01 June 2000 00/181
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Antarctica's last forest provides clues to climate change
The microscopic remains of an Antarctic forest more than 30 million years old was providing important information about global climate operation, the Minister for Industry, Science and Resources, Senator Nick Minchin announced today.
Senator Minchin said Australian scientists participating in the international Ocean Drilling Program (ODP) have dated the time when the Antarctic changed from a continent covered by vegetation to a frozen land.
Senator Minchin explained spores and pollen fossils trapped in submerged sediment buried deep beneath the polar sea provided evidence of the once cool-temperature rainforest that last covered the continent between 34 and 37 million years ago.
The Antarctic study helps scientists understand why the ice sheet formed and how the global climate operates.
"Pinpointing the time when Antarctica was first covered by an ice sheet helps scientists understand more about the fluctuations of the global climate," Senator Minchin said.
"The findings provide further evidence of the influences the oceans south of Australia have on global climate fluctuations."
Senator Minchin said the expedition uncovered spores which indicated vegetation that grew in the coastal plains of Antarctica was akin to the edges of cool-temperate rainforest now found in the highlands of Tasmania.
Although not tall, the stunted scrub of Antarctica's last forest would have been home to a variety of plants including insect-eating plants ('sundew'), and pine trees growing to approximately three metres high.
Samples revealed remnants of Southern Beech (Nothofagus). These are found occurring naturally in Tasmania, New Zealand and New Caledonia, evidence that these islands once joined Antarctica in the super-continent of Gondwana. Collected along with the spores were pebbles dropped from the earliest Antarctic icebergs.
Senator Minchin said the ODP had conducted exhaustive geological detective work to uncover what happened tens of millions of years ago to turn the cool-temperate Antarctic continent into a barren ice world.
"About 45 million years ago, Australia started to move northward away from Antarctica at a rate of approximately five centimetres per year," he said.
"By 30 million years ago, the Tasmanian land bridge had separated from Antarctica, allowing cold currents to circulate around Antarctica and cutting it off from the warm currents flowing south from the tropics.
"This created perfect conditions for ice sheets to form. By 15 million years ago most of Antarctica was a frozen continent buried deep under ice caps and vegetation vanished, unable to survive the dramatic climate change."
Senator Minchin said core samples were collected from rocks located up to 400 metres below the seabed, in water 500 metres deep in Prydz Bay in the Australian Antarctic Territory.
Dr Phillip O'Brien from Geoscience Australia and Dr Patrick Quilty of the University of Tasmania sampled the drill cores. The cores were studied by Dr Michael Macphail and Dr Elisabeth Truswell from the Australian National University.
Sediment core drilling around the Antarctic took place on the drill ship JOIDES Resolution from February to March this year. The research cruise involved 26 scientists from eight participating countries and was lead by Dr O'Brien and Dr Alan Cooper from Stanford University in California.
ODP, an international partnership of scientific institutions and governments, and the world's biggest multinational geoscience research program, explores the Earth's history and evolution. Australia is a partner in the AustraliaCanadaChinaTaipeiKorea Consortium for Ocean Drilling.
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