Ancient Antarctic ice gives up climate change secrets

12 September 2002

Prevailing theories about climate change have been challenged by new analysis from Australian and French scientists, in research to be published in the international journal Science this week.

The scientists, some of whom work with the Australian Antarctic Division, have discovered new evidence about past climatic events from analysis of an Antarctic ice core, drilled 1.2km deep at Law Dome, in the Australian Antarctic Territory near Casey Station.

Dr Tas van Ommen, one of the authors from the Australian Antarctic Division, said the research would challenge scientists world-wide to find a process that will explain these findings and improve our ability to understand and predict future patterns.

Science will publish a paper on the work this week, which studied the ice core to analyse the sequence of global climate changes triggered during an abrupt change in climate around 14,500 years ago. These changes reflect underlying links between northern and southern hemisphere climates.

Dr van Ommen explained the motivation for their study:

"Since the end of the Ice Age, the climate has been relatively stable, but the rapid changes that we are looking at are a warning that it has not always been this way. The stability of the present climate might actually be quite sensitive to any changes forced upon it."

"Some computer models suggest that the greenhouse effect may cause instability and possible abrupt changes in the future - a compelling reason to learn as much as possible", added Dr van Ommen, who is attached to the Antarctic Co-operative Research Centre at the University of Tasmania.

The 1.2 km-long ice core was drilled over several summer seasons at Law Dome, inland of Australia's Casey Station and records climate information extending back over 80,000 years.

"Law Dome has a much higher snowfall than other ice-core sites and this allows us to date changes very accurately", says Mr Vin Morgan, who led the drilling and analysis program.

Scientists compared Antarctic temperatures with Northern Hemisphere climate during a major shift that occurred around 14,500 years ago.

"If we use the conventional model, we should see changes in Antarctica following those in the north", said Vin Morgan, "but our results show the reverse, with changes in the south occurring first".

Background

The Law Dome ice core drilling project is an Australian project that commenced in December 1987 and continued over several summer seasons, being completed as the drill reached bedrock at about 1200m depth in February 1993. The core was returned to Australia where analysis of this valuable climate record continues.

The Law Dome ice core is one of only a handful of deeper cores in Antarctica. It comes from a location that has much higher snowfall than other deep cores, and was chosen because this would give a very detailed climate record back into the last Ice Age (which ended 10,000 years ago).

Although the project is Australian-led and most of the analyses have been undertaken in Australia, the project has benefited considerably through international cooperative efforts, as in this current research collaboration with French colleagues. Other nations that have participated include Denmark, Japan and the USA.