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Machinery under a steel arch.
Photo Credit: Jay Johnson/WAIS Divide
The Deep Ice Sheet Coring (DISC) drill tilts toward the borehole for coring operations during the 2010-11 field season. Later this year, the drill will be modified with a new replicate coring system to extract ice cores from the side of the present borehole that are of interest to scientists, such as abrupt climate change events.

Repeat experiment

New replicate ice core system will target abrupt climate change events

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Scientists have been extracting ice cores from Antarctica for the better part of 50 years. But no one has tried to do what a team of researchers and engineers propose at the end of this year from a field camp in one of the snowiest regions of the West Antarctic Ice Sheet (WAIS).

“No one in the world has developed a system to replicate ice cores at any chosen depth and at any chosen azimuth within an existing borehole,” said Alex Shturmakov, director of engineering and research for Ice Drilling Design and Operations (IDDO) External Non-U.S. government site at the University of Wisconsin-Madison External Non-U.S. government site. “We are very excited. It’s always interesting to work on something that nobody ever worked on before. It is an engineering challenge.”

The multiyear WAIS Divide project External Non-U.S. government site recovered an ice core 3,405 meters into the ice sheet — the deepest ice core ever drilled by an American-based team. The major drilling operations were completed during the 2010-11 field season, with the hole deepened by about 75 meters during the most recent Antarctic summer, leaving a 50-meter environmental barrier above where the ice meets bedrock to prevent accidental contamination of the subglacial water system.

Schematic of a drill.
Photo Credit: IDDO
Schematic of the replicate coring system.
[See previous article — The last core: WAIS Divide deepens borehole for research into climate change.]

The ice core represents a window back in time on the Earth’s climate. Scientists can analyze bubbles of various gases trapped in the ice — particularly the important greenhouse gas carbon dioxide — to get a sample of the ancient atmosphere. Dust and chemicals found in the ice can also provide details about past climate.

But what makes the WAIS Divide ice core particularly special is the same thing that makes it an extremely difficult place to reach and work — tons of snow. That gives researchers fat annual layers of accumulation, which translates into a high-resolution paleoclimate record for the last 62,000 years.

“Abrupt climate change is a major focus of this ice-coring effort, and so we’re going to be looking in great detail at one or two of the abrupt climate-change events,” said Jeffrey Severinghaus External Non-U.S. government site, a professor of geosciences at Scripps Institution of Oceanography External Non-U.S. government site who is heading up the replicate coring science program for the WAIS Divide project.

It took about five years for drillers to punch through nearly the entire ice sheet, recovering a single sliver of Antarctic ice. That very finite supply is coveted by many researchers, who eventually must destroy their samples to conduct various analyses. That’s where replicate coring External Non-U.S. government site comes in.

Engineers at IDDO, which designed and built the Deep Ice Sheet Coring (DISC) Drill External Non-U.S. government site used for the WAIS Divide project, have developed a system to re-enter the borehole and extract additional ice related to areas of scientific interest, such as the abrupt climate change events mentioned by Severinghaus.

Person watches tower with cables.
Photo Credit: Krissy Dahnert/IDDO
The replicate coring system being tested in Madison, Wis.

“Basically, it transforms the DISC drill into replicate coring system through the inclusion of several new components,” explained Shturmakov, the project manager for both the DISC drill and replicate coring system, which has been in development since 2009.

Components of the system were tested at the end of the 2011-12 field season after researchers conducted further measurements of the borehole itself. Shturmakov said the attempts to penetrate the ice by deviating from the borehole illustrated what needed to be addressed this summer in Madison.

“We do not plan to test [it] next season. We know what to fix and we know how to fix it,” he said, adding that full-scale tests are under way now in Madison.

Scientists hope to extract about 250 meters of new ice cores from several sections, going down more than 3,000 meters deep for one section dating back 38,000 years to a period of abrupt warming during the last glacial period.

“It’s an abrupt climate change that happened at a time when Earth’s orbit was not changing. In other words, you don’t have the complicating influence of the Earth’s orbit,” said Severinghaus, referring to the time period dubbed Interstadial 8 during the last glacial period.1 2   Next