During the 2017 summertime Arctic cruise observation campaigns, we measured over 290,000 individual submicron particles and clustered them into two inorganic classes (dominated by sea salt, accounting for 38.6% by number fraction) and five organic classes (dominated by natural and anthropogenic organics, 61.4%), presenting a distinct difference in geographic distribution. In the high Arctic and marginal ice zone (81.1–84.6°N) compared with the low Arctic (Chukchi Sea, Svalbard, and Iceland, <80°N), ocean-derived organic aerosols were more prevalent (73.6% vs. 37.1%). Specifically, we found sharp contrasts in the geographic distributions of OC-Ca (organics internally mixed with calcium, 29.0% vs. 9.4%) and OC-S (organics internally mixed with sulfate, 3.2% vs. 21.4%). Utilizing an explainable machine learning technique, we inferred that OC-Ca was driven by wind-blown sea ice and/or sea ice floes and/or bubble bursting within sea ice leads under low wind speed conditions in the high Arctic, while OC-S tended to associate with elemental carbon, sulfate, and higher temperatures, potentially originating from combustion emissions at low latitude regions.

Plain Language Summary

Knowledge of the mixing state of individual particles is essential for elucidating their sources, formation mechanisms, atmospheric processes, and assessing their climate effect in the Arctic atmosphere. Here, we investigated the origins and geographic distribution of organic aerosol types using a single-particle aerosol mass spectrometer during the 8th Chinese Arctic Expedition Research Cruise (Chinese Research Vessel Xuelong) in the summertime over the Arctic Ocean. According to the mixing state, individual organic particles were classified into several ocean-derived and anthropogenic types. Ocean-derived types were prevalent in the high Arctic compared with that of anthropogenic type in the low Arctic, and their driven factors were different. Specifically, sea ice fraction was the most important driver for the generation of ocean-derived OC-Ca (an aerosol type of organics internally mixed with calcium). OC-S (an aerosol type of organics internally mixed with sulfate) substantially increased in the low Arctic, most probably driven by combustion sources.