Algae growth fuels Greenland ice sheet melt

Algae growth as a result of climate change is making the Greenland ice sheet, a primary contributor to sea-level rise, melt faster, according to a new study.

Algae grows naturally on the ice sheet, but it thrives under a warmer climate. It makes the Greenland ice sheet, which is the second-largest ice sheet on Earth, less reflective of the sun, which means the ice absorbs more of the sun's heat. This, in turn, drives more rapid melting, according to the paper published yesterday in Geophysical Research Letters.

Researchers found that algae accounts for about 5 to 10 percent of total ice sheet melt each summer. That means algae plays a greater role in melting than previously believed, said Marek Stibal, a cryosphere ecologist at Charles University in the Czech Republic and one of the lead authors of the new study.

"As the climate warms, the area that the algae can grow in will expand, so they'll colonize more of the ice sheet," he said in a statement. "Additionally, the growing season will lengthen, so the contribution of algae to melting of the ice will probably increase over time."

Black carbon and dust have been tracked by researchers as contributors to melting of the Greenland ice sheet. Like algae, the dark particles cut down on the albedo, or reflectivity, of the otherwise white surface. The particles absorb the sun's rays and warm the Earth underneath. Stibal said typically researchers have only looked at inorganic materials when studying ice sheet behavior, but the new research suggests that biological factors also play a significant role.

"Our analysis reveals that the impact of algae on bare (snow-free) ice darkening was greater than that of other impurities and, therefore, that algal growth was a crucial control of bare ice darkening in the study area," the authors wrote. "Incorporating the darkening effect of algal growth is expected to improve future projections of the Greenland ice sheet melting."

Since the Greenland ice sheet is a major contributor to sea-level rise, the study has implications for future projections of the rate of expected rise, the study found. Further study is needed to determine how sea levels could be affected by more rapid growth of algae that is expected as a result of global warming. The study also has implications outside of the Arctic, the authors found. Other areas of the world covered in ice, including the Himalayas, also have algae on the ice, which could affect rates of melting there.

The annual report card on the Arctic released earlier this month shows a greening of the region, which is increasingly absorbing heat and warming at a rate twice as fast as the rest of the planet. As sea ice thins, it is also causing plankton blooms in areas where sunlight did not previously reach, which has increased sea surface temperatures and shifted ecosystems.