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Abstract:
Marine carbohydrates are produced by microbes in the ocean and contribute significantly to dissolved and particulate organic carbon in the seawater. Recent studies showed that the carbohydrates released by Arctic microorganisms exhibit an extraordinarily high ice nucleating activity making them potentially important ice nucleating particles (INP). These carbohydrates enter the atmosphere as part of sea spray aerosol (SSA) through wind-driven processes and eventually contribute to cloud formation processes. However, the emission processes of marine carbohydrates and their atmospheric aging are still not well understood.
Here, we present marine carbohydrates found in bulk seawater (at 1 m depth), the sea surface microlayer (SML), size-resolved aerosol particles and fog water collected in the Arctic during the PASCAL/SiPCA cruise (May-July 2017). Chemical and statistical analyses revealed a chemo-selective transfer of carbohydrates towards sodium during the sea-air transfer. Additionally, strong evidence could be found for bacterial modifications of the aerosolized carbohydrates in the atmosphere after their oceanic emission causing quick aging. Finally, we present the influence of sea ice on the sea-air transfer by forming different sea ice related environments, such as the marginal ice zone, open leads, melt ponds and the ice-free ocean with different biological activities and wind conditions.
As a consequence of the retreat of sea ice enhanced by Arctic amplification, these processes may lead to a changing availability of potential INP influencing the cloud formation and their microphysical properties.
