Preprints
https://doi.org/10.5194/acp-2020-1211
https://doi.org/10.5194/acp-2020-1211

  26 Nov 2020

26 Nov 2020

Review status: a revised version of this preprint is currently under review for the journal ACP.

Terrestrial or marine? – Indications towards the origin of Ice Nucleating Particles during melt season in the European Arctic up to 83.7° N

Markus Hartmann1, Xianda Gong1,c, Simonas Kecorius1, Manuela van Pinxteren2, Teresa Vogl1,a, André Welti1,b, Heike Wex1, Sebastian Zeppenfeld2, Hartmut Herrmann2, Alfred Wiedensohler1, and Frank Stratmann1 Markus Hartmann et al.
  • 1Experimental Aerosol and Cloud Microphysics, Leibniz Institute for Tropospheric Research, 04318, Leipzig, Germany
  • 2Atmospheric Chemistry Department, Leibniz Institute for Tropospheric Research, 04318, Leipzig, Germany
  • anow at: Remote Sensing and The Arctic Climate System, Institute for Meteorology, University of Leipzig, 04103, Leipzig, Germany
  • bnow at: Finnish Meteorological Institute, Helsinki, Finland
  • cnow at: Center for Aerosol Science and Engineering, Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, USA

Abstract. Ice nucleating particles (INPs) initiate the primary ice formation in clouds at temperatures above ca. −38° C and have an impact on precipitation formation, cloud optical properties and cloud persistence. Despite their roles in both weather and climate, INPs are not well characterized, especially in remote regions such as the Arctic. We present results from a ship-based campaign to the European Arctic in May to July 2017. We deployed a filter sampler and a continuous flow diffusion chamber for off- and online INP analysis, respectively. We also investigated the ice nucleation properties of samples from different environmental compartments, i.e., the sea surface microlayer (SML), the bulk seawater (BSW), and fog water. Concentrations of INP (NINP) in the air vary between two to three orders of magnitudes at any particular temperature and are, except for the temperatures above −10° C and below −32° C, lower than in mid-latitudes. In these temperature ranges INP concentrations are the same or even higher than in the mid-latitudes. Heating of the filter samples to 95° C for 1 hour we found a significant reduction in ice nucleation activity, i.e., indications that the INPs active at warmer temperatures are biogenic. At colder temperatures the INP population was likely dominated by mineral dust. The SML was found to be enriched in INP compared to the BSW in almost all samples. The enrichment factor (EF) varied mostly between 1 and 10, but EFs as high as 94.97 were also observed. Filtration of the seawater samples with 0.2 µm syringe filters lead to a significant reduction in ice activity, indicating the INPs are larger, and/or are associated with particles larger than 0.2 µm. A closure study showed that aerosolization of SML and/or seawater alone cannot explain the observed air-borne NINP unless significant enrichment of INP by a factor of 105 takes place during the transfer from the ocean surface to the atmosphere. In the fog water samples with −3.47° C we observed the highest freezing onset of any sample. A closure study connecting NINP in fog water and the ambient NINP derived from the filter samples shows good agreement of the concentrations in both compartments, which indicates that INPs in the air are likely all activated into fog droplets during fog events. In a case study we considered a situation during which the ship was located in the marginal sea ice zone and NINP in air and the SML were highest in the temperature range above −10° C. Chlorophyll-a measurements by satellite remote sensing point towards the waters in the investigated region being biologically active. Heat induced reduction of ice nucleating ability indicated the biogenic nature of the air-borne INPs. Similar slopes in the temperature spectra suggested a connection between the INP populations in the SML and the air. Air mass history had no influence on the observed air-borne INP population. Therefore, we conclude that during the case study collected air-borne INPs originated from a local biogenic probably marine source.

Markus Hartmann et al.

 
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Markus Hartmann et al.

Data sets

Shipborne Ice Nucleating Particle (INP) measurements in the Arctic during PS106.1 and PS106.2 Markus Hartmann, Xianda Gong, André Welti, and Frank Stratmann https://doi.pangaea.de/10.1594/PANGAEA.919194

Markus Hartmann et al.

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Short summary
Ice nucleating particles (INPs) are not well characterized in the Arctic despite their importance for the Arctic energy budget. Little is known about their nature (mineral or biogenic) and sources (terrestrial or marine and long-range transport or local). We find indications that at the beginning of the melt season, a local, biogenic, probably marine source is likely, but significant enrichment of INPs has to take place from the ocean to the aerosol phase.
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