Why is this Arctic snow turning pink?

Scientists say that an Arctic phenomenon that turns snow pink is due to a chemical reaction that occurs when sunlight hits algae in the snow. 

The Arctic conjures up images of white snow, ice, and polar bears. But this month, the Arctic landscape looks like something out of a Dr. Seuss book, with landscapes of pink snow.

What caused this strawberry hue? Was it an Arctic accident? Or polar pranksters? Neither, according to a new study published Wednesday by a team of scientists in England and Germany in the journal Nature Communications.  

Instead, the pink coloring is caused by algae, which creates an effect that can actually worsen climate change.

While this phenomenon has significant implications for the worldwide struggles with climate change, it is not a new discovery. As long ago as 1818, explorers such as British Admiral Sir John Ross noted that snow sometimes took on a pinkish hue at high altitudes.

Nineteenth-century explorers thought that the color might come from meteoric iron deposits, but modern scientists know that it comes from a kind of algae, Chlamydomonas nivalis, which, while normally green, turns red when hit by the sun.

Until recently, the pink snow remained a relatively unstudied phenomenon. The international team of researchers who published this week's study, however, were determined to change that.

To better understand what the snow could mean for the Arctic environment, researchers studied snow samples from 16 glaciers in four countries, including Sweden, Greenland, Iceland, and Norway.

What they discovered all came down to a property called albedo, or the proportion of light reflected by a surface.

Dark colored objects absorb more light, explaining why darker painted houses feel hotter in the summer time, or why it might be unpleasant to wear black T-shirts in July. The lower an object's albedo number, the more light (and consequently heat) it absorbs.

"Imagine wearing black instead of a white T-shirt in the sun. It feels much hotter," wrote Stefanie Lutz, one of the study's authors, in an email to The New York Times. "It is the same for the snow: More heat means more melting."

With its darker color, the Arctic algae decreases the albedo of glacial snow significantly. Scientists say that, on average, the presence of the red algae decreased the snow's albedo by 13 percent.

That might not sound like a lot, but it could have a significant impact on future studies of climate change, in which scientists say researchers must measure the albedo of Arctic snow.

"Our results point out that the 'bio-albedo' effect is important," said Dr. Lutz in a statement, "and has to be considered in future climate models."

Scientists like Lutz are also concerned that the rosy snow could create a problematic cycle, in which algae darkens the snow, which leads to melting and runoff, which leads to more algae growth, and so on.

Already, scientists take other albedo lowering phenomenon, such as the creation of black carbon by forest fires, into account when creating climate models, reports The New York Times.

This discovery is particularly disconcerting as the Arctic enters what looks to be another record-breaking year for Arctic ice melt. 

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