Quantcast
Environmental News for a Healthier Planet and Life

Antarctic Warming Threatens World's Second Largest Ice Shelf

Popular
Antarctic Warming Threatens World's Second Largest Ice Shelf
The edge of the Filchner-Ronne ice shelf in the Weddell Sea. Ralph Timmermann/AWI

By Tim Radford

German scientists have worked out the process that could destroy an Antarctic ice shelf the size of Iraq.


They predict that, in a few decades, the oceanographic machinery that keeps the Ronne-Filchner ice shelf in the Weddell Sea will fail. A warm ocean will begin to eat away at the 450,000 square kilometer sheet of floating ice.

And the insulating zone of cold, very salty water that had for centuries served as a natural protection for the world's second largest ice shelf will have gone. The Southern Ocean will have been irrevocably changed.

The ice will lose its anchorage on the sea floor. This had served as a brake on glacial movement from the Antarctic mainland, so the flow of glacial ice from the continent to the sea will increase.

Less sea ice forming

"We can see the first signs of this trend today," says Hartmut Hellmer, an oceanographer at the Alfred Wegener Institute's Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany.

"First of all, less sea ice is forming in the region and, secondly, oceanographic recordings from the continental shelf break confirm that warm water masses are already moving closer and closer to the ice shelf in pulses."

He and colleagues report in the Journal of Climate that the self-amplifying feedback cycle that they have identified in the Weddell Sea could be irreversible—which means that the world's second largest ice shelf would shrink dramatically.

Other research teams have predicted that the melting of the south polar ice shelves could double by 2050, that processes below the ice are causing fractures that result in huge icebergs, and that lessons from 15,000 years ago confirm that worldwide sea levels rose three meters as a consequence of a sudden warming of Antarctica.

So the German research is not a shock. But it does help climate scientists understand just how a region that had maintained a stable sheath of ice around itself for all human history could suddenly melt.

Ice shelves line 75 percent of the Antarctic coastline. The biggest ones are the Ross and Ronne-Filchner ice shelves, marked here in red and dark blue. National Snow and Ice Data Centre

The change begins in the sea itself. Ice melts in summer and freezes again in autumn and winter, releasing salt below the ice shelf to support a layer of insulating water as cold as minus 2°C. This has buffered the Ronne-Filchner ice shelf from inflowing water that is 0.8°C—almost three degrees warmer.

But rising air temperatures—and they are rising worldwide, thanks to the prodigal use of fossil fuels and the build-up of the greenhouse gas carbon dioxide—mean that less sea ice will form. And this will be the beginning of the transformation of the Weddell Sea. By 2070, changes will be visible.

"Our simulations show that there will be no turning back once the warm water masses find their way under the ice shelf, since their heat will accelerate the melting at its base," Hellmer said.

Carbon dioxide levels

"In turn, the resulting meltwater will produce an intensified overturning, which will suck even more warm water from the Weddell gyre under the ice. As such, according to our calculations, the hope that the ocean would some day run out of heat won't pan out in the long run."

The scientists start from the assumption that if humans go on burning fossil fuels at an ever-accelerating rate, carbon dioxide levels in the atmosphere will reach 700 parts per million. Through most of human history and prehistory, they have bobbed along at 280 ppm.

Right now, they stand at 400 ppm, and climates have already begun to change, with a corresponding climb in average global temperatures. Something comparable has already started to happen to the Amundsen Sea on the other side of the Antarctic Peninsula.

"When it comes to the Amundsen Sea, where warm water has already reached the continental shelf and even the grounding line of some ice shelves, we can safely say that this inflow of heat cannot be stopped; the climate regime change has already taken place," Hellmer said.

"In other words, the losses of mass of the West Antarctic Ice Sheet will intensify—just like the models predict."

Reposted with permission from Climate News Network.

The Gowanus Canal in Brooklyn, New York, a polluted nearly 2 mile-long waterway that is an EPA Superfund site. Jonathan Macagba / Moment / Getty Images

Thousands of Superfund sites exist around the U.S., with toxic substances left open, mismanaged and dumped. Despite the high levels of toxicity at these sites, nearly 21 million people live within a mile of one of them, according to the U.S. Environmental Protection Agency (EPA).

Read More Show Less
EcoWatch Daily Newsletter
The National Weather Service station in Chatham, Massachusetts, near the edge of a cliff at the Monomoy National Wildlife Refuge. Bryce Williams / National Weather Service in Boston / Norton

A weather research station on a bluff overlooking the sea is closing down because of the climate crisis.

Read More Show Less
Trending
Amsterdam is one of the Netherlands' cities which already has "milieuzones," where some types of vehicles are banned. Unsplash / jennieramida

By Douglas Broom

  • If online deliveries continue with fossil-fuel trucks, emissions will increase by a third.
  • So cities in the Netherlands will allow only emission-free delivery vehicles after 2025.
  • The government is giving delivery firms cash help to buy or lease electric vehicles.
  • The bans will save 1 megaton of CO2 every year by 2030.

Cities in the Netherlands want to make their air cleaner by banning fossil fuel delivery vehicles from urban areas from 2025.

Read More Show Less
Protestors stage a demonstration against fracking in California on May 30, 2013 in San Francisco, California. Justin Sullivan / Getty Images

A bill that would have banned fracking in California died in committee Tuesday.

Read More Show Less
EXTREME-PHOTOGRAPHER / E+ / Getty Images

By Brett Wilkins

As world leaders prepare for this November's United Nations Climate Conference in Scotland, a new report from the Cambridge Sustainability Commission reveals that the world's wealthiest 5% were responsible for well over a third of all global emissions growth between 1990 and 2015.

Read More Show Less