Pink snow was a high-latitude curiosity described by Arctic explorers such as Britain’s John Ross. Upon receiving word of the reddish snow, the London Times speculated in 1818 that the color came from meteoric iron deposits. Biologists know now that the red hue is the result of a chemical reaction within the algae Chlamydomonas nivalis and other cold-loving species. These algae are normally green, but as they start to suck up ultraviolet rays, they turn red.
What may look like an Arctic accident involving gallons of pink lemonade is, in fact, reddish algae blooming in the snow. The unusual phenomenon is also found in high altitudes, and sometimes called watermelon snow or blood snow.
Despite the Willy Wonka tinge, the snow hides a sobering reality: According to a new study, the algae cause Arctic melts, which are already happening at an unprecedented pace because of climate change,to worsen.
Although scientists had already figured out why the snow was pink, the effects that the algae had on the wintry environment remained an understudied and fairly obscure topic.
But the new research from a team of geobiologists in Germany and Britain could expand that niche status. In their paper published Wednesday in the journal Nature Communications, the researchers examined 40 red-snow samples, representing 16 glaciers and snowfields from four Arctic countries: Greenland, Norway, Sweden and Iceland. The red algae darkens the snow, they found, causing it to melt faster than its white counterpart.
Specifically, the European scientists measured the red snow’s albedo, the proportion of light reflected from a surface. It is a property of color: Dark objects, by definition, absorb a higher percentage of incoming light. When a British company, Surrey NanoSystems, created the blackest substance known to science — a paste of carbon nanotubes called Vantablack — its albedo was measured at 0.035. That is, it absorbed 99.965 percent of incoming light.
Because light is energy, objects that take in more light become hotter. Conversely, lighter-colored objects reflect more energy and stay cooler. Albedo is why Lawrence of Arabia was smart to wear white robes. It is why former energy secretary Steven Chu championed painting rooftops white to keep structures cooler, as dark gravel or shingles would mean buildings are converting light to heat.
This principle is also why scientists are concerned about darker snow — it would be a bit like a glacier tossing on a red shirt (lower albedo) instead of a plain white tee (high albedo).
The presence of red algae, on average, decreased albedo by 13 percent over the duration of the melting season. “Our results point out that the ‘bio-albedo’ effect is important and has to be considered in future climate models,” Lutz said in a statement. The researchers note that current climate-change models account for details such as black carbon from forest fires and Saharan dust. The scientists suggest algae, too, needs to be considered.
Exactly how large or small a role algae plays in melting glaciers is unclear, and the scientists plan to study it in more depth. But the geobiologists are concerned that the decrease in albedo may act like a positive feedback loop. As more algae bloom, more snow thaws — and, nourished by the unfrozen water, even more of the microorganisms are able to grow. And so on.
This study underscores the far-reaching effects of climate change, down to the smallest of organisms. A warm Arctic happens to be good news, if you are a fleck of red alga.
For polar bears, people who own real estate in Florida and global civilization generally, the outlook may not be so hot.