The ice-nucleating activity of Arctic sea surface microlayer samples and marine algal cultures

• Published in: Atmospheric Chemistry and Physics
• Main Authors: Ickes, Luisa, Porter, Grace C. E., Wagner, Robert, Adams, Michael P., Bierbauer, Sascha, Bertram, Allan K., Bilde, Merete, Christiansen, Sigurd, Ekman, Annica M. L., Gorokhova, Elena, Hoehler, Kristina, Kiselev, Alexei A., Leck, Caroline, Moehler, Ottmar, Murray, Benjamin J., Schiebel, Thea, Ullrich, Romy, Salter, Matthew E.
• Language: unknown
• Published: 2020
• Subjects: Meteorology and Atmospheric Sciences; Climate Research; Geosciences; Multidisciplinary; Arctic; Phytoplankton; Sea ice
• Online Access: https://doi.org/10.5194/acp-20-11089-2020; https://research.chalmers.se/en/publication/519973

In recent years, sea spray as well as the biological material it contains has received increased attention as a source of ice-nucleating particles (INPs). Such INPs may play a role in remote marine regions, where other sources of INPs are scarce or absent. In the Arctic, these INPs can influence water-ice partitioning in low-level clouds and thereby the cloud lifetime, with consequences for the surface energy budget, sea ice formation and melt, and climate. Marine aerosol is of a diverse nature, so identifying sources of INPs is challenging. One fraction of marine bioaerosol (phytoplankton and their exudates) has been a particular focus of marine INP research. In our study we attempt to address three main questions. Firstly, we compare the ice-nucleating ability of two common phytoplankton species with Arctic seawater microlayer samples using the same instrumentation to see if these phytoplankton species produce ice-nucleating material with sufficient activity to account for the ice nucleation observed in Arctic microlayer samples. We present the first measurements of the ice-nucleating ability of two predominant phytoplankton species: Melosira arctica, a common Arctic diatom species, and Skeletonema marinoi, a ubiquitous diatom species across oceans worldwide. To determine the potential effect of nutrient conditions and characteristics of the algal culture, such as the amount of organic carbon associated with algal cells, on the ice nucleation activity, Skeletonema marinoi was grown under different nutrient regimes. From comparison of the ice nucleation data of the algal cultures to those obtained from a range of sea surface microlayer (SML) samples obtained during three different field expeditions to the Arctic (ACCACIA, NETCARE, and ASCOS), we found that they were not as ice active as the investigated microlayer samples, although these diatoms do produce ice-nucleating material. Secondly, to improve our understanding of local Arctic marine sources as atmospheric INPs we applied two aerosolization techniques ...