Talk by David Munday

Southern Ocean Circulation & Global Climate: The Role of Mesoscale Eddies

Abstract
The Southern Ocean and the Antarctic Circumpolar Current are typically viewed as being of global significance to the Earth’s climate. In particular, isopycnals are steeply sloped across the Southern Ocean, giving a strong connection between the surface and deep ocean, and many key water masses are ventilated and/or created there. Furthermore, the presence of open latitude circles within the latitude band of Drake Passage is often taken as having a profound influence upon the existence of the Antarctic Circumpolar Current.

Recent advances suggest that the circulation of the Southern Ocean is primarily a balance between low latitude wind forcing, globally integrated diapycnal mixing, and deep water formation (in both hemispheres). Eddy processes play an essential role, with modelling studies demonstrating that coarse resolution ocean models, with or without parameterised eddies, and eddy-resolving ocean models respond in fundamentally different ways to changes in forcing. Understanding these differences, and the dynamics behind them, is of great interest to the past and future evolution of the Southern Ocean and global climate.

By drawing upon a range of idealised, eddy-permitting numerical ocean models, the dynamic response of the mesoscale eddy field to changes in, for example, wind stress and diapycnal mixing, can be examined and understood in a computationally feasible way. These experiments will be used to look at how and why the residual overturning of the Southern Ocean and the volume transport of the Antarctic Circumpolar Current respond to forcing changes. With the addition of a simple biogeochemical model, the role that mesoscale eddies play in setting atmospheric carbon dioxide concentration will also be examined.