The Antarctic ozone hole during 2020

• Main Authors: Gerald Nedoluha, Paul J. Fraser, Simon P. Alexander, Sylvia Nichol, Richard Querel, Dan Smale, Stuart I. Henderson, Paul B. Krummel, Matthew B. Tully, Andrew R. Klekociuk
• Format: Article in Journal/Newspaper
• Language: English
• Published: CSIRO Publishing 2022
• Subjects: Antarctica; ‘Black Summer fires’; climate; ozone; ozone hole; ozone hole metrics; Meteorology. Climatology; QC851-999; Environmental sciences; GE1-350; Antarctic; The Antarctic; Arrival Heights; Antarc*
• Online Access: https://doaj.org/article/78e74a46f04d4cd39957f12643f09d77

The Antarctic ozone hole remains the focus of scientific attention because of its importance to the health of the biosphere and its influence on the climate of the southern hemisphere. Here we examine the general characteristics of the 2020 Antarctic ozone hole using a variety of observational and reanalysis data and compare and contrast its behaviour with earlier years. The main feature of the 2020 ozone hole was its relatively large size, and persistence to the beginning of the 2020/2021 summer, with new maximum records being set for the ozone hole daily area and ozone mass deficit during November and December. This was in strong contrast to 2019 when the ozone hole was one of the smallest observed. We show that a key factor in 2020 was the relative stability and strength of the stratospheric polar vortex, which allowed low temperatures in the Antarctic lower stratosphere to enhance ozone depletion reactions in relative isolation from the rest of the global atmosphere. These conditions were associated with relatively weak Rossby wave activity at high southern latitudes that occurred during the strengthening westerly phase of the Quasi Biennial Oscillation as well as the emerging La Niña phase of the El Niño Southern Oscillation. A consequence of the conditions in early summer was the measurement of new maximum values of ultraviolet radiation at Australia’s three Antarctic research stations of Mawson, Davis and Casey. Indications of anomalous chlorine partitioning above Arrival Heights in Antarctica prior to the 2020 winter are provided, which may relate to effects from the 2019/2020 Australian wildfires. We also examine the effect of the downward coupling of the 2020 ozone hole to the climate of the wider southern hemisphere, which showed regional influences on surface temperature and precipitation in common with other strong vortex years.