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Marine aerosol plays a vital role in cloud‐aerosol interactions during summer in the Arctic. The recent rise in temperature and decrease in sea ice extent have the potential to impact marine biogenic sources. Compounds like methanesulfonic acid (MSA) and non‐sea‐salt sulfate (nss‐SO42−), oxidation products of dimethyl sulfide (DMS) emitted by marine primary producers, are likely to increase in concentration. Long‐term studies are vital to understand these changes in marine sulfur aerosol and potential interactions with Arctic climate. Samples were collected over three summers at two coastal sites on the North Slope of Alaska (Utqiaġvik and Oliktok Point). MSA concentrations followed previously reported seasonal trends, with evidence of high marine primary productivity influencing both sites. When added to an additional data set collected at Utqiaġvik, an increase in MSA concentration of + 2.5% per year and an increase in nss‐SO42− of + 2.1% per year are observed for the summer season over the 20‐year record (1998–2017). This study identifies ambient air temperature as a strong factor for MSA, likely related to a combination of interrelated factors including warmer sea surface temperature, reduced sea ice, and temperature‐dependent chemical reactions. Analysis of individual particles at Oliktok Point, within the North Slope of Alaska oil fields, showed evidence of condensation of MSA onto anthropogenic particles, highlighting the connection between marine and oil field emissions and secondary organic aerosol. This study shows the continued importance of understanding MSA in the Arctic while highlighting the need for further research into its seasonal relationship with organic carbon. Plain Language Summary: Particles in the Earth's atmosphere play an important role in affecting the planet's climate. Understanding the compounds that make up these aerosol particles is especially important in the Arctic where dramatic changes in temperature and sea ice extent are being observed. Aerosol resulting from biological activity in marine regions is expected to increase in concentration and therefore have greater effects on climate. Methanesulfonic acid is one such compound that can be utilized to understand the impact of marine aerosol sources. Aerosol samples were collected over three summers at two sites on the North Slope of Alaska: Utqiaġvik and Oliktok Point. The samples were analyzed for a wide range of compounds including methanesulfonic acid. The results were combined with 16 years of data from the National Oceanic and Atmospheric Administration. Concentrations of methanesulfonic acid are increasing at a rate of 2.5% per year. Methanesulfonic acid was strongly related to temperature at Oliktok Point, where most marine aerosol is from the Beaufort Sea. At Utqiaġvik, strong relationships were found between methanesulfonic acid and temperature during years when intense Arctic cyclones occurred. Key Points: Arctic MSA and non‐sea‐salt sulfate concentrations show increasing summer trends over the past two decades (2.5% and 2.1%) at Utqiaġvik, AKConcentrations of MSA at Oliktok Point are highly correlated to temperature as air masses are consistently from the Beaufort SeaSummers with Arctic cyclones have better correlation of MSA with ambient temperature [ABSTRACT FROM AUTHOR]

Number concentrations of ice-nucleating particles (NINP) in the Arctic were derived from ground-based filter samples. Examined samples had been collected in Alert (Nunavut, northern Canadian archipelago on Ellesmere Island), Utqiaġvik, formerly known as Barrow (Alaska), Ny-Ålesund (Svalbard), and at the Villum Research Station (VRS; northern Greenland). For the former two stations, examined filters span a full yearly cycle. For VRS, 10 weekly samples, mostly from different months of one year, were included. Samples from Ny-Ålesund were collected during the months from March until September of one year. At all four stations, highest concentrations were found in the summer months from roughly June to September. For those stations with sufficient data coverage, an annual cycle can be seen. The spectra of NINP observed at the highest temperatures, i.e., those obtained for summer months, showed the presence of INPs that nucleate ice up to -5 ∘ C. Although the nature of these highly ice-active INPs could not be determined in this study, it often has been described in the literature that ice activity observed at such high temperatures originates from the presence of ice-active material of biogenic origin. Spectra observed at the lowest temperatures, i.e., those derived for winter months, were on the lower end of the respective values from the literature on Arctic INPs or INPs from midlatitude continental sites, to which a comparison is presented herein. An analysis concerning the origin of INPs that were ice active at high temperatures was carried out using back trajectories and satellite information. Both terrestrial locations in the Arctic and the adjacent sea were found to be possible source areas for highly active INPs. [ABSTRACT FROM AUTHOR]

Number concentrations of ice nucleating particles (NINP) in the Arctic were derived from ground-based filter samples. Examined samples had been collected in Alert (Nunavut, Northern Canadian Archipelago on Ellesmere Island), Utqiagvik, formerly known as Barrow (Alaska), Ny Ålesund (Svalbard) and at the Villum Research Station (VRS, North Greenland). For the former two stations, examined filters span a full yearly cycle. For VRS, 10 weekly samples, mostly from different month of one year, were included. Samples from Ny Ålesund were collected during the months from March until September of one year. At all four stations, highest concentrations were found in the summer months from roughly June to September. For those stations with sufficient data coverage, an annual cycle can be seen. The spectra of NINP observed at the highest temperatures, i.e., those obtained for summer month, showed the presence of INP that nucleate ice up to - 5°C. It is know from literature that ice activivity observed at such high temperatures indicates the presence of ice active material of biogenic origin. Spectra observed at the lowest temperatures, i.e., those derived for winter month, were on the lower end of respective values reported in literature. An analysis concerning the origin of INP that were ice active at high temperatures was carried out, using back-trajectories and satellite information. Both, terrestrial locations in the Arctic and the adjacent sea were found to be possible source areas for highly active INP. [ABSTRACT FROM AUTHOR]

The Arctic ecosystem is undergoing rapid changes including warming, wetting, loss of sea ice, and thawing of permafrost. The biogenic emissions that result from these changes have the potential to affect the regional chemistry and climate through the production of secondary organic aerosol (SOA) from biogenic volatile organic compound (BVOC) emissions, while anthropogenic emissions have the potential to increase with increased local activity. Recent studies investigating marine sources of organic aerosol in the Arctic highlight the need to understand the temporality, variability and characteristics of biogenic sources in the changing system. Terrestrial sources of biogenic aerosol in the Arctic are even less understood and may be more variable from low to high Arctic regions. The study site on the North Slope of Alaska is primarily sedge/grass, moss wetland, with more vegetation than high Arctic sites. To understand the long-term impact of these sources on carbonaceous aerosol concentration and composition in the Arctic, a multi-year view is needed. This presentation will highlight summer trends in organic aerosol sources and composition over 5 years on the North Slope of Alaska (2012-2017). Sources and composition of organic aerosol will be discussed with respect to results from isotopic analysis (radiocarbon), organic and elemental carbon, organic acids (including methanesulfonic acid), biogenic SOA tracers (including pinic acid and methyl tetrols), levoglucosan, and combustion tracers (including polycyclic aromatic hydrocarbons and hopanes). [ABSTRACT FROM AUTHOR]

The rapid decrease in Arctic sea ice is motivating development and increasing oil and gas extraction activities. However, few observations of these local Arctic emissions exist, limiting the understanding of impacts on atmospheric composition and climate. To address this knowledge gap, the chemical composition of atmospheric aerosols was measured within the North Slope of Alaska oil fields during August and September 2016 using an aerosol time-of-flight mass spectrometer (ATOFMS) and a time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Plumes from oil and gas extraction activities were characterized by soot internally mixed with sulfate (matching diesel soot) and organic carbon particles containing aminium sulfate salts. Sea spray aerosol at the coastal site was frequently internally mixed with sulfate and nitrate, from multiphase chemical processing from elevated NO x and SO 2 within the oil field. Background (nonplume) air masses were characterized by aged combustion aerosol. No periods of "clean" (nonpolluted) Arctic air were observed. The composition of the nonrefractory aerosol measured with the ACSM was similar during plume and background periods and was consistent with the mass concentrations of nonrefractory particles measured by ATOFMS. Two ultrafine aerosol growth events were observed during oil field background periods and were correlated with fine mode amine-containing particles.