The role of scavenging in the seasonal transport of black carbon and sulfate to the Arctic

Abstract

In a prior study, a decade-long dataset of ground-based aerosol and carbon monoxide measurements from Barrow, Alaska (71N, 157W) was used to show that surface air in the Arctic is clean during the summer, less due to inhibited transport of pollutants from mid-latitudes, and more because of efficient wet scavenging at temperatures near freezing. Here, the analysis is extended to light-absorbing aerosols, such as black carbon, and to measurements from Alert, Canada (82N, 62W). The data imply that both light scattering and light absorbing aerosols have similar seasonal cycles, independent of location, and they are controlled nearly equally by wet scavenging. Removal is particularly efficient at high relative humidities and warm temperatures, which suggests that a future warmer and wetter Arctic may also be cleaner. Assuming aerosol pollutants generally have a warming effect in the Arctic, such an increase in wet scavenging would represent a negative Arctic climate feedback. Copyright 2011 by the American Geophysical Union.