Antarctica's sediment core confirms climate fluctuation

By Ivonne Marschall Apr 16, 2007, 17:00 GMT

Vienna - The presence of fossilized single-cell algae in sedimentary rock more than 1,280 metres beneath the Antarctic seafloor confirms large fluctuations in the continent's climate, scientists participating in the Antarctic Geological Drilling Program (ANDRILL) said on Monday.

Speaking on the sidelines of the European Geosciences Union (EGU) general assembly in Vienna, geologist Tim Naish of New Zealand's Victoria University said that, contrary to past assumptions, climate developments in the Southern Hemisphere were not isolated from the North.

'The Antarctic plays a significant role in global climate change in the last 60 million years,' Naish said. Climate fluctuations over the past 5 million years have been so extreme that the Ross Ice Shelf in the West Antarctic, a floating ice mass the size of France, oscillated in size dramatically.

Drill cores of sedimentary rock were recovered from deep beneath the Ross Ice Shelf during the first season of the 30-million-dollar project that ended in January.

The large presence of fossil diatoms, microscopic single-cell algae, was the most surprising find, confirming that large parts of the ice shelf had previously melted, the scientists explained.

Apart from providing invaluable information about our planet's past, there is hope that analysis of the 1,285-metre core recovered in Antarctica will aid predictions over future climate changes.

'Perhaps this is the window of climate change where we are heading in the next hundred years,' Naish said.

The scientists found more than 50 climate oscillations over the past 10 million years, some periods with temperatures 2 to 3 degrees Celsius warmer than today.

These past climate changes can provide valuable information about the future, North Illinois geologist Ross Powell believes.

'If we are going through this 2 to 3 degree warming in the next century, as has been predicted, we want to get a sense of how the ice sheet will react, and how fast it will react - by looking at what it has done in the past,' Powell, a co-chief scientist, with Naish on the ANDRILL project, said.

Ice shelves, huge floating bodies of ice, are extremely susceptible to climate change. The Ross Ice Shelf, strongly susceptible to melting because of warming oceans, is regarded as an important precursor to the eventual collapse of the whole west Antarctic ice sheet.

If the west Antarctic sheet melted, it is estimated that sea levels worldwide would rise by around six metres.

More than 8,000 scientists attended the EGU assembly in Austria capital, participating in over 400 sessions and workshops, covering fields from geobiology to planetary and space sciences.