Relative contributions of anthropogenic emissions to black carbon aerosol in the Arctic

Using a global air quality model with online aerosol algorithm GEM-AQ, this work first validates the performance of the model against available observations and then estimates the regional contributions to the Arctic black carbon (BC) aerosol from anthropogenic sources. The comparisons against the surface measurements at Alert and Zeppelin suggest that the Arctic BC aerosol can be predicted by the model within 15% on annual average, and the seasonality of Arctic BC is predicted by 90% and 66% at these sites, respectively. Comparisons against surface measurements in North America, Europe, and South Asia confirm that surface BC concentrations are reproduced by the model within a factor of 2 at most (104 out of 115) sites investigated. Using GEM-AQ, sensitivity experiments are conducted by reducing the anthropogenic emissions from selected regions by 20%. Based on area-weighted results for the Arctic region, model simulations suggest that Europe contributes more (up to 57%) to the lowest 5 km of the Arctic troposphere than any other region. The contribution of Asian Russia is significant near the surface (about 30% at 100 m above the surface) and decreases rapidly to less than 10% at the altitude of about 5 km in the Arctic troposphere. The contributions from South and East Asia increase with increasing altitude, and become more significant than others in the upper troposphere and the lower stratosphere, with their peak contributions of about 35% and 40%, respectively. North American contribution to the Arctic troposphere (about 10-20%) has the least variations in the vertical direction among the potential source regions affecting the Arctic.