Atmospheric particle abundance and sea salt aerosol observations in the springtime Arctic: a focus on blowing snow and leads

• Main Authors: Chen, Qianjie, Mirrielees, Jessica, Thanekar, Sham, Loeb, Nicole, Kirpes, Rachel, Upchurch, Lucia, Barget, Anna, Lata, Nurun, Raso, Angela, McNamara, Stephen, China, Swarup, Quinn, Patricia, Ault, Andrew, Kennedy, Aaron, Shepson, Paul, Fuentes, Jose, Pratt, Kerri
• Format: Text
• Language: English
• Published: 2022
• Subjects: Arctic; Sea ice; Tundra; Alaska
• Online Access: https://doi.org/10.5194/acp-2022-442; https://acp.copernicus.org/preprints/acp-2022-442/

Sea salt aerosols play an important role in the radiation budget and atmospheric composition over the Arctic, where the climate is rapidly changing. Previous observational studies have shown Arctic sea ice leads to be an important source of sea salt aerosols, and modeling efforts have also proposed blowing snow sublimation as a source. In this study, size-resolved atmospheric particle number concentrations and chemical composition were measured at the Arctic coastal tundra site of Utqiaġvik, Alaska during spring (April 3 – May 7, 2016). Blowing snow conditions were observed during 25 % of the five-week study period and were over-predicted by a commonly used blowing snow parameterization based solely on wind speed and temperature. Throughout the study, open leads were present locally. During periods when blowing snow was observed, significant increases in the number concentrations of 0.01–0.06 μm particles (factor of six, on average) and 0.06–0.3 μm particles (67 %, on average), and a significant decrease (82 %, on average) in 1–4 μm particles, were observed, compared to low wind speed periods. These size distribution changes were likely caused by the generation of ultrafine particles from leads and/or blowing snow, with scavenging of supermicron particles by blowing snow. At elevated wind speeds, both submicron and supermicron sodium and chloride mass concentrations were enhanced, consistent with wind-dependent local sea salt aerosol production. At moderate wind speeds below the threshold for blowing snow, as well as during observed blowing snow, individual sea spray aerosol particles were measured. These individual salt particles were enriched in calcium relative to sodium in seawater, due to the binding of this divalent cation with organic matter in the sea surface microlayer and subsequent enrichment during seawater bubble bursting. The chemical composition of the surface snowpack also showed contributions from sea spray aerosol deposition. Overall, these results show the contribution of sea spray aerosol ...