Evidence of Ocean and Permafrost as Sources of Bioaerosols in the Alaskan Arctic Boundary Layer
Authors: Nieto-Caballero Marina , Hill Thomas C. J. , Barry Kevin R. , McCluskey Christina S. , Douglas Thomas A. , DeMott Paul J. , Kreidenweis Sonia M. , Creamean Jessie M. 
Published: February 2023

As a result of Arctic air temperatures rising at four times the global rate, the cryosphere is rapidly thawing, releasing greenhouse gas reservoirs and metabolically active greenhouse gas-producing microorganisms. In addition, thawing cryosphere elements, such as permafrost (i.e., ground that is frozen for at least two consecutive years) and ice wedges (i.e., frozen water accumulated in ground cracks due to expansion and contraction of permafrost), can be introduced into water systems by different mechanisms. These mechanisms can include thermokarst lake formation (i.e., ice-rich permafrost areas that thaw and create surface depressions that are filled with thawed ice) and the increasingly common permafrost landslides.&#160;One of the hypotheses proposed in the multidisciplinary ARCSPIN (ARCtic Study of Permafrost Ice Nucleation) project is that microorganisms from thawed permafrost and ice wedges are discharged into water bodies in the Arctic region, and are ultimately released to the atmosphere through mechanisms such as thermokarst lake greenhouse gas bubble-bursting, and bubble-bursting due to higher wind-induced wave action on lakes, lagoons, and the open ocean. Additionally, these airborne biological particles can be a potential source of ice nucleating particles (INPs) active at warm temperatures (&#8805; -10oC), potentially altering cloud properties in Arctic regions. Arctic clouds have strong effects on regional and global energy budgets, with cloud phase (i.e., liquid or ice) being a key modulator of their interactions with radiation. Arctic mixed-phase clouds (AMPCs) are prevalent and are key in the ocean-ice-atmosphere system affected by the delicate energy balance over frozen surfaces. Ice formation in AMPCs is highly sensitive to the quantity and effects of aerosols serving as INPs.&#160;Here, we present results from a broad range of environmental samples collected during the ARCSPIN campaign in the Summer of 2021 in Northern Alaska (Utqia&#289;vik region), including air, water (i.e., sea, river, lagoon, and thermokarst lake), terrestrial (i.e., active layer, permafrost, ice wedge, and sediment), and vegetation samples. These samples were processed for 16S rRNA gene sequencing to identify and track microorganisms, showing for the first time how bioaerosols in Northern Alaska are influenced by terrestrial and water sources of the region. We additionally include results from published microbiome studies to perform source tracking analysis (Sourcetracker2), showing the potential long-range influence of ocean microorganisms, in particular, as bioaerosol sources in the Arctic. The obtained microbiome results are linked to meteorological conditions and air back trajectories calculated with NOAA&#8217;s HYSPLIT model.&#160;Data generated from the ARCSPIN study in combination with the Community Earth System Model (CESM) will be used for parameterization development and to investigate potential impacts of this unique INP source on Arctic clouds, helping to understand sources and impacts of bioaerosols in the Arctic.&#160;