Southern Ocean Circulation

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The Southern Ocean encircles Antarctica, dividing the polar regions from the warm tropical ocean. It is home to the world's strongest ocean current, the Antarctic Circumpolar Current, and is the primary location where ancient, deep ocean water is upwelled to the surface.  The Southern Ocean controls the natural release of CO₂ from the oceans, helps to absorb anthropogenic CO₂ and modulates transport of heat towards the Antarctic ice cap.
The CFP group is conducting research into the dynamics of the Southern Ocean and its role in climate using high resolution ocean and climate modelling, idealised numerical modelling and laboratory studies. Existing research programs include:

Antarctic dense water formation:
Antarctic dense water forms around the Antarctic continental shelf when sea ice growth removes freshwater from the ocean, leaving behind cold, salty and dense water that can sink to the abyss. This process forms Antarctic Bottom Water, the deepest branch of the global overturning circulation, and helps regulate ocean heat, carbon and oxygen storage. Our research investigates the dynamics controlling where and how dense water forms, why Antarctic Bottom Water has been changing in recent decades, and how future warming, sea ice change and ice shelf melt may alter this key part of the climate system.

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Warm water supply towards Antarctica:
Relatively warm Circumpolar Deep Water sits below the cold surface waters of the Southern Ocean and provides a major source of heat to the Antarctic continental shelf and ice shelves. Our research examines why the Southern Ocean is warming and how heat is transported towards Antarctica. For example, we use high-resolution ocean models to understand the roles of winds, eddies, bathymetry, shelf-slope exchange and ice-ocean feedbacks in controlling heat pathways to the Antarctic margins.

Improving models of the Southern Ocean:
Reliable projections of Antarctic and Southern Ocean change require models that can represent the coupled interactions between ocean circulation, sea ice and ice shelves. A major focus of our research is improving high-resolution ocean and climate models so they better capture Antarctic dense water formation, warm water access to the continental shelf, and ice shelf–ocean feedbacks. Working with the Consortium for Ocean and Sea Ice Modelling in Australia (COSIMA) and Australia’s climate simulator (ACCESS-NRI), we are helping develop and test Australia’s next-generation ocean modelling capability, including ACCESS-OM3 configurations that can represent ice shelf cavities and dynamic meltwater input.

Using observations in new ways to understand Southern Ocean change:
The Southern Ocean is remote, harsh and difficult to observe, particularly in winter and beneath sea ice. Our research develops new ways to use existing and emerging observations to understand how this region is changing. This includes combining satellite measurements, autonomous ocean observations, ship-based data and ocean models to infer processes that cannot be measured directly, such as dense water overflows and changes in circulation beneath sea ice.

Impact of Antarctic change on Southern Hemisphere climate: Antarctic ice loss and declining sea ice are adding freshwater to the Southern Ocean, altering ocean stratification, circulation and climate. These changes can influence not only the Antarctic margins, but also broader Southern Hemisphere climate, including temperature over Australia. Our research investigates how Antarctic meltwater and sea ice change affect the ocean and atmosphere, and how these processes should be represented in climate projections used to assess future climate risks.

Southern Ocean heat and carbon uptake:
The Southern Ocean plays a central role in slowing climate change by absorbing a large fraction of the excess heat and carbon taken up by the global ocean. This uptake is controlled by the unique circulation of the Southern Ocean, where surface waters are transformed and advected into the ocean interior, allowing heat and carbon to be stored for centuries. Our research investigates the physical processes that control Southern Ocean heat and carbon uptake, how these processes are changing, and what this means for future warming, carbon storage and regional sea level rise around Australia.

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Ocean circulation impact on ecosystems and invasive species: Ocean currents shape Southern Ocean ecosystems by transporting drifting organisms across vast distances. These pathways influence species connectivity and the potential for non-native species to reach and colonise Antarctic environments. Our research investigates how Southern Ocean circulation connects ecosystems, how climate change may alter these pathways, and what this means for biodiversity, ecosystem resilience and the future risk of biological invasions.

Eddies in the Southern Ocean: 
The Southern Ocean is filled with energetic eddies: swirling features tens of kilometres wide that strongly influence ocean circulation and climate. Eddies help regulate the Antarctic Circumpolar Current, shape the overturning circulation, and transport heat, carbon and nutrients across ocean fronts. Our research investigates the dynamics that generate and sustain Southern Ocean eddies, how they respond to changing winds and buoyancy forcing, and how their effects can be better represented in climate models.

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