PETERSBURG – Last week, the Petersburg High School LeConte Glacier survey team tracked the latest movements of the tidal glacier after surveying its terminus earlier this month.
Students traveled by skiff and helicopter to the site where they measured LeConte’s terminus, or the point of the face of the glacier furthest out.
They used vertical and horizontal plane measuring instruments called theodolites.
“To make it easier for ourselves, there are stakes driven into the rocks so we can set up on the same points year after year after year,” junior Kyle Hagerman said.
PHS instructor Paul Bowen began the program in 1983 and Petersburg students have been surveying the glacier every year since then. PHS teacher Victor Trautman currently oversees the program.
The survey is a voluntary activity and student’s who participate don’t receive any school credit. They train every Wednesday during their lunch break where they shoot angles and practice using the theodolites on the streets in town.
“You have to practice a whole year before you get to go,” senior Cynthia Benitz said. “You get selected from surveyors in the community. Once you’re selected you usually survey the entire year and then the following year in May you get to go [to the glacier]. You basically practice for almost two years before you get to go.”
For the last three decades, the glacier’s path has fluctuated but has been relatively stable since 1998. Snow pack effects the glaciers movement rather than temperature. Trautman said the LeConte Glacier is best used to compare to valley glaciers, such as Baird, which is directly climate related.
“If LeConte is stationary and Baird is retreating you can say it’s probably related to temperature,” Trautman said. “If they are both retreating that’s probably snow pack. The snow pack drives both of them. The more snow, the more push it gets. It’s like stepping on toothpaste. It squeezes it out.”
LeConte has been advancing the past several years.
“We’re anxious to see this year if things are different because of the mild winter,” Hagerman said.
Hagerman, Benitz, Shalie Dahl, Sierra Streuli, Diane Murph and Fran Abbott participated in this year’s survey and spent last Wednesday evening, along with students in training, at school with Trautman triangulating their measurements with scaled sketches of the glacier.
“Those guys are the workers,” Trautman said. “All I do is sit back and prod them and poke them.”
After an evening of poking and prodding, they found the southern half of the glacier’s terminus has advanced about 50 to 60 feet while the northern half has receded about 100 feet.
“The face of the glacier has probably changed but because of the variability it’s still kind of in the same spot,” Hagerman said.
The glacier also changes with the seasons but May, when the survey is conducted, is the month when they can measure the most striking changes.
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