By Christiana Freitag
Medill Reports, Nov. 3, 2024
Trekking up windy and swampy fjords of southwestern Norway, University of Maine graduate researcher Katie Westbrook searched for a boulder – but not just any boulder. Westbrook was looking for an ideal ridge of boulders called moraines that could reveal mysteries about the last ice age.
In Lysefjord, Westbrook and fellow glacial geologists used samplings from boulders to build out the chronology of Norwegian glaciers. Examining moraines, such as the iconic Esmark Moraine where researchers first discovered evidence of Earth’s ice ages in the 1820s, Westbrook and her research team uncovered chronologies consistent across Northern and Southern hemispheres, giving climatologists a better understanding of the global timeline of the last ice age. The timeline reinforces the global nature of climate change that we are seeing currently at an accelerating pace.
“The timing of when these moraines were constructed is exactly the same as in the Southern Hemisphere as well as other places across the whole planet,” Westbrook said.
The 52 samplings that Westbrook collected in August 2023 enabled her to confirm a timescale for Scandinavian glacial melt during the Antarctic Cold Reversal during the Last Glacial Maximum. After a full year of waiting for her collection results, Westbrook’s samples revealed that the moraines in Lysefjord were formed 12.8 thousand years ago, meaning the boulders were freed from a retreating glacier that tossed them aside. That’s the approximate time when the Birch Hill moraines in New Zealand were shed from a comparable glacial system in the Southern Hemisphere.
“So when we’re developing a hypothesis for ice ages in the late glacial period and the climate dynamics that caused the slight variation during the warming, they need to take into account that this is a global event,” Westbrook said.
Westbrook presented her findings from her month-long fieldwork at the 2024 Comer Climate Conference, an annual fall event held in southwestern Wisconsin. The conference invited leading climate researchers from around the world to present their breakthrough findings. They included Aaron Putnam, the University of Maine associate professor of Earth and Climate Sciences who is Westbrook’s adviser and a leader in the research determining that ice ages were synchronized across both hemispheres. University of Main Ph.D. candidate Tricia Hall Collins partnered with Westbrook on the Lysefjord fieldwork.
Westbrook, Collins and Putnam collected quartz with a cosmogenic isotope of beryllium – an isotope created by cosmic ray bombardment from 2,900-foot-tall fjords in Norway. Westbrook prioritized the mouth of Lysefjord and extracted quartz from the moraine boulders to later count the number of isotope atoms of beryllium-10. The counting is done at the labs back home. Since beryllium-10 accumulates at predictable rates after boulders are freed from a glacier, the amount of it present offers a time machine for the retreat of the last ice age. Subsequent moraines tossed aside in the glacial retreat will be younger, with ages based on beryllium-10 levels, and that reveals the pace at which the ice melted during the last ice age.
“We’re trying to understand how the climate system operates,” Putnam said. “That sets the stage for us to understand when you perturb it, like how humans are doing now, we can predict how it might behave in the future.
Westbrook’s findings builds off Putnam’s research on Esmark Moraine, supporting a 1824 hypothesis by Jans Esmark that Norwegian moraines were established by large volumes of ice that covered entire continents. Esmark’s hypothesis was published over a decade prior to Louis Agassiz’s theory on ice ages and is often considered the beginning of glacial studies.
“Esmark was the very first evidence that Earth ever experienced an ice age,” Putnam said.
Mentored himself by acclaimed climatologist George Denton, Putnam is now passing the baton onto the next generation of researchers such as Westbrook. Putnam has made a career in understanding what ice can reveal about the past and future of Earth’s climate systems.
“What’s happening today is happening everywhere,” Putnam explained. “And the place you can see it most clearly is the ice. Glaciers are incredibly sensitive to climate change. Small incremental changes in temperature can drive large glacial responses, which we’ve seen everywhere we’ve gone.”
Lysefjord provided ideal conditions for mapping glacial systems, with some of the most prominent rock moraines in the world. To Westbrook, Lysefjord is one of the best places to do this type of climate work, having her fair share of ideal moraines to choose from. Westbrook explained that the perfect boulders to examine needed to be at the top of ridges, had minimal erosion and were large enough that “trolls couldn’t push them over.”
When reflecting on her work in Lysefjord at the Comer Conference, Westbrook eagerly shared the prime rock moraine samplings she found and the Norwegian troll lore in the area.
“If I have any outliers in my dataset, we can just blame it on the trolls for moving them,” Westbrook said.
Photo at top: Katie Westbrook extracting quartz for beryllium-10 isotopes from rock moraines in Lysefjord, Norway. (Courtesy of Katie Westbrook)
