World’s largest ice sheet still appears stable

Scientists from New Zealand and Australia have used mountains as giant "dipsticks' to analyse the history of the world's largest ice sheet.

Researchers at Victoria University of Wellington, Macquarie University in Sydney and the Australian Nuclear Science & Technology Organisation (ANSTO) have published an article this week in the American journal, Geology. It throws a new light on the size of the East Antarctic Ice Sheet during the last ice age.

The ice sheet is centred on the South Pole and lies on the Indian Ocean side of the Transantarctic Mountains.

"The East Antarctic Ice Sheet, the world's largest, contains enough water to increase sea levels by 60 m and is one of the most significant features in the Earth's global climate system," said Dr Andrew Mackintosh, senior lecturer in Victoria's School of Geography, Environment & Earth Sciences.

"But we knew little of its size and mass 20,000 years ago during the last ice age, when sea levels were 120 m lower than they are now. If we're to predict the response of the ice sheet to modern climate change, it is essential we understand how it reacted to the last major change in global temperatures."

It had been suggested that during the last ice age, the East Antarctic Ice Sheet was massively bigger in both height and breadth.

"To understand the ice sheet's size during the last ice age, we used mountains that pierce the ice sheet in Mac Robertson Land as geological dipsticks," said Macintosh. "Rocks were gathered and analysed to determine how long ago they were deposited while their height showed how thick the ice sheet was in the past."

The Victoria and Macquarie team, along with scientists at the Australian Nuclear Science & Technology Organisation, found that the East Antarctic Ice Sheet has remained relatively stable for the last 20,000 years.

"The East Antarctic Ice Sheet reached its present volume about 6,000 years ago when global sea levels stabilised," said Macintosh.

"Its sluggish response is in dramatic contrast to the West Antarctic ice sheet which has retreated continuously since this time and is a significant risk today.

"Our research suggests changes in sea levels due to global warming will not be caused by changes in East Antarctic Ice Sheet " yet. Most sea level rise in the short term will instead be sourced from the melting of valley glaciers, thermal expansion of the oceans, and from retreat of the Greenland and West Antarctic ice sheets."