Invasive shrubs and soot pollution both have the potential to alter the surface energy balance and timing of snow melt in the Arctic.
Shrubs reduce the amount of snow lost to sublimation on the tundra during the winter leading to a deeper end-of-winter snowpack. The shrubs also enhance the absorption of energy by the snowpack during the melt season by converting incoming solar radiation to longwave radiation and sensible heat. Soot deposition lowers the albedo of the snow, allowing it to more effectively absorb incoming solar radiation and thus melt faster.
Now there is a new paper providing affirmation of this effect.