Black carbon aerosols in Arctic snow (oppstart 2009)

Snow covered surfaces have relatively high albedo and most of the incoming 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 climate. 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 contributes to a warming of the climate. Measuring the BC content of snow and deriving the corre sponding 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, an d ultimately deriving the implications for albedo of measured BC content. The project brings together two leading groups, a Norwegian/Swedish group (NPI/CICERO/MISU) and a US group (U. Washington and U. Hawaii) that both 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 optimize the procedures that are commo n at the participating working groups.