The anthropogenically enhanced melting of snow and ice masses on Earth are controlled by changes in surface albedo. Such changes in turn are primarily a consequence of increased delivery of light absorbing impurities (LAI) to snow and ice surfaces. In both Alpine and Polar glaciers and ice sheets, traditionally, it was assumed that the main culprit among LAI were wind delivered industrial or wild fire black carbon (soot) and mineral dust. Although we recently recognised the importance and role of pigmented snow and ice algae in changing albedo in the Arctic , isolating the microbial contribution (bio-albedo) from the other albedo affecting LAI is not trivial. I will first discuss our results on the variations in diversity, function and metabolic activity of snow and ice algae from mixed ‘omic' and geochemical approaches in a Pan Arctic study. I will than contrast these with recent results from the Greenland Ice Sheet (GrIS) where we quantify both biological and nonbiological LAI particulates and show that the close interactions between microbes, soot and minerals in highly dynamic snow-ice transition zones play the crucial role in enhancing melting. Finally, I will show how we upscale the ground based findings through satellite data and ice sheet wide modelling. As climate warms, the biologically driven processes will increasingly contribute to the darkening of the GrIS, yet these effects are currently not included in predictive global numerical models and we aim to change this over the next few years.
 Lutz, S. et al. (2016) Nature Commun. 7, doi:10.1038/ncomms11968.