• Copernicus Atmosphere Monitoring Service (CAMS) reveals unusually small ozone hole closed much earlier than in previous years

    photo:ECMWF Copernicus Atmosphere Monitoring Service (CAMS)

    The smallest Antarctic ozone hole to appear in 35 years made an unusually early disappearance, according to scientists from the Copernicus Atmosphere Monitoring Service (CAMS) who have been monitoring its activity since August. CAMS is implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Union.

    The ozone hole forms annually over Antarctica during southern spring. This year it was smaller than average and has now virtually disappeared, according to the CAMS data. Most years, the ozone hole starts to appear in August, reaching a maximum size in October before finally closing again in late November to December. Its early closure at the beginning of November is unusual.

    CAMS scientists noticed that the 2019 ozone hole did not grow as rapidly during late August than in previous years. “A sudden stratospheric warming over Antarctica led to a less stable and warmer polar vortex than usual, resulting in reduced ozone depletion,” explains CAMS Senior Scientist Antje Inness. This made the 2019 ozone hole one of the smallest since the mid-1980s and resulted in an unusually short ozone hole season.

    photo:ECMWF Copernicus Atmosphere Monitoring Service (CAMS);desc:Timeline of Southern Hemisphere ozone hole area in million km² in different years.

    “The facts that the 2019 ozone hole has been exceptionally small and that it closed early are no indication that the ozone layer is recovering faster than expected. It simply illustrates the very large variability of ozone holes from one year to another. The healing of the ozone layer will still take several decades and the international monitoring efforts of ozone and ODS play a crucial role in making sure that we keep on the right track,” comments Vincent-Henri Peuch, Head of the Copernicus Atmosphere Monitoring Service (CAMS).

    The ozone layer protects all life on Earth from harmful solar ultraviolet (UV) radiation. In the late 20th century, human emissions of Ozone Depleting Substances (ODS), such as Chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFC), adversely affected the ozone layer, resulting in annual ozone depletion events (“holes”) over Polar regions.

    CAMS monitors and forecasts ozone hole activity by combining measurements from satellite with a numerical model to provide quality-assured information about the state of the ozone layer - in a similar way to weather forecasts. Thereby, CAMS contributes to international efforts to preserve the ozone layer by continually monitoring and delivering high quality data about its current state.

    photo:ECMWF Copernicus Atmosphere Monitoring Service (CAMS);desc:Total column ozone analysis (in Dobson Units) from CAMS on 5 November 2019 (left) and 5-day forecast for the same day (right) showing how well CAMS predicted the ozone hole closure.

    The ozone hole first appeared decades ago, caused by harmful man-made emissions into the atmosphere of chemicals arising from aerosols, refrigerants, pesticides and solvents. However, the 1987 Montreal Protocol has been signed by 196 states and the European Union, within which the main ozone-depleting chemicals were phased out. This worldwide action has led to the gradual repair of the ozone layer and ozone values are expected to return to pre-1980s levels by 2060.

    More information and a 3D animation of the current status of the ozone hole is available on the CAMS website.

    How the Antarctic ozone hole is formed

    Chlorine and bromine-containing substances accumulate within the polar vortex where they remain chemically inactive in the darkness. Temperatures in the vortex can fall to below -78 degrees Celsius and Polar stratospheric clouds can form, which play an important part in the chemical reactions. As the sun rises over the pole, chemically-active chlorine and bromine atoms are released in the vortex and rapidly destroy ozone molecules, causing the hole to form.

    In 2019, the polar vortex was unusually warm and was also weaker than normal allowing more mixing with ozone-rich air from outside the vortex. These two effects limited the extent of ozone destruction during September and October 2019 over Antarctica.

    photo:ECMWF Copernicus Atmosphere Monitoring Service (CAMS);desc:Monthly mean total column ozone anomaly for October 2019 (left), monthly mean total column ozone for October 2019 (centre) and October ozone climatology (right) showing how anomalously high ozone values over the South Pole were in October 2019. Ozone columns are given in Dobson Units and the climatology was calculated as mean over the years 2003-2018 from the CAMS reanalysis of atmospheric composition.

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