If You See Pink Snow, This Is What It Means

Winter brings icy white snow to the mountains each year. But recently, people reported encountering something out of the ordinary: pink snow. It also earned the nicknames “watermelon snow” and “glacier blood” for its rosy appearance.

While it seems “cute,” scientists are concerned about its potential environmental impact. But what causes snow to turn pink in the first place? Here’s what you need to know.

What is Pink Snow?

When pink snow appears, it means blooming green algae called Chlamydomonas nivalis (C. nivalis) is present in the snowpack.

According to Smithsonian Magazine, C. nivalis isn’t exclusive to North America. The alga blooms in mountain ranges throughout the world, and it isn’t anything new; scientists have studied this photosynthetic organism for more than 100 years.

Pink snow isn’t some random, inexplicable phenomenon. According to Scientific American, C. nivalis reacts to UV rays when exposed to the sun. This green alga requires a natural “sunscreen” to protect its chlorophyll molecules, the ones necessary for photosynthesis.

At rest or in its zygote stage, green alga employs natural UV-absorbing pigments called carotenoids for protection from harsh UV rays. Those pigments cause the pink color as the C. nivalis algae to concentrate on its surface through melting or evaporation. This natural biochemical sunscreen makes the baby algae appear orange or reddish under a microscope, creating pink snow.

Where is Pink Snow Found?

Researchers and bystanders commonly see pink-hued snow in the Western United States. In the summer of 2022, scientists scouted for pink snow in Utah, Montana, Wyoming, Washington and Oregon. According to Wired, it also appears in Alaska.

Scott Hotaling, a professor in the Watershed Sciences Department at Utah State University, recently told KUER’s Kristine Weller, “There’s a lot of evidence now that shows that these algal blooms contribute rather significantly to overall melt of snowpack around the West.”

If the snow melts faster than normal, it could throw off the delicate balance of natural water supplies and stream temperatures, thus furthering drought in the West.

For now, researchers are still investigating unanswered questions linked to these algae blooms. If you spot pink snow next time you’re in the mountains, you’ll know it isn’t your eyes playing tricks on you!