New research has identified a lesser-known form of ozone playing an important role in warming the Southern Ocean – one of Earth’s main cooling systems.
Ozone is a gas composed of three oxygen atoms. Many studies have described ozone in the stratosphere and its role in protecting people from the sun’s harmful ultraviolet rays. Closer to the ground, in the troposphere, ozone is harmful to humans.
New research from UC Riverside scientists reveals that this lower-level ozone is adding a lot of heat to the Southern Ocean — more than scientists previously realized.
This discovery has just been published in the journal Natural climate change.
“People haven’t paid much attention in the past to ground-level ozone in terms of ocean heat absorption. According to our models, they should be,” said Wei Liu, a climatologist at the ‘UCR and lead author of the new study.
The oceans remove most of the carbon and heat that enters the atmosphere when humans burn fossil fuels. The Southern Ocean, also known as the Antarctic Ocean, collects a third of all excess carbon in the global atmosphere and around 75% of the excess heat collected by the world’s oceans.
It is important to understand this heating in order to be able to control it. Increased ocean warming contributes to well-documented problems of sea level rise.
To further this understanding, Liu and an international team of scientists explored climate model simulations with changes in ozone levels between 1955 and 2000. These model simulations isolated stratospheric and tropospheric ozone from other influences on climates. Southern Ocean temperatures, allowing them to see how each factor contributes.
While stratospheric and tropospheric ozone contribute to the warming of the Southern Ocean, the team found that the latter contributes more.
“Historically, about a third of ocean warming is attributable to ozone. Of that third, about 40% comes from the stratosphere and the rest from the troposphere,” Liu said.
In the 1980s, growing concern about a pollution-generated hole in the protective upper ozone layer led to the Montreal Protocol. A historic environmental agreement, it codified the will of the 198 members of the United Nations to regulate the chemicals that generate this hole.
Although satellite images still show low levels of stratospheric ozone over Antarctica, there have been improvements.
“Since the protocol was ratified, ozone depletion has recovered somewhat in the stratosphere, and climate models predict that it will continue to gradually recover,” Liu said.
Liu thinks the results of this study are helpful in showing where people can make other changes that will improve the environment.
Volatile organic compounds, or VOCs, from products like pesticides, tobacco smoke, and automobiles are gases that form the building blocks of ground-level ozone. The same goes for nitrogen oxides produced by combustion or carbon monoxide from furnaces, gas stoves and automobile exhaust. Many of these products can be modified to produce fewer VOCs.
“Ground-level ozone is an air pollutant,” Liu said. “If we reduce our production from that, we get the double benefit of less air pollution and most likely, less warming of the Southern Ocean as well.”
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Material provided by University of California – Riverside. Original written by Jules Bernstein. Note: Content may be edited for style and length.