Aerosol Properties across the North Slope of Alaska: Sources and Distributions from Utqiagvik (formerly Barrow) to Oliktok Point

Description

Recent studies indicate that aerosol in the Arctic has appreciably offset greenhouse gas warming and sea ice loss (Najafi et al. 2015, Gagne et al. 2015); at the same time, observations show a warming of the Arctic region that is still much greater than the global average due to Arctic Amplification mechanisms (Serreze and Barry 2011.) Air-quality regulations are manifesting in declining aerosol burdens across the Arctic, so the rate of warming and sea ice loss may accelerate in the future. The radiative forcing potential of aerosol is dictated by the source and evolution after emission, so characterizing aerosol property distributions relative to source is essential for predicting future Arctic climate system responses to other anthropogenic changes. Here, we assemble aerosol measurements from a range of platforms and locations to assess how aerosol sources and properties distribute horizontally and vertically from the relatively pristine site of Utqiagvik to Oliktok Point on Prudhoe Bay. Airborne measurements from the U.S. Department of Energy’s Atmospheric Radiation Measurement Airborne Carbon Measurements (ARM-ACME-V) campaign during the summer of 2015 provide valuable insight into the vertical and spatial heterogeneity of aerosols. We compare these observations to previous airborne field campaign measurements and preliminary observations from the ARM Unmanned Aerial System/Tethered Balloon System Program at these sites to delineate the diversity in the vertical distribution of aerosols over several time periods. These airborne data are contextualized in a long-term, seasonal analysis of ground-based in situ and remote-sensing observations of aerosol properties to evaluate the sources of aerosol in the boundary layer as compared to the free troposphere. Our findings establish patterns of aerosol properties consistent with known sources and transport patterns across the North Slope: more numerous, smaller particles surrounding Oliktok Point, likely from oil extraction activities; biomass burning aerosol aloft from long-range transport originating in boreal forests; and seasonal cycles of properties near the surface that reflect changing sources as surface cover and circulation pattern vary throughout the year.