The quasi-stationary pattern of the Antarctic total ozone has changed during the last 4 decades, showing an eastward shift in the zonal ozone minimum. In this work, the association between the longitudinal shift of the zonal ozone minimum and changes in meteorological fields in austral spring (September–November) for 1979–2014 is analyzed using ERA-Interim and NCEP–NCAR reanalyses. Regressive, correlative and anomaly composite analyses are applied to reanalysis data. Patterns of the Southern Annular Mode and quasi-stationary zonal waves 1 and 3 in the meteorological fields show relationships with interannual variability in the longitude of the zonal ozone minimum. On decadal timescales, consistent longitudinal shifts of the zonal ozone minimum and zonal wave 3 pattern in the middle-troposphere temperature at the southern midlatitudes are shown. Attribution runs of the chemistry–climate version of the Australian Community Climate and Earth System Simulator (ACCESS-CCM) model suggest that long-term shifts of the zonal ozone minimum are separately contributed by changes in ozone-depleting substances and greenhouse gases. As is known, Antarctic ozone depletion in spring is strongly projected on the Southern Annular Mode in summer and impacts summertime surface climate across the Southern Hemisphere. The results of this study suggest that changes in zonal ozone asymmetry accompanying ozone depletion could be associated with regional climate changes in the Southern Hemisphere in spring.
The distribution of total column ozone over Antarctica is significantly non-uniform during austral spring, i.e., in September–November (Wirth, 1993; Malanca et al., 2005; Grytsai et al., 2007a; Agosta and Canziani, 2010, 2011). This has particularly been the case since the early 1980s due to the presence of ozone depletion associated with the ozone hole (Chubachi, 1984; Farman et al., 1985; Chubachi and Kajiwara, 1986; Stolarski et al., 1986; Solomon, 1999). The total ozone distribution predominantly characterizes the stratosphere layer, where a sharp ozone maximum is usually observed at altitudes of 15–25 km (Chubachi, 1984; Solomon et al., 2005). Therefore, strong variations in the total ozone distribution are due mainly to stratospheric chemistry and dynamics (Wirth, 1993; Gabriel et al., 2011). The ozone hole is located inside the polar stratospheric vortex, which is a cyclonic structure that impedes mixing between high-latitude and midlatitude air masses (Brasseur et al., 1997). The polar vortex is under the influence of large-scale planetary waves, which disturb the vortex edge region (Wirth, 1993; Quintanar and Mechoso, 1995) and the vortex location relative to the pole (Waugh and Randel, 1999). The scale of the waves in the zonal direction is typically characterized by zonal wave number, which is equal to the ratio of the corresponding great circle circumference at a given latitude to the wave length (Hirota and Hirooka, 1984; Hio and Yoden, 2004). The stationary part of the wave structure in the Southern Hemisphere (SH) spring stratosphere is mainly determined by a planetary wave with zonal number 1 (Hartmann et al., 1984; Quintanar and Mechoso, 1995; Ialongo et al., 2012), i.e., wave 1. The role of planetary waves was especially important in the unusual SH stratospheric warming in 2002 (Varotsos, 2002; Allen et al., 2003; Hoppel et al., 2003). Both wave-1 and wave-2 activity during austral winter and spring caused strong deceleration and warming of the stratospheric polar vortex, its anomalous splitting and ozone hole breakup in September 2002 (Varotsos, 2002; Nishii and Nakamura, 2004; Newman and Nash, 2005; Peters et al., 2007; Grassi et al., 2008; Peters and Vargin, 2015).
In spring, the ozone distribution in the Antarctic region is asymmetrical with a maximum in the Australian longitudinal sector and a minimum in the Atlantic longitudes (Grytsai et al., 2005; Agosta and Canziani, 2011). Previous studies have revealed the tendency of the Antarctic polar vortex to exhibit an eastward shift in orientation (Huth and Canziani, 2003), in the ozone minimum location (Grytsai et al., 2005; Malanca et al., 2005; Grytsai et al., 2007a, b; Agosta and Canziani, 2010, 2011; Grytsai, 2011; Hassler et al., 2011) and in the phase of wave 1 in stratospheric temperature (Lin et al., 2010). This eastward shift has been described as possibly connected with a change in tropospheric stationary waves (Grytsai et al., 2007a), tropospheric jet structure (Hio and Hirota, 2002; Agosta and Canziani, 2011) and its strengthening (Wang et al., 2013), and stratospheric ozone and volcanic aerosol concentration (Lin et al., 2010). The quasi-stationary wave (QSW) activity increases typically in austral spring (Randel, 1988), and its enhancement leads to larger vortex asymmetry, a decrease in ozone hole area and net stratospheric ozone loss. It has been noted that the decreased (increased) asymmetry in the ozone distribution is associated with the eastward (westward) phase shift of the zonal minimum from both observations at the southern high latitudes (Grytsai et al., 2008; Agosta and Canziani, 2011) and climate model simulations for the northern high latitudes (Gabriel et al., 2007).
It has been revealed that the Antarctic ozone depletion in spring influences the trend in the Southern Annular Mode (SAM) in summer towards the high-index polarity that leads to a range of significant summertime surface climate changes (Thompson et al., 2011). Recent studies have indicated that a stabilization of the spring ozone depletion has occurred from the mid- or late 1990s (Grytsai, 2011; Salby et al., 2011; Kuttippurath et al., 2013; Dameris and Godin-Beekmann, 2014; Solomon et al., 2016). This stabilization relates to the total area of the ozone hole, minimum total ozone values, ozone mass deficit and duration of the ozone hole season. Chemistry–climate models have displayed a general minimum in Antarctic ozone during 2000–2005 (Siddaway et al., 2013) and slow ozone recovery in the 21st century (Dameris and Godin-Beekmann, 2014). In turn, ozone recovery is expected to continue to impact the SH surface climate (Thompson et al., 2011). This work is focused on the recent tendencies in the zonal asymmetry of the Antarctic total ozone in austral spring and their possible relations to the SH atmospheric anomalies.
In this study, gridded monthly mean satellite measurements of the total ozone
column (TOC) are used to estimate tendencies in the Antarctic
quasi-stationary pattern. We restrict our analysis to the
September–November (SON) period (austral spring), when the zonal asymmetry in total
column ozone is most pronounced. We use measurements from the Total Ozone
Mapping Spectrometer (TOMS)
The original data are available with 1
Figure 1b shows long-term changes in the zonal TOC asymmetry at
65
Regression, correlation and composite analyses were used to relate the QSW
TOC minimum (QSW
First, we compare the long-term changes in total ozone (Fig. 2a) and the
longitudinal position of the quasi-stationary ozone minimum (Fig. 2b) at
65
Cubic polynomial fits are shown by thick curves in Fig. 2. These fits are
included to highlight the long-term variations in each of the time series and
are not done in consideration of any particular underlying physical process.
In the early 2000s, the decadal tendencies indicated by the slope of the
polynomial fit changed sign both in ozone (from decreasing levels to
increasing levels, Fig. 2a) and in ozone minimum longitudes (from eastward
shift to westward shift, Fig. 2b). Comparison of polynomials from
Map of longitudinal locations of zonal QSW maximum (red) and zonal
QSW minimum (blue) at seven latitudes between 50 and 80
On comparing Fig. 2a and b, there appears to be some consistency in the
epoch of inflexion in the tendencies of both the column amount and the
maximum eastward longitude shift of the zonal TOC minimum (around 2000). The
eastward shift in the QSW structure over Antarctica has been described
previously (Huth and Canziani, 2003; Grytsai et al., 2005, 2007a; Malanca et
al., 2005; Agosta and Canziani, 2010, 2011; Lin et al., 2010; Grytsai, 2011;
Hassler et al., 2011). Eastward shift speeds of about
15–20
Long-term tendencies in the QSW minimum/maximum longitudes at the seven
latitudes between 50 and 80
Ozone mass deficit and position of the quasi-stationary minimum in
the ozone distribution at 60
Longitude of MSR TOC ozone minimum (QSW
The two curves in Fig. 4 illustrate the similarity in the interannual
variations and decadal changes of the QSW
Simultaneous negative deviations are observed in the years of large (1988)
and major (2002) stratospheric warmings (vertical lines in Fig. 4). Both
anomalous events in the SH stratosphere were associated with enhanced
planetary wave activity (Varotsos, 2003a; Allen et al., 2003; Baldwin et al.,
2003; Grytsai et al., 2008). As seen from Fig. 4, relatively small ozone mass
deficits (high total ozone levels) correspond to the westward shift of the
QSW
The results of Figs. 2–4 show that the eastward shift in the TOC zonal minimum longitude in the Antarctic region occurred during the 1980s–1990s and was accompanied by rapid and intense ozone loss. This decadal tendency appears to have stopped in the early 2000s and became of possibly reverse sign later in the 2000s and 2010s. Generally, the behavior of the zonal TOC minimum in Figs. 2b and 3 follows the decadal change in the severity of the ozone hole due to international controls on ozone-depleting substances (ODSs; Salby et al., 2011; Solomon et al., 2016), with increasing depletion of the Antarctic ozone in the 1980s and 1990s, and its leveling off and the possible start of recovery in the 2000s–2010s (Siddaway et al., 2013). Significant decadal changes in the SH polar ozone are coupled with the stratospheric thermal regime (e.g., Crook et al., 2008); because of the zonal asymmetry in the ozone heating, they impact planetary wave propagation (Albers and Nathan, 2012) and regional climate change in both the troposphere and the stratosphere (Gillett et al., 2009; Waugh et al., 2009). Couplings between changes in the QSW structure in Antarctic total column ozone and in atmospheric variables are analyzed below.
Regression coefficient of the TOC QSW minimum longitude against
ERA-Interim climatological anomalies of
To determine the most reliable mean tendencies, we have created a time series
for the QSW
We next consider the regression between the time series of Fig. 5 and SON
average climatological anomalies of ERA-Interim meteorological variables. We
first produce monthly climatological anomalies for each gridded monthly
average variable at the native horizontal resolution by subtracting the
associated long-term monthly mean (over 1979–2014 for ERA-Interim and
1981–2010 for NCEP–NCAR). We then produce averages of the anomalies in grid
boxes of 10
The RC distributions as in Fig. 6a and b but for RC between the
QSW
The RC distribution in Fig. 6a shows an annular pattern that is similar to a
classic Southern Annular Mode pattern in SH climate variability, with
pressure or geopotential height anomalies of opposite sign at the middle and
high latitudes (Thompson and Wallace, 2000). Negative (positive) regression
coefficients at the high (middle) SH latitudes indicate that the QSW
A positive polarity of the annular mode is accompanied by strengthening of
the subpolar westerlies in the SH troposphere and stratosphere and cooling of
polar cap regions (Thompson and Wallace, 2000). The RC maximum around
60
Zonally asymmetric components of the SH circulation, which are most marked in
the austral winter and spring (Mo and Higgins, 1998; Fogt et al., 2012a), are
also presented in Fig. 6. Three positive RC anomalies at the SH midlatitudes
(grid boxes 1, 2 and 3 in Fig. 6a) demonstrate the presence of a QSW3
structure. The highest negative RC anomaly between grid boxes 2 and 3 is
spatially close to the subpolar negative anomaly at grid box 4 and is
possibly combined effect of QSW1 and QSW3 (Mo and Higgins, 1998). A
significant negative RC anomaly near West Antarctica (grid box 4 in Fig. 6a
with an explained variance of 35 %) is spatially coincident with the “pole
of variability” in the Amundsen–Bellingshausen Sea low (ABSL) region (Fogt
et al., 2012b, and references therein; Turner et al., 2013; Raphael et al.,
2016). The midlatitude QSW3 patterns extended to sub-Antarctic latitudes are
seen also in the RC distribution for
Anomaly composites with respect to the mean climatology for
1979–2014 of ERA-Interim surface meteorological variables for (left) the
lower 20th percentile of mean SON QSW
The presence of the QSW3 structure in Fig. 6b introduces regional anomalies
into the surface temperature distribution. The patterns suggest that, when the
QSW
Zonal asymmetry in the SH troposphere circulation is closely coupled with the
Pacific–South American (PSA) mode (Mo and Higgins, 1998). The PSA pattern in
the RC distribution in Fig. 6 is of insignificant intensity, whereas
pronounced meridional wave trains are seen in the Indian–Australian sector and
Atlantic–South American sector (
All patterns of Fig. 6 are reproduced in correlations with the same variables
using the NCEP–NCAR reanalysis data (Supplement 3, Fig. S2), confirming the
reliability of the results. In general, Fig. 6 and Supplement Fig. S2 show
that interannual variations of the SON QSW
Anomaly composites for the lower 20th percentile of the QSW
It generally is seen from Fig. 7 that transition from the westernmost
longitudes (left column) to the easternmost longitudes (right column) is
accompanied by the reversal in the sign of the anomalies. The western
(eastern) longitudes correspond to negative (positive) zonal wind anomaly
around 60
Note that the SP anomaly composites show the QSW3-like structure at the SH
midlatitudes, which is more intense and shifted to the east in the case of
the easternmost QSW
The SST anomaly composites demonstrate a relationship of the extreme
QSW
The SAM, QSW3 and SST patterns seen from Fig. 7 are fully reproduced with the
same variables of the NCEP–NCAR reanalysis (Supplement 3, Fig. S3). This is
evidence that the QSW
Regression of the QSW
As in Fig. 7 but for ERA-Interim meteorological variables at
200 hPa:
As noted from Fig. 6c, the regression coefficient distribution for
It is important to note the eastward shift of the anomalies between the
westernmost and easternmost QSW
In connection between the changes in the QSW structure in total ozone and
atmospheric parameters, the clear eastward shift in the QSW3 patterns at the
SH midlatitudes (Fig. 7b and e and Fig. 9c and g) is of particular interest.
This tendency is analyzed in more detail using the correlative relationships
between the QSW
The linear correlation between time series of the QSW
Longitude–height cross section of the correlation between the
QSW
A clear separation between the QSW1 pattern above the tropopause (peak values
of
The strong correlation in the stratosphere (between 200 and 20 hPa, or 12
and 26 km, respectively, in Fig. 10), firstly, demonstrates close coupling
between the QSW
An important feature of the QSW3 pattern in the troposphere is its
altitudinal location: the three correlation maxima are located predominantly
in the middle troposphere, and their peak values are at about 500 hPa
(Fig. 10). The correlation is significantly lower at 1000 hPa, which could
explain relatively weak SST anomalies at the SH midlatitudes in Fig. 7c and
f. Therefore, the mid-tropospheric pressure level of 500 hPa was chosen to
search for possible decadal changes in the
correlations between the anomalies in air temperature and the QSW
It is seen that the significant positive correlation peaks (black contours in
Fig. 11) shift eastward between 1979–1992 and 1990–2003 by 30–60
Correlation between the QSW
A significant negative anomaly of the correlation coefficient
(
It can be summarized that common decadal tendencies in total ozone (Fig. 2a),
QSW minimum location in the total ozone (Fig. 2b), QSW1 pattern in the lower
stratosphere (Fig. 9a and e), and QSW3 pattern in the troposphere (Figs. 7b, e
and 11) and lower stratosphere (Fig. 9c and g) exist. On an interannual
timescale, the SAM- and QSW1
In general, the results of Sect. 3 show that the QSW
The evolution of zonal asymmetry in Antarctic total ozone during 1979–2014 with respect to the changes in the meteorological variables in the SH troposphere and lower stratosphere has been presented in the previous section. Regressive, correlative and anomaly composite analyses show that longitudinal shift of the quasi-stationary zonal TOC minimum has a close relationship with changes in the TOC level itself and with the SAM, QSW and SST patterns. Here we discuss our results in the context of the published literature, including analysis of chemistry–climate model attribution simulations.
Analysis covers the austral spring months September–November and the changes
in the seasonally averaged longitude of the QSW
The results of this work show that, on interannual and decadal timescales,
the QSW
Generally, planetary wave activity contributes significantly to the
interannual variability of the ozone hole size, depth and duration (Kodera
and Yamazaki, 1989; Allen et al., 2003; Varotsos, 2002, 2004; Ialongo et al.,
2012). However, wave activity did not undergo such significant decadal
decrease to cause the decadal tendency in ozone depletion and, therefore,
cannot be a contributing factor to the systematic QSW
Thus, interaction between the planetary waves and ozone could underlay the observed evolution of the asymmetric ozone hole: (i) zonal asymmetry in Antarctic ozone is initially induced by the QSW propagating from the troposphere and (ii) significant change in the TOC level occurs within asymmetric ozone hole, causing change in zonally asymmetric ozone heating that, (iii) through the feedback processes, could result in the QSW structure modification.
As is known, positive SAM polarity is associated with enhanced
westerlies around Antarctica and decreased surface pressure and air
temperature in the polar region (Thompson and Wallace, 2000). The eastward
shift of the QSW minimum in total ozone is accompanied by similar indications
of the positive SAM polarity: strengthening of zonal wind around Antarctica
(
Our results do not give information on the direction of the
“QSW
Nevertheless, such a feedback possibility cannot be fully excluded, at least
on interannual timescales. As shown by Son et al. (2013), stratospheric
ozone concentration in September is strongly correlated with the SAM index in
October, with
Thus, the appearance of the SAM-like patterns in our relationships (Figs. 6, 7 and 9) can be interpreted in two ways that are influenced by interannual variability: first, the strength and pattern of the circulation in the spring SH troposphere can conceivably play a significant role in determining the location of the QSW structure in the stratosphere, and, second, the QSW structure in the stratosphere can potentially provide a downward influence on the tropospheric circulation. This could mean that assumed feedback processes of the asymmetric ozone loss (noted in Sect. 4.1 with respect to the QSW structure in the stratosphere) may spread into the troposphere in the springtime. The results by Son et al. (2013) demonstrate such a possibility using an ozone index for the SH polar area. However, ozone variability in the SH polar area is typically combined with ozone asymmetry variability (Fig. 2), and the combined effect of the ozone itself and ozone asymmetry could affect the interannual variability of SH surface climate in spring noted in Son et al. (2013).
Unlike the SAM pattern, the atmospheric QSW3 pattern in the midlatitude
troposphere demonstrates long-term changes (Fig. 11) consistent with both the
ozone loss tendency (Fig. 2a and 4, black curve) and the QSW
Those ridge locations correspond to the correlation maxima in Fig. 11a and b for
the periods 1979–1992 and 1984–1997, respectively, which cover the
last 2 decades of the time interval in Raphael (2004). The largest eastward
shift of the QSW3 pattern occurred between the 1980s and 1990s (Fig. 11a and
c, respectively). The central ridge that is located on average near
180
Note that in the years of maximum ozone hole area (easternmost QSW
As seen from Fig. 11a and Fig. S6a in the Supplement, both reanalyses show
negative correlation anomalies over Australia and East Antarctica in the
first time interval 1979–1992 (pre-ozone-hole and first ozone hole years,
westernmost QSW
The QSW1 structure in the lower stratosphere covers the middle and high SH
latitudes and, in the two reanalyses, shows consistent eastward shift
between the westernmost and easternmost locations of the QSW
Overall, the long-term shifts in the QSW3 centers and the QSW1 pattern show a
temporal evolution that is qualitatively similar to decadal changes in both
ozone depletion (Figs. 2a and 4, black curve) and the shift of
QSW
Simulated influence of the greenhouse gases (GHGs) increase on the eastward phase shift in the stratospheric stationary waves (Wang et al., 2013) indicates the possible contribution of the first mechanism. This model simulation links eastward phase shift to the strengthening of the subtropical jet driven by greenhouse gas forcing via sea surface warming. Induced eastward shift is projected by the model to the end of the 21st century (Wang et al., 2013).
Agosta and Canziani (2011) have shown that there are significant interactions/coupling between the ozone layer, the troposphere and the stratosphere during the austral spring, which can be traced by the phase changes in TOC and QSW1 in the stratosphere. Such changes and troposphere–stratosphere interactions, by Agosta and Canziani (2011), are linked to both the upward and downward propagation of quasi-stationary wave anomalies. Taking into account the results by Son et al. (2013) and the results of our work, the second of the mentioned mechanisms that suggests contribution of ozone change may be more effective in the recent decades.
A clear difference between the SST anomaly patterns for the westernmost and
easternmost QSW
The difference between the two regions of the tropical Pacific in their coupling
with the QSW structure in the SH stratosphere was noted by Lin et al. (2012).
By Lin et al. (2012), a westward QSW phase shift is seen for negative SST
anomalies (La Niña events) in the eastern Pacific, and an eastward shift is
seen for warm SST anomalies in the central Pacific. The results of Fig. 7c
and Fig. S3c in the Supplement show a similar association between the
westernmost QSW
In the individual years, a large westward phase shift in the QSW
In the case of 2002 this is counter to the expectation from Lin et al. (2012) based on the prevailing positive central Pacific SST anomaly (McPhaden, 2004) and disagrees with Fig. 7f and Fig. S3f in the Supplement, since a negative SST anomaly exists in this region.
Note that Fig. 7f and Fig. S3f in the Supplement show a significant negative SST anomaly in the
South Pacific and positive SST anomalies in the western tropical Pacific and
in the Atlantic. Similarly to the PSA mode in the Pacific sector, a
poleward-propagating Rossby wave train could be driven by the Atlantic SST anomalies
(e.g., Li et al., 2014). Combined influences of the wave train could result
in other phase shift direction in the SH stratosphere planetary waves than
from positive anomaly in the central tropical Pacific in Lin et al. (2012).
In particular, the SH extratropical Rossby wave activity that propagated into
the stratosphere in the spring of 2002 (Nishii and Nakamura, 2004; Peters et
al., 2007) could also have contributed to the observed QSW
In general, the results of Sect. 3 reveal indications of the connection between changes in zonal asymmetry in Antarctic total ozone and changes in zonally symmetric (SAM) and zonally asymmetric (QSW1 and QSW3) patterns in the SH circulation, as well as in the SST patterns. These results are, in general, in agreement with known evidence of coupling between Antarctic ozone and SAM (Thompson and Wallace, 2000; Waugh et al., 2009; Thompson et al., 2011), the SH QSW structure (Agosta and Canziani, 2011; Wang et al., 2013) and the SSTs (Kodera and Yamazaki, 1989; Grassi et al., 2008). These couplings allow us to identify the SH regions where climate changes in spring are accompanied by ozone asymmetry changes.
We now turn to chemistry–climate model simulations to further examine long-term changes in the QSW pattern. Here we consider simulations for the Chemistry-Climate Model Initiative (CCMI) (Eyring et al., 2013) produced by the chemistry–climate version of the Australian Community Climate and Earth System Simulator (ACCESS-CCM; Stone, 2015; Stone et al., 2016).
Specifically, we examine a future projection simulation which includes all forcings (REF-C2 scenario) and two sensitivity simulations, one with fixed ODSs (SEN-C2-fODSs scenario) and another with GHGs (SEN-C2-fGHGs scenario), which are described in detail by Stone (2015). The REF-C2 simulation covers the period 1960–2100 and includes evolving concentrations of GHGs and ODSs; the SEN-C2-fODS and SEN-C2-fGHG simulations are similar to REF-C2 except that ODSs and GHGs, respectively, are separately fixed at 1960 levels.
The ACCESS-CCM simulations favorably reproduce general characteristics of
ozone depletion and stratospheric stationary waves compared with observations
and various similar models (Stone, 2015; Stone et al., 2016). In Fig. S7a of
the Supplement we show the longitude–height cross section of the correlation between temperature and
QSW
Stone (2015) has investigated the long-term shift in the Southern Hemisphere
TOC patterns in spring and summer in relation to GHG and ODS changes, where
the phase of the wave-1 component of the TOC (obtained from a zonal Fourier
decomposition) was analyzed in a similar manner to Grytsai et al. (2007a). By
regressing the wave phase against measures of GHG and ODS forcing, Stone (2015)
finds that ODS forcing explains a significant fraction of the
long-term variability in the wave-1 longitude compared with GHG in spring at
50 and 60
While Stone (2015) only examined the wave-1 phase, we show in Fig. 12
long-term trends in QSW
Variation of QSW
Overall we conclude from the simulations that ozone depletion is providing a
strong influence on the QSW
We have examined the variability of the minimum in the quasi-stationary
pattern in total column ozone in spring at high southern latitudes using
observations and model simulations. Our main results are as follows:
In interannual variations, the longitude of the QSW minimum in total
ozone is in close association with the SAM index, the QSW1 On the decadal timescale, consistency between the longitudinal shifts
of the QSW minimum in total ozone (Fig. 2b) and the QSW3 pattern in the
mid-tropospheric temperature (Fig. 11) has been shown. The SST anomalies over the Pacific and Atlantic basins contribute to the
variability in the QSW minimum location. Based on the results from our attribution experiments with the ACCESS-CCM
climate model, increased levels of ODSs and GHGs both tend to shift the
QSW
Regression, correlation, anomaly composite and model analyses show that longitudinal variability
at the location of the quasi-stationary zonal TOC minimum has a close relationship
with variability in the TOC level itself, in the SAM
Chemistry–climate models predict that the Antarctic ozone will return to the
1980 level in the second half of the 21st century, in the 2050–2070 period
(Siddaway et al., 2013; Dameris and Godin-Beekmann, 2014; Solomon et al.,
2016), and the period of ozone recovery will take approximately 3 times longer
than did the growth epoch of the ozone hole (approximately 2000–2060 and
1980s–1990s, respectively). From our simulations, recovery in ozone levels
during the next 2–3 decades will allow the QSW
Based on ideas developed by Gennadi Milinevsky, Asen Grytsai performed data development and provided analysis with contribution from Gennadi Milinevsky, Andrew Klekociuk, Oleksandr Evtushevsky and Kane Stone. Gennadi Milinevsky, Andrew Klekociuk and Oleksandr Evtushevsky provided additional explanation of the outputs. Asen Grytsai prepared the manuscript with contributions from Gennadi Milinevsky, Andrew Klekociuk and Oleksandr Evtushevsky.
The authors declare that they have no conflict of interest.
Authors thank the two anonymous referees for their comments and helpful
suggestions. TOMS and OMI daily total ozone data were provided by the Ozone
Processing Team, NASA Goddard Space Flight Center, USA, from their Web site
at