The phenomenon of "dark snow" is when the snow starts turning black in colour due to an increasing amount of soot from forest fires and ultra-fine particles of "black carbon" resulting from incomplete combustion of fossil fuels from diesel engines that are getting collected and deposited on these ice caps thousands of miles away from industrial centers.
Leading glaciers to melt faster than ever, as the white snow loses its ability to reflect back Sunlight also known as the albedo effect, which in turn creates a situation where more solar heat is absorbed and the melting accelerates. This is being observed everywhere from the Himalayas to the Arctic.
Recently the world's highest glacier, Khumbu, of the Himalayan region has started to turn visibly darker as particles of fine dust are blown by fierce winds, settling on the bright, fresh snow. If you were to calculate the albedo change from the disappearance of the last of the summer ice in 2012 it would be equivalent to the effect of all the extra carbon dioxide that we have added to the atmosphere in the last 25 years.
The dark snow project is an initiative started by professor Jason box in its aftermath in 2014. He believes that the result of this could lead to Arctic seafloor to release carbon and if even a small fraction of that carbon mixes with the atmosphere it could lead to a larger catastrophe.
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