Abstract

Key features of the Southern Ocean (such as the Antarctic Circumpolar Current and meridional overturning circulation) show centennial oscillations in many of the CMIP6 models. These oscillations can be linked to changes in convection and formation of dense water which go on to influence the state of the whole Southern Ocean. This seminar will briefly discuss the range of behaviour seen in the pre-industrial control runs for these models, before examining the response of Southern Ocean centennial variability to climate forcing. The response to a range of CMIP6 warming scenarios will be examined, demonstrating a cessation of the oscillations and a significant reduction in the production of dense water, even in weaker forcing scenarios. These changes will then be examined further through novel idealised forcing simulations with gradual 1% annual increases in CO2 as well as abrupt warming and cooling scenarios. There will also be a discussion of how these oscillations affect our future projections and how we should consider the uncertainty in these projections.