Interpretation of Arctic Black Carbon Measurements with a Chemical Transport Model

Abstract

Black carbon is a pollutant of concern in the Arctic; however models struggle to accurately simulate its seasonal cycle observed from in-situ measurements. This work aims to examine the contribution of different types of emissions from various regions to this cycle using the GEOS-Chem model. Base model emissions were modified by introducing a seasonal cycle on the existing emissions from domestic wood burning, and the addition of gas flaring emissions. To assess the efficacy of these changes, comparisons were made with ground measurements performed at Alert, Barrow, and Ny-Alesund, along with airborne measurements performed by the PAMARCMiP aircraft campaign. The best agreement was found at Alert and Barrow with the simulation using all modifications. The Ny-Alesund site, due to its elevation, had a different cycle than the one observed at the other sites which the model had difficulty in recreating. Vertical profiles obtained from PAMARCMiP showed good agreement, however the effects of the emissions changes diminished rapidly with altitude. Source regions of pollution in the model were assessed as well. The major source region at altitudes above the planetary boundary layer was found to be East Asia in the winter, spring and fall, while biomass burning was a major contributor during the summer. Closer to the ground, Europe and East Asia were the major contributors, with smaller contributions from North Asia and North America.