Dramatic Retreat: Atop the North Cascades’ Vanishing Glaciers
Story by John Thompson
Images and video by Rhys Logan
Mount Baker’s glaciers are disappearing, and Western Washington University graduate student Monica Villegas and Professor of Environmental Studies Andy Bach are working to better understand not only why this is happening, but how quickly.
Mount Baker sits in the heart of the North Cascades range about 30 miles south of the U.S./Canada border, and is the third-highest peak in Washington state, behind only Mount Rainier and Mount Adams. In 1999, the weather station at the ski area there recorded the highest single season of snowfall ever, at more than 95 feet of snow, which makes the plight of its glaciers even more ominous.
“The glaciers on Baker are receding at an alarming rate,” said Bach. “In the 20 years I have been studying them, I have seen huge changes. The more information we can gather about how quickly these glaciers are shrinking, the better we can understand and document how climate change is impacting our local environment.”
Villegas , Bach, and undergraduate assistants Marissa Wall (Renton) and Keith Martin spent this past summer focusing on the rate of retreat of Mount Baker’s Easton Glacier, a massive tongue of ice on the mountain’s south flank.
Glaciers form atop mountains like Baker — which set the world record for snowfall in a single season in 1999 — through a process of snowfall, pressure, and compaction, as snow goes through the process of being turned from new snow into a substance called firn and finally into sky-blue, super-dense glacial ice.
Given enough snowfall over enough winters, the glacier will grow and flow downslope under the influence of gravity, its sheer bulk and size transforming the mountain’s valley from the usual “V” shape into a huge “U” shaped glacial trough. In the case of the Easton glacier, the western edge of its trough is familiar to many local hikers as the upper part of the popular Railroad Grade trail.
Glaciers are hugely impactful to regional climate in many ways; for example, their ice-cold summer runoff is a huge boon to the returning salmon in rivers like the Nooksack and Skagit. Snow that falls on Baker in the winter to later become glacial ice is stored away to be slowly released over the summer, as opposed to the rain falling in the foothills and lowlands which runs off during the wet season.
“As our glaciers disappear, we will have lower stream flows in future summers and warmer water in the rivers because there won’t be that cold water added…it will be another hit to salmon,” he said.
Shifting patterns, retreating glaciers
Should weather patterns change and snowfall levels drop, a glacier may undergo what is called retreat — when instead of growing and continuing its push downhill, it shrinks and pulls back up the valley it has carved in the mountainside, leaving a massive glacial trough its wake. This is what has happened with the Easton Glacier, and Villegas and Bach are searching for answers. If they could plot the glacier’s furthest terminus, they could see more precisely how far and how fast the retreat has occurred.
But what could an empty, rock-strewn valley tell them?
The answers are in the trees that have begun to grow in these landscapes.
“The idea was to move in a transect from the base of the glacier down the valley, just beyond where we know from historical photos from the early 1900s that the glacier’s terminus was, and sample the trees along that transect,” said Villegas. “The transect ended up being more than two miles long.”
Bach said that distance alone was worth taking on the project.
“For a glacier the size of Easton to have retreated that far — about 3.5 kilometers in about 150 years, is stunning,” he said.
At each sample point, Villegas took tree cores from the bases of the 10 trees nearest to the sample point’s center. Each core is a cross-section of the tree’s growth cycle, and by counting the core’s rings under a microscope, an age for that tree can be determined.
“Each core is like an almanac into that tree’s life,” Villegas said. “We can tell so much about the weather patterns that contributed to the behavior of the glacier from looking at those rings.”
The farther down the valley they went, the older the trees became, and vice-versa.
“This tells us in general terms where the ice was at any given time,” said Villegas. “The tree can’t start growing until the glacier has retreated past its location. So knowing the ages of the trees in the valley gives us an accurate map of where the terminus was.”
Using this methodology, Villegas was able to figure out that the glacier had actually pushed farther south than had been originally thought, making its retreat even more dramatic.
Now that she has completed gathering the cores, Villegas will accumulate all the summer’s research into her master’s thesis.
“It was an amazing summer,” Villegas said, a point echoed by her undergrad assistants as well.
Wall said the experience of doing real field work on a project of this scope was incredibly valuable.
“Seeing how the research was done, recording the data, using that data to better understand glacial retreat … it was such a good learning experience,” she said. “And at the end of the summer, having spent all that time in the valley, it was surprising how sad and emotional the idea of this glacier just disappearing made me feel.”
“What an incredible summer,” he said. “I guess what was most surprising was how you had the think and react on the fly as an instrument broke or there was some unanticipated occurrence. I’m starting my own research project this winter, and I am much more confident now, with this experience under my belt.”
Bach said he has been wanting to help with this research for years, after first visiting the valley in 1996 with WWU geologist Paul Thomas.
“And I finally found the right students to take it on,” he said.
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