Spread of Dark Algae Could Hasten Melt of Greenland Ice Sheet

Dark algae are spreading across the Greenland ice sheet as snow cover retreats. Their dark color causes the ice to absorb more heat from the sun, accelerating melting. And according to a new study, the harsh conditions atop the ice sheet will do little to slow the algae’s advance.

Researchers used advanced imaging to examine individual cells of Ancylonema, finding the algae can thrive in places where nutrients are scarce. “They don’t require large amounts of external nutrients to grow, which means that as the ice sheet continues to melt and expose more bare ice, these algae are well-positioned to expand their coverage,” said study coauthor James Bradley of Queen Mary University of London.

In the summer of 2017, algal blooms caused the western edge of the Greenland ice sheet to shed at least 10 percent more water than it would have otherwise, an alarming figure given that Greenland is the biggest source of fresh water now fueling sea level rise.

“Understanding these algal blooms is critical for predicting future ice sheet behavior and sea level rise,” Bradley said. The new study, published in Nature Communications, suggests that as warming intensifies and snow further retreats, “we are likely to see a self-sustaining cycle where more algae lead to more melting.”

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