The Climate Crisis Is Turning Antarctic Snow Green

Dr. Matt Davey sampling snow algae at Lagoon Island, Antarctica. Sarah Vincent

Antarctica is a polar continent, but it's not just a vast land of ice and snow. Along the coastal areas moss, lichens, and algae all grow. However, the continent, like the rest of the planet, is experiencing higher temperatures due to the climate crisis and this has allowed algae to spread further than ever before. Now, scientists have created the first large-scale map of microscopic algae blooms on the Antarctic Peninsula. The researchers say this "green snow" is likely to spread as global temperatures increase.

The British team from the University of Cambridge and the British Antarctic Survey used the European Space Agency's Sentinel 2 satellite to map the algae blooms. Microscopic algae can bloom on the surface of snow, tinting it green or orange or even red. You might be wondering why this is a bad thing: algae that sit on the surface of snow blocks its ability to reflect the Sun's rays, instead causing it to absorb it, and increasing its chance of melting. White snow reflects around 80 percent of the Sun's radiation, while green snow only reflects about 45 percent. 

In Nature Communication, the team reported 1,679 distinct blooms covering a combined 1.9 square kilometers across the peninsula, two-thirds of which were on small low-altitude islands. The algae only bloom within a certain temperature range, around the water freezing point, which occurs between November and February. It can’t survive if it's too hot or too cold. The polar regions are warming faster than anywhere else on the planet, so some of these islands may lose their summer snow cover, while the coastal regions of the continent will experience a significant increase in algae blooms over the coming decades.

"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," lead author Dr. Andrew Gray, a researcher at the University of Cambridge and NERC Field Spectroscopy Facility, Edinburgh, said in a statement.

The blooms are influenced by the birds and mammals that live in Antarctica and in particular their excrement, which are a source of nutrients. They found 60 percent of the detected blooms are within 5 kilometers (3.1 miles) of a penguin colony, as well near other birds’ nesting sites, and where seals come to rest ashore.

The team also estimated that these blooms, which act as a carbon sink, remove 479 tonnes of atmospheric COper year – equivalent to the emission of 486 planes traveling between New York and London.

The researchers plan to explore measuring the algae spread further, including other algae in future studies, conducting field-work in the Southern continent, and keeping an eye on how the southernmost continent greens over the coming years.

“I think we will get more large blooms in the future," Gray told The Guardian. "Before we know whether this has a significant impact on carbon budgets or bio albedo, we need to run the numbers.”


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