By Irina Petropavlovskikh, CIRES and GML scientist
The ozone hole over Antarctica occurs annually and is a result of the industrial production in the 1950-1970s of ozone-depleting substances. These substances were used as refrigerants or in fire extinguishers. Unfortunately, once in the stratosphere, these chemicals destroyed the ozone layer which protects life on Earth. The Montreal Protocol, signed by all nations in 1986, developed a protection plan for the ozone layer and banned production of ozone-depleting substances. Currently, the ozone layer is on the mend, thanks to the Montreal Protocol and its amendments.
This year is showing signs of the seasonal ozone hole beginning to develop over Antarctica. During the winter, polar stratospheric clouds (or PSC) that contain ice particles form. Their surfaces contain chemicals that enhance ozone destruction in the stratosphere. This process is activated when the sun comes back after the six-month polar night— around September 21 over the South Pole.
The top right plot shows the timeline of ozone observations taken in Antarctica. The data are collected by ozonesonde instruments launched on meteorological balloons. The balloons ascend into the stratosphere to measure ozone levels, and the instruments send signals to the station through the radio waves.
The most severe reduction in ozone levels typically occurs between 14 and 21 km (maximum of ozone and altitude of polar stratospheric clouds). The decline in the ozone layer starts in September and continues through December (see the blue symbols showing data collected in 2023, the red symbols showing 2024 data and the gray envelope showing the spread of historical data from 1986 through 2021). As is evident in the plot, the decline in ozone started at the beginning of September and is coming close to the minimum values typically observed at the beginning of October.
The plot at the bottom shows the timeline of temperatures measured at the 14-21 km altitude. Note that PSCs form when temperatures drop below -83 degrees C. The figure on the right shows the location of the “ozone hole” (i.e., the area of reduced ozone shown in blue) over Antarctica. These data come from satellites (i.e., NOAA/NASA JPSS OMPS instrument).
These plots show the vertical distribution of ozone (left panel) and temperatures (right panel) captured by balloon instruments launched on September 18, 2024 from NOAA’s South Pole station. The red line shows the ozone levels between the surface and 30 km. Although the ozone levels are reduced between 14-21 km in comparison to the levels observed in August (not shown), they are within the expected range of ozone variability (i.e., the gray envelope) that suggests that the ozone layer is not declining. In fact, some evidence exists that it is showing signs of recovery.
