The Australian Antarctic Program's research into past climate (palaeoclimate) aims to:
- reconstruct East Antarctic climate and climate ‘forcings’ (factors that influence climate, such as volcanic eruptions and greenhouse gases) over the past 2000 years
- reconstruct Southern Hemisphere and global climate over the past 2000 years
- improve our understanding of the links between polar climate and Australian climate
- improve our ability to predict long-term variability for climate variables such as regional rainfall and temperature, the Southern Annular Mode and the El Nino Southern Oscillation Index
- develop long-term ice and sediment records covering key periods of climatic variation, particularly the last 1.4 million years
Our two research areas are palaeo records in ice cores, and climate evolution.
Palaeo records in ice cores
As Antarctic snowfall accumulates from year to year, the snow at the surface gets buried and compressed to form solid ice. This ice carries information about the state of the climate when the snow originally fell. By drilling down into this old ice and recovering an ice core, the information can be extracted to help understand past climate.
Climate records in ice cores allow us to identify natural climate variability and climate forcings (such as volcanic eruptions, solar activity and greenhouse gases) and to then assess changes above this natural variability caused by human activities. They also allow us to identify connections between Australian and polar climate and information about past sea-ice and ice-sheet extent.
Our research focuses on developing a high resolution, well-dated climate record from Antarctica over recent millennia. To do this scientists are analysing existing ice cores and recovering new ice cores from suitable areas in East Antarctica where snow accumulation allows for good dating (such as the Aurora Basin and Law Dome).
For about 2.5 million years, ice ages had come and gone in a regular 41,000 year cycle. But about 900,000 years ago something in the Earth’s climate system changed and the cycles switched to an ice age every 100,000 years.
These glacial cycles are linked to small variations in the Earth’s orbit around the sun, which changes the amount of solar radiation reaching the Earth. But the changes in solar radiation are too small to directly produce the large temperature changes needed to move in and out of ice ages. A range of natural amplifying phenomena in the Earth’s climate system must be driving the switch. Scientists need to understand these amplifiers (climate forcings and feedbacks) to better understand the climate system and make realistic predictions of future natural or human-induced changes.
Very old ice cores (more than 1 million years old) could identify the role that carbon dioxide feedback played in the shift in glacial-interglacial cycles. This could help scientists understand whether the current human-driven changes in atmospheric composition, beyond the levels that existed during past interglacials, will drive the Earth System into another semi-stable state (like today) that does not involve glaciation or deglaciation.
There are sites in the Australian Antarctic Territory that could provide such old ice cores. Analysis of such cores, and of existing cores extracted from Law Dome, will allow scientists to study large climate shifts on glacial timescales. Analysis of ocean sediment cores will also complement the ice core record and allow scientists to document the response of biological organisms to climate change.
This research will answer three key questions:
- What changes have occurred in Antarctic and Southern Hemisphere climate on glacial-interglacial timescales?
- What are the climate forcings and feedbacks responsible for these changes?
- What processes link climate variations in the northern and southern hemispheres, especially during periods of abrupt climate change?