Indicators of Antarctic ozone depletion: 1979 to 2019

Abstract

Abstract. The National Institute of Water and Atmospheric Research/Bodeker Scientific (NIWA–BS) total column ozone (TCO) database and the associated BS-filled TCO database have been updated to cover the period 1979 to 2019, bringing both to version 3.5.1 (V3.5.1). The BS-filled database builds on the NIWA–BS database by using a machine-learning algorithm to fill spatial and temporal data gaps to provide gap-free TCO fields over Antarctica. These filled TCO fields then provide a more complete picture of wintertime changes in the ozone layer over Antarctica. The BS-filled database has been used to calculate continuous, homogeneous time series of indicators of Antarctic ozone depletion from 1979 to 2019, including (i) daily values of the ozone mass deficit based on TCO below a 220 DU threshold; (ii) daily measures of the area over Antarctica where TCO levels are below 150 DU, below 220 DU, more than 30 % below 1979 to 1981 climatological means, and more than 50 % below 1979 to 1981 climatological means; (iii) the date of disappearance of 150 DU TCO values, 220 DU TCO values, values 30 % or more below 1979 to 1981 climatological means, and values 50 % or more below 1979 to 1981 climatological means, for each year; and (iv) daily minimum TCO values over the range 75 to 90∘ S equivalent latitude. Since both the NIWA–BS and BS-filled databases provide uncertainties on every TCO value, the Antarctic ozone depletion metrics are provided, for the first time, with fully traceable uncertainties. To gain insight into how the vertical distribution of ozone over Antarctica has changed over the past 36 years, ozone concentrations, combined and homogenized from several satellite-based ozone monitoring instruments as well as the global ozonesonde network, were also analysed. A robust attribution to changes in the drivers of long-term secular variability in these metrics has not been performed in this analysis. As a result, statements about the recovery of Antarctic TCO from the effects of ozone-depleting substances cannot be made. That said, there are clear indications of a change in trend in many of the metrics reported on here around the turn of the century, close to when Antarctic stratospheric concentrations of chlorine and bromine peaked.

On Recent Large Antarctic Ozone Holes and Ozone Recovery Metrics

“…( 2018 ) reported significant ozone recovery through a reduction of the areas displaying exceptionally deep loss (e.g., under 175 Dobson Units [DU]) in recent years. Indicators of ozone recovery, such as minimum polar cap mean TCO and stratospheric partial columns, among others, were also reported in Bodeker and Kremser ( 2021 ).…”

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2021

“…The UVI values measured at Marambio were amongst the highest recorded during the last 30 years in Antarctica and are comparable with summertime UVI maxima at subtropical sites such as San Diego (32° N) [11]. Despite the abnormally low stratospheric ozone and high UVI in late spring of 2020, the healing of the Antarctic ozone hole due to the implementation of the Montreal Protocol is still on track, as evidenced by the observed continuing decline in stratospheric ozone depletion during September-the key month for chemical ozone destruction [8]-and the general trend of all metrics quantifying Antarctic ozone depletion pointing towards recovery of the ozone hole [12].…”

Antarctic planetary wave spectrum under different polar vortex conditions in 2019 and 2020 based on total ozone column data

“…A commonly used threshold TOC value to delineate the border of the ozone hole is 220 Dobson Units (DU). The area within this threshold, which is a measure of the ozone hole's size, attains its largest value in the Antarctic region in mid-Septem-ber -mid-October (Bodeker & Kremser, 2021). At this time, its area typically exceeds that of the Antarctic continent.…”