Boulders as big as soccer balls show that a thinning of West Antarctic glaciers has become 20 times faster in recent decades and may hold clues to future sea level rise, scientists said. Rocks trapped in glacier ice start to react like clockwork when exposed to the air because of a bombardment of cosmic rays, private TV channel reported.
Scientists studied boulders by three glaciers to find how long they have been out of the ice and so judge the pace of thinning. No one even saw Antarctica before sailors spotted the coast in 1820 so there are scant historical records and little understanding of how ice sheets might react to rising temperatures linked to global warming.
The area of West Antarctica studied, the Amundsen Sea Embayment, is of especial concern because much of the bedrock under the ice is below sea level.
The weight of the ice keeps it in place but scientists fear it could float loose.
If that happened, world sea levels would rise by 1.5 metres. If all of Antarctica melted over thousands of years it would raise sea levels by 57 metres, drowning many of the world's biggest cities and many low lying islands.
Mike Bentley from the University of Durham said "when rocks are left high and dry by thinning glaciers they are exposed to high energy cosmic rays, which bombard the rocks."
"This creates atoms of particular elements that we can extract and measure in the laboratory, the longer they have been exposed the greater the build up of these elements," he said in a statement.