When Ted Scripps Fellows come to Colorado to study, they don’t typically expect to be surrounded by polar ice in 40-below temperatures, even in January.
But such was the case when fellows visited the National Ice Core Laboratory in Lakewood, Colo., on a program field trip. Here, though, the ice was locked inside thousands of thin silver cylinders in a freezer unit within the vast suburban complex that is the Denver Federal Center. Inside each cylinder are data that provide scientists with records of ancient climate patterns.
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| Scripps Fellows & CEJ staff shiver inside the ice freezer. (Photo/John Kotlowski) |
The freezer is at the center of the National Ice Core Laboratory, a facility for storing, curating and studying ice cores recovered from the polar ice sheets and high mountain glaciers of the world. The lab is jointly operated funded by the U.S. Geological Survey and the National Science Foundation.
Its purpose is to get information about the climate history of the Earth, obtained by studying the composition of the Earth’s atmosphere over time. Through analyzing gases in air bubbles trapped in the layers of compressed ice, scientists can reconstruct past climate states of the Earth, including temperature changes over millennia.
The lab’s technical director, Todd Hinkley, explained that studying past climate fluctuations can help scientists better understand the factors that prompt such shifts and potentially help them predict future climate change.
Ice core samples are more thorough than other means of assessing climate history, including tree rings, coral and sediments from the ocean floor. The lab’s web site explains that “an ice core from the right site can contain an uninterrupted, detailed climate record extending back hundreds of thousands of years. This record can include temperature, precipitation, chemistry and gas composition of the lower atmosphere, volcanic eruptions, solar variability, sea-surface productivity and a variety of other climate indicators. It is the simultaneity of these properties recorded in the ice that makes ice cores such a powerful tool in paleoclimate research.”
Geoff Hargreaves, the lab’s curator, served as the fellows’ tour guide through the lab. Sporting a ponytail that reaches to the middle of his back and a long, wavy gray beard, Hargreaves looks like a modern-day biblical patriarch. The facial hair comes in handy, he acknowledged, when every bit of extra warmth is welcome for someone who spends as much time as he does in sub-zero temperatures.
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| National Ice Core Lab curator Geoff Hargreaves sports a rime-coated beard. (Photo/John Kotlowski) |
Hargreaves helped fellows don heavy parkas for their foray into the freezer, stacked to the ceiling with shelves of cylinders containing the unique collection that Hargreaves oversees. Once inside, his beard hairs were quickly coated in white frost as he explained how the ice core samples made their way from the Earth’s most remote regions to the Lakewood warehouse.
Polar core samples are obtained from Antarctica and Greenland, drilled from deep sheets of ancient ice that has never melted. Greenland samples offer 1/4 million years of data, while Antarctic cores reveal at least 1/2 million years of information and the ability to extrapolate much farther back.
The oldest site is Vostok in Antarctica, where cores have been drilled to a depth of 3,623 meters, or 2 1/4 miles. Beneath the Vostok ice sheet lies a 1,000-meter-deep ancient lake the size of Lake Ontario, created when the weight of the ice above exerted pressure so strong that the friction melted the lowest layers.
The lab, which is the most comprehensive storage facility of its kind in the world, has more than 14,000 meters of ice available for scientists to examine. The cores, which are 3 to 5.2 inches in diameter, are obtained via a lengthy and expensive drilling process. Gas bubbles do not begin to form until the ice is 60 to 100 meters deep, and it can take three to four years to drill a very deep core at a cost of $20,000 per meter, according to Hargreaves. The deepest cores have been drilled to bedrock.
Antarctica’s severe climate allows drilling only during the southern summer from October through January. The last flight out is at the end of February, when the ice cores are loaded onto a ship bound northward.
Preserving them until they reach Colorado is an involved process. The cores are cut into 1-meter pieces, sealed in plastic bags labeled liberally with arrows to note the “up end,” put into silver tubes to reflect heat-inducing light, then placed into insulated shipping containers and stored under the snowpack until it’s time to transport them. The ice must remain at -15º C or colder once it is out of the ground or the gases within will begin to migrate.
The containers are flown aboard a ski-equipped LC130 airplane to McMurdo Station by a frigid pilot who must fly without heat in order to keep the ice cold enough. There, it is loaded into a freezer on board ship and brought to Port Hueneme, Calif., where it is moved onto freezer trucks and taken to the National Ice Core Lab in Lakewood. Each truck is accompanied by an empty truck that is kept cold, in order to transfer the ice in case of an accident or breakdown. Hargreaves explained that it’s cheaper to pay $2,000 for an extra truck than to lose a single meter of ice, which costs $3,000-$20,000 per meter to obtain.
Once the ice cores are safely ensconced in the lab’s freezer, they are available for scientists to study, either at the lab or another research site. Pieces of ice are sent out in vacuum-insulated boxes that keep the ice at -20º C for a week, in any ambient temperature.
Researchers may examine the ice in solid condition or melt it in order to do core gas analysis. In any case, they receive only a piece of the core sample, not the whole diameter, in order to leave a good portion of it as archive. An archive of the entire Vostok core is kept at the lab, Hargreaves said, since it is the coldest and safest repository in the world.
Paleoclimatologists such as Jim White, a University of Colorado geology professor and scientist with the Institute of Arctic and Alpine Research, rely upon core samples from the National Ice Core Lab to further their knowledge of what causes climatic shifts. White spoke to the Ted Scripps Fellows about his research during a seminar leading up to the fellows’ visit to the lab.
White is particularly interested in rapid climate change. The evidence he has uncovered suggests that temperature fluctuations sometimes occur as abrupt spikes, rather than gradual trends.
White’s research team has studied ice samples from the Siple Dome core in Antarctica to deduce that air temperatures there rose up to 18 degrees Fahrenheit in just a few decades as the last ice age began to wane some 19,000 years ago, the largest and most abrupt warming spike ever recorded in the Southern Hemisphere.
The timing of the warming correlates with an abrupt sea-level rise documented by researchers at Australian National University and with less dramatic warming increases seen in the Byrd and Vostok ice cores from Antarctica.
“The signal we see in the Siple Dome core is so strong, we can speculate it may have been the trigger area for the end of the glacial period,” White said. Because of its coastal location, Siple Dome would have been climatically sensitive to events like partial collapses of the West Antarctic Ice Sheet, which would have caused seas to rise globally.
Understanding events like these can help climatologists get a better grasp on the matrix of forces that influence climate change, especially as they seek to discern the more recent role of human beings in global warming. The ancient ice samples stored at the national Ice Core Laboratory are providing some of the keys to unlock those complex mysteries.
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