The Unprecedented Ozone Loss in the Arctic Winter and Spring of 2010/2011 and 2019/2020

Abstract

Polar ozone depletion has been a major environmental threat for humanity since the late 1980s. The 2011 Arctic winter caught much global attention because of the amount of ozone loss (2.3–3.4 ppmv at 450–475 K potential temperature), and a similar loss was also observed in the 2020 winter (2.5–3.5 ppmv at 400–500 K). Since the difference between the winter of 2010/11 and 2019/20 in terms of ozone loss is small, we investigate the change in terms of polar processing in these years, as that would help future projections of ozone recovery in polar regions. The ozone loss estimated by different methods (passive tracer and vortex descent) shows the highest loss in April in both years 2011 and 2020, but the peak ozone loss altitude was different. The overall ozone loss was more extensive in the lower stratosphere in 2020, but a relatively large loss occurred at higher altitudes in 2011. Prolonged chlorine activation was evident in 2020, longer than that in 2011, which also enhanced loss in the lower stratosphere in 2020. The situation in 2020 resulted in very small values of column ozone, which were below 220 DU for more than 3 weeks, and a near-complete ozone loss (93%) at certain altitudes in the lower stratosphere. The ozone loss in 2020 was similar to that in the Antarctic and was triggered by the presence of a strong and stable polar vortex with zonal winds of constant velocity (40–45 ms–1) and temperature conditions favoring large areas of polar stratospheric clouds (PSCs) (10 million km2) for most of the winter. The relatively lower values of momentum flux suggest that the tropospheric forcing was lower in 2020. Therefore, both winters had less disturbed and long-lasting polar vortices allowing lower temperatures, large areas of PSCs, and longer periods of severe chlorine activation, which in turn led to the record-breaking ozone loss of the levels found in the Antarctic vortex for some days.

Technical note: Northern midlatitude baseline ozone – long-term changes and the COVID-19 impact

“…As Steinbrecht et al (2021) note, the largest Arctic ozone depletion event on record occurred in the spring of 2020. That depletion was more significant than past events, particularly at lower altitudes (13-18 km), as illustrated in Wohltmann et al ( 2020), Manney et al (2020) and Ardra et al (2022). Thus in comparing 2011 and 2020, as was done by Steinbrecht et al (2021), the reduction in tropospheric mean ozone due to a diminished stratospheric influx was likely smaller in 2011.…”

“…Additionally, stratosphere-to-troposphere exchange (STE) of ozone may also have played an important role (Polvani et al, 2018;Griffiths et al, 2020;Abalos et al, 2020). The Arctic ozone depletion in 2020 was the largest observed to date (Wohltmann et al, 2020;Weber et al, 2021) and was especially pronounced in the lower stratosphere (Ardra et al, 2022). This depletion likely reduced the STE of ozone coincident with, but independent of, the reduction of precursor emissions due to COVID-19.…”

Record Low Arctic Stratospheric Ozone in Spring 2020: Measurements of Ground-Based Differential Optical Absorption Spectroscopy in Ny-Ålesund during 2017–2021

“…The most severe Arctic ozone depletion lasted for nearly a month, from March to April 2020 [19]. Between mid-February and late March 2020, the persistence of unusually faint wave activities in the Arctic led to an abnormally persistent and cold vortex [20][21][22]. A prolonged cold vortex in the spring of 2020 accelerated the chemical depletion of ozone while hindering ozone transport from outside the vortex [23][24][25].…”

The impact of dehydration and extremely low HCl values in the Antarctic stratospheric vortex in mid-winter on ozone loss in spring

“…2019; Wohltmann et al, 2020;Dameris et al, 2021;Grooß and Müller, 2021;von der Gathen et al, 2021;Ardra et al, 2022).…”