Unusual high values of aerosol optical depth evidenced in the Arctic during summer 2011

Climatologically, high Aerosol Optical Depth (AOD500 nm) >0.1 during spring and very low AODs (∼0.05) during the summer months persist over the Arctic. Unusually high values of AOD are unknown to be observed during Arctic summers; however using MICROTOPS II, we report AOD500 nm values >0.1 at Ny-Ålesund (78.9°N, 11.9°E), Spitsbergen, Arctic, during June and July 2011. The AODs derived from the Aerosol Robotic Network (AERONET) at Hornsund (77.0°N, 15.5°E) (close to Ny-Ålesund) also revealed AOD values more than 0.1 during June and July 2011. The size distribution analysis revealed dominance of fine mode particles in June 2011, and fine and coarse mode particles in July 2011. The HYSPLIT trajectories and NCEP wind anomalies showed that these fine and coarse mode particles were a result of long range transport from landmasses around the Arctic.