Jamie Morton is the NZ Herald's science reporter.

Cold warning from Antarctica's past

The East Antarctic Ice Sheet makes up much of Antarctica. Photo / Getty Images
The East Antarctic Ice Sheet makes up much of Antarctica. Photo / Getty Images

Another major study has pointed to the alarming potential impact of climate change on the East Antarctic Ice Sheet - the vast "sleeping giant" of the frozen continent.

The EAIS, which makes up much of Antarctica, has long been regarded by scientists to be much more stable when compared with the smaller, 25 million square kilometre West Antarctic Ice Sheet, which satellite measurements estimated was losing more than 150 cubic kilometres of ice each year.

While satellite observations have indicated parts of the EAIS were currently thinning in response to a warming ocean, a recent Australian expedition managed to reach the typically inaccessible Totten Glacier gain some of the first direct evidence.

This ultimately meant the wider ice sheet's contribution to future sea level rise could be much greater than realised.

If all of it melted, the EAIS would contribute an equivalent of around 50 metres of sea level rise - the vast majority of the total 58 metres that could come from the continent.

A New Zealand-led study published overnight in the journal Nature Communications has now shed further light on this potential.

By studying rocks at different elevations beside the East Antarctic sheet, the research team concluded that a period of rapid glacier thinning occurred in the recent geological past, and persisted for several centuries.

Of particular concern was the potential for "marine ice sheet instability", where an initial retreat of ice margins into deepening valleys could lead to continued, unstable ice loss.

The new research, led by Victoria Postdoctoral Research Fellow Dr Richard Jones, indicated that the processes leading to instability could be initiated by just minor climate warming.

"The finding is very important for predicting Antarctica's future contribution to sea level change," Dr Jones said.

"Particularly when considering that the EAIS contains enough vulnerable ice to raise sea level by tens of metres.

"It might only require a small amount of climate variation to initiate runaway ice loss, and it could continue for centuries to millennia."

While this process had been posited for many years, the study presented the first directly recorded evidence that it has taken place in the past, providing new insight into the future behaviour of rapidly changing parts of Antarctica today.

A major strength of the study was combining numerical modelling experiments that simulate glacier retreat with geological data processed in Victoria University's world-class cosmogenic nuclide laboratory.

The laboratory studies rare isotopes produced through the interaction of cosmic radiation with minerals on the Earth's surface, which allows for the calculation of the age of a rock surface.

"Most research has previously focused on the West Antarctic Ice Sheet, which makes these observations from East Antarctica all the more significant."

- NZ Herald

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