Abstract
This study investigates the response of the Southern Ocean sea surface temperature (SST) and Antarctic sea ice to stratospheric ozone recovery, focusing on the timescale and seasonality of the response. The response is quantified by contrasting two 21st century ensemble simulations conducted with the Goddard Earth Observing System Chemistry-Climate Model: one with decreasing ozone depleting substances (ODSs) and the other with fixed 2005 levels of ODSs. In our simulations the response to ozone recovery has large seasonal variations, but it does not show a two-timescale behavior. Ozone recovery causes Southern Ocean SST warming in austral summer and cooling in other seasons. Ozone recovery mitigates Antarctic sea ice decrease in the 21st century in austral spring, fall, and winter. However, the summer Antarctic sea ice extent is not affected by ozone recovery despite strong surface warming, because the warming occurs north of the sea ice edge. The absence of summer sea ice response likely results from the model bias of underestimating summer sea ice climatology. The summer surface warming response is associated with cooling directly below the mixed layer. Temperature tendency budget analysis shows that reduced vertical mixing plays a critical role in driving this vertical dipole temperature response. We also find that the impact of the vertical temperature advection on SST depends not only on changes in upwelling, but also on changes in vertical temperature gradient.
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