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The Southern Ocean is a key contributor to global climate. It regulates the absorption of CO₂ into the ocean, plays a key role in ocean heat uptake and most likely influenced abrupt climate variability in the past. However, the processes that limit Southern Ocean circulation occur at very fine scales, and thus are difficult to observe and expensive to model. Therefore, less is known about the Southern Ocean than any other ocean basin.

This project will focus on using high-resolution global ocean-sea ice models to better understand the influence of the Southern Ocean on global climate. We will concentrate on the dynamics of small-scale processes, such as eddies, fronts and jets, which cannot be resolved by regular climate models. Our tool of choice will be a suite of models being developed by the COSIMA consortium, running on the National Computational Infrastructure. Recent results from these models has allowed us to determine that westerly winds and ocean eddies in the Southern Ocean have increased in intensity in recent decades, leading to the possibility that upwelling of ancient, carbon-rich water in the Southern Ocean may have increased. However, there remains much to learn about the climatic role of this system, including:

• How does the vertical structure of eddies and jets respond to changes in surface forcing?
• Have ultra-fine scale submesoscale fronts also changed in recent decades?
• How well do ocean models represent the small-scale physics of eddies, fronts and jets?
• How important are mixed layer parameterisations in this region of the ocean?

This project will contribute to the goals of the ARC Centre of Excellence for Climate Extremes.