Preprints
https://doi.org/10.5194/egusphere-2023-2780
https://doi.org/10.5194/egusphere-2023-2780
04 Jan 2024
 | 04 Jan 2024

Measurement report: The ice-nucleating activity of lichen sampled in a northern European boreal forest

Ulrike Proske, Michael P. Adams, Grace C. E. Porter, Mark Holden, Jaana Bäck, and Benjamin J. Murray

Abstract. Ice nucleating particles (INPs) facilitate heterogeneous freezing of cloud droplets and thus modify cloud properties. Hence, it is important to understand the sources of INPs. During the HyICE-2018 campaign, which took place in the boreal forest of Hyytiälä, substantial concentrations of biological INPs were observed despite many potential biological sources of INPs being snow covered. A potential source of INP that were not covered in snow were lichens that grow on trees, hence we investigated these lichens as a potential source of biological INPs in this boreal forest environment. INPs derived from lichen sampled during HyICE-2018 are shown to nucleate ice at temperatures as warm as -5 °C in aqueous solutions extracted from 0.03 g ml-1 lichen. In particular, we identify two species of INPs active at -16 and -18 °C and smaller than 2 µm in size, which makes them good candidates for atmospheric INPs. These particles are smaller than whole lichen spores. In species specific tests we show that the four investigated lichen species harbour differently sized INPs, which might suggest that some species of lichen are more important as a source of INPs than others. This study shows that lichen from a European Boreal forest harbour INPs, which may be especially important in habitats where few other biological INP sources are present, such as in a snow covered environment. The great terrestrial abundance of lichen INPs calls for further research to combine their ice nucleating ability with dispersal studies to evaluate the flux of lichenous INPs into the atmosphere as well as to what extent these particles reach heights and locations where they might influence cloud properties.

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Ulrike Proske, Michael P. Adams, Grace C. E. Porter, Mark Holden, Jaana Bäck, and Benjamin J. Murray

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2780', Anonymous Referee #1, 13 Jan 2024
    • CC1: 'Reply on RC1', Benjamin Murray, 15 Jan 2024
  • RC2: 'Referee report on "Measurement report: The ice-nucleating activity of lichen sampled in a northern European boreal forest"', Anonymous Referee #2, 06 Feb 2024
Ulrike Proske, Michael P. Adams, Grace C. E. Porter, Mark Holden, Jaana Bäck, and Benjamin J. Murray

Data sets

Data for the publication "The ice-nucleating activity of lichen sampled in a northern European boreal forest" U. Proske et al. https://doi.org/10.5281/zenodo.8355809

Ulrike Proske, Michael P. Adams, Grace C. E. Porter, Mark Holden, Jaana Bäck, and Benjamin J. Murray

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Short summary
Ice nucleating particles aid freezing of water droplets in clouds and thus modify clouds' properties. During a campaign in the boreal forest in Finland, substantial concentrations of biological ice nucleating particles were observed, despite many of their potential biological sources being snow covered. We sampled lichen in this location and tested its ice nculeation ability in the laboratory. We find that indeed the lichen harbours INPs, which may be important in such snow covered environments.