Importance of Atmospheric Transport on Methanesulfonic Acid (MSA) Concentrations in the Arctic Ocean During Summer Under Global Warming

The climatic effects of aerosols derived from dimethyl sulfide (DMS) (e.g., methanesulfonic acid [MSA]) have long been of concern, particularly in the rapidly warming Arctic Ocean. Melting sea ice and increase in primary productivity can result in increased DMS emissions and MSA. However, the processes affecting MSA are complex. In addition to local sources, atmospheric chemistry processes, deposition, long-distance transport, and regional heterogeneities influence MSA. This study used aerosol samples from the Chinese Polar Research Expedition during the summer of 2010-2016 and divided them into the Chukchi Sea (CS), high Arctic Ocean (HAO), and sea near Greenland (NG) to study the factors that influence the changes in MSA. For CS, MSA concentrations were primarily influenced by long-distance transport from the Bering Sea air mass. Moreover, owing to the North Atlantic Oscillation, an increase in the Bering Sea temperature and a decrease in rainfall during air mass transport led to a significant increase in the concentration of MSA in the CS in 2016. When the sea ice concentration was between 0.2 and 0.6, high solar radiation likely promoted MSA formation in the HAO. For NG, the sources, rainfall and atmospheric chemical processes influenced the variations in MSA. This study highlights the importance of MSA transport in the CS and sea ice for MSA in the HAO under global warming. Plain Language Summary The Arctic is the most sensitive region in the world to climate change. Melting sea ice and rising temperatures are affecting the ecosystems of the Arctic Ocean. Methanesulfonic acid (MSA) are generated by the oxidation of dimethyl sulfide (DMS) produced by marine phytoplankton after being released into the atmosphere. DMS-derived aerosols in the Arctic Ocean substantially contribute to regional new particle formation and cloud condensation nuclei formation. This could have implications for climate in the Arctic Ocean. As MSA is a good indicator of DMS-derived aerosols, comprehensively understanding how environmental changes influence MSA concentrations is crucial to clarify how emission sources and aerosol-cloud interactions. This study demonstrates that the spatial and temporal distribution characteristics of MSA and their major influencing factors during summer in different sea areas of Arctic Ocean. The findings highlight that although the Chukchi Sea is one of the regions where the Arctic Ocean has warmed and marine primary productivity has increased significantly, the interannual variability of the MSA in this region is mainly influenced by the long-distance transport from the Bering Sea. However, for the High Arctic Ocean regions, sea ice contributes significantly to local MSA concentrations.