Simulation of Record Arctic Stratospheric Ozone Depletion in 2020

Abstract

In the Arctic winter/spring of 2019/2020, stratospheric temperatures were exceptionally low until early April and the polar vortex was very stable. As a consequence, significant chemical ozone depletion occurred in the Arctic polar vortex in spring 2020. Here, we present simulations using the Chemical Lagrangian Model of the Stratosphere that address the development of chlorine compounds and ozone in the Arctic stratosphere in 2020. The simulation reproduces relevant observations of ozone and chlorine compounds, as shown by comparisons with data from the Microwave Limb Sounder, Atmospheric Chemistry Experiment‐Fourier Transform Spectrometer, balloon‐borne ozone sondes, and the Ozone Monitoring Instrument. Although the concentration of chlorine and bromine compounds in the polar stratosphere has decreased by more than 10% compared to peak values around the year 2000, the meteorological conditions in winter/spring 2019/2020 caused unprecedented ozone depletion. The lowest simulated ozone mixing ratio was about 40 ppbv. Because extremely low ozone mixing ratios were reached in the lower polar stratosphere, chlorine deactivation into HCl occurred as is normally observed in the Antarctic polar vortex. The depletion in partial column ozone in the lower stratosphere (potential temperature from 350 to 600 K, corresponding to about 12–24 km) in the vortex core was calculated to reach 143 Dobson Units, which is more than the ozone loss in 2011 and 2016, the years which —until 2020— had seen the largest Arctic ozone depletion on record.

Exceptional loss in ozone in the Arctic winter/spring of 2019/2020

“…On the other hand, the Antarctic ozone column loss is about twice that of the Arctic (about 150-160 DU) but slightly lower (about 100-120 DU) in warm winters (1988 and 2002) and in early years (e.g. 1979-1985) of ozone loss there (Huck et al, 2005;Tilmes et al, 2006;Kuttippurath et al, 2015). The analyses suggest that even the partial column ozone loss in the Arctic winter of 2020 is about 115 DU at 350-550 K, which is higher than that of the Arctic winter of 2011 and similar to that of the loss found in the Antarctic winters of 1979-1985, 2002, and 2019. Since the ozone loss in the Arctic winter of 2020 is up to the levels of that found in some Antarctic winters, we examined the occurrence of extremely low TCO values using data from OMPS and MERRA-2; the results are presented in Dameris et al, 2021).…”

“…The peak ozone loss in the Antarctic happens at around 500 K, and the loss is severe from 400 to 600 K for 5 months continuously from August to November (Tilmes et al, 2006;Huck et al, 2005;Sonkaew et al, 2013;Kuttippurath et al, 2015;Kirner et al, 2015). In contrast, the cold Arctic winters are normally shorter and maximum ozone loss occurs at around 425-475 K for a period of about 2 months from mid-January to mid-March (e.g.…”

The Arctic Temperature Response to Global and Regional Anthropogenic Sulfate Aerosols

“…Previous studies have also reported high cloud formation in the lower stratosphere (between 50 and 200 hPa) in the Arctic both during the winter and summer seasons (Fadnavis et al, 2019;Cairo and Colavitto 2020). Arctic clouds in the stratosphere in winter (polar stratospheric clouds) occur because of low stratospheric temperatures (e.g., Grooß and Müller, 2021;Tritscher et al, 2021). During summer, the negative anomalies in the high cloud in the upper troposphere (300-150 hPa) may be associated with the transport of sulfate aerosols mostly occurring above the tropopause (Fadnavis et al, 2019).…”

Chemical Evolution of the Exceptional Arctic Stratospheric Winter 2019/2020 Compared to Previous Arctic and Antarctic Winters

“…The quantitative estimation of ozone loss in the same air mass (as opposed to the accumulated loss in different air masses at a given pressure level discussed so far) in the winter 2019/2020 is covered in detail elsewhere (e.g., Feng et al, 2021;Grooß & Müller, 2021;Manney et al, 2020;Wohltmann et al, 2020), and we will only give a short comparison of our results to other studies. The maximum in the simulated ozone loss profile averaged over the vortex obtained with a passive ozone tracer (see Wohltmann et al, 2020) Manney et al (2020) give a value of 2.8 ppm for the MLS match approach and a vortex-averaged descent approach.…”