East Antarctic Ice Sheet More Sensitive to Climate Changes than Previously Thought
09.02.2011 - Water & Oceans, Ice & Snow, Antarctic
A recent study, published in the journal Geology, suggests that climate change might be having a more considerable impact on the East Antarctic Ice Sheet than previously thought. The East Antarctic Ice Sheet (EAIS) holds enough ice to raise global sea levels by about 60 metres, yet because surface temperatures are well below freezing point, its ice was considered to be relatively stable.
However, new field-based studies of ice sheet response to climate warming and sea level increase after the last ice age (which lasted from about 110,000 years ago to about 10,000 years ago) suggest that parts of the ice sheet may respond more rapidly to global climate change than previously assumed.
In their research, Dr Duanne White and Associate Professor Damian Gore of Macquarie University in Australia and Dr David Fink from the Australian National Nuclear Research and Development Organisation (ANSTO) looked at large ice streams that drain a large proportion of the snow that falls on the Antarctic Ice Sheet into the sea, investigating changes in ice sheet elevation in the Lambert Glacier-Amery Ice Shelf region – which drains an estimated 15% of East Antarctica’s ice – to see how it had reacted to past climate and sea level changes. With the logistical support of the Australian Antarctic Division, the researchers spent three summers trawling across the mountain ranges that flank the Lambert Glacier ice stream, collecting numerous boulders scattered across the surface deposited by the ice when it was higher than today.
The team then used the ANTARES particle accelerator at ANSTO to measure the concentration of rare, long-lived radioactive isotopes in the rocks using a new, innovative technique called cosmogenic surface exposure dating. These radioisotopes are produced in the rock when they are bombarded by high energy cosmic rays that penetrate the Earth’s atmosphere, effectively creating “nuclear clocks” which measure the time since the boulder was released from its icy prison. By correlating exposure age with altitude, the researchers used the mountain ranges that protrude above the ice sheet as ‘dipsticks’ to measure past ice sheet elevation.
The results indicate that at the end of the last ice age, ice thickness in the Lambert Glacier ice streaming region began to decrease about six thousand years earlier than ice sheet retreat measured at adjacent coastal regions, and that there was a reduced delay between regional climate warming and resultant lowering of the ice stream several hundred kilometers inland. They concluded that ice stream regions of the East Antarctic Ice Sheet show an enhanced sensitivity to climate warming and sea level rise than previously assumed.