“Red snow” algae accelerating glacier melt in the Arctic

Posted by on Jul 13, 2016

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Scientists have discovered a troubling new characteristic of the tough algae that grow on the surface of Arctic glaciers: not only do they turn the glacier surfaces red, they accelerate the melting of the ice.

Across the Arctic, from Greenland to Sweden, glacier ice is turning red in what has been termed “watermelon snow.” The phenomenon has become increasingly common in recent years, yet little is known about the algae or their broader environmental impacts.  

"watermelon snow" (wiki)

“watermelon snow” (Source: Will Beback)

A recent study, published June 22 in Nature Communications, has shed light on the red snow, reporting that the algae are contributing to glacier melting and climate change in the Arctic.

The Arctic region covers the majority of the Earth’s northern pole, and contains over 275,500 square kilometers of glaciers. It is also one of the most vulnerable regions to climate change, warming at a rate nearly twice the global average.  According to NASA, the rate of Arctic warming from 1981 to 2001 was a staggering 8 times larger than the rate of melting over the last 100 years. Given the severity of glacier melt in the region, understanding the factors that impact melting rates is crucial to preserving the Arctic ecosystem.

Albedo is one of the most important influences on glacier melt, and the presence of red algae is now speeding up the process. Due to their red pigmentation, algal blooms on ice substantially darken the surface of the glaciers and change their albedo—or the amount of light reflected off of the surface of an object.

Just as black concrete is much hotter to the touch than a pale sidewalk, glaciers covered in red algae absorb more light and melt at a faster rate than clean white ice. This sets off a chain reaction of additional melting, as the meltwater creates a habitat for algae to colonize, and low-albedo rocks and dirty ice underneath glaciers are exposed.

Global albedo showing high reflectivity in the Arctic. Image courtesy Crystal Schaaf, Boston University, based upon data processed by the MODIS Land Science Team

Global albedo showing high reflectivity (red) in the Arctic. Image courtesy Crystal Schaaf, Boston University, based upon data processed by the MODIS Land Science Team

The research team, led by Stefanie Lutz of the University of Leeds, found that the algal blooms are decreasing snow albedo by as much as 13 percent over the course of the melt season in the summer. The phenomenon is widespread.

Forty red snow samples were taken between July 2013 and July 2014 from a total of 16 glaciers in Svalbard, Northern Sweden, Greenland, and Iceland. Results were similar across the board in the different regions. Local ecology, geography, and mineralogy did not have an impact on the ability of the algae to bloom—they are cosmopolitan, able to colonize and spread easily across an ecosystem.

Locations of the 16 glaciers and snow fields across the Arctic, where 40 sites of red snow were sampled (Nature Communications)

Locations of the 16 glaciers and snow fields across the Arctic, where 40 sites of red snow were sampled (Source: Nature Communications)

While the researchers found a rich diversity of bacteria in the glacier samples, the algae did not show the same pattern. Instead, results revealed that the spread of red algae was almost entirely attributable to a small group of algal species–the Chlamydomonadaceae being the most common. Six taxa groups made up over 99 percent of the algae species found in all Arctic locations. These finding set the Arctic apart from other terrestrial ecosystems, which tend to be less homogenous, and indicate that these few species of algae can survive and thrive under a wide range of conditions, and are also likely to spread to other locations.

algal cell (Chlamydomonas nivalis) responsible for red coloration of mountain snow packs (wiki)

algal cell (Chlamydomonas nivalis) responsible for red coloration of mountain snow packs (Source: USDA)

This makes the findings of the study even more pertinent, as red snow will become an increasingly common phenomenon while glacier melt accelerates. According to the study, “Extreme melt events like that in 2012, when 97% of the entire Greenland Ice Sheet was affected by surface melting, are likely to reoccur with increasing frequency in the near future as a consequence of global warming.”
Lutz and the research team conclude that there is a need for this “bio-albedo” effect to be incorporated in future climate models in order to accurately predict the speed and location of glacier melting in the arctic and prepare for the wide range of environmental impacts that will follow.

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