Tropical and high-latitude influence on Southern Hemisphere extra-tropical circulation (#1029)
Antarctic ozone hole recovery and an increase in the concentration of greenhouse gases are both expected to affect the southern hemisphere climate in several ways. In this study, the ACCESS 1.0 coupled climate model is used to quantify the effects of Antarctic ozone recovery and greenhouse gas increase on Southern hemisphere (SH) circulation patterns and, in particular, on the Southern Annular mode. Previous studies have shown that stratospheric ozone depletion and greenhouse gases both act to intensify the SH westerlies. Antarctic ozone changes affect the high-latitude lower stratosphere whereas greenhouse gases are known to cause amplified warming in the tropical upper troposphere; both of these effects have been linked to changes in SH subtropical jet. However, the mechanism and the contribution of these changes to the intensification of SH westerlies requires better understanding. In this study, we aim to quantify the contributions of the tropics and the high latitudes on SH extratropical circulation. Three different experiments are carried out, one follows the business-as-usual RCP 8.5 forcing, a second follows RCP 8.5 but ozone is kept constant at 2005 levels and a third follows the RCP 8.5 scenario however greenhouse gas forcing is kept constant at 2005 levels. This design is configured to separate out the influence of ozone and greenhouse gases under future climate scenarios. The model runs are ongoing and results will be presented at the conference.