By studying rocks at different elevations beside the East Antarctic Ice Sheet (EAIS), a New Zealand-led team concluded that a period of rapid glacier thinning occurred in the recent geological past, and persisted for several centuries.
Satellite observations show that parts of the Antarctic ice sheet are currently thinning in response to a warming ocean. Of particular concern is 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 Postdoctoral Research Fellow Dr Richard Jones, indicates that the processes leading to instability can be initiated by just minor climate warming.
"The finding is very important for predicting Antarctica's future contribution to sea level change," says Dr Jones. "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 has been posited for many years, the study presents 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 recording past ice surface lowering.
"Most research has previously focused on the West Antarctic Ice Sheet, which makes these observations from East Antarctica all the more significant," says Dr Jones.
The field work and data collection conducted as part of this study were captured in a video and can be viewed at https://vimeo.com/80447422.
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