In Utah, above 6,000 or 7,000 feet, pink snow can be found. It looks like someone sprayed some watermelon-flavored syrup on the snow surface.
Despite the color, it’s actually a green algae species. The most common genus is chlamydomonas nivalis and it generally blooms on snowfields in the Midwest during summer.
Scott Hotaling, an assistant professor of Watershed Sciences at Utah State University, said there’s a point when there’s enough water content in the snow to induce a life cycle change for this algae. When they bloom, that’s when they turn pink.
The blooms can be bright magenta, but often just have a pinkish tint. The brighter the color, the denser the algae blooms.
Hotaling said part of the reason for the red color is so they can absorb solar radiation. This warms them up and causes biochemical reactions to happen more readily. It also has a secondary benefit for the algae — melting snow.
When the snow melts around them, there is more water to further the life of the algae. However, what’s good for algae isn’t necessarily good for people.
“There’s a lot of evidence now that shows that these algal blooms contribute rather significantly to overall melt of snowpack around the West,” Hotaling said.
Jordan Clayton, the supervisor of the Utah Snow Survey, said snowmelt contributes about 95% of the state’s water supply. The survey measures snow to figure out how much water is stored on the state’s mountains, and therefore how much water can be expected as the snowpack melts. These forecasts, Clayton said, are crucial for water managers so they can anticipate how reservoirs will fill up and how streams will rise.
How much snow falls is just as important as when it melts. The best outcome is for snow to melt in late spring or early summer and have it all come down in a short amount of time. This is because when it melts quickly, the soil saturates completely. This allows water to flow on top of the ground, down the valley and into reservoirs.
The pink-hued algae could cause snow to melt sooner, which wouldn’t be ideal. When the snow starts melting earlier in the year, the whole melt is spread over a longer period of time. Clayton said this causes a higher percentage of water to be lost to upstream areas, reducing runoff efficiency.
However, this algae isn’t new. Hotaling said it has been around as long as human civilization. The algae can act similarly to dust on snow. When dust is picked up and deposited on snowpack, it also absorbs more solar radiation and causes snow to melt faster.
Clayton said the decreased reflectivity of the darker shades also contributes to the snow melting. For example, try placing a leaf on top of snow.
“Watch as the sun comes out. Watch that leaf kind of burn its way down through the bottom of your snowpack where the rest remains intact,” Clayton said.
The difference between the algae and dust is that these algae might be increasing under climate change. More research is needed, but Hotaling said more CO2 in the atmosphere, warmer days and more nitrogen being deposited from the shrinking Great Salt Lake all could contribute to more algal blooms.
“That will certainly affect Utah’s water supply in a way that it hasn’t historically,” Hotaling said.
