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
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).