Glaciologist Dr Jason Box gathers samples of cryoconite from the lower section of the Petermann glacier. Cryoconite is the term used to describe a collection of impurities which gather on the surface of the ice. Dr Box intends to have these analysed in a lab on return from Greenland. Previous samples taken from other glaciers in Greenland have contained traces of lead and cadmium. Cryoconite also effects the changing albedo (reflectance) of sections of Greenland's glaciers, because it adds a darker coating to the existing lighter ice; darker parts of the spectrum absorb more heat, thereby accelerating melt rates of the areas of ice immediately below the cryoconite layer.