The atmospheric Ozone has undergone distinct changes during the second half of the twentieth century. The effect of these changes on ocean heat uptake has been unclear.
A new study by the University of Reading suggests that Ozone may be weakening one of the Earth’s most important cooling mechanisms. Scientists revealed that the changes to ozone levels in both stratosphere and troposphere contributed to Southern Ocean interior warming.
It is responsible for almost a third of the ocean warming bordening Antarctica in the second half of the 20th century. Deep and rapid warming in the Southern Ocean affects its role as one of the main areas to absorb excess heat as it warms.
Dr. Michaela Hegglin, an Associate Professor in atmospheric chemistry and one of the study’s authors, said: “Ozone close to Earth’s surface is harmful to people and the environment, but this study reveals it also has a big impact on the ocean’s ability to absorb excess heat from the atmosphere.”
“These findings are an eye-opener and hammer home the importance of regulating air pollution to prevent increased ozone levels and rising global temperatures.”
Using models, scientists simulated changes in ozone levels in the upper and lower atmosphere between 1955 and 2000. They isolated them from other influences and increased the currently poor understanding of their impact on the Southern Ocean heat uptake.
Decrease in Ozone in the upper atmosphere and increase in the lower atmosphere lead to the warming seen in the upper 2km of the ocean waters in the high latitudes by overall greenhouse gas increases.
Increased Ozone in the lower atmosphere caused 60% of the overall Ozone. It causes warming seen in the Southern Ocean over the period studied.
Hegglin said, “This was surprising because tropospheric ozone increases are mainly thought of as a climate forcing in the Northern hemisphere since that is where the main pollution occurs.”
“We have known that ozone depletion high in the atmosphere has affected surface climate in the Southern Hemisphere. Our research has shown that ozone increases in the lower atmosphere due to air pollution, which occurs primarily in the Northern Hemisphere and ‘leaks’ into the Southern Hemisphere, is a serious problem.”
“There is hope to find solutions, and the success of the Montreal Protocol at cutting CFC use shows that international action is possible to prevent damage to the planet.”
- Liu, W., Hegglin, M.I., Checa-Garcia, R. et al. Stratospheric ozone depletion, and tropospheric ozone increases drive Southern Ocean interior warming. Nat. Clim. Chang. (2022). DOI: 10.1038/s41558-022-01320-w