Summertime pollution events in the Arctic and potential implications

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Abstract

[1] Arctic summertime aerosols are examined here on the basis of column integrated and surface aerosol measurements made at Barrow (North Slope of Alaska) between 1998 and 2003. Although the site generally exhibits low aerosol burden in the summer, events of high loadings occur 8 days per summer. During the pollution episodes, the potential source contribution function from Russia is dominant (being about 40%). The source locations in Russia are mainly situated in the central and eastern parts. South Asia, Europe and North America each contribute 6% to the observed high aerosol loading. Source locations in south Asia lie in northern China and northern Japan, while those in Europe lie mainly in northern U.K. and Estonia. The North American sources are situated in northern Canada and Alaska. Over the 6-year period, 10 ± 4 days per summer season show elevated levels of surface aerosol absorption. The pollution events with the highest aerosol absorption appear to be associated with smoke from wild fires burning in northwest Canada. Diurnally averaged top of the atmosphere direct radiative forcing ΔFTOA (550 nm) at Barrow lie between −1.50 W m−2 and 1.19 W m−2 in summer with an annual mean of −0.53 ± 0.11 W m−2. Given low Arctic summertime surface albedo (<30%), a positive ΔFTOA results when the single scattering albedo is 0.85 or lower. Summertime direct surface radiative forcing (550 nm) ranges between −3.2 W m−2 and −29 W m−2 for observed cases of aerosol optical depth at the site.

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