Marine carbohydrates in Arctic aerosol particles – connections to oceanic emissions and in-situ processing

Carbohydrates are important components of marine organic aerosol particles and may influence Arctic cloud formation and properties, yet their sources and atmospheric fate remain poorly understood. We present the first year-round measurements of combined and dissolved carbohydrates (CCHOaer; DFCHOaer) in aerosol particles collected throughout the annual cycle of the MOSAiC expedition in 2019-2020. CCHOaer were detected in all seasons (0.5-17 ng m⁻³), and contributed between 0.03 and 2.2% (mean 0.3%) to the particulate mass. Their molecular composition was relatively stable and dominated by glucose, xylose, and galactose, with additional presence of uronic acids in summer. Both, CCHOaer and DFCHOaer showed pronounced summer maxima and seasonal variability that partially aligned with chlorophyll-a, nanophytoplankton, and heterotrophic microorganisms, indicating enhanced biological contributions after sea ice melt. The summer increase in DFCHOaer also coincided with warmer temperatures and higher humidity. In winter, the presence of carbohydrates may be sustained by microbial degradation or viral lysis of organic material in under-ice environments. CCHOaer and DFCHOaer concentrations showed no direct correlation to wind speed or air mass origins instead displaying a high variability in summer. The seasonal behavior of CCHOaer in Arctic aerosol particles differed from primary marine tracers like sodium that was associated with direct oceanic sources in summer and blowing snow in winter. This contrast suggests that carbohydrates, while possibly originated from marine biological sources, undergo significant atmospheric modification that overlay direct source signatures. Strong correlations between CCHOaer and low-molecular-weight organic acids further point to photochemical oxidation as an additional driver of secondary carbohydrate processing. CCHOaer displayed seasonal trends similar to warm-temperature ice-nucleating particles and hyper-fluorescent aerosol particles, supporting their role within a broader Arctic bioaerosol particle population. Overall, our results indicate that marine ecosystems provide a continuous source of atmospheric carbohydrates, but their composition is strongly modified by both biotic and abiotic processes, particularly in summer.Acknowledgement: This work was supported by the DFG funded Transregio-project TRR 172 “Arctic Amplification (AC)3“.