Airborne microbes from thawing permafrost landscapes in the Arctic - Arctic Study of Permafrost Ice Nucleation. Airborne microbes from thawing permafrost landscapes in the Arctic (ARCSPIN project)

Rapid warming in the Arctic, outpacing global rates by up to four times, is leading to significant changes in cryospheric landscapes including permafrost thaw, loss of summer sea ice, and ice sheet retreat. This study focuses on Northern Alaska’s thawing of permafrost, reintroducing ancient microorganisms to the environment. These microbes, previously preserved in frozen tundra soils, are spreading to thermokarst lakes, rivers, and the Arctic Ocean, altering the composition of these water systems. Permafrost microbes can be exposed and introduced to the atmosphere via various mechanisms. Here, we explore the local microbial sources of bioaerosols in Northern Alaska, assessing a broad range of environmental samples including terrestrial, water bodies, and vegetation. Although seawater and brackish water are the predominant bioaerosol sources, we present the first evidence of signatures of permafrost-originating microbes and their corresponding contribution to bioaerosols in permafrost-laden regions. This forewarns the importance of permafrost thawing for future atmospheric impacts, as it is highly enriched with ice nucleating particles (INPs), rare aerosols that play a critical role in altering cloud properties, precipitation patterns, and the overall radiative budget despite their low atmospheric concentrations. Rising Arctic temperatures accelerate the thawing of permafrost, which can lead to an increase in airborne permafrost-derived microbes and concentrations of biological INPs active at warm sub-zero temperatures. Such changes can result in increased precipitation, further increasing permafrost thaw. Our findings emphasize the complex interactions between terrestrial changes and cloud processes in the Arctic, identifying a potential positive feedback mechanism that may speed up permafrost thaw.