Study of Dimethyl sulfide, Sulfate Aerosols and Ice Nucleation Particles in the Arctic Summer

• Main Author: Ghahremaninezhadgharelar, Roghayeh
• Other Authors: Norman, Ann-Lise, Reuten, Christian, Smith, Wendy Lani
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: Graduate Studies 2016
• Subjects: Environmental Sciences; climate change; Arctic; Lancaster Sound; Climate change
• Online Access: http://hdl.handle.net/11023/3525; https://doi.org/10.11575/PRISM/27919

Aerosols drive significant radiative forcing and affect Arctic climate. Despite the importance of these aerosols in Arctic climate change, there are some key uncertainties in the estimation of their effects and sources. Size-segregated aerosol, SO2 and precipitation samples were collected on board the Canadian Coast Guard Ship Amundsen in the Arctic during July 2014, to utilize the isotopic composition of sulfate to address the contribution of anthropogenic, biogenic and sea salt sources in formation/growth of aerosol. More than 63% of the average sulfate concentration in the fine aerosols (<0.49 μm) was from biogenic sources. For most samples, δ34S values for SO2 and fine aerosols were similar, suggesting gas-to-particle conversion. δ34S apportionment for precipitation samples suggested a relatively low contribution of the biogenic sulfate source (14±8%) and high contribution of sea salt (82±10%). Also, the size distribution of ice nucleation particles (INPs) in the immersion mode was determined for solid particles smaller than 0.45 μm and soluble aerosol in the size range of 0.49-7.2 μm. Large particles (3.0-7.2 μm), were more efficient INPs. In addition, vertical distributions of atmospheric dimethyl sulfide were sampled aboard the research aircraft Polar 6 near Lancaster Sound in July 2014 and on pan-Arctic flights in April 2015. Larger mean DMS mixing ratios were present during April 2015 (campaign-mean of 116±8 pptv) than July 2014 (campaign-mean of 20±6 pptv). A strong decrease was observed in DMS mixing ratios with altitude in July 2014. In contrast, DMS mixing ratios sampled in April 2015 exhibited a relatively more uniform campaign-mean vertical profile and increased with altitude on some flights. These results highlight the role of open water below the flight as the source of DMS during July 2014, and the influence of long-range transport of DMS from further afield in the Arctic during April 2015. In general, the high biogenic fraction of sulfate fine aerosol and relatively high DMS mixing ratios ...