The big melt: Antarctica’s retreating ice may re-shape Earth – ‘We have to stop it; or we have to slow it down as best as we can’Posted by Jim at Sunday, March 01, 2015
By Luis Andres Henao and Seth Borenstein
28 February 2015
CAPE LEGOUPIL, Antarctica (Associated Press) – From the ground in this extreme northern part of Antarctica, spectacularly white and blinding ice seems to extend forever. What can't be seen is the battle raging thousands of feet (hundreds of meters) below to re-shape Earth.
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, recurving 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.
Here on the Antarctic peninsula, where the continent is warming the fastest because the land sticks out in the warmer ocean, 49 billion tons of ice (nearly 45 billion metric tons) are lost each year, according to NASA. The water warms from below, causing the ice to retreat on to land, and then the warmer air takes over. Temperatures rose 5.4 degrees Fahrenheit (3 degrees Celsius) in the last half century, much faster than Earth's average, said Ricardo Jana, a glaciologist for the Chilean Antarctic Institute.
As chinstrap penguins waddled behind him, Peter Convey of the British Antarctic Survey reflected on changes he could see on Robert Island, a small-scale example and perhaps early warning signal of what's happening to the peninsula and rest of the continent as a whole.
"I was last here 10 years ago," Convey said during a rare sunny day on the island, with temperatures just above freezing. "And if you compare what I saw back then to now, the basic difference due to warming is that the permanent patches of snow and ice are smaller. They're still there behind me, but they're smaller than they were." [...]
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.
"Changing the climate of the Earth or thinning glaciers is fine as long as you don't do it too fast. And right now we are doing it as fast as we can. It's not good," said Rignot, of NASA. "We have to stop it; or we have to slow it down as best as we can. " [more]