Abstract
Abstract. Aerosol measurements at Barrow, Alaska during the past 30 years have identified the long range transport of pollution associated with Arctic Haze as well as ocean-derived aerosols of more local origin. Here, we focus on measurements of aerosol chemical composition to assess (1) trends in Arctic Haze aerosol and implications for source regions, (2) the interaction between pollution-derived and ocean-derived aerosols and the resulting impacts on the chemistry of the Arctic boundary layer, and (3) the response of aerosols to a changing climate. Aerosol chemical composition measured at Barrow, AK during the Arctic haze season is compared for the years 1976–1977 and 1997–2008. Based on these two data sets, concentrations of non-sea salt (nss) sulfate (SO4=) and non-crustal (nc) vanadium (V) have decreased by about 60% over this 30 year period. Consistency in the ratios of nss SO4=/ncV and nc manganese (Mn)/ncV between the two data sets indicates that, although emissions have decreased in the source regions, the source regions have remained the same over this time period. The measurements from 1997–2008 indicate that, during the haze season, the nss SO4= aerosol at Barrow is becoming less neutralized by ammonium (NH4+) yielding an increasing sea salt aerosol chloride (Cl−) deficit. The expected consequence is an increase in the release of Cl atoms to the atmosphere and a change in the lifetime of volatile organic compounds (VOCs) including methane. In addition, summertime concentrations of biogenically-derived methanesulfonate (MSA−) and nss SO4= are increasing at a rate of 12 and 8% per year, respectively. Further research is required to assess the environmental factors behind the increasing concentrations of biogenic aerosol.
Highlights
Arctic haze, defined here as the occurrence each winter and spring of increased aerosol concentrations and decreased visibility, was reported as early as the late 1800s (Nordenskiold, 1883; Garrett and Verzella, 2008)
Quinn et al.: Decadal trends in aerosol chemical composition at Barrow, Alaska: 1976–2008 was a factor of 5 higher in aerosol originating from Europe than from the northeast U.S The higher ratios measured in Europe were attributed to the abundance of ferrous and nonferrous industries and the lower ratios in the NE US were attributed to the residual oil burned for residential heating in the winter
The broad winter to early spring maximum in nss SO=4 has been attributed to an initial transport of anthropogenic nss SO=4 produced in mid-latitude source regions and the transport and subsequent oxidation of SO2 to SO=4 as light levels increase enroute to and within the Arctic itself (Barrie and Hoff, 1984)
Summary
Arctic haze, defined here as the occurrence each winter and spring of increased aerosol concentrations and decreased visibility, was reported as early as the late 1800s (Nordenskiold, 1883; Garrett and Verzella, 2008). Quinn et al.: Decadal trends in aerosol chemical composition at Barrow, Alaska: 1976–2008 was a factor of 5 higher in aerosol originating from Europe than from the northeast U.S The higher ratios measured in Europe were attributed to the abundance of ferrous and nonferrous industries and the lower ratios in the NE US were attributed to the residual oil burned for residential heating in the winter Based on these regional values and taking into account the expected decrease in the ratio with transport due to the different size distributions of Mn and V, Rahn (1981) concluded that Europe was a more significant source region for Arctic aerosol than the NE US. We present trends in summertime nss SO=4 and MSA− and changes in the composition of the inorganic fraction of the aerosol that have occurred at Barrow over the past decade and the implications associated with this changing aerosol composition
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