Earth and Climate Sciences
From the outside, a plug of ice extracted from the depths of an Antarctic glacier might look like just that: ice. But that cylinder of frozen water contains an invisible layer cake of data about Earth’s atmosphere over thousands of years.
Bess Koffman studies these ice cores, looking for clues about how wind patterns and dust levels have changed over time. Like tree rings or layers of mud at the bottom of a lake, ice can function as an “archive,” storing past details that help us understand the current climate, says Koffman, an assistant professor of geology at Colby.
Dust has a significance that reaches far beyond the top of your television. Both in the past and today, airborne particles in the atmosphere reflect sunlight and contribute to cloud formation, producing a cooling effect. They also carry nutrients such as iron to the oceans, Koffman explained, feeding algae “that are working as the lungs of the world, removing carbon dioxide and pumping oxygen back out into the atmosphere.”
Glaciers grind up a lot of dust. So do humans. The complex effects of farming around the world, from deforestation to fertilization runoff, also include dust that is “cooling the atmosphere just a tiny bit,” Koffman said. The details about that grit—where it comes from, how much there is, and where it lands—have mind-boggling implications, touching everything from air temperature to marine life.
By melting an ice core one meter at a time and using advanced equipment to exhaustively analyze its contents, Koffman is able to see how dust composition in Antarctica has changed over time. Bigger dust particles, for example, point to stronger winds, which in turn affect ocean currents that influence how fast ice melts.
Koffman, who grew up in Maine, became interested in ice core research during her junior year at Minnesota’s Carleton College, where she heard lectures from visiting glaciologist Richard Alley. Inspired, she read Alley’s book about ice core research in Greenland, The Two-Mile Time Machine.
Upper left, Dartmouth College student Julianne DeAngelo, right, collects snow samples in a clean suit while Meg Yoder ’19, left, prepares the snow wall for stratigraphy measurements during research with Assistant Professor of Geology Bess Koffman on the Kahiltna Glacier in Alaska this summer. Upper right, DeAngelo measures snow-pit stratigraphy. Refrozen melt layers can be seen as bright lenses in the snow wall. The thickness and frequency of these layers informs scientists about past temperature conditions on the glacier. A second, neighboring pit is used to back-light the snow wall. Lower left, Yoder uses a high-precision GPS to track glacier motion. Lower right, Koffman and team prepare to depart Denali Base Camp aboard a ski-equipped Twin Otter plane. Pictured, from left to right, are Koffman, Yoder, DeAngelo, and Dartmouth students Victor Cabrera and Eleanor Dowd.
“I just found it really fascinating,” she said. “He highlighted the fact that there are so many things we don’t yet understand about the climate.” She went on to conduct research in Antarctica, earning a Ph.D. in earth and climate sciences at the University of Maine.
One of the questions Koffman is exploring is how ongoing climate change will influence the natural sources of dust-derived nutrients in the ocean. How will marine algae respond to these nutrients? Will that response have implications for ecosystems and fisheries? Understanding these dynamics will be important in managing marine fisheries, she says, as well as the sustainability of communities that depend on them.
That analysis is now being done in new facilities at Colby in the Mudd Building, including a walk-in refrigerator and freezer for storage of sediment and ice cores, and a purpose-built geochemistry laboratory. The freezer contains ice cores from several sites in Antarctica, which research students will analyze in coming years. Additional ice from Alaska, drilled during a research trip in summer 2013, will be brought to the Colby lab in the near future.
Koffman is also interested in the best ways to engage students. She recently published a paper on how making scientific argumentation part of a college course can improve learning. “The idea is that you want to get students grappling with the evidence as much as possible,” she says. She also plans to bring students into the lab and out in the field—going to local lakes, for example, to send a coring device into the mud.
It’s a chance to inspire young students in the same way that glaciologist Alley inspired her as an undergrad. “I wanted to do something that I felt was relevant for society,” she says of her research. “I felt like studying past climate would elucidate processes that are relevant for understanding our climate today and into the future.”
Portrait by Heather Perry ‘93