Aerosols derived from the combustion of fossil fuels supply organic matter to Alaskan glaciers, reports a study published online in Nature Geoscience this week. The findings suggest that human activities may affect organic matter in glaciers. During periods of ice melt, glacier meltwaters run into rivers and coastal waters, where they fuel biological activity. Aron Stubbins and colleagues examined the age and composition of organic matter in glacier surface waters and glacier outflow in Alaska. They detected large quantities of old, yet biologically available organic matter, and show that aerosols, rich in fossil fuel combustion products, are the most likely source of this material. As such, the researchers suggest that human activities have amplified the export of organic matter from glaciers.