The result of algae that paint the snow pink.
It looks like the makings of a delicious snow cone, but this pink “watermelon snow” is the consequence of snow-dwelling algae that contain a reddish pigment and thrive in freezing water. Though dormant throughout the winter, these algae bloom during the spring and summer as the Arctic sun beats down on blankets of snow.
Pink snow may look pretty, but a new study published in the journal Nature Communications reports that its role in climate change has previously been underestimated.
The addition of color darkens the snow, reducing its albedo — the amount of light reflected by a surface — which causes the snow to heat up and melt faster.
“Imagine wearing black instead of a white T-shirt in the sun. It feels much hotter,” lead author Stefanie Lutz from the German Research Centre for Geosciences GFZ told The New York Times. “It is the same for the snow: More heat means more melting.”
The researchers collected samples from 40 red snow sites, including glaciers and snow fields, across the Arctic. Snow algae and other microbes in the samples were genetically sequenced.
Although bacterial species appeared to differ from place to place, the researchers determined that the same few species of snow algae were likely responsible for accelerating glacier melting throughout the Arctic.
Over the course of one Arctic melting season, snow algal blooms were shown to reduce albedo by 13 percent, which could translate to a disproportionate increase in glacier melting. When low albedo triggers glacier melting, this drives more snow algae growth and surface darkening, thus leading to further acceleration of melting.
"Our results point out that the "bio-albedo" effect is important and has to be considered in future climate models," Lutz stated in a press release.