New ice cores expand view of climate history

11/18/05

CORVALLIS, Ore. – Two new studies of gases trapped in Antarctic ice cores have extended the record of Earth's past climate almost 50 percent further, adding another 210,000 years of definitive data about the makeup of the Earth's atmosphere and providing more evidence of current atmospheric change.

The research is being published in the journal Science by participants in the European Project for Ice Coring in Antarctica. It's "an amazing accomplishment we would not have thought possible" as recently as 10 years ago, said Ed Brook, a professor of geosciences at Oregon State University, who analyzed the studies in the same issue of this professional journal.

"Not long ago we thought that previous ice studies which go back about 500,000 years might be the best we could obtain," said Brook, who is also the co-chair of the International Partnerships in Ice Coring Sciences, a group that's helping to plan future ice core research efforts around the world.

"Now we have a glimpse into the past of up to 650,000 years, and we believe it may be possible to go as much as one million years or more," Brook said. "This will give us a fuller picture of Earth's past climates, the way they changed and fluctuated, and the forces that caused the changes. We'll be studying this new data for years."

As the data become more solid about the atmospheric conditions of the past, it's becoming increasingly clear that the current conditions of the past 200 years are a distinct anomaly, Brook said.

"The levels of primary greenhouse gases such as methane, carbon dioxide and nitrous oxide are up dramatically since the Industrial Revolution, at a speed and magnitude that the Earth has not seen in hundreds of thousands of years," Brook said. "There is now no question this is due to human influence."

The ice cores being taken from Greenland, Antarctica and other sites provide an invaluable record of Earth's past climates, researchers say. By testing the gases and trace elements found trapped in these cores, scientists gain a better understanding of how climate and atmospheric gases interact and evolve.

"We predict, for instance, that rising levels of greenhouse gases will warm our climate," Brook said. "There's evidence that this is happening right now, and it would be interesting to find out if the same thing has happened at times in the distant past. And there are also concerns we're exploring about rapid shifts in climate."

Analysis of the older cores just removed from Antarctica, Brook said, are consistent with some of the quick changes in methane and carbon dioxide levels that are related to abrupt climate change. However, it also appears that the natural climate cycles in the distant past – the development and retreat of Ice Ages, for instance – were smaller in magnitude and had less fluctuation in atmospheric gases than what the Earth is now experiencing.

There are critical questions that work of this type may help answer, researchers say. One of the most obvious is the relationship between increasing levels of greenhouse gases and global warming. But there are also concerns that the Earth's climate may have changed very abruptly at times in the past, in complex interactions between the atmosphere, ocean currents and ice sheets.

Past studies of gases trapped in Greenland and Antarctic ice cores have suggested that Earth's temperature can sometimes change amazingly fast, warming as much as 15 degrees in some regions within a couple of decades. At the same time, there are concerns about the change of major ocean currents, such as those in the North Atlantic Ocean, that are responsible for the comparatively mild climate of much of Europe. If that "thermohaline circulation pattern" were to abruptly shut down, as has happened at times in the past, it could plunge much of the European continent into a climate more closely resembling that of central Canada.

According to Brook, continuing research will help to address many of these questions. The international committee he co-chairs, which involves representatives from 17 nations, is considering such work as a very deep ice coring project in Antarctica that might provide a record of atmospheric gases 1.2 million years ago, or even further back in time. Other studies are also anticipated in Greenland and the Arctic.

Some of these projects will require drilling in challenging locations on very old ice, Brook said, at considerable cost in initiatives that require international cooperation.

"Ice cores are the cornerstones of global change research," Brook said. "They have played a central role in showing how closely climate and greenhouse gas concentrations were linked in the past, and they are demonstrating also that very abrupt climate switches can occur."

Source: Eurekalert & others

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