First time in 44 years. Scientists discovered an unusual anomaly over Antarctica and gave an explanation for it
In July 2024, record warming occurred in the Antarctic stratosphere, disrupting the polar vortex and affecting global weather. This rare event, which occurred for the first time in 44 years of observations, differs significantly from the frequent warming in the Arctic.
Experts say the unprecedented warming of the stratosphere over Antarctica could affect weather phenomena and ozone levels in the Southern Hemisphere. And this is no longer a good signal, writes SciTechDaily.
According to scientists, July temperatures in the stratosphere above Antarctica are usually around minus 80 degrees Celsius. However, on July 7, the temperature there jumped 15°C, setting a record for the warmest July temperatures seen in the stratosphere in the Antarctic region. Then on July 22, the temperature dropped and then rose 17°C on August 5.
These sudden stratospheric warming events surprised NASA Goddard Space Flight Center atmospheric scientists Lawrence Coy and Paul Newman. "The July event was the earliest stratospheric warming ever observed in the entire 44-year history of NASA's Global Modeling and Assimilation Office (GMAO)," Coy said.
Impact on the polar vortex
Scientists say westerly winds in the stratosphere swirl around the South Pole in winter, moving at about 300 kilometers per hour, forming what is known as the polar vortex. But sometimes something happens to disrupt this symmetrical circumpolar flow, causing the winds to weaken and change the shape of the flow. Instead of overtaking the South Pole, the polar vortex becomes elongated and the winds weaken. And this weakening of the winds leads to a significant warming of the stratosphere over Antarctica.
Potential vorticity.
Source: NASA
Comparison of events in the Southern and Northern Hemispheres
Unlike the Arctic, where sudden stratospheric warming events occur about once a year, the polar vortex in the Southern Hemisphere is usually much less active. "Sudden warming occurs in Antarctica once every five years or so, much less frequently than in the Arctic," Lawrence Coy said.
The reason for this is likely because the Northern Hemisphere has more topography that can disrupt wind flow in the troposphere, the layer of air closest to the ground. These large-scale tropospheric weather systems move up into the stratosphere and disrupt the polar vortex, the scientist says.
July also saw unusual weather in the Antarctic troposphere. Temperatures 4 C above average covered large parts of the Antarctic continent. And for the Antarctic region as a whole, July 1991 was the fifth warmest July on record.
For the Arctic, July was the warmest July on record.
Source: NASA
Impacts on weather and ozone concentrations
Scientists also continue to investigate the origin of surface perturbations that lead to stratospheric disturbance. "Changes in sea surface temperature and sea ice can disrupt these large-scale weather systems in the troposphere that propagate upward. But understanding why these systems evolve is very hard," Paul Newman added.
Scientists have shown that the unexpected warming in the stratosphere is linked to an increase in ozone concentrations over Antarctica. The stratospheric ozone layer protects life on Earth by absorbing ultraviolet light, which damages the DNA of plants, animals and humans and can lead to skin cancer.
Experts note that the change in circulation with warming in the stratosphere attracts ozone from other latitudes to the polar region. So far in 2024, the ozone hole over the Southern Hemisphere was smaller than usual.
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