Seminar

Abstract

NOAA's Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) airborne research project took place in the Alaskan Arctic in April 2008. Layers of dense smoke, mixed with fossil fuel pollution, were frequently encountered at altitudes from near the surface to 7 km. Transport models demonstrate that the smoke originated from agricultural and forest fires in Russia, and had been transported over distances >5000 km. There is no substantive evidence for precipitation scavenging and removal of the smoke particles between the time they were emitted and the time they were observed above the Arctic surface. Given the lack of scavenging, the dense smoke layers aloft may not have contributed substantially to changes in snow albedo postulated to drive large climate feedbacks. Furthermore, direct radiative forcing from the smoke aerosol is calculated to be small and to cool the surface. Aerosol concentrations very near the sea-ice surface were smaller than those aloft, suggesting a deposition process from within this shallow layer to the sea-ice. The relevance of these findings to the "Arctic haze" phenomenon and to climate forcing in the Arctic will be discussed.