Organic and Elemental Carbon in Central Greenland Air and Snow: Towards a Better Understanding of Sources, Source Regions, and Radiative Forcing

There is growing evidence that both natural and anthropogenic aerosols are playing an important role in the radiation balance of the Arctic (Quinn et al., 2008). In particular, light absorbing carbon compounds (i.e. elemental carbon, EC, and specific organic species) from anthropogenic combustion sources and biomass burning have the potential to impact both direct and indirect radiative forcing over the Arctic. In addition, the deposition of light absorbing aerosols to snow can modify snow albedo and hence influence climate. Organic aerosols deposited to snow also contain a wealth of information on their specific sources, and can potentially provide insight into the linkage between anthropogenic emissions, atmospheric concentrations and climatic impacts. Although it should be noted that organic compounds are also involved in snow photochemical processes, and therefore may not be readily preserved after deposition.

At this time the impact of carbonaceous aerosols on climate and snow photochemistry is poorly understood for the Arctic. This is particularly true for Greenland, where measurements of both organic (OC) and elemental carbon (EC) in the air and snow as well as the associated aerosol chemical, physical and optical properties are sparse. We will present data based on intensive field campaigns that took place during the summers of 2005 and 2006 at Summit, Greenland that focused on the link between carbonaceous particulate matter in the air and snow. In particular, it is apparent that particulate associated organic compounds degrade in surface snow due to photochemical processes. The simultaneous measurements also allowed for the estimation of the air-snow transfer function of light absorbing black carbon. We will also present estimates of direct aerosol radiative forcing due to light absorbing aerosols and discuss the potential feedback links with surface snow physical properties. In addition, back trajectories will be discussed in terms of atmospheric black carbon concentrations to better understand source regions of light absorbing aerosols. We will also discuss specific sources of carbonaceous aerosols reaching Summit based on measurements of specific organic tracers.