Fire and ice

November 10, 2015

Researchers are using ice to chart the history of fires in the Southern Hemisphere.

Fire and ice

A project to chart the history of fires in the Southern Hemisphere during the past 100,000 years is using a surprising natural resource: ice.

The record of bushfires in Australia, South Africa and South America is revealed in tiny particles of soot trapped in deep ice across Antarctica.

Led by Dr Ross Edwards, an Associate Professor in physics and astronomy at the John De Laeter Centre for Isotope Research, the research is being carried out by a Curtin University team that’s collaborating with an international group of scientists to analyse a 750 m-long core drilled from pristine Antarctic ice.

The concentrations of soot in the ice are minute (ranging from 20 parts per trillion to one part per billion) and extremely sensitive equipment is needed to detect them. “It took many years to come up with a method to analyse and detect these tiny particles,” says Edwards.

“Most of the fires on Earth are in the Southern Hemisphere, and the only way to understand the long-term impact of soot on the atmosphere is through Antarctic ice,” he explains.

“Antarctic ice is like the Earth’s hard drive. Up to now we’ve only been able to open a few of its folders, but now we’re starting to see that there is much more information than we thought.”

Antarctica is ideal for studying Southern Hemisphere fires. “It’s the remotest region on Earth, so any particles that get there are really well mixed, giving the background levels. Of course, there are no natural fires there. It’s a remote viewing point,” Edwards says.

Tracking bushfire history could shed light on past ecosystems and increase our understanding of Earth’s climate. Edwards hopes to go all the way back to a period before the El Niño Southern Oscillation phenomenon (which drives the climate in the Southern Hemisphere) became established. He also hopes to quantify the human influence on fires, by looking at ice that formed before people arrived in South America and Australia.

“The problem now is that we are overwhelmed with data and it takes a long time to work through it,” Edwards says.

Ways to work out from which continent the soot has come are still being developed, but Edwards has already noticed that fires were most common when Australia had been through a wet period. High rainfall in the interior of Australia leads to more vegetation growth, which then fuels fires when the dry weather returns.

Next, Edwards wants to analyse a core that covers a million years of data – and he’s already working with national and international collaborators to develop that project.

Clare Pain

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