Absorbing aerosol in the troposphere of the Western Arctic during the 2008 ARCTAS/ARCPAC airborne field campaigns

In spring of 2008, NASA and NOAA funded the ARCTAS and ARCPAC airborne field campaigns as contributions to POLARCAT, a core IPY activity. During the campaigns the NASA DC-8, P-3B, and NOAA WP-3D research aircraft conducted over 150 hours of in-situ sampling between 0.1 and 12 km throughout the Western Arctic north of 55oN (i.e. Alaska to Greenland). Each aircraft was equipped with multiple wavelength measurements of aerosol scattering and absorption as well as direct measurements of black carbon and supermicrometer aerosol. Although CO was elevated in discrete layers, campaign averaged vertical profiles from each aircraft were relatively uniform below 6 km. In contrast, average profiles of aerosol extinction and black carbon peaked in the middle troposphere and decreased towards the surface. The fine mode fraction of extinction was highest near the tropopause, lowest in the middle troposphere, and increased toward the surface. We use ancillary measurements of trace gases (e.g. CO, acetonitrile) and aerosol composition (e.g. TOF-AMS) to discriminate absorbing aerosol of urban/industrial origin from absorbing aerosol generated from biomass burning. We then discuss the frequency and relative contribution of these sources of light absorbing carbon and mineral dust to the total burden of absorbing aerosol in the troposphere of the Western Arctic.