Oregon State University

College of Earth, Ocean, and Atmospheric Sciences

A Glacier in Retreat

Zoe Kilmer

Undergraduate Zoe Kilmer conducting research at Columbia Glacier in Alaska to learn why the glacier is retreating.

Columbia Glacier winds through the Chugach Mountains of Alaska — a crooked finger of ice pointing to Prince William Sound. As a tidewater glacier, it flows directly into the sea. Columbia is also in rapid retreat, shrinking more than 20 kilometers in the past three decades. This last part raises eyebrows for some researchers at the College of Earth, Ocean, and Atmospheric Sciences (CEOAS) at Oregon State, including undergraduate student Zoe Kilmer.

“In the last 900 years, the glacier was pretty stable,” says Kilmer, a bioresource research and environmental sciences double major and co-author on a recent paper about Columbia. “But recent decades have shown a very dramatic retreat.”

To be fair, tidewater glaciers can be a tad fitful, the wild cards amongst their glacial kin. One can be shrinking while another right next to it can be growing. So, Kilmer and her advisor, Anders Carlson, a glacial geologists, sought to answer whether the Columbia retreat was random or in response to recent warming. Understanding the cause behind the Columbia retreat is important, Carlson says, since tidewater glaciers are the largest contributors to global average sea-level rise, other than Greenland and Antarctica. In addition, Columbia’s meltwater could change the circulation and ecology of Prince William Sound, home to some of the most significant salmon runs in the state of Alaska.

“The freshwater input from these glaciers affects local currents and locations of productivity that can change fisheries habitat,” he says. “That’s important for both tourism and the economy.”

Undercover Undergrad

Kilmer and Carlson pieced together clues about Columbia over the last millennium, when humans had much less influence over the climate. If they still saw the signal of retreat from 1,000 years ago, maybe the current shrinking is random and humans are off the hook. But if not…

To reconstruct Columbia’s history, Kilmer turned to marine sediments, the leftovers from grinding glaciers. As Columbia retreated, it sloughed across a fault line and deposited sediments. Rocks from either side of the fault showed different magnetic and geochemical properties. Scientists can look at these properties to uncover where the sediment started its journey, how far it traveled and whether the glacier had crossed the fault line before.

Kilmer ventured into the Alaskan hinterland with graduate student David Leydet, collecting river sediment samples near Columbia Glacier. They boarded a skiff to explore the glacier terminal, hiked in the mountains and camped in the wind-thrown Thompson Pass. Kilmer was a key detective in the field and lab, Carlson says.

“She pulled the field work off and did a phenomenal job of conducting all the follow-up work. I had the idea and ran some things by her, but she really did everything,” he says.

Data from the sediment record were then compared to tree-ring data, as tree growth varies depending on the climate and can be used to reconstruct past conditions. Altogether, the evidence supported that Columbia Glacier has not retreated to its current position at any point in the last millennium. Translation: human-caused warming is the likely culprit.

“We can say that recent increases in temperature have contributed to this retreat,” Kilmer says.

Carlson puts it in more stoic terms: “Roughly 1°C warming has permanently gotten rid of the Columbia Glacier. It’s not coming back any time soon. That means that all other glaciers in the area could be irreversibly gone, they just haven’t started retreating yet.”

Eye Witness

For Kilmer, an avid angler who grew up in the outdoor Mecca of Bend, Ore., her research was eye opening — literally.

“So much of what we learn about climate change is unseen,” she says. “But we’re seeing these incredible areas disappear, and that matters in our lifetime. This glacier has retreated 20 kilometers in recent history. What is it going to do in another 30?”

Carlson has been asking himself the same question, hoping to apply lessons from the Columbia study to other nearby glaciers.

“We think that by showing we can do this at Columbia Glacier, we can do a similar thing for the largest glaciers in North America,” he says. “It’s a proof of concept. Let’s now apply it to some place where we have little or no data.”

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