Contribution of primary biological aerosol particles to low-level Arctic cloud condensation nuclei

• Mixed-phase clouds (MPC) are key players in the Arctic climate system due to their role in modulating solar and terrestrial radiation. Such radiative interactions critically rely on the ice content of MPC which, in turn, partly depends on the availability of ice nucleating particles (INP). INP sources and concentrations are poorly understood in the Arctic. Recently, INP active at high temperatures were linked to be primary biological aerosol particles (PBAP). Here, we investigated for a full year the PBAP abundance and variability within cloud residuals, directly sampled by a multiparameter bioaerosol spectrometer coupled to a ground-based counterflow virtual impactor inlet at the Zeppelin Observatory (475 m asl), Ny-Ålesund, Svalbard. PBAP concentrations (10−3–10−2L−1) and contributions to coarse-mode aerosol (1 in every 103–104) within cloud residuals were found to be close to those expected for concentrations of high-temperature INP. Transmission electron microscopy also confirmed the presence of PBAP, most likely bacteria, within the cloud residual samples. Seasonally, our results reveal an elevated presence of PBAP within cloud residuals during the summer. Parallel water vapor isotope measurements points towards a link between summer clouds and regionally sourced air masses. Low-level MPC were predominantly observed at the beginning and end of summer, and one explanation for their presence is the existence of high-temperature INP. In this study, we present observational evidence that PBAP might play a role in determining the phase of low-level Arctic clouds, with potential implications for the Arctic climate given ongoing changes in the hydrological and biogeochemical cycles that influence the PBAP flux in and towards the Arctic.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Meteorologi och atmosfärforskning (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Meteorology and Atmospheric Sciences (hsv//eng)

Keyword

Bioaerosol

Mixed-phase clouds

Arctic

Cloud condensation nuclei

Ice nucleating particles

atmosfärvetenskap och oceanografi

Atmospheric Sciences and Oceanography

Publication and Content Type

vet (subject category)

ovr (subject category)