Melting ice sheets on coast threaten to raise sea levels

In the extreme northern part of Antarctica, spectacularly white and blinding ice seems to extend forever. What can’t be seen is the battle raging underfoot to reshape the planet.

Water is eating away at the Antarctic ice, melting it where it hits the oceans. As the ice sheets slowly thaw, water pours into the sea — 118 billion metric tons of ice per year for the past decade, according to US National Aeronautics and Space Administration satellite calculations. That’s enough ice melt to fill more than 1.3 million Olympic swimming pools. And the melting is accelerating.

In the worstcase scenario, Antarctica’s melt could push sea levels up 3 meters worldwide in a century or two, reshaping heavily populated coastlines.

Parts of Antarctica are melting so rapidly it has become “ground zero of global climate change without a doubt”, said Harvard University geophysicist Jerry Mitrovica.

Last month, scientists noticed in satellite images that a giant crack in an ice shelf on the peninsula called Larsen C had grown by about 20 km in 2014. Ominously, the split broke through a type of ice band that usually stops such cracks. If it keeps going, it could cause the breaking off of a giant iceberg about the size of Brunei, about 4,600 to 6,400 sq km, said British Antarctic Survey scientist Paul Holland. And there’s a small chance it could cause the entire Scotlandsized Larsen C ice shelf to collapse as its sister shelf, Larsen B, did in a dramatic way in 2002.

‘A wild card’

A few years back, scientists figured Antarctica as a whole was in balance, neither gaining nor losing ice. Experts worried more about Greenland. But once they got a better look at the bottom of the world, the focus of their fears shifted.

“Before, Antarctica was a wild card,” said University of Washington ice scientist Ian Joughin. “Now I would say it’s less of a wild card and more scary than we thought before.”

Scientists estimate it will take 200 to 1,000 years to melt enough ice to raise seas by 10 feet, maybe only 100 years in a worstcase scenario. If that plays out, developed coastal cities such as New York and Guangzhou could face up to $1 trillion a year in flood damage within a few decades, and countless other population centers will be vulnerable.