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Solomon, A.I., Polvani, L.M., Abernathey, R.P., and Smith, K.L. (18-Dec-14)

Observations have revealed systematic changes in the temperature and salinity of the Southern Ocean since 1960. These trends reflect the evolving exchange of heat and momentum between atmosphere and ocean and are, in part, driven by anthropogenic emissions. The key question is: which emissions are most important, greenhouse gases or ozone depleting substances? We answer this question using CESM-WACCM, a comprehensive climate model with interactive stratospheric chemistry, coupled to state-of-the-art land, ocean and sea-ice components. We find that the changes in Southern Ocean temperature South of 60S are primarily due to the presence of a seasonal ozone hole, and between 60S and 40S the trends are driven in equal measure by ozone depletion and all other forcings combined. Furthermore, we demonstrate substantial changes in the model's ocean salinity, and show that these are greatly enhanced by formation of the ozone hole, a fact that has not been previously reported.