The Big Importance of Tiny Particles of Dust
Geology professor Bess Koffman heads to the Yukon to learn more about high-latitude dust
This summer, Associate Professor of Geology Bess Koffman and Audrey Lemoine ’25 flew by helicopter to remote locales in the Yukon, surprised grizzly bears (from a distance), and marveled at the Canadian territory’s vast landscape of mountains, glaciers, and rivers.
They did it all for science.
Koffman and Lemoine went to Canada in June for an international research expedition to collect samples of high-latitude dust, something that affects weather, the climate system, and the environment but is not well understood.
“High-latitude dust is sort of underappreciated in general, but people are starting to realize how important it is in the climate, and that was the overarching goal,” said Koffman, a geochemist and climate scientist, whose research program analyzes mineral dust and volcanic ash preserved in layers of glacial ice. “We’re interested in seeing how dust has accumulated on the landscape, knowing that the dust has been produced by glaciers, and that the glaciers have fluctuated through time.”
An international team
For this trip, Koffman, Lemoine, and a team of collaborators from the Uppsala University in Sweden and the University of Montreal headed to Kluane Lake Research Station near the Saint Elias Mountains in western Yukon. From there, they accessed a total of 12 sites by helicopter and four-wheel-drive truck, including the ends of four glaciers.
The data the Colby contingent gathered and are now analyzing in a laboratory in the Mudd Science Building will add to global knowledge about high-altitude dust by providing what Koffman called a “fingerprint” of its specific isotopic composition.
“One of the main things we’re doing here at Colby is adding to the catalog, essentially,” she said. “By learning what this dust area looks like geochemically, we can trace the dust to downwind sites, and fingerprint it and say, ‘This came from the Yukon.’”
The team of scientists received funding from INTERACT, the European Commission’s Arctic monitoring and research program, and from Colby’s Buck Lab for Climate and the Environment. The Buck Lab provided support for a day of helicopter time so the group could access four hard-to-reach glaciers that drain from the Saint Elias Mountains.
“The helicopter was just incredible,” Koffman said. “We were able to sample directly at the glaciers because of it.”
‘This incredibly dusty place’
Fittingly enough, the scientists did their work in a location that’s known for being dusty. After the last ice age ended around 18,000 years ago, the glaciers started to recede, a process that has gathered speed in recent years. Until 2016, meltwater from the Kaskawulsh Glacier drained through the Ä’ąy Chù (Slims River) and ultimately flowed north to its outlet in the Bering Sea.
That spring, though, the glacier melted enough that the drainage abruptly switched to a different river, the Kaskawulsh, that ultimately joins the Alsek River and flows south to the Gulf of Alaska. This shift from one river’s flow to another is called river piracy, Koffman said, and although it’s a known phenomenon, this was the first documented case in modern times.
“The effect of that was shutting off the water supply [to the Ä’ąy Chù],” Koffman said. “So now there’s this valley that’s just packed with all this glacial sediment that’s been traveling down for hundreds of years. Now it’s just as if the glacier doesn’t exist anymore, but it produced all this dust. And so it’s this incredibly dusty place.”
Even on a clear day, she said, you could see the dust—something that’s very interesting to dust-studying scientists. Mineral-rich, wind-borne dust, or loess, deposits there have been accumulating for around 12,000 years.
“It’s just glorious. It’s beautiful, and the dust is clearly there,” Koffman said.
She and Lemoine gathered samples from the dry river valley and also from the Alsek River, where the glacial melt now flows. That river has fast-moving, cold water that is brown because of the sediment carried in it.
Lemoine, an environmental science and geology double major, is helping to process those samples. She’s doing her senior thesis on Yukon dust, looking at how trace metals in the meltwater can be a source of nutrients in iron-limited ecosystems, such as in the Gulf of Alaska. It meant a lot to her to have the opportunity to go into the field to do the collection work, and she will always remember flying to glaciers on the helicopter and gathering water samples from the cold river.
“Before, I was getting the lab experience, but I didn’t really know where samples came from,” she said. “I think it was really cool to have gone there and collected them myself.”
A return to the field
The Yukon research trip marked the first time that Koffman had gone into the field since before the Covid pandemic. In 2018, she went to Denali National Park with student research assistants Taylor Methven ’20 and Meg Yoder ’19 to collect samples for a study that eventually traced lead pollution there and at Arctic sites to its source, which is predominantly in China.
“I haven’t been to the field to do research in a more remote place for quite some time,” Koffman said. “It made me feel more like a scientist. This is part of my identity, too— I’m not just a lab rat. It was good to get back out there.”
For the professor, it matters that all students have the opportunity to be part of doing science. Her lab tends to be attractive to women and non-binary people, which is something that is not always the case in STEM fields of study, and is all the more critical for that reason, she said. Koffman even co-led a study and published an article last November in Nature Geoscience that looks at the persistent gender gap within ice core science and concluded that collaboration between women is a key factor in closing the gap.
“I think just because women are drawn maybe more to climate research, and they’re drawn to working with a younger woman scientist,” she said. “It’s very important that they can see themselves as scientists, and that they can decide to pursue science.”
This summer, Koffman received the Next Generation Award from the American Quaternary Association for “committed and creative leadership in advancing inclusion, diversity, equity, and access in science.”
“I just try to pull people in and make them feel like they’re valuable,” she said, “and that even if they’re new and fresh, they can still have some perspective to share.”
