COAL BANK PASS – Fort Lewis College students spent nearly 20 minutes digging a large snow pit until it was above their heads. As they sheared snow off the side of the pit walls, they revealed distinct layers of dust trapped in the snow.

Nine undergraduate students traveled to Coal Bank Pass on Tuesday for their environmental research course and a field tour with Jeff Derry, executive director of Silverton’s Center for Snow and Avalanche Studies.

The students learned about dust on snow, snowpack and water resources while gaining field experience that will help guide them through their studies and into their careers.

“A lot of students in this major want to solve environmental problems and that means being able to talk and engage across a wide range of different fields of science,” said Heidi Steltzer, a professor of environment and sustainability at FLC and the course leader.

Steltzer, who coordinates FLC’s environmental science degree program, organized the field tour with Derry so students could learn more about the effects of dust on snow and the energy balance of snowpack at the time of year when dust events typically affect Southwest Colorado.

The class first snowshoed to a monitoring site where Derry and Steltzer spoke about snow-water equivalent, the metric water managers use to estimate runoff in spring, and the need for more robust scientific monitoring to understand the impact of climate change on the region’s water resources.

“We don’t do enough monitoring of our environment,” Steltzer said.

“The goal was never for these SNOTEL (monitoring) sites to characterize long-term change in the snowpack. The goal was annual water supply, so they aren’t ideally located to tell the story of change over time,” she said.

Students then dug snow trenches to examine dust and learn some of the measurement techniques they would need if they decided to pursue careers in snow science.

It was while measuring snow density and analyzing dust layers that Derry, who helps run the Colorado Dust-on-Snow program, broke down the impact of dust on snowpack and interconnected physics that ultimately lead to snowmelt.

Driven in part by land-use practices, storms across Utah, Arizona, Colorado and New Mexico kick up dust that is then deposited in Southwest Colorado.

“(The storms) originate mainly down south, so in the San Juans we’re the first hit and hardest hit,” Derry said.

The dust darkens the snow, lowering its “albedo,” a measurement of how much sunlight the snow reflects.

Because the sun, not temperature, drives snowmelt in Colorado’s mountains, the darkening of the snow has a significant impact.

“It increases the absorption of solar radiation in the snowpack, warming and melting the snowpack faster than it would have normally,” Derry said.

That’s the easy part.

Dust can also exacerbate snowmelt by spurring latent heat. Latent heat is the energy released when something undergoes a phase change, say from a solid to a liquid or a liquid to a gas.

Melting snow releases latent heat, as does melted snow as it refreezes.

“Solar radiation is melting this top bit of the snow and the water that’s melting percolates down into the snowpack and refreezes,” Derry said, pointing to the top layer of snow. “When that water freezes, it’s releasing latent heat, so it’s warming the snowpack.”

The more snow the energy-absorbing dust melts, the more latent heat the melting snow produces. In turn, this latent heat melts more snow, amplifying the effects of the dust.

“I love latent heat,” Derry said. “If you want to know what’s going on with the snowpack nine out of 10 times, follow the latent heat.”

As the snow melts, it then exposes plants and soils to the sun and Southwest Colorado’s arid climate. That forces them to shed more water into the atmosphere, drying out the landscape.

A 2010 study by researchers with the Center for Snow and Avalanche Studies found that the Colorado River loses 5% of its flow annually to the effects of dust on snow, amounting to about 250 billion gallons of water each year.

While fresh snow in the spring can help to limit some these effects, it is not a panacea. The sun can penetrate up to a foot beneath the snow surface, so a layer of dust buried several inches under the snow can still increase melting, Derry said.

And other studies have shown that dust in the San Juan Mountains is only getting worse, he said.

Steltzer organized the field tour in part so that students could see the dust in layers of snow and begin to visualize the effects.

“When you see it, then it starts to make more sense why it’s going to have such a big impact on water supply,” she said.

Steltzer’s motivations extend to the students’ future studies at FLC and their careers. Opportunities like these help students to refine their interests as they progress through school, she said.

“I like being able to go to different areas (and) meeting different people who work in this field and seeing where we could eventually end up and if we wanted to pursue that career,” said Jessica Anaruk, a student on the trip.

The opportunity to expand their professional network was one reason why Lauren DeLaRosa, a junior majoring in environmental studies, felt the field tours with experts like Derry were valuable for students.

“My favorite thing about something like this where we get to meet with someone new is the opportunity to make connections and network,” DeLaRosa said. “It’s cool getting to use our teachers as a resource and then when they bring in other resources it just creates this wealth of knowledge that we’re given. It’s an opportunity to expand our sources for our future projects and (the) people that we know we can rely on in the future.”

For Ben Violett, a junior environmental studies major, the field work generated ideas for his upcoming environmental colloquium course, when students design and tackle their own environmental projects.

In speaking about snow samples, Derry mentioned to students that analysts with the U.S. Geological Survey found microplastics in samples the Center for Snow and Avalanche Studies had taken in the San Juan Mountains.

“It gives me ideas for the future,” Violett said. “I thought the microplastics being found in the snow was interesting so I was going try to look into that later.”

With field exercises like these, a staple of Steltzer’s class, students also develop their field skills and the training they will need to transition into their chosen fields.

“Most employers want to hire somebody who can step into the space and quickly get up to speed on the tasks that they’re going to need to be able to do, so I try to bring in the hands-on experiences in the field,” Steltzer said.

The goal of Steltzer and the Environment and Sustainability Department is to extend the practice and knowledge students gain at FLC far beyond their time at the college.

“We want to help them think about, ‘What do I want to do with what I’m going to learn in college?’ And then chart their own course,” she said.

ahannon@durangoherald.com