Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures

<p>Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell...

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Main Authors: R. Wagner, L. Ickes, A. K. Bertram, N. Els, E. Gorokhova, O. Möhler, B. J. Murray, N. S. Umo, M. E. Salter
Format: Article
Language:English
Published: Copernicus Publications 2021-09-01
Series:Atmospheric Chemistry and Physics
Online Access:https://acp.copernicus.org/articles/21/13903/2021/acp-21-13903-2021.pdf
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author R. Wagner
L. Ickes
A. K. Bertram
N. Els
E. Gorokhova
O. Möhler
B. J. Murray
N. S. Umo
M. E. Salter
author_facet R. Wagner
L. Ickes
A. K. Bertram
N. Els
E. Gorokhova
O. Möhler
B. J. Murray
N. S. Umo
M. E. Salter
author_sort R. Wagner
collection DOAJ
description <p>Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea spray aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 <span class="inline-formula">K</span> are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (<i>Skeletonema marinoi</i>). The particles were suspended in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 <span class="inline-formula">K</span>, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about <span class="inline-formula">5×10<sup>10</sup></span> <span class="inline-formula">m<sup>−2</sup></span> at an ice saturation ratio of 1.3. Much smaller densities in the range of 10<span class="inline-formula"><sup>8</sup></span>–10<span class="inline-formula"><sup>9</sup></span> <span class="inline-formula">m<sup>−2</sup></span> were observed at temperatures between 220 and 235 <span class="inline-formula">K</span>, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are 2 orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the number of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how instrumental parameters like the aerosolisation method and the ice nucleation measurement technique might affect the comparability of the results amongst different studies.</p>
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spelling doaj.art-04714451c59e4151b37ea5122f6a72fe2022-12-21T22:42:25ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242021-09-0121139031393010.5194/acp-21-13903-2021Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperaturesR. Wagner0L. Ickes1A. K. Bertram2N. Els3E. Gorokhova4O. Möhler5B. J. Murray6N. S. Umo7M. E. Salter8Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, GermanyDepartment of Space, Earth and Environment, Chalmers, Gothenburg, SwedenDepartment of Chemistry, University of British Columbia, Vancouver, CanadaDepartment of Ecology, University of Innsbruck, Innsbruck, AustriaDepartment of Environmental Science and Analytical Chemistry & Bolin Centre for Climate Studies, Stockholm University, Stockholm, SwedenInstitute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, GermanySchool of Earth and Environment, University of Leeds, Leeds, United KingdomInstitute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, GermanyDepartment of Environmental Science and Analytical Chemistry & Bolin Centre for Climate Studies, Stockholm University, Stockholm, Sweden<p>Sea spray aerosol particles are a recognised type of ice-nucleating particles under mixed-phase cloud conditions. Entities that are responsible for the heterogeneous ice nucleation ability include intact or fragmented cells of marine microorganisms as well as organic matter released by cell exudation. Only a small fraction of sea spray aerosol is transported to the upper troposphere, but there are indications from mass-spectrometric analyses of the residuals of sublimated cirrus particles that sea salt could also contribute to heterogeneous ice nucleation under cirrus conditions. Experimental studies on the heterogeneous ice nucleation ability of sea spray aerosol particles and their proxies at temperatures below 235 <span class="inline-formula">K</span> are still scarce. In our article, we summarise previous measurements and present a new set of ice nucleation experiments at cirrus temperatures with particles generated from sea surface microlayer and surface seawater samples collected in three different regions of the Arctic and from a laboratory-grown diatom culture (<i>Skeletonema marinoi</i>). The particles were suspended in the Aerosol Interaction and Dynamics in the Atmosphere (AIDA) cloud chamber and ice formation was induced by expansion cooling. We confirmed that under cirrus conditions, apart from the ice-nucleating entities mentioned above, also crystalline inorganic salt constituents can contribute to heterogeneous ice formation. This takes place at temperatures below 220 <span class="inline-formula">K</span>, where we observed in all experiments a strong immersion freezing mode due to the only partially deliquesced inorganic salts. The inferred ice nucleation active surface site densities for this nucleation mode reached a maximum of about <span class="inline-formula">5×10<sup>10</sup></span> <span class="inline-formula">m<sup>−2</sup></span> at an ice saturation ratio of 1.3. Much smaller densities in the range of 10<span class="inline-formula"><sup>8</sup></span>–10<span class="inline-formula"><sup>9</sup></span> <span class="inline-formula">m<sup>−2</sup></span> were observed at temperatures between 220 and 235 <span class="inline-formula">K</span>, where the inorganic salts fully deliquesced and only the organic matter and/or algal cells and cell debris could contribute to heterogeneous ice formation. These values are 2 orders of magnitude smaller than those previously reported for particles generated from microlayer suspensions collected in temperate and subtropical zones. While this difference might simply underline the strong variability of the number of ice-nucleating entities in the sea surface microlayer across different geographical regions, we also discuss how instrumental parameters like the aerosolisation method and the ice nucleation measurement technique might affect the comparability of the results amongst different studies.</p>https://acp.copernicus.org/articles/21/13903/2021/acp-21-13903-2021.pdf
spellingShingle R. Wagner
L. Ickes
A. K. Bertram
N. Els
E. Gorokhova
O. Möhler
B. J. Murray
N. S. Umo
M. E. Salter
Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
Atmospheric Chemistry and Physics
title Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
title_full Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
title_fullStr Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
title_full_unstemmed Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
title_short Heterogeneous ice nucleation ability of aerosol particles generated from Arctic sea surface microlayer and surface seawater samples at cirrus temperatures
title_sort heterogeneous ice nucleation ability of aerosol particles generated from arctic sea surface microlayer and surface seawater samples at cirrus temperatures
url https://acp.copernicus.org/articles/21/13903/2021/acp-21-13903-2021.pdf
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