New analysis suggests that the unusually large hole in the Arctic's ozone layer last year was caused by record-breaking temperatures in the North Pacific.
Although the huge hole that engulfed almost the entire ozone layer above it closed in spring, there is a possibility it could form more often in the future.
Researchers have used satellite data to create a series simulations that showed high sea surface temperatures in North Pacific can lower Arctic's westerly winds.
These winds can blow through winter and spring, and, according to atmospheric models if they become cold enough for a long enough time, they can cause the formation of polar cloud. Clouds in the stratosphere at the North and South Poles are key ingredients in severe ozone loss.
"The record Arctic ozone losses in spring 2020 indicate that current-day ozone-depleting substances can still cause severe springtime ozone destruction in the Arctic stratosphere," said Yongyun Hu, an ocean and atmospheric scientist at Peking University in China.
"These results indicate that severe ozone losses are likely to occur in near future, as long as North Pacific warm ocean surface temperature anomalies and other dynamical processes remain strong."
We all know that every spring, a huge hole forms in the ozone layer over Antarctica. However, Arctic ozone is more resilient.
The planetary waves between the atmosphere and ocean in the Northern Hemisphere is stronger than those in the Southern Hemisphere. It is because the winter winds in the Northern Hemisphere are too warm to allow polar clouds formation in the stratosphere.
However, when the Northern Pacific surface is warmer than normal, studies in the past have shown that some planetary waves may grow weaker, which can reduce the temperature of stratospheric vortex.
This seems to be what happened in 2020's spring. Researchers noticed a weakening in a planetary wave called "wavenumber-1" as a result of the formation of a hole in the Arctic ozone layer.
The Arctic's unusually cold winds between February 2020 and April 2020 can be attributed to a decrease in wavenumber-1 strength, according to a long-range model.
A hole wouldn't have formed if the wave hadn't stopped.
Hu explains that the Arctic's record Arctic ozone losses in spring 2020 is a sign that current-day ozone-depleting substances can still cause severe springtime Arctic ozone depletion."
"These results indicate that severe ozone losses are likely to occur in near future, as long as North Pacific warm ocean surface temperature anomalies and other dynamical processes remain strong."
These results may also be used to help explain past mysterious ozone losses. For example, in spring 2011, another large hole appeared in the Arctic's ozone layer. This was without any apparent reason. Although it is not yet clear what caused this, the authors believe that warm sea surface temperatures in North Pacific may have also been responsible.
We are unable to say for sure if these spikes in ocean temperature were caused by natural variability or human-caused global heating. However, as the oceans on our planet absorb more heat from climate change, it is possible that the Arctic ozone layer will be prone to more holes.
The study was published in Advances in Atmospheric Sciences.
