Publication Date:
2014-04-29
Description:
[1] During the late 20 th century, Antarctic ozone depletion and increasing greenhouse gases (GHGs) conspired to generate conspicuous atmospheric circulation trends in the Southern Hemisphere (SH), contributing to a poleward intensification of the oceanic super-gyre circulation. Forcing of Antarctic ozone depletion dominated the observed trends during the depletion period (1979-2005), but Antarctic ozone is projected to recover by the middle of the 21 st century. The recovery provides a mechanism for offsetting the impact from increasing GHG emissions. To what extent will the recovery of ozone mitigate SH atmosphere and ocean circulation trends expected from increasing GHGs? We examine climate model outputs from the Representative Concentration Pathways 4.5 and 8.5 (RCP4.5 and RCP8.5, respectively) emission scenario experiments, submitted to the Coupled Model Intercomparison Project phase 5. Both scenarios are subject to the effect of ozone recovery. We show that during the recovery period (2006-2045), there is little trend of the poleward shift of the super-gyre circulation under either RCP scenario in austral summer, due to the dominance of ozone recovery. Further, under RCP8.5 the trend in winter, a season in which ozone recovery has little impact, is greater (more poleward) than in summer, opposite to the seasonality of trends during the depletion period. Under RCP4.5, with the contribution from ozone recovery, the summer poleward shift is projected to stabilise into the post-recovery decades, whereas under RCP8.5, the summer poleward shift accelerates in the post-recovery period, presenting a vastly different ocean circulation future.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
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