Antarctica is made up of two ice sheets, East and West. Along with Greenland, they are the world’s three largest ice sheets.
Researchers have been observing that West Antarctica is melting.
Ricarda Winkelmann of the Potsdam Institute for Climate Impact Research (PIK), in Germany, explains that the melting is happening in a kind of chain reaction: the ice rests on bedrock that is slanted.
Once the ice starts melting at the point where it hits the bedrock, the slant makes it melt increasingly faster. This is called the instability mechanism.
And once it starts, it’s irreversible.
“If you cross a certain threshold, you will basically lose that entire basin,” Winkelmann told RFI on the sidelines of the Cop21 climate conference, north of Paris. And some scientists say that threshold has already been crossed.
“In part of the West Antarctic ice sheet, in the Amundsen sector, the tipping point has already been crossed. And this sector alone is worth about a metre of global sea level rise.”
If the entire West Antarctic ice sheet melts, it will raise global sea levels by 3.3 meters. This is a process that would take centuries, if not millennia.
But the rate is not clear. Jonathan Bamber, a professor of glaciology at the University of Bristol, says the speed the sea level rise – and therefore the rate of the melting ice – makes all the difference.
“If it’s a millimetre a year, which is 10 centimetres a century, we can adapt to that,” he told RFI. “In a thousand years from now, who knows what capacity we’ll have to cope with that. But if it’s 10 times that, if it’s a centimetre a year, we have really, really big problems.”
A metre a year of sea level rise would displace large parts of Bangladesh’s population, for example. The Netherlands would be uninhabitable.
“A metre of sea level rise would be ‘bye-bye’ to all the atolls in the western Pacific,” says Bamber. “It’s unthinkable. A meter over a century is really very, very serious.”
He puts the power of whether or not it will rise that quickly in the hands of policy makers who are making decisions about carbon emissions, which will affect climate change.
“If we take really positive action, strong, radical action: decisions that might seem a bit painful in the short-term, I think we can save the planet from some of the worst scenarios that I can think of,” he said.
Among the worst scenarios are if all of Antarctica melts, which would raise sea levels by 58 metres.
Winklemann was the lead author of a study published in September that said that if all the fossil fuels on the planet are burned, all of Antarctica will definitely melt.
And though this is on a long timescale, Winklemann says this should still be a concern.
“The changes in the climate system that we’re bringing about right now are really having consequences on these long time scales,” she said. “We really need to think of sea level rise as a commitment, and we really need to decide what our legacy is supposed to be.”
And that legacy is what is being discussed at the Cop21 conference. The scientists are here to tell us what the effects are, and it’s up to the rest of us to do something about it.
Source: rfi afrique