Newsroom staff
8 December 2014:
A new model reconstructing Antarctica's ice sheet evolution over the past 25,000 years has been created thanks to a University of Canberra geologist's research.
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Assistant professor in earth systems Duanne White's work on the paleo-glacial evidence of change in the region was instrumental in informing a new simulation built by a team of scientists from the Antarctic Research Centre.
Recently published in the prestigious journal Nature Communications, the model provides the most accurate simulation of how rapidly the continent has melted in the past.
Dr White, who has worked closely with the team led by University of Wellington's Nick Golledge, explained that the West Antarctic sheet is already contributing to a rise in the sea level, and that irreversible collapse of that sector of the ice sheet may be irreversible.
"We know very little about how Antarctica will respond to climate change in the future, but it's something we need to figure out fast because Antarctica's ice sheets are likely to be the main driver of the sea level rise in the future."
Dr Golledge's study showed that when the ice sheets began to melt, the ocean around Antarctica became layered, or stratified, and the warm water at the bottom of these layers causes the ice sheet to melt even faster. This happened around 14,000 years ago, with the model suggesting Antarctica produced a global sea level rise of nearly three metres over just a few centuries.
Current oceanographic observations around Antarctica show that the ocean is once again becoming more layered, so the ice sheet could begin to collapse more quickly than before.
"20 years ago we couldn't understand what drove the change we saw in the ice sheet in the past," the University's Institute for Applied Ecology researcher said. "But this new model is one of the first tools that can let us go back and reliably tell what happened in the past. That means it would be more accurate at making projections for the future too."
To accurately map how the ice sheets in Antarctica have shifted over tens of thousands of years, Dr White used a technique known as cosmogenic dating to analyse the rocks and sediment that were once covered in ice.
Cosmogenic dating involves analysing the amount of isotopes found in the rocks and sediment to figure out how long they'd been exposed to cosmic radiation after the ice retreated.
"I can map where the ice sheet has been in the field and then date when the ice was in that position," Dr White said. "We can then compare that evidence to past local climate information to get a sense of how that impacted the ice melting process."
Simulation of Antarctic Sheet evolution over the last 25,000 years by Dr Nick Golledge's research team at the Antarctic Research Centre, University of Wellington, New Zealand. Courtesy of Nature Communications
Dr White is currently working with the Antarctic Research Centre to publish research on how quickly we can expect to see sea levels rise in the coming years, with the hope that policy makers will use their research to make changes to help mitigate climate change and protect coastal populations.
"I'm working towards better understanding how quickly the ice sheet might collapse if we do warm the planet up two to four degrees Celsius," he said.
"Recent evidence from the Pliocene, which was the last time we saw temperatures similar to what we're expecting in the future, indicates Antarctica lost enough ice to increase sea levels by five to 10 metres. Looking at more recent events will help us understand whether ice sheet collapse at this scale can happen in just a few centuries, or whether it will take many thousand years more," Dr White explained.
"What's happened in the past isn't always a direct guide of what will happen in the future. But if we input that data into climate models, we can make informed projections based on previous behaviour."
