Scientists say 3 trillion tons of ice has disappeared since 1992. Indication towards climate change

WASHINGTON: An international team of ice experts said in a new study that the melting of Antarctica is increasing at a striking rate, with about 3 trillion tons of ice disappearing since 1992. In the last quarter century, the southernmost continent ice sheet which was a key indicator of climate change has melted into enough water to cover Texas to a depth of nearly 13 feet (4 meters), scientists calculated. All that water has made global oceans rise about three-tenths of an inch (7.6 millimeters).

From the year 1992 to 2011, Antarctica has lost almost around 84 billion tons of ice a year (76 billion metric tons). From 2012 to 2017, the melt rate increased to more than 241 billion tons a year (219 billion metric tons), according to a study on Wednesday in the journal Nature .

"I think we should be worried. That doesn't mean we should be desperate. Things are happening. They are happening faster than we expected." said University of California Irvine's Isabella Velicogna, one of the 88 co-authors

Part of West Antarctica, where most of the melting occurred, "is in a state of collapse," said co-author Ian Joughin of the University of Washington.

The study is the second of assessments planned every several years by a team of scientists working with NASA and the European Space Agency. Their mission is to produce the most comprehensive look at what's happening to the world's vulnerable ice sheets in Antarctica and Greenland.

Unlike single-measurement studies, this team looks at ice loss in 24 different ways using 10 to 15 satellites, as well as ground and air measurements and computer simulations, said lead author Andrew Shepherd of the University of Leeds in England. It's possible that Antarctica alone can add about half a foot (16 centimeters) to sea level rise by the end of the century, Shepherd said. 

Seas also rise from melting land glaciers elsewhere, Greenland's dwindling ice sheet and the fact that warmer water expands.
"Under natural conditions we don't expect the ice sheet to lose ice at all," Shepherd said. "There are no other plausible signals to be driving this other than climate change."

“Forces that are driving these changes are not going to get any better in a warming climate," said University of Colorado ice scientist Waleed Abdalati, a former NASA chief scientist who wasn't part of the study team.

In Antarctica, it's mostly warmer water causing the melt. The water nibbles at the floating edges of ice sheets from below. Warming of the southern ocean is connected to shifting winds, which are connected to global warming from the burning of coal, oil and natural gas, Shepherd said.

More than 70 percent of the recent melt is in West Antarctica. The latest figures show East Antarctica is losing relatively little ice a year  about 31 tons (28 metric tons) since 2012. It was gaining ice before 2012. So far scientists are not comfortable saying the trend in East Antarctica will continue.