Melting of Antarctica’s ice sheet speeding up
The melting of Antarctica is accelerating at an alarming rate, with about 3 trillion tonnes of ice disappearing since 1992, an international team of ice experts says in a new study.
In the last quarter of a century, the southernmost continent’s ice sheet – a key indicator of climate change – melted into enough water to cover Texas to a depth of nearly 4m, scientists calculated.
All that water made global oceans rise about 7.6mm.
From 1992 to 2011, Antarctica lost nearly 76 billion tonnes of ice a year. From 2012 to 2017, the melt rate increased to more than 219 billion tonnes, according to the study, published yesterday 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 coauthor Ian Joughin of the University of Washington.
The study is the second in a series of assessments planned every few 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 is happening to the world’s vulnerable ice sheets in Antarctica and Greenland.
Unlike single-measurement studies, the team looked 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.
‘‘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.’’
Shepherd cautioned that it was not a formal study that determined human fingerprints on climate events.
The forces driving the 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 was not part of the study team.
In Antarctica, it is mostly warmer water causing the melt. The water nibbles at the floating edges of ice sheets from below.
Warming of the Southern Ocean was connected to shifting winds, which were connected to global warming from the burning of coal, oil and natural gas, Shepherd said.
More than 70 per cent of the recent melt is in West Antarctica. The latest figures show that East Antarctica is losing relatively little ice a year. It was gaining ice before 2012.
Another study published in Nature yesterday found that the East Antarctic ice sheet didn’t retreat significantly 2 million to 5 million years ago, when heattrapping carbon dioxide levels were similar to what they are now. – AP