Long‐Term Trends for Marine Sulfur Aerosol in the Alaskan Arctic and Relationships With Temperature

Abstract

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-SO 4 2−), 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-SO 4 2− 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.

Large seasonal and interannual variations of biogenic sulfur compounds in the Arctic atmosphere (Svalbard; 78.9° N, 11.9° E)

“…2a and 3b). As confirmed in other studies (e.g., Arnold et al, 2010;Park et al, 2013;Mungall et al, 2016), the atmospheric DMS mixing ratio generally corresponded to the phytoplankton biomass in the oceans surrounding Svalbard (Figs. 2a and S3).…”

Equal abundance of summertime natural and wintertime anthropogenic Arctic organic aerosols

“…3) are consistent among the stations, with much higher concentrations in May-June, the main season of phytoplankton blooms. The range of maximum concentrations at ALT and Utqiaġvik (UTQ) (~20-30 ng m −3 ) is comparable to those of previous measurements of MSA from these stations by ion chromatography 62,63 . The highest weekly averaged MSA-OA levels, which exceed 100 ng m −3 , occur at GRU, Villum Research Station (VRS) and ZEP.…”

“…Factor identification is aided by organic marker, major ion and EC measurements (Methods and Supplementary Text 3). Source 2), sorted in descending order of the station annual average, and percent contribution to the particulate mass (including non-sea salt sulfate, nitrate, ammonium, EC and estimated sea salt 63 ). The dashed blue lines connect winter and summer contributions at each station (no winter samples for G and T, and U winter samples were not analysed for ions).…”

“…Adapted from Hugo Ahlenius/GRID-Arendal (https://www.grida.no/resources/8378). b, Station-specific average total OA mass concentrations (whiskers are 1 standard deviation, s.d., corresponding to sample-to-sample variability) based on a statistical analysis of the water-soluble fraction to obtain factor recoveries (Supplementary Text 4) in the polar night (winter) versus midnight sun (summer) periods (Supplementary Table2), sorted in descending order of the station annual average, and percent contribution to the particulate mass (including non-sea salt sulfate, nitrate, ammonium, EC and estimated sea salt63 ). The dashed blue lines connect winter and summer contributions at each station (no winter samples for G and T, and U winter samples were not analysed for ions).…”

Modification of the Conversion of Dimethylsulfide to Methanesulfonic Acid by Anthropogenic Pollution as Revealed by Long-Term Observations

“…The Arctic Ocean has been extensively examined in studies focusing on global warming. − However, there is limited research pertaining to the Bering Sea, which is one of the most productive marine ecosystems and a significant producer of dimethyl sulfopropionate (DMSP) . Moreover, the Bering Sea experienced abnormally rapid warming and recorded sea surface temperatures (SSTs) in 2016, thereby providing a natural place for studying the relationship between climate warming and MSA.…”