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Antarctic ice samples: What do they say about global warming?

Antarctic ice core samples, up to 150,000 years old, may help scientists estimate whether it will take 50 years - or 500 years - for the Ross Ice Shelf to collapse at the current rate of climate change.

By Nick Perry and Rod McGuirkAssociated Press / April 6, 2013

Scientist Nancy Bertler holds the final section of ice she collected from a half-mile under Antarctica's surface in a laboratory freezer, near Wellington, New Zealand. Antarctica's pristine habitat provides a laboratory for scientists studying the effects of climate change.

(AP Photo/Nick Perry)

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Wellington, New Zealand

Nancy Bertler and her team took a freezer to the coldest place on Earth, endured weeks of primitive living and risked spending the winter in Antarctic darkness, to go get ice — ice that records our climate's past and could point to its future.

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They drilled out hundreds of ice cores, each slightly longer and wider than a baseball bat, from the half-mile-thick ice covering Antarctica's Roosevelt Island. The cores, which may total 150,000 years of snowfall, almost didn't survive the boat ride to New Zealand because of a power outage.

Bertler hopes the material will help her estimate how long the Ross Ice Shelf would last under the current rate of climate change before falling apart.

Evidence from the last core her team hauled out needs further study, but it contains material that Bertler said appeared to be marine sediment that formed recently — at least in geological terms measured in thousands of years.

That would bolster scientists' suspicions that the shelf could collapse again if global temperatures keep rising, triggering a chain of events that could raise sea levels around the world.

"From a scientific point of view, that's really exciting. From a personal point of view, that's really scary," said Bertler, a senior research fellow at the Antarctic Research Centre at the Victoria University of Wellington.

The ice shelf acts as a natural barrier protecting massive amounts of ice in West Antarctica, and that ice also could fall into the ocean if the shelf fell apart. Scientists say West Antarctica holds enough ice to raise sea levels by between 2 meters (6.5 feet) and 6 meters (20 feet) if significant parts of it were to collapse.

Ted Scambos, the lead scientist at the National Snow and Ice Data Center at the University of Colorado, said that even under the worst case scenario he thinks it would take at least 500 years for West Antarctica's ice to melt.

However, he said a discovery of sediment would indicate a significant portion of the ice shelf is under threat of becoming unstable again, and that the implications were "huge."

Bertler hopes the material she recovered will help her to estimate by the end of this year whether it will take 50 years or 500 years for the ice shelf to collapse at the current rate of climate change. Those answers should prove important for policymakers who, she said, may need to decide whether to build sea walls or move populations to higher ground.

Bertler's project is one of scores that take place on Antarctica every Southern Hemisphere summer. To scientists, the continent's pristine habitat offers a unique record of the planet's weather and a laboratory for studying the effects of climate change.

Studies indicate that while the Arctic has suffered what scientists consider to be alarming rates of ice loss in recent years, the Antarctic ice shelf has remained relatively stable despite having have lost ice in recent decades.

Research in Antarctica creates huge logistical and personal challenges.

Bertler's camp on Roosevelt Island is a three-hour flight from the nearest permanent Antarctic outposts, Scott Base and McMurdo Station. The island is surrounded by the Ross Ice Shelf, the world's largest mass of floating ice, covering an area the size of Spain.

Even during the spring and summer months when Bertler's team was working there, the temperature sometimes dropped to minus 25 C (minus 13 F) and there were frequent storms and thick fog.

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