"The World's Fate" Hangs on Antarctica's Melting Ice
February 28, 2015
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 — 130 billion tons of ice (118 billion metric tons) per year for the past decade, according to NASA satellite calculations. That's the weight of more than 356,000 Empire State Buildings, enough ice melt to fill more than 1.3 million Olympic swimming pools. And the melting is accelerating.
In the worst case scenario, Antarctica's melt could push sea levels up 10 feet (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 geophysicist Jerry Mitrovica.
Just 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 12 miles (20 kilometers) 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 somewhere between the size of Rhode Island and Delaware, about 1,700 to 2,500 square miles (4,600 to 6,400 square kilometers), said British Antarctic Survey scientist Paul Holland. And there's a small chance it could cause the entire Scotland-sized Larsen C ice shelf to collapse like its sister shelf, Larsen B, did in a dramatic way in 2002.
"Before Antarctica was much of 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."
Over at NASA, ice scientist Eric Rignot said the melting "is going way faster than anyone had thought. It's kind of a red flag."
What's happening is simple physics. Warm water eats away at the ice from underneath. Then more ice is exposed to the water, and it too melts. Finally, the ice above the water collapses into the water and melts.
Climate change has shifted the wind pattern around the continent, pushing warmer water farther north against and below the western ice sheet and the peninsula. The warm, more northerly water replaces the cooler water that had been there. It's only a couple degrees Fahrenheit warmer than the water that used to be there, but that makes a huge difference in melting, scientists said.
The world's fate hangs on the question of how fast the ice melts.
At its current rate, the rise of the world's oceans from Antarctica's ice melt would be barely noticeable, about one-third of a millimeter a year. The oceans are that vast.
But if all the West Antarctic ice sheet that's connected to water melts unstoppably, as several experts predict, there will not be time to prepare. Scientists estimate it will take anywhere from 200 to 1,000 years to melt enough ice to raise seas by 10 feet, maybe only 100 years in a worst case 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.