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July 6, 2009

Ice Core Secrets Could Reveal Answers to Global Warming

Ancient ice cores provide clues to future climate change

At the Stable Isotope Lab in Boulder, Colo., scientists are doing a lot of the same things that those CSI folks do on TV. But instead of being "crime scene investigators," these experts are more like "cold scene investigators." Geoscientists like lab director Jim White work primarily with one raw material: ancient ice, in the form of ice cores.

The ice cores come from Greenland and Antarctica. And, says White, they hold secrets from thousands of years ago.

"Inside this ice core is trapped the environment from about 50 thousand years ago," said White, showing a two-foot core. "You can see some bubbles in here, that's the atmosphere. We can take this ice core, we can crush it up, we can remove the air that is inside of here, and find out how much C02 (carbon dioxide) is in here; methane and other greenhouse gases were in the atmosphere at the time when this ice core was formed," he said.

Scientists have only been deciphering the pages of these frozen books for about 40 years. The information extracted from this ice could play a critical role in understanding and preparing for any imminent changes to our planet from global warming.

"So it's not just that the past tells us what happened, but the past gives us some clues about what could occur in the future," said White.

White's recent analysis of Greenland ice cores, a National Science Foundation (NSF)-supported project, has revealed some important clues about rapid climate changes near the end of the last ice age, about 11,700 years ago.

The climate changes White has documented unfolded dramatically, in only about five decades.

"So what we saw were changes in temperature of 20 to 30 degrees Fahrenheit, in a human lifetime, and a doubling of snowfall in one or two years. Now what could cause those kinds of changes?" asked White.

The likeliest triggers include ocean circulation, which today keeps northern Europe from being frigid. Atmospheric circulation, like the jet stream, may also have switched patterns. Changes in sea ice, like the dramatic retreat being observed right now in the Arctic, could also have contributed to that warming thousands of years ago.

Besides being able to determine the greenhouse gases in the ancient ice, scientists have another surprising forensic tool.

"There's a thermometer that lurks within the ice," said White. "This particular thermometer is not one that's based on the expansion of a liquid, like mercury thermometers. This one is based on the ratio of heavy hydrogen to light hydrogen. The more heavy hydrogen you have, the warmer the cloud was that had the snow. The less heavy hydrogen, the lighter it was. It's just as good a thermometer," he said.

Most people know little about Greenland and the ice that stretches about two miles below sea level. So why should we care about its ice melting?

"Greenland contains something in the neighborhood of 20 feet of sea-level rise, were the entire Greenland ice sheet to melt," said White.

"And if that land ice goes into the ocean, you'd raise sea level in the neighborhood of 20 feet. That's obviously significant. That would inundate, drown, major cities like Miami, Houston, Oakland, New Orleans. It would be all around the world. So it's important to recognize how much ice is up there," he said.

The "pages" of each ice core are like roadmaps.

"We've learned how to read this book better and better, to extract from it the information that's here," said White.

But unlike those CSI shows, these scientists at the University of Colorado at Boulder's Institute of Arctic and Alpine Research (INSTAAR) don't come up with the answers to current climate change at the end of an hour. There is a lot more to learn, to determine if the situation on Earth right now will play out the same way it did thousands of years ago.

"I would say we're still flying blind when it comes to, 'Is there a rapid change on its way?'" said White.

Miles O'Brien, Science Nation Correspondent
Marsha Walton, Science Nation Producer

Any opinions, findings, conclusions or recommendations presented in this material are only those of the presenter grantee/researcher, author, or agency employee; and do not necessarily reflect the views of the National Science Foundation.