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SDSU postdoctoral researcher Dave Ferris, in the background, and researcher Inger Seierstad of the University of Copenhagen are shown on site in Antarctica packing an ice core in mesh netting to help protect it during transport.

BROOKINGS - Scientists nationwide are studying an ice core from Antarctica to learn about changes in Earth’s atmosphere — and SDSU will help provide the crucial timeline to pinpoint those changes over time.

Collaborating as part of the National Science Foundation's West Antarctic Ice Sheet Divide (WAIS Divide) Ice Core Project, a South Dakota State University team is one of three research labs working to date the ice core year by year.

Drilling of a long ice core at the West Antarctica location of the WAIS Divide Ice Core Project began late last year and will go on for at least the next two years. SDSU will be processing samples from the ice core for perhaps the next four years under the direction of associate professor Jihong Cole-Dai in the Department of Chemistry and Biochemistry.

Postdoctoral researcher Dave Ferris of the SDSU Department of Chemistry and Biochemistry was a member of the West Antarctica field team from late November 2007 until late January 2008. During this first drilling season the team of scientists and engineers drilled 580 meters of ice core, or 1,900 feet. Eventually they hope to recover an ice core reaching to the ice sheet bottom at 3,465 meters, or 11,360 feet — about two miles.

The dust, chemicals and air trapped in the ice will provide information about the past 100,000 years of Earth’s climate, including what scientists hope will be a year-by-year record stretching back perhaps 40,000 years. Scientists know they won’t be able to annually date the entire ice core because the annual signals that separate one year from another become closer and harder to separate deeper in the ice pack.

Other research groups will perform measurements on the ice including carbon dioxide concentrations and temperatures. Ferris said the work by SDSU and the other two labs that are dating the ice core will help put the measurements by the other research groups in context.

“You might be able to determine the carbon dioxide level at 500 meters deep, but what does that tell you unless you can put a date to it?” Ferris said.

Dating the ice core

The three research groups that are dating the ice core from WAIS Divide are using three different methods. They will also compare their results and try to reconcile differences. From an earlier shallow test core of just over 100 meters covering nearly 500 years, the three groups found their various methods were all within a year or two of each other.

The method SDSU uses to date the ice core relies on chemistry. Associate professor Jihong Cole-Dai has arranged a panel of instruments in a configuration of his own design so that SDSU can process about 12 meters of ice per day, a centimeter at a time.

The ice is first melted and then the water is analyzed so that the levels of ions — essentially the dissolved minerals — can be charted to produce an ion chromatogram. It shows visually the levels of ions of magnesium, sodium and sulfate.

Ferris explained sodium and magnesium are found in seawater, and get into the air from bubbles bursting over the open sea and eventually fall onto the ice sheet with snow. Since the quantity of sea ice covering the ocean around Antarctica fluctuates with season, there’s a seasonal shift from winter to summer in the amount of sea salt that is blown inland. As the scientists melt the ice core, those seasonal differences show up, centimeter by centimeter, as highs and lows in the levels of sodium and magnesium. Charting the levels of ions in ice samples becomes a visual record of those seasonal shifts in the atmosphere.

“As we melt we’ll take an ion chromatogram for every centimeter to get the ion concentrations for that centimeter, we can then plot all the ion concentrations over depth,” Ferris said. “What you do then is go back and start counting the increases and decreases in salt content, just like tree rings.”

In addition, SDSU researchers pay attention to sulfate levels. Occasionally there are very strong sulfate signals because of volcanic activity. That can provide a way of crosschecking the record, since scientists know when some volcanic eruptions occurred. For instance, scientists are confident that there was an eruption in A.D. 1259. When the number of years counted up to this event matches its age, it verifies the accuracy of the counting.

Ferris, who is hoping to return to Antarctica next season, said it’s exciting that SDSU science is a crucial part of the Antarctic research to pinpoint how and when Earth’s atmosphere and climate changed.

“The work that is being done right here in South Dakota is going to have an effect on how the discussion continues,” Ferris said.

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