Local Production of Arctic Sea Spray Aerosol in the Fall-Winter Transition

The Arctic is rapidly warming, causing reductions in sea ice extent and thickness. This is resulting in increasing areas of open water, which can act as a source of sea spray aerosol generated by bubble bursting at the sea surface. Changing local marine biogeochemistry is expected to have an increasing impact on the Arctic aerosol population. However, measurements of the Arctic atmosphere under these changing conditions are challenging and limited, especially during the fall-winter transition, when sea ice freeze-up is delayed. As such, there is little knowledge of how the changing ecosystem will influence the regional atmosphere and climate. To investigate Arctic sea spray aerosol particles during the fall-winter transition, we present measurements of individual particles collected during the November – December 2018 Aerosols in the Polar Utqiaġvik Night (APUN) field campaign in coastal Utqiaġvik, Alaska. The morphology and chemical composition of individual atmospheric particles ranging in diameter from 0.1–1.8 μm were measured using computer-controlled scanning electron microscopy with energy dispersive X-ray spectroscopy (CCSEM-EDX) and Raman microspectroscopy. CCSEM-EDX was used to identify individual sea salt aerosol particles and investigate their elemental composition, with an emphasis on quantifying organic carbon content. Using Raman microspectroscopy, we identified marine-derived organics within the individual sea salt aerosol particle coatings. The majority of the sea spray aerosol particles were identified as being produced from nearby open water, rather than being long-range transported. These measurements of sea spray aerosol during the coastal Arctic fall-winter transition will further our understanding of the connections between delayed sea ice freeze-up, seawater microbiology, and aerosol particle composition in the changing Arctic environment.