Oceans and marine ice in the Southern Hemisphere

Autonomous Underwater Vehicles (AUVs) such as this one being deployed in the Southern Ocean, can map the underside of sea ice using an upward looking sonar.
Autonomous Underwater Vehicles (AUVs) such as this can map the underside of sea ice using an upward looking sonar. (Photo: Wendy Pyper)
Part of an ocean mooring being deployed in the Southern Ocean.

This stream is investigating the extent of large-scale physical, biological and biogeochemical (nutrient) change occurring in the Southern Ocean and marine ice environment. (This environment includes sea ice, ice shelves and icebergs.) A better understanding of these changes will allow scientists to define which changes can be attributed to human activity and which are caused by natural variability. This information will be included in models used by the Intergovernmental Panel on Climate Change (IPCC).

The stream is divided into four research areas:

Stream Implementation Plan

Sea ice interactions with the climate system and ecosystems

Sea ice changes affect both biological production and climate ‘feedbacks’. Biological production includes the growth of algae or krill - changes in which affect organisms higher up the food chain, such as whales and penguins. Climate feedbacks amplify or diminish the effects of climate change caused by climate ‘forcings’ (such as greenhouse gases which warm the Earth). As the Earth warms, sea ice melts, opening up dark ocean channels which absorb more sunlight, causing more melting.

Understanding the interactions between sea ice, the surrounding ocean and the atmosphere is critical for accurate climate projections and understanding future ecosystem changes.

Research in this stream investigates:

  • How is the Antarctic sea ice environment changing on regional scales?
  • What is the impact of environmental changes on primary production and ecosystem dynamics in the Southern Ocean?

Scientists are studying sea ice extent, thickness, concentration, drift and snow thickness above the ice using a range of remote sensing technologies (such as satellites and Argo floats) and on-ice field measurements in all seasons.

Products resulting from this research will include maps of regional sea ice thickness and models for improved weather forecasting and climate studies.

Southern Ocean processes, variability and change

The circulation of the Southern Ocean influences climate, sea level, nutrient cycles and biological productivity at regional and global scales. A change in the circulation of the Southern Ocean is expected to have large and widespread effects, including a reduced ability of the ocean to absorb atmospheric carbon dioxide. However, a lack of observations makes it difficult to document and interpret patterns of change.

Research in this stream investigates:

  • How and why are the Southern Ocean circulation and water properties changing?
  • What is the impact of circulation changes on other parts of the climate system?

Scientists are studying eddies, air-sea-ice interactions, water mass formation, the structure and variability of the Antarctic Circumpolar Current and mixing between the Southern Ocean and lower latitude waters. They are also conducting sustained observation of Southern Ocean circulation patterns using remote sensing technology (such as satellites), ship-based measurements and ocean moorings.

If scientists can replicate current conditions and reproduce patterns of past oceanic change (through modelling) as a result of this work, they will be better able to project future change.

Ice-ocean interaction and the Southern Ocean freshwater budget

Changes to the freshwater balance of the Southern Ocean could affect the strength of the global overturning circulation. This circulation transports heat around the world’s oceans, which means it has a strong influence on global and regional climates. Increased freshwater in the Southern Ocean (due to ice sheet melt, ice shelf collapse and sea ice melt) could slow the overturning circulation, driving an abrupt change in climate.

Research in this stream investigates:

  • How will a warming ocean affect floating ice shelves, ice tongues and sea ice around Antarctica?
  • How will changes in ice melt and other processes affect ocean stability and the overturning circulation?

Scientists are using remote sensing technologies (from satellites, ships and aircraft), autonomous underwater vehicles (AUVs), ocean moorings, borehole measurements through ice shelves (such as on the Amery ice shelf) and other field measurements, to collect data through all seasons. The data will be used in climate and ocean models.

Southern Ocean biogeochemical processes in the climate system

The Southern Ocean absorbs about one sixth of our current annual emissions of carbon dioxide (CO2). This uptake will not continue at current rates if climate change reduces the rate of the global overturning circulation which moves atmospheric CO2 into the deep ocean. Changes in biological processes will also affect CO2 uptake and supply of the trace nutrient iron – which is important for phytoplankton (microscopic marine algae) growth. Reduced production by phytoplankton means reduced atmospheric CO2 uptake.

Assessing the ability of the Southern Ocean to continue contributing to the control of atmospheric CO2 levels is a major uncertainty in assessing future global carbon budgets.

The transfer of other greenhouse gases between the ocean and atmosphere is also poorly understood, including oxygen, methane from sub-glacial and ice shelf environments, and dimethyl sulphide from phytoplankton and bacterial communities.

This research stream investigates:

  • How do Southern Ocean biochemical and ecosystem processes feed back to the climate system?
  • How will changes to these processes affect the rate of CO2 uptake by the ocean?

Scientists are undertaking continuous monitoring of greenhouse gases over the Southern Ocean and observations of CO2 concentrations in seawater using automated systems such as buoys, floats and gliders with biogeochemical sensors.

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This page was last updated 2015-07-16.