Large Circulation Patterns Strongly Modulate Long-Term Variability of Arctic Black Carbon Levels and Areas of Origin

Black Carbon (BC) aerosol is a major climate forcer in the Arctic. Here, we present 15 years (2001–2015) of surface observations of the aerosol absorption coefficient b _abs (corresponding to Equivalent BC), obtained at the Zeppelin Observatory, Ny Ålesund, Svalbard, coupled with backward transport modeling with Flexpart in order to calculate the Potential Source Contribution Function (PSCF) for BC. The observed long-term variability superimposed on a strong annual cycle is studied as a function of large-scale circulation patterns represented by monthly index values for the North Atlantic Oscillation (NAO) and the Scandinavian pattern (SCAN). We find a 35% increase of b _abs values at Zeppelin during the SCAN ⁻ phase in the winter half-year compared to the SCAN ⁺ phase but no significant difference in b _abs values between the NAO index phases. Both NAO and SCAN induce significant regional variability on the areas of origin of b _abs, mainly Siberia, Europe, and North America.