Ozone (O3) in the stratosphere filters out ultraviolet radiation that is harmful to biological systems. Certain chemicals that we release into the atmosphere, such as chlorofluorocarbons (CFCs), cause ozone molecules to break apart, depleting the ozone layer.
For monitoring this process in terms of its boundary, ozone levels are measured over mid-latitudes (away from the poles), since that is where most humans and human activity are found. To keep out enough ultraviolet radiation, our goal is to keep the concentration of ozone in the stratosphere at or above .
Ozone (O3) in the stratosphere filters out ultraviolet (UV) light that is harmful to biological systems. We're familiar with UV light causing sunburns; without the ozone "layer" it would be much more intense. It could hurt animals and plants, including food crops, and affect animal behaviour and other aspects of ecosystems.
Some of the novel entities that we've released into the atmosphere, particularly CFCs (chlorofluorocarbons), destroy ozone by breaking the molecules apart. Weather patterns cause these materials to collect near the poles, especially the south pole, and the unusual conditions of Antarctic winter and spring enable these materials to do serious damage to the stratospheric ozone. In the mid-1980's, it was discovered that the ozone over the Antarctic had become so depleted it was called a "hole".
Soon after this discovery, researchers identified the cause, and nations around the world agreed to find ways to stop the release of CFCs and other ozone-harming substances into the atmosphere. The Antarctic ozone "hole" is still there, in part because these substances remain in the atmosphere for a long time, but it is no longer growing. In fact, recent evidence (Reiny 2018, Strahan 2018) suggests it is starting to recover.
Some examples of connections to other Earth-system processes:
Stratospheric ozone depletion is caused by the introduction to the stratosphere of certain novel entities, as discussed in the novel entities process tab. These substances include CFCs, which are used as refrigerants. In this way aerosol loading can affect ozone depletion (Lade et al., 2020).
Because of the harm that UV radiation can do to plants and animals, ozone depletion lets more UV radiation through the atmosphere, impacting biosphere integrity.
Ozone depletion is connected to biogeochemical flows because nitrous oxide is an ozone depleting substance. Main sources of nitrous oxide are from agricultural processes, and energy and industrial applications.
Tropospheric ozone is a greenhouse gas which affects climate change, however as many ozone depleting substances in the stratosphere are greenhouse gases in the troposphere, the relationship of ozone and climate change is complex (Lade et al., 2020). Climate change and the increase of carbon dioxide in the atmosphere cools the stratosphere because more heat is trapped in the lower levels of the atmosphere. The cooling of the stratosphere slows the rate of ozone depleting reactions (Lade et al., 2020).
Examples of STEM curriculum
Gas Laws; Chemical Reactions; Types of Electromagnetic Radiation; Parts of the Atmosphere; Bonding; Molecular Structure; Free-Radical Reactions; Catalytic Processes; Chemical Change