The fate of Pine Island and Thwaites glaciers in Antarctica is in the balance — and so is that of all our cities

http://www.news.com.au/technology/environment/climate-change/the-fate-of-pine-island-and-thwaites-glaciers-in-antarctica-is-in-the-balance-and-so-is-that-of-all-our-cities/news-story/cd363c1430b2788154f5bb14b44c1c39

TWO enormous glaciers could soon irrevocably reshape our future. They’re melting. They’re fragmenting. And a cataclysmic collapse of an entire Antarctic ice sheet may be just decades away.

Jamie Seidel
News Corp Australia NetworkNovember 25, 201711:55am

PINE Island. Thwaites.

These two names are likely to become increasingly familiar in future years.

They’re among Antarctica’s biggest and fastest-melting glaciers.

But what makes these different is that they’re fed from ice sitting on solid ground.

This ice does not displace the ocean.

That means all the water that melts off them must be added to the total mass forming the world’s seas.

Current calculations put that at roughly 3.4 meters [11 feet].

According to US meteorologist Eric Holthaus, that’s enough to inundate every coastal city on our planet.

“There’s no doubt this ice will melt as the world warms,” Holthaus writes. “The vital question is when.”

And that’s the thing.

Scientists used to think it would take thousands of years for Antarctica’s ice sheets to melt under a warming atmosphere.

But new evidence shows it could happen within a few decades.

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Traces remain of the last time Earth underwent a major climate-change event — the end of the most recent ice age 11,000 years ago.

That evidence points to a rapid collapse of the Pine Island and Thwaites glaciers.

•••••

The cause is in the region’s geology.

The sea gets deeper beneath the glaciers’ outflow.

So every new iceberg exposes taller and taller cliffs.

“Ice gets so heavy that these taller cliffs can’t support their own weight,” Holthaus writes. “Once they start to crumble, the destruction would be unstoppable.”

Given the unabated rise in carbon emissions, the study concluded that a 2m rise in sea levels was now much more likely than the 1m predicted under earlier models. But a worst-case carbon-atmosphere model shows a full 3.4m could be unleashed if West Antarctica’s ice reserves were unlocked.

•••••

A one-metre rise in sea levels would cause frequent flooding in almost all coastal settlements. At 2m, some of the worlds biggest cities — including Shanghai and Ho Chi Minh City — would simply be swallowed by the sea.

At 3.4m, the majority of the planet’s fertile — and densely habited — coastal regions would be inundated.

Such scenarios are just decades away.

Holthaus says these key glaciers could conceivably collapse within 20 to 50 years.

“The new evidence says that once a certain temperature threshold is reached, ice shelves of glaciers that extend into the sea, like those near Pine Island Bay, will begin to melt from both above and below, weakening their structure and hastening their demise, and paving the way for ice-cliff instability to kick in.”

Iceberg after iceberg would break away in an unstoppable chain-reaction.

And the landlocked ice sheet behind them — no longer contained by a floating ice shelf — would start to slip faster and faster.

•••••

“A wholesale collapse of Pine Island and Thwaites would set off a catastrophe. Giant icebergs would stream away from Antarctica like a parade of frozen soldiers. All over the world, high tides would creep higher, slowly burying every shoreline on the planet ...”

Such an event would unleash a human tide of refugees unlike anything seen in history — hundreds of millions of people displaced by rising seawater.

•••••

The science isn’t yet certain. Not enough is understood about the mechanics of glaciers or the physics of ice to be sure. But climate researchers agree the new evidence is pointing in a deeply disturbing direction.

“Next to a meteor strike, rapid sea-level rise from collapsing ice cliffs is one of the quickest ways our world can remake itself,” Holthaus says. “This is about as fast as climate change gets.”