"Soot deposits" refer to black, powdery or flaky substances made up of carbon particles that accumulate on surfaces like chimneys or stoves when burning fossil fuels like coal or oil. Full definition
Warmer average temperatures due to climate change are the main reason for the increased melting, though black soot deposits on ice is probably also contributing through increased absorption of heat. (earthtimes.org)
Black soot deposited on Tibetan glaciers has contributed significantly to the retreat of the world's largest non-polar ice masses, according to new research by scientists from NASA and the Chinese Academy of Sciences. (giss.nasa.gov)
Based on these figures, I suppose that the West Greenland ice melting was larger in the 1930 - 1950 period than in the 1985 - 2005 period... Alternative explanations may be that the Greenland ice melting has nothing to do with temperature, but with more insolation (less clouds), less precipitation, more soot deposit,... (realclimate.org)