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Climate Hustle

The Dark Snow team investigates the source of soot that's accelerating Greenland ice melt

Posted on 24 July 2014 by John Abraham

Around the planet, wildfires are becoming larger and more destructive. This summer, a series of wildfires enveloped large areas of Canada’s Boreal forest, blanketing western North America with smoke. One key question is, do these fires have an effect on climate by darkening Arctic ice with layers of soot, causing more sunlight to be absorbed by the ice?

For the second year, the Dark Snow Project science team has taken to the ice on Greenland to investigate the forces driving Greenland's ice loss. They are looking at the causes of surface darkening on the ice sheet that's been observed over the last decade.

The Dark Snow Project is a collaborative effort between a multidisciplinary, international group of experts. The driving questions are, what's causing the steady darkening of the Greenland Ice Sheet that has been observed in the past decade? Is it an important cause of ice melt? Does it represent yet another climate "feedback" which is accelerating global change?

Peter Sinclair, Dark Snow Participant. Peter Sinclair, Dark Snow Participant.

A number of natural processes cause ice to darken. The simple process of melting causes ice crystals to deform and reflect less light. In addition, pollen, sea spray, desert dust, pollution from industry and shipping cause darkening. However, there are also other causes.

Recently, newly published research strengthens the idea that wildfire soot has driven extensive melt over the ice sheet, and in addition, that layers of refrozen water are themselves darkening factors that drive further melt.

In addition to increased wildfires, the Dark Snow Team will be investigating the impact of algae and microbes, which, increasingly favored by warming temperatures, are gaining a larger foothold on the ice.

Dark Snow biologist Dr. Marek Stibal has found that a species of algae living on the ice produces a very special pigment that acts as a sunscreen, protecting it against the intense summer glare. The pigment is the very same molecule that gives black tea its color. The dark pigment, visible in many photos of ice during melt season, is an important, but not well understood, part of the darkening process.

As warmer temperatures spread over larger areas of the ice, more liquid water is made available - a vital factor for algae growth. In addition, scientists wonder whether industrial pollution may be delivering key nutrients like nitrogen and phosphorus to the ice, further driving algae growth.

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