The

ClO then breaks another O3 molecule releasing the Cl, and the cycle starts over again.

• Estimated that 1 Cl can destroy 100,000 O3 molecules

Oops… We’ve got a hole

• A thinning of the stratospheric ozone that occurs over the poles during the spring

The ozone layer above Antarctica started thinning in 1979, but not discovered until 1985

1985 50%-98% thinner than should be

Also decreasing in the Artic

This shows the thickness of the Earth's ozone layer on January 27th from 1982 to 2012. This atmospheric layer protects Earth from dangerous levels of solar ultraviolet radiation. The thickness is measured in Dobson units, in this image, smaller amounts of overhead ozone are shown in blue, while larger amounts are shown in orange and yellow. These ozone measurements begin with the Nimbus 7 satellite; continue with the Earth Probe Total Ozone Mapping Spectrometer (EP TOMS); the Ozone Monitoring Instrument (OMI) aboard the Aura satellite; and the most recent, the Ozone Mapper Profiler Suite (OMPS) aboard the satellite Suomi National Polar-orbiting Partnership (NPP). Suomi NPP is a partnership between NASA, NOAA and the Department of Defense. Credit: NASA/NOAA

How did it happen?

• Polar stratospheric clouds formed during winter by the polar vortex Composed of water and nitric acid

– Cl2 is formed on them from CFCs Spring returning

Sunlight comes and splits the Cl2 into Cl

– Roughly 70% can be destroyed in the spring Causes thinning

Can we transfer it?

Ground level ozone We call it smog

Unfortunately, O3 is very chemically reactive and will not make through the troposphere to reach the stratosphere And we do not have the technology to pump it up

there.

What is the affect of the thinning?

More UV passes through since we are using a lower SPF – Damages DNA causing mutation

• Susceptible to skin cancer

Kill off phytoplankton Disrupts aquatic food chains

Interfere with photosynthesis Kill egg of amphibians

So, what can we do?

Montreal Protocol 1987: Limits the amount of CFCs produced

Copenhagen, Denmark 1992: eliminate most CFCs by 1995 USA ban all harmful substances by 2000

• Will remain active in the stratosphere for 60-120yrs.