Measurements of Black Carbon aerosols in Arctic snow - interpretation of effect on snow reflectance

Snow covered surfaces have relatively high albedo and most of the incoming solar radiation is reflected. Consequently, the temporal evolution of surface albedo in the Arctic is of high relevance for the surface energy balance, melting processes and climat e. BC particles emitted by fossil fuel and biomass combustion, transported to the Arctic and deposited in the snow and ice reduce the albedo of the surface and thus have the potential of contributing to a warming of the climate. Measuring the BC content o f snow and deriving the corresponding alteration of the reflective properties of the snow is not straightforward. Key issues include: Sampling procedures, melting and filtering procedures, equipment used (preparing of filters etc.), methods for analyzing the filter for BC content, and ultimately deriving the implications for albedo of measured BC content. The proposed project brings together two leading groups, a Norwegian/Swedish group (NPI/CICERO/MISU) and a US group (U. Washington and U. Hawaii) that b oth are performing measurements of BC in snow and ice to derive the corresponding albedo changes. Common field campaigns (2007 and 2008) are planned at Ny-Ålesund (Svalbard) and Barrow (Alaska). The intercomparison of methods will be used to improve and o ptimize the procedures that are common at the participating working groups. Finally a workshop with wider participation also from climate modelers is planned to be held in Ny-Ålesund in 2009. For young scientists, this international collaboration with mut ual visits will give possibilities of improving their scientific network and gathering experience.