Antarctica's ice sheet is melting three times faster than before

WASHINGTON - AP

The melting of Antarctica is accelerating at an alarming rate, with about 3 trillion tons of ice disappearing since 1992, an international team of ice experts said in a new study.

In the last quarter century, the southern-most continent's ice sheet - a key indicator of climate change - melted into enough water to cover Texas to a depth of nearly 4 meters, scientists calculated. All that water made global oceans rise about three-tenths of 7.6 millimeters.

From 1992 to 2011, Antarctica lost nearly 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, according to the study in the journal Nature .

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

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.

Outside experts praised the work as authoritative.

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 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."