Climate Processes and Change

Large ice shelves such as the Amery Ice Shelf interact with the ocean and contribute to the formation of water masses important to global ocean circulation. Photo: MODIS AQUA satellite

Climate Processes and Change investigates the role of Antarctica and the Southern Ocean in the global climate system. Its main focus is to address uncertainties identified in the Fourth Assessment Report (2007) of the Intergovernmental Panel on Climate Change (IPCC). This report highlighted the lack of climate data from the Southern Ocean, the sea ice zone and Antarctica in general. It also noted a need for greater understanding of the role the region may have in slowing the rate of climate change and of the future behaviour of the ice sheet and its contribution to sea level rise.

Research in this theme will contribute to the IPCCs update on the state of climate change through the Fifth Assessment Report in 2013–14 and to other assessments that may follow. It will also feed into Australia’s national framework for climate change science to manage climate change impacts and develop adaptation and mitigation strategies for climate change.

The theme is organised into four research streams:

• The Antarctic ice sheet
• Oceans and marine ice in the Southern Hemisphere
• Atmospheric processes and change
• Antarctic palaeoclimate

The Southern Ocean overturning circulation carries layers of warm near-surface water and cold deep water in alternate directions resulting in a net transport of heat. Photo: CSIRO

Research questions to be investigated through these streams include:

• What are the processes controlling ice loss from the ice sheet in both East and West Antarctica, and how will these influence future sea level rise?
• Is the ‘global overturning circulation’ (circulation of the world’s oceans) likely to change with future warming, and what impact will this have?
• How much heat and carbon will the Southern Ocean be able to take up and store in the future?
• Is the development of better climate system models inhibited by poor understanding of certain high latitude (polar) atmospheric processes?
• What can the record of past climates tell us about current and future climate change?

Research in the theme will:

• improve the ability to detect and attribute change in the Antarctic region;
• improve the performance of earth system models through a better representation of Southern Ocean and Antarctic processes within the models;
• enhance our ability to adapt to the impact of global change through a better understanding of changes in ocean carbon cycles, sea level rise, regional climate variability and physical and biological changes in the Southern Ocean.

This research feeds into:

• IPCC Fifth Assessment Report
• Australia’s National Framework for Climate Change Science
• United Nations Framework Convention on Climate Change (Kyoto Protocol)
• World Climate Research Program – Climate and Cryosphere project
• International Partnerships in Ice Core Sciences (IPICS)
• SCAR Antarctica and the global climate system

Theme Leader: Dr Tas van Ommen

What have we learnt so far?

This large buoy is part of a mooring being deployed in the Southern Ocean. Photo: Aaron Spurr

Climate Processes and Change research will build on more than 50 years of climate research in Antarctica. Much of our current understanding of Antarctic climate processes has been documented in the 2008 report Australia’s Contribution to Antarctic Climate Science.

Our research has confirmed that the Southern Ocean is warming more rapidly than the global ocean average and that dense (cold and salty) bottom water formed near Antarctica has freshened in some locations and warmed in others.

Bottom water is a major driver of the global overturning circulation of the ocean. The processes that lead to the formation of bottom water involve complex interactions between ocean circulation, winds blowing off the ice sheet, and sea ice formation. These have been better understood through in situ (‘in position’ or on location) measurements and mooring deployments, satellite remote sensing, and numerical modelling.

For the past decade, Australia has been one of a few nations undertaking major field research programs on Antarctic sea ice characteristics and processes and their potential response to climate change. Our marine science program has also made major advances in understanding ocean carbon uptake and its link to the ‘biological pump’ (biological processes that transport carbon from the surface to the ocean’s depths) and the interaction of the ocean with ice beneath ice shelves.

Sorsdal Glacier Photo: Barbara Wienecke

Extensive land-based surveys of East Antarctica have contributed to our understanding of the ice sheet ‘mass budget’ (gain and loss of ice from the Antarctic continent) and ‘dynamics’ (the motion within the ice sheet, such as glacier flow). These surveys include the multi-national airborne survey ‘ICECAP’, which is using ice-penetrating radar and other geophysical systems to map characteristics of the ice and underlying bedrock over vast areas of Antarctica. Results from this work will be used to produce accurate models to predict future changes to the ice sheets.

Ice cores hold records of atmospheric gases that are used in most climate and atmospheric chemistry model simulations of past centuries. Ice cores from coastal regions of the Australian Antarctic Territory have revealed the carbon cycle history and past sea ice extent. More recently they have been used to identify links between sea surface temperature changes and the circulation of the Southern and Indian oceans; and links between Antarctic snowfall and rainfall patterns in southern Australia.

An Automatic Weather Station at Casey Photo: Tod Iolovski

Australian automatic weather station networks have defined the surface climate of large parts of the East Antarctic ice sheet. They have also monitored changes to temperatures and winds in the higher atmosphere, and their coupling with processes in the troposphere (0–15 km above Earth). Our Antarctic observations of the higher atmosphere have also:

• revealed connections between ozone concentrations and the size and intensity of the polar vortex
• characterised the winds and waves in the mesosphere (50–95 km above Earth)
• identified changes in atmospheric tides over the last three decades
• used the dust trail of a meteorite to verify atmospheric transport models

This past research provides a solid foundation for addressing current uncertainties. Until 2014 much of our glaciological work will be conducted through the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC) research programs.

Our research involves the collation and analysis of existing data as well as the collection of new field data and remotely-sensed satellite data. Data will be integrated with national and international observing systems, including the Southern Ocean Observing System and the Integrated Marine Observing System.