Identification of trends and interannual variability of sulfate and black carbon in the Canadian High Arctic: 1981–2007

Trends and interannual variations of the Canadian High Arctic aerosol record at Alert, Canada (82.5 degrees N), from 1981 to 2007 are investigated and attributed to the influences of anthropogenic emissions and long-range transports. Sulfate and black carbon (BC) atmospheric mass concentrations declined from the mid 1980s to the late 1990s but have been relatively steady since. These tendencies are closely associated with those of the anthropogenic emissions of Eurasia (Europe and the Asian part of the former Soviet Union) and North America (United States and Canada). Interannual variations correlate with two indices derived from the 700 hPa geopotential heights. Variations in the emissions and the geopotential height indices can be used to reproduce up to 75% of the variations of the observed Arctic sulfate and BC mass concentrations. Over the 27 years of observational record, the relative contribution to sulfate and BC at Alert from Eurasia has decreased from more than 90% to about 75%. During the same time, the contributions from North American emissions has increased from less than 10% to about 25%. The increasing influence from North America was due to the faster reductions of sulfur and black carbon emissions in Eurasia during the period of these observations.