Antarctic ice sheet comes under threat
Increasing carbon emissions could propel us into a world that hasn’t existed for millions of years, and put the existence of the Antarctic ice sheet under threat.
Those are the findings of a new study published in the Nature Geoscience journal, looking at how sensitive the ice sheet might be to climate change.
Lead author Richard Levy, from GNS Science and Victoria University of Wellington, said the study showed the ice sheet was ‘‘highly sensitive’’ to changes in temperature.
It was most at risk when the Earth’s tilt was steeper – as it is now – and polar ranges were more exposed to the sun.
But unlike other historical periods when the Earth was at a steep tilt, this time rising carbon dioxide levels are posing an even greater threat.
‘‘What’s saved us in the past is carbon dioxide levels have been low enough that sea ice has grown. We’ve got to keep emissions as low as we can, otherwise we will go back to levels not seen in 14 million years.’’
At that time, carbon levels were around 400 parts per million (ppm) – low enough for sea ice to emerge. But human activity had resulted in levels now going beyond that, putting sea ice at risk if emissions were not kept in check.
‘‘This study adds to our knowledge of the history and behaviour of Antarctica’s ice sheets and is yet more proof that urgent action is needed on emissions,’’ said co-author Professor Tim Naish, of Victoria University’s Antarctic Research Centre.
‘‘Persistent sea ice appears to have helped maintain a degree of stability in the Antarctic ice sheet. We cannot afford to lose it.’’
The Earth took about 40,000 years to complete a cycle from a high tilt to a less dangerous lower one, Levy said.
While it would be centuries before any serious changes to the ice sheet took effect, emissions needed to be lowered now to limit the impact.