Climate change is turning Antarctica's snow green

We tend to think of snow as white only, but snow of a different color happens fairly often.

For example, there’s red or pink “watermelon” snow recently seen in Yosemite, orange snow when dust from the Sahara collided with a Siberian storm and, of course, the yellow snow that one should never eat.

If anyplace should have consistently white snow, it's Antarctica, the frozen, virtually uninhabited continent at the bottom of the earth. But a warming climate is slowly changing that.

For the first time, scientists from University of Cambridge and the British Antarctic Survey have mapped out vast patches of green snow on the Antarctic Peninsula, according to a study published in Nature Communications earlier this month. The team used satellite data from 2017-2019 supplemented with ground-level measurements. The green color is caused by colonies of microscopic algae.

The researchers found 1,679 separate blooms of green algae on the snow surface visible from space, Matt Davey, leader of the study and a professor in the University of Cambridge’s Department of Plant Sciences, told Earther.

Red and orange algae were also discovered on the peninsula, which has been heating up faster than any other part of Antarctica. In February a nine-day heat wave melted 20% of an Antarctic island's snow cover. The continent also experienced its hottest day on record that month, 64.9 degrees Fahrenheit.

The bright green algae thrives in areas where snowmelt runoff is fertilized by penguin, seal and seabird excrement “providing hot spots of nitrogen and phosphate in an otherwise typically oligotrophic [low in plant nutrients] environment,” the scientists wrote. The algae blooms were usually within a few miles of penguin colonies.

While the algae does remove a small amount carbon dioxide from the atmosphere, it also absorbs more heat, accelerating snowmelt.

Researchers expect the algae to spread to higher elevations.

"As Antarctica warms, we predict the overall mass of snow algae will increase, as the spread to higher ground will significantly outweigh the loss of small island patches of algae," Dr. Andrew Gray, lead author of the study, said in a statement reported by CNN.

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Mike Moffitt is an SFGATE Digital Reporter. Email: moffitt@sfgate.com. Twitter: @Mike_at_SFGate