Wilkes Basin in East Antarctica
May 6, 2014

Pulling The Plug In East Antarctica Could Result In Domino Effect Of Sea Level Rise

April Flowers for redOrbit.com - Your Universe Online

A new study from the Potsdam Institute for Climate Impact Research (PIK) reveals that a persistent ice discharge into the ocean could be triggered by the melting of just a small volume of ice on East Antarctica's shore. Such a persistent discharge could result in unstoppable sea level rise for thousands of years to come, according to computer simulations of the Antarctic ice flow using improved data of the ground profile underneath the ice sheet.

"East Antarctica's Wilkes Basin is like a bottle on a slant," said Matthias Mengel in a recent statement. "Once uncorked, it empties out."

Currently a rim of ice at the coast of Wilkes Basin — the largest region of marine ice on rocky ground in East Antarctica — works like a cork in a bottle to hold the ice in place. The rising temperature of the oceans can cause ice loss on the coast, despite the Antarctic air remaining frigid, making the relatively small cork disappear. The cork's disappearance would trigger a long term sea level rise of 10 to 13 feet.

"The full sea-level rise would ultimately be up to 80 times bigger than the initial melting of the ice cork," said Anders Levermann, head of PIK's research area, Global Adaptation Strategies. "Until recently, only West Antarctica was considered unstable, but now we know that its ten times bigger counterpart in the East might also be at risk," said Levermann, who is also a lead author of the sea level change chapter of the most recent scientific assessment report by the Intergovernmental Panel on Climate Change, IPCC.

The IPCC report projects Antarctica's total sea level contribution to approximately 6 inches within this century. "If half of that ice loss occurred in the ice-cork region, then the discharge would begin. We have probably overestimated the stability of East Antarctica so far," says Levermann.

There is a region of ice called the grounding line. This is where the ice on the continent meets the sea and begins to float. Beneath that ice, the rocky ground forms a huge inland sloping valley that is below sea level. Melting, such as that suggested by the new study published in Nature Climate Change, would make the grounding line retreat.

It would become a vicious cycle. The retreating grounding line would push the rim of the ice facing the ocean higher than before. The ice would be pushed into the ocean where it would break off and melt, starting the cycle again. The warmer the oceans become, the faster the cycle will repeat.

In the researcher's simulations, complete ice discharge from the affected region in East Antarctica takes five thousand to ten thousand years. The discharge would continue relentlessly until the entire basin is emptied of ice once it starts, however. The researchers say that this is true even if the global warming. "This is the underlying issue here", said Mengel. "By emitting more and more greenhouse gases we might trigger responses now that we may not be able to stop in the future."

The team cautions that such extensive sea level rise would change everything we know of planet Earth.