Pink Snow Is Not a Cute Phenomenon—Here’s Why

The scientists used the device to record the snow’s albedo, a measure of what fraction of the sunlight beaming down is reflected back up. Red snow means lower albedo, which means more absorbed sunlight and faster snowmelt. Other factors also influence albedo, including dirt, dust and ash from wildfires. Sand from the Gobi Desert can blow all the way to the Pacific Northwest, while dust from the shrinking Great Salt Lake sometimes coats the Wasatch Mountains. The team also measured the pigment concentration of the snow with a second spectroradiometer to figure out how much of the red color spectrum, most likely from the snow algae, was present.

A bighorn sheep supervised from a jagged cliff high above us as the team worked through the rest of their routine: measuring the water content of the snow, collecting bags of snow samples, and taking a snow core that revealed two layers of algal blooms, including a distinct rusty band a few inches below the surface.

Later that day, in a lab at the University of Montana’s Flathead Lake Biological Station, Elser and Almela Gomez would use the samples to test which inputs help snow algae grow. They’ll melt the snow, mix it together, and add nutrients like nitrogen and phosphorus. Then, after five to 10 days under grow lights in a cold incubator, they’ll measure the chlorophyll levels to see how much the algae grew. 

The two types of nutrients come from different places. Previous work suggests that the phosphorus is found in rocks ground up by glacial movement, while nitrogen is blown in from the chemical fertilizers and manure in agricultural areas. The researchers suspect that both types of nutrients encourage algae growth, but they’re particularly interested in nitrogen. They believe algal blooms might be especially common in the Intermountain Rockies due to wind patterns, and they’re hoping to learn more about the dynamics involved. 

The team’s work is part of the small but growing field of snow algae research. The scientists hope to figure out what allows snow algae to thrive, and where it’s most likely to live. The Living Snow Project, a citizen science initiative created by Western Washington University researchers, asked skiers, climbers and hikers to help collect pink snow samples. Scientists have also converged on surging algal blooms in the French Alps. 

Learning what influences snow algae growth is an important step in understanding a changing water supply. More algae potentially means more melt, and knowing where algae might quicken snowmelt is especially crucial for the drought-prone Western US. Gradual snowmelt is good; it creates a more predictable water supply downstream for reservoirs, and infuses streams with the cold water that fisheries and other aquatic life rely on throughout hot summer months. Rapid snowmelt, however, brings a host of other problems. 

Elser compared the snow’s role to ice in a cocktail. “The ice is melting, but your drink is still nice and cold until that last piece of ice goes away,” he said. “Then it’s like, ‘What happened? My drink is warm.’” If snow algae hastens snowmelt or melts all the snow quickly, streams may end up warmer than usual and have less water as the summer advances. “It’s a pretty big deal,” said Scott Hotaling, a member of the snow algae research team and an assistant professor at Utah State University who studies changing mountain ecosystems. “We talk about the whole West being in a drought, and if there’s going to be another factor that perpetuates earlier melt, that’s important.”