Climate change, in conjunction with human-induced pressures, is altering polar environments. Specifically, the Antarctic Peninsula (AP) has undergone a pronounced warming trend surpassing the rest of the Southern Hemisphere landmasses, resulting in surface melting, ice loss, and ecosystem modifications. Similarly, the Arctic region has witnessed a transition from snowfall to rainfall, prompting inquiry into whether such a climate shift will manifest in the Antarctic Peninsula. Atmospheric rivers (ARs) play a pivotal role in the long-distance transport of heat and moisture, particularly the conveyance of moisture from subtropical to polar regions.

This phenomenon has notable impacts on the Antarctic region, including intensified snowfall, rainfall, and major surface melt events.

Moreover, ARs serve as conduits for the long-range dispersion of microorganisms, although the specific microbial species involved remain uncertain. Nonetheless, these microorganisms may play crucial roles in cloud formation serving as ice nucleation particles (INP) and cloud condensation nuclei (CCN). The moisture carried by atmospheric rivers creates conducive environments for the activation of microbial cells in nucleation processes. The objective of this exploratory project is to characterize the microbial tracer composition of precipitation events in Antarctica and relate them to the thermodynamic structure of the boundary layer and entire troposphere and precipitation properties. These comprehensive and versatile data collections will allow us to gain insights into the changing climate over the warming AP and understand specific impacts on the drivers of microbial biodiversity.
The project will use a unique approach by combining measurements from three different Antarctic research expeditions in the region of the northern AP and Weddell Sea, during which intense precipitation sample collection will be done for stable water isotope and microbiological analysis. The first expedition is the Southern Ocean Clouds (SOC) expedition organized by British Antarctic Survey (BAS), taking place in the Southern Atlantic Ocean northwestern AP-Weddell Sea in November-December 2024. These measurements will be analyzed in the context of other SOC projects focusing on the aerosol-cloud interactions, particularly exploring the connection between precipitation microbial composition and cloud CCN and INP measurements. The second expedition is organized by the Brazilian Antarctic Program conveying measurements in the Atlantic and northern Antarctic Peninsula from November 2024 until March 2025 with a focus on the aerosol composition, amount and sources. The third expedition is the annual fieldwork conducted in the framework of the Portuguese Polar Program projects at the King Sejong station on King George Island, northern Antarctic Peninsula, where observations of precipitation profiles, cloud microphysical properties and troposphere thermodynamic profiles have been as part of other ongoing projects by the current proposal PI. Microbiological and isotope analysis of precipitation samples collected during these expeditions as part of MICROANT will be studied in relationship wtih the thermodynamic structure of the troposphere-lower atmosphere (observed using radiosondes) and aerosol, cloud and precipitation microphysical measurements conducted during these expeditions via other projects. As the duration of the exploratory project is short, the analysis will be focused on specific events contrasting the biogenic and microphysical precipitation properties during atmospheric rivers (with more distant sources of moisture and biogenic material) compared to other weather events when moisture and aerosol sources are more local. Particular emphasis will be given to the role of snow on sea ice compared to the oceanic sources of biogenic aerosols. MICROANT is innovative pursuing an interdisciplinary approach linking microbiological, meteorological and water cycle environmental domains, providing unique observational insights and promoting early career researchers training and leadership both in pursuing new endeavors towards better understanding of climate change impacts and knowledge sharing.