Dust and soot might not be behind the observed darkening of the Greenland ice sheet (pictured).
Tiny particles of dirt absorb sunlight that would be reflected into space by ice — contributing to local warming. Satellite measurements suggest that the amount of sunlight reflected by Greenland's icy surface has been decreasing since 2001.
But surveys of the snow in northwest Greenland conducted in 2013 and 2014 by Chris Polashenski at the US Army Cold Regions Research and Engineering Laboratory in Fort Wainwright, Alaska, and his colleagues, found that the concentration of dark-coloured particles was much the same as in previous decades. Rather than dirtier ice, the declining reflectivity seen in satellite measurements could be due to a degrading sensor on NASA's Earth-observing satellite Terra.
Geophys. Res. Lett. http://doi.org/8kg (2015)
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Arctic snow is not becoming dirtier. Nature 526, 613 (2015). https://doi.org/10.1038/526613d
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DOI: https://doi.org/10.1038/526613d
