Bacterial Bioaerosols Involved in Ice Nucleation and Cloud Formation: Connections to Shifting Precipitation Patterns in the Antarctic Peninsula

With the ongoing warming trend on the Antarctic Peninsula (AP), the amount, intensity, and frequency of precipitation is projected to increase by the end of the 21st century. The future of precipitation phase—whether rainfall will dominate snowfall over the AP—remains uncertain. Warm weather events occurring over the AP have been showing frequent snowfall to rainfall transitions, particularly during atmospheric rivers (AR) (Chyhareva et al., 2021; Wille et al., 2021; Gorodetskaya et al., 2023).

ARs are long corridors of anomalously high water vapour transport, which bring heat and moisture towards polar regions and, notably, can also facilitate the transport of aerosols (Lapere et al., 2021). When the sources of moisture and aerosols co-occur within ARs, aerosols can be scavenged and deposited as precipitation on ice-sheet surfaces.

In pristine environments such as Antarctica, aerosols of natural origin play an important role in cloud and precipitation formation (Mallet et al., 2023). Bioaerosols, specifically bacteria, can serve as potent ice-nucleating particles, facilitating the formation of ice and influencing precipitation formation, especially in mixed-phase clouds.

This study aims to identify culturable bacteria present in precipitation samples—rainfall, snowfall, and surface snow following precipitation events—collected in the northern AP, on King George Island, in the vicinity of the King Sejong station. Bacterial isolates were identified using 16S rDNA gene sequencing, revealing key differences in culturable biodiversity between rainfall and snowfall samples. Genera known for exhibiting ice-nucleating activity, Pseudomonas and Stenotrophomonas, were predominantly recovered from rainfall. Additionally, potentially novel strains were recovered from rainfall samples. Surface snow samples following precipitation events exhibited high culturable biodiversity, including Spirosoma sp. and Bacillus sp. strains, which are adapted to the extreme conditions of aerial and polar environments.

These results highlight a shift from snowfall to rainfall-dominated precipitation in the AP may impact the local biodiversity, and the newly introduced ice-nucleating strains can further impact the Antarctic climate. Bacteria associated with ice nucleating activity were recovered from precipitation, indicating bacteria can impact the polar aerosol budget, cloud dynamics and climate of the AP.

Future analysis of AR-associated precipitation is key to determining the atmospheric transport of bioaerosols and is a necessary component for understanding the current warming trend of the AP.

Acknowledgements:  PROPOLAR (Portuguese Polar Program) projects APMAR/TULIP/APMAR2/APMAR2025 and FCT project MAPS (2022.09201.PTDC) and MicroANT (2023.15890.PEX)

References:

Chyhareva, A., et al (2021). Precipitation phase transition in austral summer over the Antarctic Peninsula. Ukr. Ant. J., https://doi.org/10.33275/1727-7485.1.2021.664

Gorodetskaya, I., et al. (2023). Record-high Antarctic Peninsula temperatures and surface melt in February 2022: A compound event with an intense atmospheric river. npj Clim. Atmos. Sci. https://doi.org/10.1038/s41612-023-00529-6

Lapere, S., et al. (2024). Polar aerosol atmospheric rivers: Detection, characteristics, and potential applications. J. Geophys. Res.: Atmospheres, 129(2). https://doi.org/10.1029/2023JD039606

Mallet, M., et al. (2023). Untangling the influence of Antarctic and Southern Ocean life on clouds. Elementa: Sci. Anthropocene, 11(1). https://doi.org/10.1525/elementa.2022.00130

Wille, J. D., et al. (2021). Antarctic atmospheric river climatology and precipitation impacts. J. Geophys. Res.: Atmospheres, 126(8), e2020JD033788

Keywords: Antarctic Peninsula, precipitation, bioaerosols, culturable biodiversity, ice-nucleation