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In Greenland, Ice Unlocks Climate Change History

October 19, 2009 at 12:00 AM EDT
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Scientists dig deep into Greenland's ice to unearth the history of climate change. Climatologist and Climate Central correspondent Heidi Cullen reports.
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JIM LEHRER: Next tonight: boring deep into the Greenland to understand climate history.

The story comes from Heidi Cullen, a climatologist and correspondent for Climate Central, a nonpartisan research group for journalists and scientists.

HEIDI CULLEN: Far in the north of Greenland, a team of climate scientists from 14 nations, including the U.S., has just completed its first season of drilling a 1.6-mile core of solid ice.

J.P. STEFFENSEN, field operations manager, North Greenland Eemian Ice Drilling Project: What you see here is a piece of ice from the climate change between the last glacial and the present climate. It’s about 11,000 years old. And it contains a lot of tiny little bubbles of the ancient atmosphere.

HEIDI CULLEN: J.P. Steffensen is the field operations manager for the North Greenland Eemian ice drilling project, or NEEM, the project’s ultimate goal, to unlock the climate history trapped inside those tiny bubbles.

JEFF SEVERINGHAUS, professor of geosciences, Scripps Institution of Oceanography: The beautiful thing about an ice core is that it’s got all of these different indicators, atmospheric composition, temperature, mean ocean temperature, dust. All these kinds of indicators are on exactly the same time scale.

HEIDI CULLEN: Jeff Severinghaus, a scientist at the Scripps Institution of Oceanography, is working with NEEM scientists to reconstruct all those indicators, in the hope of learning more about a period in climate history known as the Eemian.

The Eemian period started about 130,000 years ago, and we know it lasted about 15,000 years before the Earth plunged back into an ice age.

JEFF SEVERINGHAUS: NEEM is really trying to get a record of the last time that the Earth was warmer than today. So, it’s an analogue for what our future looks like under global warming.

HEIDI CULLEN: During the Eemian, temperatures were somewhere between five and nine degrees Fahrenheit warmer than today, a scenario that climate models suggest could happen again by the end of the century if present trends continue.

JEFF SEVERINGHAUS: It’s a very, very realistic scenario for what we may experience in the next 100 to 200 years.

MAN: We’re getting older and older. With every meter we’re melting, we’re getting back to the future.

HEIDI CULLEN: Thirty feet below the surface in this huge trench carved from the snow is where this ice core research begins.

J.P. STEFFENSEN: The newest thing we have now at NEEM that nobody else has tried is a very sophisticated analytical system. It’s called continuous flow analysis, where, actually, in the field, you cut a slab of the ice core, a thin rod of ice following the length of the ice. And you tilt that vertically. And you melt it on a hot plate from one end.

And then, as it melts, you do the analysis, millimeter by millimeter.

MAN: You can hear the bubbles coming out of the ice.

HEIDI CULLEN: The samples are also cut, bagged, and boxed up, and then shipped to research centers around the world.

J.P. STEFFENSEN: We call it the post office.

'Complicated' logistics

HEIDI CULLEN: The logistics of ice core drilling are far from simple.

J.P. STEFFENSEN: It's just complicated. And I hate complications. I like to things to run smoothly.

HEIDI CULLEN: The operation starts in a small town of Kangerlussuaq on Greenland's west coast.

J.P. STEFFENSEN: My first season was in 1980. So, that's 29 years ago. And that was a marriage for life.

HEIDI CULLEN: Keeping the operation running smoothly is his wife and fellow scientist, Dorthe Dahl-Jensen, NEEM's project leader.

DORTHE DAHL-JENSEN, coordinator, North Greenland Eemian Ice Drilling Project: I work mostly as the coordinator of the project, trying to get the drill teams and the scientists and the logistics people and the airplanes to come.

HEIDI CULLEN: The airplanes come courtesy of the 109th Airlift Wing of the New York Air Force National Guard...

WOMAN: Approach five-one-five.

HEIDI CULLEN: ... and pilots like George Alston.

LT. COL. GEORGE ALSTON, 109th Airlift Wing, New York Air Force National Guard: Well, we're the only unit in the world that flies the specialized LC-130 aircraft, a C-130 on skis, which allows us to support the scientific efforts. I can take these large airplanes and land them on skis.

HEIDI CULLEN: But getting to the ice drilling camp is just part of the challenge.

VASILII PETRENKO, University of Colorado: It's always light. So, when you first get here, it may be a little hard to sleep. And it takes a couple of nights to get used to it. But then you get so tired from work and from not sleeping the nights before, that it no longer becomes a problem.

HEIDI CULLEN: Vasilii Petrenko is a scientist at the University of Colorado.

VASILII PETRENKO: It's a very simple life. It's kind of like a frontier outpost. We sleep in -- mostly in those red structures that you see behind me. They're called weather ports.

Unlocking data from the ice

HEIDI CULLEN: While the NEEM field camp may look like a frontier outpost on the surface, Petrenko and others are engaged in very sophisticated scientific research underground.

VASILII PETRENKO: One of the things that we see in the ice cores is a strong correlation between carbon dioxide levels and temperatures. So, at times of warm temperatures, carbon dioxide is high. At times of cold temperatures, carbon dioxide is low, which, you know, reinforces what science has been showing recently, that carbon dioxide does cause warming.

HEIDI CULLEN: And that warming leads to melting.

The Greenland ice sheet contains enough ice to raise the global sea level by 23 feet, a worst-case scenario associated with global warming. Satellite data from the NASA GRACE mission show that Greenland's reservoir of ice has plummeted in recent years, about 340 billion tons of ice melt in 2007 alone, about the same as San Francisco Bay draining completely every week for a year.

Scientists hope this new ice core will tell them how much of Greenland's ice melted during the Eemian period, when global sea level was 13 to 20 feet higher, a finding that could be crucial in determining how much and how quickly sea level could rise over the next several centuries.

DORTHE DAHL-JENSEN: We know from all the other ice cores we have drilled that we find ice from that Eemian period in the ice cores. And that process immediately tells us that, even though it was warmer over Greenland, it wasn't warm enough for the whole Greenland ice sheet to disintegrate.

And that's something that's debated a lot, how much warming we will need in the future before the Greenland ice sheet will -- will totally disappear, before we go beyond the tipping point.

HEIDI CULLEN: Now that this drill season has come to an end, the scientists are heading home, where they will continue working to unlock the climate history trapped inside those tiny, but telling bubbles.

JIM LEHRER: You can find out more about the scientists in Greenland and watch an interview with one of the C-130 pilots. Just follow a link from our Web site, NewsHour.PBS.org, to Climate Central.