Past and future changes in the dynamical containment of Antarctic ozone depletion modelled using a chemistry-climate model

Previous analysis has shown that the dynamical properties of the Antarctic vortex provide strong constraints on the area within which chemical ozone depletion can occur [Bodeker et al., 2002]. In particular it was shown that the size of the dynamical vortex had not changed at all over the period 1979 to 1998 while the size of the Antarctic ozone hole (O₃<220 DU) had grown, encroaching towards the size of the larger dynamical vortex. More recent complimentary studies have shown that temperatures close to the vortex edge exhibit strong control over the size of the Antarctic ozone hole [Newman et al., 2004]. These temperatures, which affect both the size of the Antarctic ozone hole and the strength of the polar night jet, will be affected by future greenhouse gas concentrations and the severity of Antarctic ozone depletion itself. Therefore, interactions between stratospheric chemistry and radiation in this collar region of the vortex, and their feedbacks, are likely to influence the rate at which the size of the Antarctic ozone hole will change in the future, and perhaps the containment properties of the vortex. It is important to ensure that current chemistry-climate models (CCMs) used to predict how the global ozone layer will evolve over the coming decades, adequately incorporate these processes. To this end, we have calculated daily meridional profiles (by equivalent latitude) of the meridional impermiability, κ [Bodeker et al., 2002], based on NCEP/NCAR reanalyses, and of total column ozone, based on the NIWA assimilated total column ozone data base [Bodeker et al., 2001], over the period 1979 to 2004. These were then compared with similar meridional profiles calculated using output from a run of the Unified Model with Eulerian Transport and Chemistry (UMETRAC), a three-dimensional CCM. Comparisons over the period 1979 to 2004 are used to verify the extent to which the model can capture the historical encroachment of the area of Antarctic ozone depletion over the area of the dynamical vortex, while model results out to 2019 are used to assess how the interplay of chemistry and changes in the temperature of structure of the stratosphere (driven by changes in ozone and greenhouse gases) will affect the future evolution of the size of the Antarctic ozone hole.

References

Bodeker, G.E., J.C. Scott, K. Kreher, and R.L. McKenzie, Global ozone trends in potential vorticity coordinates using TOMS and GOME intercompared against the Dobson network: 1978-1998, Journal of Geophysical Research, 106 (D19), 23029-23042, 2001.

Bodeker, G.E., H. Struthers, and B.J. Connor, Dynamical containment of Antarctic ozone depletion, Geophysical Research Letters, 29 (7), 10.1029/2001GL014206, 2002.

Newman, P.A., S.R. Kawa, and E.R. Nash, On the size of the Antarctic ozone hole, Geophysical Research Letters, 31, L21104, doi:10.1029/2004GL020596, 2004.